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Overview
Comment:Further updates to comments in pager.c.
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SHA1: 5f4c17a33fd442d66c1bf75af9b21954f6906897
User & Date: dan 2010-08-06 12:00:27.000
Context
2010-08-06
13:53
Merge trunk changes into experimental branch. (check-in: aef6698c73 user: dan tags: experimental)
12:00
Further updates to comments in pager.c. (check-in: 5f4c17a33f user: dan tags: experimental)
09:43
Modify test_journal.c to work with pre-allocated databases. (check-in: 4894a5d210 user: dan tags: experimental)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/pager.c.
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#define FILEHANDLEID(fd) ((int)fd)

/*
** The Pager.eState variable stores the current 'state' of a pager. A
** pager may be in any one of the seven states shown in the following
** state diagram.
**
**                            NONE <------+------+
**                              |         |      |
**                              V         |      |
**               +---------> READER-------+      |
**               |              |                |
**               |              V                |
**               |<-------WRITER_INITIAL-----> ERROR
**               |              |                ^  
**               |              V                |
**               |<------WRITER_CACHEMOD-------->|
**               |              |                |
**               |              V                |
**               |<-------WRITER_DBMOD---------->|
**               |              |                |
**               |              V                |
**               +<------WRITER_FINISHED-------->+
**
**
** List of state transitions and the C [function] that performs each:
** 
**   NONE              -> READER              [sqlite3PagerSharedLock]
**   READER            -> NONE                [pager_unlock]
**
**   READER            -> WRITER_INITIAL      [sqlite3PagerBegin]
**   WRITER_INITIAL    -> WRITER_CACHEMOD     [pager_open_journal]
**   WRITER_CACHEMOD   -> WRITER_DBMOD        [syncJournal]
**   WRITER_DBMOD      -> WRITER_FINISHED     [sqlite3PagerCommitPhaseOne]
**   WRITER_***        -> READER              [pager_end_transaction]
**
**   WRITER_***        -> ERROR               [pager_error]
**   ERROR             -> NONE                [pager_unlock]
** 
**
**  NONE:
**
**    The pager starts up in this state. Nothing is guaranteed in this
**    state - the file may or may not be locked and the database size is
**    unknown. The database may not be read or written.
**
**    * No read or write transaction is active.
**    * Any lock, or no lock at all, may be held on the database file.
**    * The dbSize, dbOrigSize and dbFileSize variables may not be trusted.
**
**  READER:
**
**    In this state all the requirements for reading the database in 
**    rollback (non-WAL) mode are met. Unless the pager is (or recently
**    was) in exclusive-locking mode, a user-level read transaction is 
**    open. The database size is known in this state.
**
**    A connection running with locking_mode=normal enters this state when
**    it opens a read-transaction on the database and returns to state
**    NONE after the read-transaction is completed. However a connection
**    running in locking_mode=exclusive (including temp databases) remains in
**    this state even after the read-transaction is closed. The only way
**    a locking_mode=exclusive connection can transition from READER to NONE
**    is via the ERROR state (see below).
**
**    TODO: Maybe WAL connections should behave like locking_mode=exclusive
**          connections and remain in READER state even when there is no
**          active read transaction.
** 
**    * A read transaction may be active (but a write-transaction cannot).
**    * A SHARED or greater lock is held on the database file.
**    * The dbSize variable may be trusted (even if a user-level read 
**      transaction is not active). The dbOrigSize and dbFileSize variables
**      may not be trusted at this point.
**    * If the database is a WAL database, then the WAL connection is open.
**    * Even if a read-transaction is not open, it is guaranteed that 
**      there is no hot-journal in the file-system.
**
**  WRITER_INITIAL:
**
**    The pager moves to this state from READER when a write-transaction
**    is first opened on the database.













**
**    * A write transaction is active.
**    * If the connection is open in rollback-mode, a RESERVED or greater 
**      lock is held on the database file.
**    * If the connection is open in WAL-mode, a WAL write transaction
**      is open (i.e. sqlite3WalBeginWriteTransaction() has been successfully
**      called).
**    * The dbSize, dbOrigSize and dbFileSize variables are all valid.
**    * The contents of the pager cache have not been modified.
**    * The journal file may or may not be open.
**    * Nothing (not even the first header) has been written to the journal.
**
**  WRITER_CACHEMOD:





**
**    * A write transaction is active.
**    * A RESERVED or greater lock is held on the database file.
**    * The journal file is open and the first header has been written 
**      to it, but the header has not been synced to disk.
**    * The contents of the page cache have been modified.
**







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#define FILEHANDLEID(fd) ((int)fd)

/*
** The Pager.eState variable stores the current 'state' of a pager. A
** pager may be in any one of the seven states shown in the following
** state diagram.
**
**                            OPEN <------+------+
**                              |         |      |
**                              V         |      |
**               +---------> READER-------+      |
**               |              |                |
**               |              V                |
**               |<-------WRITER_LOCKED------> ERROR
**               |              |                ^  
**               |              V                |
**               |<------WRITER_CACHEMOD-------->|
**               |              |                |
**               |              V                |
**               |<-------WRITER_DBMOD---------->|
**               |              |                |
**               |              V                |
**               +<------WRITER_FINISHED-------->+
**
**
** List of state transitions and the C [function] that performs each:
** 
**   OPEN              -> READER              [sqlite3PagerSharedLock]
**   READER            -> OPEN                [pager_unlock]
**
**   READER            -> WRITER_LOCKED       [sqlite3PagerBegin]
**   WRITER_LOCKED     -> WRITER_CACHEMOD     [pager_open_journal]
**   WRITER_CACHEMOD   -> WRITER_DBMOD        [syncJournal]
**   WRITER_DBMOD      -> WRITER_FINISHED     [sqlite3PagerCommitPhaseOne]
**   WRITER_***        -> READER              [pager_end_transaction]
**
**   WRITER_***        -> ERROR               [pager_error]
**   ERROR             -> OPEN                [pager_unlock]
** 
**
**  OPEN:
**
**    The pager starts up in this state. Nothing is guaranteed in this
**    state - the file may or may not be locked and the database size is
**    unknown. The database may not be read or written.
**
**    * No read or write transaction is active.
**    * Any lock, or no lock at all, may be held on the database file.
**    * The dbSize, dbOrigSize and dbFileSize variables may not be trusted.
**
**  READER:
**
**    In this state all the requirements for reading the database in 
**    rollback (non-WAL) mode are met. Unless the pager is (or recently
**    was) in exclusive-locking mode, a user-level read transaction is 
**    open. The database size is known in this state.
**
**    A connection running with locking_mode=normal enters this state when
**    it opens a read-transaction on the database and returns to state
**    OPEN after the read-transaction is completed. However a connection
**    running in locking_mode=exclusive (including temp databases) remains in
**    this state even after the read-transaction is closed. The only way
**    a locking_mode=exclusive connection can transition from READER to OPEN
**    is via the ERROR state (see below).




** 
**    * A read transaction may be active (but a write-transaction cannot).
**    * A SHARED or greater lock is held on the database file.
**    * The dbSize variable may be trusted (even if a user-level read 
**      transaction is not active). The dbOrigSize and dbFileSize variables
**      may not be trusted at this point.
**    * If the database is a WAL database, then the WAL connection is open.
**    * Even if a read-transaction is not open, it is guaranteed that 
**      there is no hot-journal in the file-system.
**
**  WRITER_LOCKED:
**
**    The pager moves to this state from READER when a write-transaction
**    is first opened on the database. In WRITER_LOCKED state, all locks 
**    required to start a write-transaction are held, but no actual 
**    modifications to the cache or database have taken place.
**
**    In rollback mode, a RESERVED or (if the transaction was opened with 
**    BEGIN EXCLUSIVE) EXCLUSIVE lock is obtained on the database file when
**    moving to this state, but the journal file is not written to or opened 
**    to in this state. If the transaction is committed or rolled back while 
**    in WRITER_LOCKED state, all that is required is to unlock the database 
**    file.
**
**    IN WAL mode, WalBeginWriteTransaction() is called to lock the log file.
**    If the connection is running with locking_mode=exclusive, an attempt
**    is made to obtain an EXCLUSIVE lock on the database file.
**
**    * A write transaction is active.
**    * If the connection is open in rollback-mode, a RESERVED or greater 
**      lock is held on the database file.
**    * If the connection is open in WAL-mode, a WAL write transaction
**      is open (i.e. sqlite3WalBeginWriteTransaction() has been successfully
**      called).
**    * The dbSize, dbOrigSize and dbFileSize variables are all valid.
**    * The contents of the pager cache have not been modified.
**    * The journal file may or may not be open.
**    * Nothing (not even the first header) has been written to the journal.
**
**  WRITER_CACHEMOD:
**
**    A pager moves from WRITER_LOCKED state to this state when a page is
**    first modified by the upper layer. In rollback mode the journal file
**    is opened (if it is not already open) and a header written to the
**    start of it. The database file on disk has not been modified.
**
**    * A write transaction is active.
**    * A RESERVED or greater lock is held on the database file.
**    * The journal file is open and the first header has been written 
**      to it, but the header has not been synced to disk.
**    * The contents of the page cache have been modified.
**
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**    they upgrade to writers, they may inadvertently corrupt the database
**    file. To avoid this hazard, the pager switches into the ERROR state
**    instead of READER following such an error.
**
**    Once it has entered the ERROR state, any attempt to use the pager
**    to read or write data returns an error. Eventually, once all 
**    outstanding transactions have been abandoned, the pager is able to
**    transition back to NONE state, discarding the contents of the 
**    page-cache and any other in-memory state at the same time. Everything
**    is reloaded from disk (and, if necessary, hot-journal rollback peformed)
**    when a read-transaction is next opened on the pager (transitioning
**    the pager into READER state). At that point the system has recovered 
**    from the error.
**
**    Specifically, the pager jumps into the ERROR state if:







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**    they upgrade to writers, they may inadvertently corrupt the database
**    file. To avoid this hazard, the pager switches into the ERROR state
**    instead of READER following such an error.
**
**    Once it has entered the ERROR state, any attempt to use the pager
**    to read or write data returns an error. Eventually, once all 
**    outstanding transactions have been abandoned, the pager is able to
**    transition back to OPEN state, discarding the contents of the 
**    page-cache and any other in-memory state at the same time. Everything
**    is reloaded from disk (and, if necessary, hot-journal rollback peformed)
**    when a read-transaction is next opened on the pager (transitioning
**    the pager into READER state). At that point the system has recovered 
**    from the error.
**
**    Specifically, the pager jumps into the ERROR state if:
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**
**    Condition (3) is necessary because it can be triggered by a read-only
**    statement executed within a transaction. In this case, if the error
**    code were simply returned to the user, the b-tree layer would not
**    automatically attempt a rollback, as it assumes that an error in a
**    read-only statement cannot leave the pager in an internally inconsistent 
**    state.




**    
**
** Notes:
**
**   * A pager is never in WRITER_DBMOD or WRITER_FINISHED state if the
**     connection is open in WAL mode. A WAL connection is always in one
**     of the first four states.
**
**   * Normally, a connection open in exclusive mode is never in PAGER_NONE
**     state. There are two exceptions: immediately after exclusive-mode has
**     been turned on (and before any read or write transactions are 
**     executed), and when the pager is leaving the "error state".
**
**   * See also: assert_pager_state().
*/
#define PAGER_NONE                  0
#define PAGER_READER                1
#define PAGER_WRITER_INITIAL        2
#define PAGER_WRITER_CACHEMOD       3
#define PAGER_WRITER_DBMOD          4
#define PAGER_WRITER_FINISHED       5
#define PAGER_ERROR                 6

/*
** The Pager.eLock variable is almost always set to one of the 







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**
**    Condition (3) is necessary because it can be triggered by a read-only
**    statement executed within a transaction. In this case, if the error
**    code were simply returned to the user, the b-tree layer would not
**    automatically attempt a rollback, as it assumes that an error in a
**    read-only statement cannot leave the pager in an internally inconsistent 
**    state.
**
**    * The Pager.errCode variable is set to something other than SQLITE_OK.
**    * There are one or more outstanding references to pages (after the
**      last reference is dropped the pager should move back to OPEN state).
**    
**
** Notes:
**
**   * A pager is never in WRITER_DBMOD or WRITER_FINISHED state if the
**     connection is open in WAL mode. A WAL connection is always in one
**     of the first four states.
**
**   * Normally, a connection open in exclusive mode is never in PAGER_OPEN
**     state. There are two exceptions: immediately after exclusive-mode has
**     been turned on (and before any read or write transactions are 
**     executed), and when the pager is leaving the "error state".
**
**   * See also: assert_pager_state().
*/
#define PAGER_OPEN                  0
#define PAGER_READER                1
#define PAGER_WRITER_LOCKED         2
#define PAGER_WRITER_CACHEMOD       3
#define PAGER_WRITER_DBMOD          4
#define PAGER_WRITER_FINISHED       5
#define PAGER_ERROR                 6

/*
** The Pager.eLock variable is almost always set to one of the 
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** at the system level, but it is never set to a more exclusive value.
**
** This is usually safe. If an xUnlock fails or appears to fail, there may 
** be a few redundant xLock() calls or a lock may be held for longer than
** required, but nothing really goes wrong.
**
** The exception is when the database file is unlocked as the pager moves
** from ERROR to NONE state. At this point there may be a hot-journal file 
** in the file-system that needs to be rolled back (as part of a NONE->SHARED
** transition, by the same pager or any other). If the call to xUnlock()
** fails at this point and the pager is left holding an EXCLUSIVE lock, this
** can confuse the call to xCheckReservedLock() call made later as part
** of hot-journal detection.
**
** xCheckReservedLock() is defined as returning true "if there is a RESERVED 
** lock held by this process or any others". So xCheckReservedLock may 
** return true because the caller itself is holding an EXCLUSIVE lock (but
** doesn't know it because of a previous error in xUnlock). If this happens
** a hot-journal may be mistaken for a journal being created by an active
** transaction in another process, causing SQLite to read from the database
** without rolling it back.
**
** To work around this, if a call to xUnlock() fails when unlocking the
** database in the ERROR state, Pager.eLock is set to UNKNOWN_LOCK. It
** is only changed back to a real locking state after a successful call
** to xLock(EXCLUSIVE). Also, the code to do the NONE->SHARED state transition
** omits the check for a hot-journal if Pager.eLock is set to UNKNOWN_LOCK 
** lock. Instead, it assumes a hot-journal exists and obtains an EXCLUSIVE
** lock on the database file before attempting to roll it back. See function
** PagerSharedLock() for more detail.
**
** Pager.eLock may only be set to UNKNOWN_LOCK when the pager is in 
** PAGER_NONE state.
*/
#define UNKNOWN_LOCK                (EXCLUSIVE_LOCK+1)

/*
** A macro used for invoking the codec if there is one
*/
#ifdef SQLITE_HAS_CODEC







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** at the system level, but it is never set to a more exclusive value.
**
** This is usually safe. If an xUnlock fails or appears to fail, there may 
** be a few redundant xLock() calls or a lock may be held for longer than
** required, but nothing really goes wrong.
**
** The exception is when the database file is unlocked as the pager moves
** from ERROR to OPEN state. At this point there may be a hot-journal file 
** in the file-system that needs to be rolled back (as part of a OPEN->SHARED
** transition, by the same pager or any other). If the call to xUnlock()
** fails at this point and the pager is left holding an EXCLUSIVE lock, this
** can confuse the call to xCheckReservedLock() call made later as part
** of hot-journal detection.
**
** xCheckReservedLock() is defined as returning true "if there is a RESERVED 
** lock held by this process or any others". So xCheckReservedLock may 
** return true because the caller itself is holding an EXCLUSIVE lock (but
** doesn't know it because of a previous error in xUnlock). If this happens
** a hot-journal may be mistaken for a journal being created by an active
** transaction in another process, causing SQLite to read from the database
** without rolling it back.
**
** To work around this, if a call to xUnlock() fails when unlocking the
** database in the ERROR state, Pager.eLock is set to UNKNOWN_LOCK. It
** is only changed back to a real locking state after a successful call
** to xLock(EXCLUSIVE). Also, the code to do the OPEN->SHARED state transition
** omits the check for a hot-journal if Pager.eLock is set to UNKNOWN_LOCK 
** lock. Instead, it assumes a hot-journal exists and obtains an EXCLUSIVE
** lock on the database file before attempting to roll it back. See function
** PagerSharedLock() for more detail.
**
** Pager.eLock may only be set to UNKNOWN_LOCK when the pager is in 
** PAGER_OPEN state.
*/
#define UNKNOWN_LOCK                (EXCLUSIVE_LOCK+1)

/*
** A macro used for invoking the codec if there is one
*/
#ifdef SQLITE_HAS_CODEC
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  Pgno iSubRec;                /* Index of first record in sub-journal */
#ifndef SQLITE_OMIT_WAL
  u32 aWalData[WAL_SAVEPOINT_NDATA];        /* WAL savepoint context */
#endif
};

/*
** A open page cache is an instance of the following structure.

**
** errCode

**   The Pager.errCode variable is only ever non-zero when the condition
**   (Pager.eState==PAGER_ERROR) is true. 
**
**   Pager.errCode may be set to SQLITE_FULL, SQLITE_IOERR or one of the
**   SQLITE_IOERR_XXX sub-codes.
**
** dbSize, dbOrigSize, dbFileSize


**
**   Managing the size of the database file in pages is a little complicated.
**   The variable Pager.dbSize contains the number of pages that the database
**   image currently contains. As the database image grows or shrinks this
**   variable is updated. The variable Pager.dbFileSize contains the number
**   of pages in the database file. This may be different from Pager.dbSize
**   if some pages have been appended to the database image but not yet written
**   out from the cache to the actual file on disk. Or if the image has been
**   truncated by an incremental-vacuum operation. The Pager.dbOrigSize variable
**   contains the number of pages in the database image when the current

**   transaction was opened. 
**
** changeCountDone
**
**   This boolean variable is used to make sure that the change-counter 
**   (the 4-byte header field at byte offset 24 of the database file) is 
**   not updated more often than necessary. 
**
**   It is set to true when the change-counter field is updated, which 
**   can only happen if an exclusive lock is held on the database file.
**   It is cleared (set to false) whenever an exclusive lock is 
**   relinquished on the database file. Each time a transaction is committed,
**   The changeCountDone flag is inspected. If it is true, the work of
**   updating the change-counter is omitted for the current transaction.
**
**   This mechanism means that when running in exclusive mode, a connection 
**   need only update the change-counter once, for the first transaction
**   committed.
**
** dbModified
**
**   The dbModified flag is set whenever a database page is dirtied.
**   It is cleared at the end of each transaction.
**
**   It is used when committing or otherwise ending a transaction. If
**   the dbModified flag is clear then less work has to be done.
**
** journalStarted
**
**   This flag is set during a write-transaction after the first 
**   journal-header is written and synced to disk.
**
**   After this has happened, new pages appended to the database 
**   do not need the PGHDR_NEED_SYNC flag set, as they do not need
**   to wait for a journal sync before they can be written out to
**   the database file (see function pager_write()).
**   
** setMaster
**
**   When PagerCommitPhaseOne() is called to commit a transaction, it may
**   (or may not) specify a master-journal name to be written into the 
**   journal file before it is synced to disk.
**
**   Whether or not a journal file contains a master-journal pointer affects 
**   the way in which the journal file is finalized after the transaction is 
**   committed or rolled back when running in "journal_mode=PERSIST" mode.
**   If a journal file does not contain a master-journal pointer, it is
**   finalized by overwriting the first journal header with zeroes. If,
**   on the other hand, it does contain a master-journal pointer, the
**   journal file is finalized by truncating it to zero bytes, just as if
**   the connection were running in "journal_mode=truncate" mode.
**
**   Journal files that contain master journal pointers cannot be finalized
**   simply by overwriting the first journal-header with zeroes, as the
**   master journal pointer could interfere with hot-journal rollback of any
**   subsequently interrupted transaction that reuses the journal file.
**
**   The flag is cleared as soon as the journal file is finalized (either
**   by PagerCommitPhaseTwo or PagerRollback). If an IO error prevents the
**   journal file from being successfully finalized, the setMaster flag
**   is cleared anyway.
**
** doNotSpill, doNotSyncSpill
**
**   When enabled, cache spills are prohibited.  The doNotSpill variable
**   inhibits all cache spill and doNotSyncSpill inhibits those spills that
**   would require a journal sync.  The doNotSyncSpill is set and cleared 
**   by sqlite3PagerWrite() in order to prevent a journal sync from happening 
**   in between the journalling of two pages on the same sector.  The
**   doNotSpill value set to prevent pagerStress() from trying to use
**   the journal during a rollback.
**
** subjInMemory
**
**   This is a boolean variable. If true, then any required sub-journal
**   is opened as an in-memory journal file. If false, then in-memory
**   sub-journals are only used for in-memory pager files.




















































*/
struct Pager {
  sqlite3_vfs *pVfs;          /* OS functions to use for IO */
  u8 exclusiveMode;           /* Boolean. True if locking_mode==EXCLUSIVE */
  u8 journalMode;             /* One of the PAGER_JOURNALMODE_* values */
  u8 useJournal;              /* Use a rollback journal on this file */
  u8 noReadlock;              /* Do not bother to obtain readlocks */







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  Pgno iSubRec;                /* Index of first record in sub-journal */
#ifndef SQLITE_OMIT_WAL
  u32 aWalData[WAL_SAVEPOINT_NDATA];        /* WAL savepoint context */
#endif
};

/*
** A open page cache is an instance of struct Pager. A description of
** some of the more important member variables follows:
**
** eState
**
**   The current 'state' of the pager object. See the comment and state
**   diagram above for a description of the pager state.
**

** eLock
**

**   For a real on-disk database, the current lock held on the database file -
**   NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK.
**
**   For a temporary or in-memory database (neither of which require any


**   locks), this variable is always set to EXCLUSIVE_LOCK. Since such
**   databases always have Pager.exclusiveMode==1, this tricks the pager
**   logic into thinking that it already has all the locks it will ever
**   need (and no reason to release them).
**
**   In some (obscure) circumstances, this variable may also be set to
**   UNKNOWN_LOCK. See the comment above the #define of UNKNOWN_LOCK for
**   details.
**
** changeCountDone
**
**   This boolean variable is used to make sure that the change-counter 
**   (the 4-byte header field at byte offset 24 of the database file) is 
**   not updated more often than necessary. 
**
**   It is set to true when the change-counter field is updated, which 
**   can only happen if an exclusive lock is held on the database file.
**   It is cleared (set to false) whenever an exclusive lock is 
**   relinquished on the database file. Each time a transaction is committed,
**   The changeCountDone flag is inspected. If it is true, the work of
**   updating the change-counter is omitted for the current transaction.
**
**   This mechanism means that when running in exclusive mode, a connection 
**   need only update the change-counter once, for the first transaction
**   committed.
**


















** setMaster
**
**   When PagerCommitPhaseOne() is called to commit a transaction, it may
**   (or may not) specify a master-journal name to be written into the 
**   journal file before it is synced to disk.
**
**   Whether or not a journal file contains a master-journal pointer affects 
**   the way in which the journal file is finalized after the transaction is 
**   committed or rolled back when running in "journal_mode=PERSIST" mode.
**   If a journal file does not contain a master-journal pointer, it is
**   finalized by overwriting the first journal header with zeroes. If
**   it does contain a master-journal pointer the journal file is finalized 
**   by truncating it to zero bytes, just as if the connection were 
**   running in "journal_mode=truncate" mode.
**
**   Journal files that contain master journal pointers cannot be finalized
**   simply by overwriting the first journal-header with zeroes, as the
**   master journal pointer could interfere with hot-journal rollback of any
**   subsequently interrupted transaction that reuses the journal file.
**
**   The flag is cleared as soon as the journal file is finalized (either
**   by PagerCommitPhaseTwo or PagerRollback). If an IO error prevents the
**   journal file from being successfully finalized, the setMaster flag
**   is cleared anyway (and the pager will move to ERROR state).
**
** doNotSpill, doNotSyncSpill
**
**   When enabled, cache spills are prohibited.  The doNotSpill variable
**   inhibits all cache spill and doNotSyncSpill inhibits those spills that
**   would require a journal sync.  The doNotSyncSpill is set and cleared 
**   by sqlite3PagerWrite() in order to prevent a journal sync from happening 
**   in between the journalling of two pages on the same sector.  The
**   doNotSpill value set to prevent pagerStress() from trying to use
**   the journal during a rollback.
**
** subjInMemory
**
**   This is a boolean variable. If true, then any required sub-journal
**   is opened as an in-memory journal file. If false, then in-memory
**   sub-journals are only used for in-memory pager files.
**
**   This variable is updated by the upper layer each time a new 
**   write-transaction is opened.
**
** dbSize, dbOrigSize, dbFileSize
**
**   Variable dbSize is set to the number of pages in the database file.
**   It is valid in PAGER_READER and higher states (all states except for
**   OPEN and ERROR). 
**
**   dbSize is set based on the size of the database file, which may be 
**   larger than the size of the database (the value stored at offset
**   28 of the database header by the btree). If the size of the file
**   is not an integer multiple of the page-size, the value stored in
**   dbSize is rounded down (i.e. a 5KB file with 2K page-size has dbSize==2).
**   Except, any file that is greater than 0 bytes in size is considered
**   to have at least one page. (i.e. a 1KB file with 2K page-size leads
**   to dbSize==1).
**
**   During a write-transaction, if pages with page-numbers greater than
**   dbSize are modified in the cache, dbSize is updated accordingly.
**   Similarly, if the database is truncated using PagerTruncateImage(), 
**   dbSize is updated.
**
**   Variables dbOrigSize and dbFileSize are valid in states 
**   PAGER_WRITER_LOCKED and higher. dbOrigSize is a copy of the dbSize
**   variable at the start of the transaction. It is used during rollback,
**   and to determine whether or not pages need to be journalled before
**   being modified.
**
**   Throughout a write-transaction, dbFileSize contains the size of
**   the file on disk in pages. It is set to a copy of dbSize when the
**   write-transaction is first opened, and updated when VFS calls are made
**   to write or truncate the database file on disk.
**
** errCode
**
**   The Pager.errCode variable is only ever used in PAGER_ERROR state. It
**   is set to zero in all other states. In PAGER_ERROR state, Pager.errCode 
**   is always set to SQLITE_FULL, SQLITE_IOERR or one of the SQLITE_IOERR_XXX 
**   sub-codes.
**
**   If Pager.errCode is set to SQLITE_IOERR or one of its subcodes, then
**   this value is immediately returned when ever any sqlite3PagerXXX() method
**   that returns an error code is called. If it is set to SQLITE_FULL,
**   then it is returned whenever any such sqlite3PagerXXX() method except
**   for PagerAcquire() or PagerLookup() is called.
**
**   TODO: Review the SQLITE_FULL/PagerAcquire() exception. Is it a good idea?
**         If so, are there bugs whereby shared-cache clients can see 
**         uncommitted data when the pager is in the ERROR state?
**
*/
struct Pager {
  sqlite3_vfs *pVfs;          /* OS functions to use for IO */
  u8 exclusiveMode;           /* Boolean. True if locking_mode==EXCLUSIVE */
  u8 journalMode;             /* One of the PAGER_JOURNALMODE_* values */
  u8 useJournal;              /* Use a rollback journal on this file */
  u8 noReadlock;              /* Do not bother to obtain readlocks */
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  ** operates.
  **
  ** The 'state' variable is described in more detail along with the
  ** descriptions of the values it may take - PAGER_UNLOCK etc. Many of the
  ** other variables in this block are described in the comment directly 
  ** above this class definition.
  */
  u8 eState;                  /* Pager state (NONE, READER, WRITER_INITIAL..) */
  u8 eLock;                   /* Current lock held on database file */
  u8 changeCountDone;         /* Set after incrementing the change-counter */
  u8 setMaster;               /* True if a m-j name has been written to jrnl */
  u8 doNotSpill;              /* Do not spill the cache when non-zero */
  u8 doNotSyncSpill;          /* Do not do a spill that requires jrnl sync */
  u8 subjInMemory;            /* True to use in-memory sub-journals */
  Pgno dbSize;                /* Number of pages in the database */







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  ** operates.
  **
  ** The 'state' variable is described in more detail along with the
  ** descriptions of the values it may take - PAGER_UNLOCK etc. Many of the
  ** other variables in this block are described in the comment directly 
  ** above this class definition.
  */
  u8 eState;                  /* Pager state (OPEN, READER, WRITER_LOCKED..) */
  u8 eLock;                   /* Current lock held on database file */
  u8 changeCountDone;         /* Set after incrementing the change-counter */
  u8 setMaster;               /* True if a m-j name has been written to jrnl */
  u8 doNotSpill;              /* Do not spill the cache when non-zero */
  u8 doNotSyncSpill;          /* Do not do a spill that requires jrnl sync */
  u8 subjInMemory;            /* True to use in-memory sub-journals */
  Pgno dbSize;                /* Number of pages in the database */
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#endif

#ifndef NDEBUG 
/*
** Usage:
**
**   assert( assert_pager_state(pPager) );



*/
static int assert_pager_state(Pager *p){
  Pager *pPager = p;

  /* State must be valid. */
  assert( p->eState==PAGER_NONE
       || p->eState==PAGER_READER
       || p->eState==PAGER_WRITER_INITIAL
       || p->eState==PAGER_WRITER_CACHEMOD
       || p->eState==PAGER_WRITER_DBMOD
       || p->eState==PAGER_WRITER_FINISHED
       || p->eState==PAGER_ERROR
  );

  /* Regardless of the current state, a temp-file connection always behaves







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#endif

#ifndef NDEBUG 
/*
** Usage:
**
**   assert( assert_pager_state(pPager) );
**
** This function runs many asserts to try to find inconsistencies in
** the internal state of the Pager object.
*/
static int assert_pager_state(Pager *p){
  Pager *pPager = p;

  /* State must be valid. */
  assert( p->eState==PAGER_OPEN
       || p->eState==PAGER_READER
       || p->eState==PAGER_WRITER_LOCKED
       || p->eState==PAGER_WRITER_CACHEMOD
       || p->eState==PAGER_WRITER_DBMOD
       || p->eState==PAGER_WRITER_FINISHED
       || p->eState==PAGER_ERROR
  );

  /* Regardless of the current state, a temp-file connection always behaves
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  /* If changeCountDone is set, a RESERVED lock or greater must be held
  ** on the file.
  */
  assert( pPager->changeCountDone==0 || pPager->eLock>=RESERVED_LOCK );
  assert( p->eLock!=PENDING_LOCK );

  switch( p->eState ){
    case PAGER_NONE:
      assert( !MEMDB );
      assert( pPager->errCode==SQLITE_OK );
      assert( sqlite3PcacheRefCount(pPager->pPCache)==0 || pPager->tempFile );
      break;

    case PAGER_READER:
      assert( pPager->errCode==SQLITE_OK );
      assert( p->eLock!=UNKNOWN_LOCK );
      assert( p->eLock>=SHARED_LOCK || p->noReadlock );
      break;

    case PAGER_WRITER_INITIAL:
      assert( p->eLock!=UNKNOWN_LOCK );
      assert( pPager->errCode==SQLITE_OK );
      if( !pagerUseWal(pPager) ){
        assert( p->eLock>=RESERVED_LOCK );
      }
      assert( pPager->dbSize==pPager->dbOrigSize );
      assert( pPager->dbOrigSize==pPager->dbFileSize );







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  /* If changeCountDone is set, a RESERVED lock or greater must be held
  ** on the file.
  */
  assert( pPager->changeCountDone==0 || pPager->eLock>=RESERVED_LOCK );
  assert( p->eLock!=PENDING_LOCK );

  switch( p->eState ){
    case PAGER_OPEN:
      assert( !MEMDB );
      assert( pPager->errCode==SQLITE_OK );
      assert( sqlite3PcacheRefCount(pPager->pPCache)==0 || pPager->tempFile );
      break;

    case PAGER_READER:
      assert( pPager->errCode==SQLITE_OK );
      assert( p->eLock!=UNKNOWN_LOCK );
      assert( p->eLock>=SHARED_LOCK || p->noReadlock );
      break;

    case PAGER_WRITER_LOCKED:
      assert( p->eLock!=UNKNOWN_LOCK );
      assert( pPager->errCode==SQLITE_OK );
      if( !pagerUseWal(pPager) ){
        assert( p->eLock>=RESERVED_LOCK );
      }
      assert( pPager->dbSize==pPager->dbOrigSize );
      assert( pPager->dbOrigSize==pPager->dbFileSize );
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           || p->journalMode==PAGER_JOURNALMODE_WAL 
      );
      break;

    case PAGER_ERROR:
      /* There must be at least one outstanding reference to the pager if
      ** in ERROR state. Otherwise the pager should have already dropped
      ** back to NONE state.
      */
      assert( pPager->errCode!=SQLITE_OK );
      assert( sqlite3PcacheRefCount(pPager->pPCache)>0 );
      break;
  }

  return 1;
}

/*





** (gdb) printf "%s", print_pager_state(pPager)
*/
static char *print_pager_state(Pager *p){
  static char zRet[1024];

  sqlite3_snprintf(1024, zRet,
      "Filename:      %s\n"
      "State:         %s errCode=%d\n"
      "Lock:          %s\n"
      "Locking mode:  locking_mode=%s\n"
      "Journal mode:  journal_mode=%s\n"
      "Backing store: tempFile=%d memDb=%d useJournal=%d\n"
      "Journal:       journalOff=%lld journalHdr=%lld\n"
      , p->zFilename
      , p->eState==PAGER_NONE            ? "NONE" :
        p->eState==PAGER_READER          ? "READER" :
        p->eState==PAGER_WRITER_INITIAL  ? "WRITER_INITIAL" :
        p->eState==PAGER_WRITER_CACHEMOD ? "WRITER_CACHEMOD" :
        p->eState==PAGER_WRITER_DBMOD    ? "WRITER_DBMOD" :
        p->eState==PAGER_WRITER_FINISHED ? "WRITER_FINISHED" :
        p->eState==PAGER_ERROR           ? "ERROR" : "?error?"
      , (int)p->errCode
      , p->eLock==NO_LOCK         ? "NONE" :
        p->eLock==RESERVED_LOCK   ? "RESERVED" :
        p->eLock==EXCLUSIVE_LOCK  ? "EXCLUSIVE" :
        p->eLock==SHARED_LOCK     ? "SHARED" :
        p->eLock==UNKNOWN_LOCK    ? "UNKNOWN" : "?error?"
      , p->exclusiveMode ? "exclusive" : "normal"
      , p->journalMode==PAGER_JOURNALMODE_MEMORY   ? "memory" :
        p->journalMode==PAGER_JOURNALMODE_OFF      ? "off" :







|










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|







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           || p->journalMode==PAGER_JOURNALMODE_WAL 
      );
      break;

    case PAGER_ERROR:
      /* There must be at least one outstanding reference to the pager if
      ** in ERROR state. Otherwise the pager should have already dropped
      ** back to OPEN state.
      */
      assert( pPager->errCode!=SQLITE_OK );
      assert( sqlite3PcacheRefCount(pPager->pPCache)>0 );
      break;
  }

  return 1;
}

/*
** Return a pointer to a human readable string in a static buffer
** containing the state of the Pager object passed as an argument. This
** is intended to be used within debuggers. For example, as an alternative
** to "print *pPager" in gdb:
**
** (gdb) printf "%s", print_pager_state(pPager)
*/
static char *print_pager_state(Pager *p){
  static char zRet[1024];

  sqlite3_snprintf(1024, zRet,
      "Filename:      %s\n"
      "State:         %s errCode=%d\n"
      "Lock:          %s\n"
      "Locking mode:  locking_mode=%s\n"
      "Journal mode:  journal_mode=%s\n"
      "Backing store: tempFile=%d memDb=%d useJournal=%d\n"
      "Journal:       journalOff=%lld journalHdr=%lld\n"
      , p->zFilename
      , p->eState==PAGER_OPEN            ? "OPEN" :
        p->eState==PAGER_READER          ? "READER" :
        p->eState==PAGER_WRITER_LOCKED   ? "WRITER_LOCKED" :
        p->eState==PAGER_WRITER_CACHEMOD ? "WRITER_CACHEMOD" :
        p->eState==PAGER_WRITER_DBMOD    ? "WRITER_DBMOD" :
        p->eState==PAGER_WRITER_FINISHED ? "WRITER_FINISHED" :
        p->eState==PAGER_ERROR           ? "ERROR" : "?error?"
      , (int)p->errCode
      , p->eLock==NO_LOCK         ? "OPEN" :
        p->eLock==RESERVED_LOCK   ? "RESERVED" :
        p->eLock==EXCLUSIVE_LOCK  ? "EXCLUSIVE" :
        p->eLock==SHARED_LOCK     ? "SHARED" :
        p->eLock==UNKNOWN_LOCK    ? "UNKNOWN" : "?error?"
      , p->exclusiveMode ? "exclusive" : "normal"
      , p->journalMode==PAGER_JOURNALMODE_MEMORY   ? "memory" :
        p->journalMode==PAGER_JOURNALMODE_OFF      ? "off" :
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  sqlite3BitvecDestroy(pPager->pInJournal);
  pPager->pInJournal = 0;
  releaseAllSavepoints(pPager);

  if( pagerUseWal(pPager) ){
    assert( !isOpen(pPager->jfd) );
    sqlite3WalEndReadTransaction(pPager->pWal);
    pPager->eState = PAGER_NONE;
  }else if( !pPager->exclusiveMode ){
    int rc;                       /* Error code returned by pagerUnlockDb() */
    int iDc = isOpen(pPager->fd)?sqlite3OsDeviceCharacteristics(pPager->fd):0;

    /* If the operating system support deletion of open files, then
    ** close the journal file when dropping the database lock.  Otherwise
    ** another connection with journal_mode=delete might delete the file







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  sqlite3BitvecDestroy(pPager->pInJournal);
  pPager->pInJournal = 0;
  releaseAllSavepoints(pPager);

  if( pagerUseWal(pPager) ){
    assert( !isOpen(pPager->jfd) );
    sqlite3WalEndReadTransaction(pPager->pWal);
    pPager->eState = PAGER_OPEN;
  }else if( !pPager->exclusiveMode ){
    int rc;                       /* Error code returned by pagerUnlockDb() */
    int iDc = isOpen(pPager->fd)?sqlite3OsDeviceCharacteristics(pPager->fd):0;

    /* If the operating system support deletion of open files, then
    ** close the journal file when dropping the database lock.  Otherwise
    ** another connection with journal_mode=delete might delete the file
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    ** is necessary.
    */
    rc = pagerUnlockDb(pPager, NO_LOCK);
    if( rc!=SQLITE_OK && pPager->eState==PAGER_ERROR ){
      pPager->eLock = UNKNOWN_LOCK;
    }

    /* The pager state may be changed from PAGER_ERROR to PAGER_NONE here
    ** without clearing the error code. This is intentional - the error
    ** code is cleared and the cache reset in the block below.
    */
    assert( pPager->errCode || pPager->eState!=PAGER_ERROR );
    pPager->changeCountDone = 0;
    pPager->eState = PAGER_NONE;
  }

  /* If Pager.errCode is set, the contents of the pager cache cannot be
  ** trusted. Now that there are no outstanding references to the pager,
  ** it can safely move back to PAGER_NONE state. This happens in both
  ** normal and exclusive-locking mode.
  */
  if( pPager->errCode && !MEMDB ){
    pager_reset(pPager);
    pPager->changeCountDone = pPager->tempFile;
    pPager->eState = PAGER_NONE;
    pPager->errCode = SQLITE_OK;
  }

  pPager->journalOff = 0;
  pPager->journalHdr = 0;
  pPager->setMaster = 0;
}







|





|




|





|







1679
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1681
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1684
1685
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1687
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1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
    ** is necessary.
    */
    rc = pagerUnlockDb(pPager, NO_LOCK);
    if( rc!=SQLITE_OK && pPager->eState==PAGER_ERROR ){
      pPager->eLock = UNKNOWN_LOCK;
    }

    /* The pager state may be changed from PAGER_ERROR to PAGER_OPEN here
    ** without clearing the error code. This is intentional - the error
    ** code is cleared and the cache reset in the block below.
    */
    assert( pPager->errCode || pPager->eState!=PAGER_ERROR );
    pPager->changeCountDone = 0;
    pPager->eState = PAGER_OPEN;
  }

  /* If Pager.errCode is set, the contents of the pager cache cannot be
  ** trusted. Now that there are no outstanding references to the pager,
  ** it can safely move back to PAGER_OPEN state. This happens in both
  ** normal and exclusive-locking mode.
  */
  if( pPager->errCode && !MEMDB ){
    pager_reset(pPager);
    pPager->changeCountDone = pPager->tempFile;
    pPager->eState = PAGER_OPEN;
    pPager->errCode = SQLITE_OK;
  }

  pPager->journalOff = 0;
  pPager->journalHdr = 0;
  pPager->setMaster = 0;
}
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
static int pager_end_transaction(Pager *pPager, int hasMaster){
  int rc = SQLITE_OK;      /* Error code from journal finalization operation */
  int rc2 = SQLITE_OK;     /* Error code from db file unlock operation */

  /* Do nothing if the pager does not have an open write transaction. */
  assert( assert_pager_state(pPager) );
  assert( pPager->eState!=PAGER_ERROR );
  if( pPager->eState<PAGER_WRITER_INITIAL && pPager->eLock<RESERVED_LOCK ){
    return SQLITE_OK;
  }

  releaseAllSavepoints(pPager);
  assert( isOpen(pPager->jfd) || pPager->pInJournal==0 );
  if( isOpen(pPager->jfd) ){
    assert( !pagerUseWal(pPager) );







|







1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
static int pager_end_transaction(Pager *pPager, int hasMaster){
  int rc = SQLITE_OK;      /* Error code from journal finalization operation */
  int rc2 = SQLITE_OK;     /* Error code from db file unlock operation */

  /* Do nothing if the pager does not have an open write transaction. */
  assert( assert_pager_state(pPager) );
  assert( pPager->eState!=PAGER_ERROR );
  if( pPager->eState<PAGER_WRITER_LOCKED && pPager->eLock<RESERVED_LOCK ){
    return SQLITE_OK;
  }

  releaseAllSavepoints(pPager);
  assert( isOpen(pPager->jfd) || pPager->pInJournal==0 );
  if( isOpen(pPager->jfd) ){
    assert( !pagerUseWal(pPager) );
1830
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1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
**
** If the pager has not already entered the error state, but an IO or
** malloc error occurs during a rollback, then this will itself cause 
** the pager to enter the error state. Which will be cleared by the
** call to pager_unlock(), as described above.
*/
static void pagerUnlockAndRollback(Pager *pPager){
  if( pPager->eState!=PAGER_ERROR && pPager->eState!=PAGER_NONE ){
    assert( assert_pager_state(pPager) );
    if( pPager->eState>=PAGER_WRITER_INITIAL ){
      sqlite3BeginBenignMalloc();
      sqlite3PagerRollback(pPager);
      sqlite3EndBenignMalloc();
    }else if( pPager->eLock>=RESERVED_LOCK && !pPager->exclusiveMode ){
      assert( pPager->eState==PAGER_READER );
      pager_end_transaction(pPager, 0);
    }







|

|







1891
1892
1893
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1895
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1900
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**
** If the pager has not already entered the error state, but an IO or
** malloc error occurs during a rollback, then this will itself cause 
** the pager to enter the error state. Which will be cleared by the
** call to pager_unlock(), as described above.
*/
static void pagerUnlockAndRollback(Pager *pPager){
  if( pPager->eState!=PAGER_ERROR && pPager->eState!=PAGER_OPEN ){
    assert( assert_pager_state(pPager) );
    if( pPager->eState>=PAGER_WRITER_LOCKED ){
      sqlite3BeginBenignMalloc();
      sqlite3PagerRollback(pPager);
      sqlite3EndBenignMalloc();
    }else if( pPager->eLock>=RESERVED_LOCK && !pPager->exclusiveMode ){
      assert( pPager->eState==PAGER_READER );
      pager_end_transaction(pPager, 0);
    }
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  /* If this page has already been played by before during the current
  ** rollback, then don't bother to play it back again.
  */
  if( pDone && (rc = sqlite3BitvecSet(pDone, pgno))!=SQLITE_OK ){
    return rc;
  }
  assert( pPager->eState>=PAGER_WRITER_CACHEMOD 
       || (pPager->eState==PAGER_NONE && isMainJrnl)
  );

  /* When playing back page 1, restore the nReserve setting
  */
  if( pgno==1 && pPager->nReserve!=((u8*)aData)[20] ){
    pPager->nReserve = ((u8*)aData)[20];
    pagerReportSize(pPager);







|







2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
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2060
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2062
  /* If this page has already been played by before during the current
  ** rollback, then don't bother to play it back again.
  */
  if( pDone && (rc = sqlite3BitvecSet(pDone, pgno))!=SQLITE_OK ){
    return rc;
  }
  assert( pPager->eState>=PAGER_WRITER_CACHEMOD 
       || (pPager->eState==PAGER_OPEN && isMainJrnl)
  );

  /* When playing back page 1, restore the nReserve setting
  */
  if( pgno==1 && pPager->nReserve!=((u8*)aData)[20] ){
    pPager->nReserve = ((u8*)aData)[20];
    pagerReportSize(pPager);
2044
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2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
           (isMainJrnl?"main-journal":"sub-journal")
  ));
  if( isMainJrnl ){
    isSynced = pPager->noSync || (*pOffset <= pPager->journalHdr);
  }else{
    isSynced = (pPg==0 || 0==(pPg->flags & PGHDR_NEED_SYNC));
  }
  if( (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_NONE)
   && isOpen(pPager->fd)
   && isSynced
  ){
    i64 ofst = (pgno-1)*(i64)pPager->pageSize;
    testcase( !isSavepnt && pPg!=0 && (pPg->flags&PGHDR_NEED_SYNC)!=0 );
    assert( !pagerUseWal(pPager) );
    rc = sqlite3OsWrite(pPager->fd, (u8*)aData, pPager->pageSize, ofst);







|







2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
           (isMainJrnl?"main-journal":"sub-journal")
  ));
  if( isMainJrnl ){
    isSynced = pPager->noSync || (*pOffset <= pPager->journalHdr);
  }else{
    isSynced = (pPg==0 || 0==(pPg->flags & PGHDR_NEED_SYNC));
  }
  if( (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
   && isOpen(pPager->fd)
   && isSynced
  ){
    i64 ofst = (pgno-1)*(i64)pPager->pageSize;
    testcase( !isSavepnt && pPg!=0 && (pPg->flags&PGHDR_NEED_SYNC)!=0 );
    assert( !pagerUseWal(pPager) );
    rc = sqlite3OsWrite(pPager->fd, (u8*)aData, pPager->pageSize, ofst);
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
*/
static int pager_truncate(Pager *pPager, Pgno nPage){
  int rc = SQLITE_OK;
  assert( pPager->eState!=PAGER_ERROR );
  assert( pPager->eState!=PAGER_READER );
  
  if( isOpen(pPager->fd) 
   && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_NONE) 
  ){
    i64 currentSize, newSize;
    /* TODO: Is it safe to use Pager.dbFileSize here? */
    rc = sqlite3OsFileSize(pPager->fd, &currentSize);
    newSize = pPager->pageSize*(i64)nPage;
    if( rc==SQLITE_OK && currentSize!=newSize ){
      if( currentSize>newSize ){







|







2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
*/
static int pager_truncate(Pager *pPager, Pgno nPage){
  int rc = SQLITE_OK;
  assert( pPager->eState!=PAGER_ERROR );
  assert( pPager->eState!=PAGER_READER );
  
  if( isOpen(pPager->fd) 
   && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN) 
  ){
    i64 currentSize, newSize;
    /* TODO: Is it safe to use Pager.dbFileSize here? */
    rc = sqlite3OsFileSize(pPager->fd, &currentSize);
    newSize = pPager->pageSize*(i64)nPage;
    if( rc==SQLITE_OK && currentSize!=newSize ){
      if( currentSize>newSize ){
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
** other writers or checkpointers.
*/
static int pagerBeginReadTransaction(Pager *pPager){
  int rc;                         /* Return code */
  int changed = 0;                /* True if cache must be reset */

  assert( pagerUseWal(pPager) );
  assert( pPager->eState==PAGER_NONE || pPager->eState==PAGER_READER );

  /* sqlite3WalEndReadTransaction() was not called for the previous
  ** transaction in locking_mode=EXCLUSIVE.  So call it now.  If we
  ** are in locking_mode=NORMAL and EndRead() was previously called,
  ** the duplicate call is harmless.
  */
  sqlite3WalEndReadTransaction(pPager->pWal);







|







2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
** other writers or checkpointers.
*/
static int pagerBeginReadTransaction(Pager *pPager){
  int rc;                         /* Return code */
  int changed = 0;                /* True if cache must be reset */

  assert( pagerUseWal(pPager) );
  assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );

  /* sqlite3WalEndReadTransaction() was not called for the previous
  ** transaction in locking_mode=EXCLUSIVE.  So call it now.  If we
  ** are in locking_mode=NORMAL and EndRead() was previously called,
  ** the duplicate call is harmless.
  */
  sqlite3WalEndReadTransaction(pPager->pWal);
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819

/*
** TODO: Description here.
*/
static int pagerPagecount(Pager *pPager, Pgno *pnPage){
  Pgno nPage;                     /* Value to return via *pnPage */

  assert( pPager->eState==PAGER_NONE );
  nPage = sqlite3WalDbsize(pPager->pWal);
  if( nPage==0 ){
    i64 n = 0;                    /* Size of db file in bytes */
    assert( isOpen(pPager->fd) || pPager->tempFile );
    if( isOpen(pPager->fd) ){
      int rc = sqlite3OsFileSize(pPager->fd, &n);
      if( rc!=SQLITE_OK ){







|







2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880

/*
** TODO: Description here.
*/
static int pagerPagecount(Pager *pPager, Pgno *pnPage){
  Pgno nPage;                     /* Value to return via *pnPage */

  assert( pPager->eState==PAGER_OPEN );
  nPage = sqlite3WalDbsize(pPager->pWal);
  if( nPage==0 ){
    i64 n = 0;                    /* Size of db file in bytes */
    assert( isOpen(pPager->fd) || pPager->tempFile );
    if( isOpen(pPager->fd) ){
      int rc = sqlite3OsFileSize(pPager->fd, &n);
      if( rc!=SQLITE_OK ){
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
*/
static int pagerOpenWalIfPresent(Pager *pPager){
  int rc = SQLITE_OK;
  if( !pPager->tempFile ){
    int isWal;                    /* True if WAL file exists */
    Pgno nPage;                   /* Size of the database file */

    assert( pPager->eState==PAGER_NONE );
    assert( pPager->eLock>=SHARED_LOCK || pPager->noReadlock );
    rc = pagerPagecount(pPager, &nPage);
    if( rc ) return rc;
    if( nPage==0 ){
      rc = sqlite3OsDelete(pPager->pVfs, pPager->zWal, 0);
      isWal = 0;
    }else{







|







2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
*/
static int pagerOpenWalIfPresent(Pager *pPager){
  int rc = SQLITE_OK;
  if( !pPager->tempFile ){
    int isWal;                    /* True if WAL file exists */
    Pgno nPage;                   /* Size of the database file */

    assert( pPager->eState==PAGER_OPEN );
    assert( pPager->eLock>=SHARED_LOCK || pPager->noReadlock );
    rc = pagerPagecount(pPager, &nPage);
    if( rc ) return rc;
    if( nPage==0 ){
      rc = sqlite3OsDelete(pPager->pVfs, pPager->zWal, 0);
      isWal = 0;
    }else{
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){
  i64 szJ;                 /* Effective size of the main journal */
  i64 iHdrOff;             /* End of first segment of main-journal records */
  int rc = SQLITE_OK;      /* Return code */
  Bitvec *pDone = 0;       /* Bitvec to ensure pages played back only once */

  assert( pPager->eState!=PAGER_ERROR );
  assert( pPager->eState>=PAGER_WRITER_INITIAL );

  /* Allocate a bitvec to use to store the set of pages rolled back */
  if( pSavepoint ){
    pDone = sqlite3BitvecCreate(pSavepoint->nOrig);
    if( !pDone ){
      return SQLITE_NOMEM;
    }







|







2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){
  i64 szJ;                 /* Effective size of the main journal */
  i64 iHdrOff;             /* End of first segment of main-journal records */
  int rc = SQLITE_OK;      /* Return code */
  Bitvec *pDone = 0;       /* Bitvec to ensure pages played back only once */

  assert( pPager->eState!=PAGER_ERROR );
  assert( pPager->eState>=PAGER_WRITER_LOCKED );

  /* Allocate a bitvec to use to store the set of pages rolled back */
  if( pSavepoint ){
    pDone = sqlite3BitvecCreate(pSavepoint->nOrig);
    if( !pDone ){
      return SQLITE_NOMEM;
    }
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
    assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) );
    if( (pPager->memDb==0 || pPager->dbSize==0)
     && sqlite3PcacheRefCount(pPager->pPCache)==0 
     && pageSize && pageSize!=pPager->pageSize 
    ){
      char *pNew;                 /* New temp space */
      i64 nByte = 0;
      if( pPager->eState>PAGER_NONE && isOpen(pPager->fd) ){
        rc = sqlite3OsFileSize(pPager->fd, &nByte);
        if( rc!=SQLITE_OK ) return rc;
      }
      pNew = (char *)sqlite3PageMalloc(pageSize);
      if( !pNew ){
        rc = SQLITE_NOMEM;
      }else{







|







3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
    assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) );
    if( (pPager->memDb==0 || pPager->dbSize==0)
     && sqlite3PcacheRefCount(pPager->pPCache)==0 
     && pageSize && pageSize!=pPager->pageSize 
    ){
      char *pNew;                 /* New temp space */
      i64 nByte = 0;
      if( pPager->eState>PAGER_OPEN && isOpen(pPager->fd) ){
        rc = sqlite3OsFileSize(pPager->fd, &nByte);
        if( rc!=SQLITE_OK ) return rc;
      }
      pNew = (char *)sqlite3PageMalloc(pageSize);
      if( !pNew ){
        rc = SQLITE_NOMEM;
      }else{
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
**
** Regardless of mxPage, return the current maximum page count.
*/
int sqlite3PagerMaxPageCount(Pager *pPager, int mxPage){
  if( mxPage>0 ){
    pPager->mxPgno = mxPage;
  }
  if( pPager->eState!=PAGER_NONE && pPager->mxPgno<pPager->dbSize ){
    pPager->mxPgno = pPager->dbSize;
  }
  return pPager->mxPgno;
}

/*
** The following set of routines are used to disable the simulated







|







3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
**
** Regardless of mxPage, return the current maximum page count.
*/
int sqlite3PagerMaxPageCount(Pager *pPager, int mxPage){
  if( mxPage>0 ){
    pPager->mxPgno = mxPage;
  }
  if( pPager->eState!=PAGER_OPEN && pPager->mxPgno<pPager->dbSize ){
    pPager->mxPgno = pPager->dbSize;
  }
  return pPager->mxPgno;
}

/*
** The following set of routines are used to disable the simulated
3692
3693
3694
3695
3696
3697
3698
















3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
**
** If everything is successful, SQLITE_OK is returned. If an IO error 
** occurs, an IO error code is returned. Or, if the EXCLUSIVE lock cannot
** be obtained, SQLITE_BUSY is returned.
*/
static int pager_write_pagelist(Pager *pPager, PgHdr *pList){
  int rc;                              /* Return code */

















  /* At this point there may be either a RESERVED or EXCLUSIVE lock on the
  ** database file. If there is already an EXCLUSIVE lock, the following
  ** call is a no-op.
  **
  ** Moving the lock from RESERVED to EXCLUSIVE actually involves going
  ** through an intermediate state PENDING.   A PENDING lock prevents new
  ** readers from attaching to the database but is unsufficient for us to
  ** write.  The idea of a PENDING lock is to prevent new readers from
  ** coming in while we wait for existing readers to clear.
  **
  ** While the pager is in the RESERVED state, the original database file
  ** is unchanged and we can rollback without having to playback the
  ** journal into the original database file.  Once we transition to
  ** EXCLUSIVE, it means the database file has been changed and any rollback
  ** will require a journal playback.
  */

  /* Normally, this function is called in WRITER_DBMOD state.
  **
  ** However it may be called in WRITER_CACHEMOD state if the page being
  ** written (and all other pages that reside on the same disk sector) was
  ** a free-list leaf page at the start of the transaction. In that case
  ** the database file is not really being modified, so it is Ok to write
  ** to it in CACHEMOD state.
  */
  assert( !pagerUseWal(pPager) );
  assert( pPager->eState==PAGER_WRITER_DBMOD
       || pPager->eState==PAGER_WRITER_CACHEMOD 
  );
  assert( pPager->eState==PAGER_WRITER_DBMOD 
       || (pList->pDirty==0 && pList->pgno<=pPager->dbFileSize)
  );

  rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);

  /* If the file is a temp-file has not yet been opened, open it now. It
  ** is not possible for rc to be other than SQLITE_OK if this branch
  ** is taken, as pager_wait_on_lock() is a no-op for temp-files.
  */
  if( !isOpen(pPager->fd) ){







>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>

















<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<







3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792

















3793
3794
3795
3796
3797
3798
3799
**
** If everything is successful, SQLITE_OK is returned. If an IO error 
** occurs, an IO error code is returned. Or, if the EXCLUSIVE lock cannot
** be obtained, SQLITE_BUSY is returned.
*/
static int pager_write_pagelist(Pager *pPager, PgHdr *pList){
  int rc;                              /* Return code */

  /* Normally, this function is called in WRITER_DBMOD state.
  **
  ** However it may be called in WRITER_CACHEMOD state if the page being
  ** written (and all other pages that reside on the same disk sector) was
  ** a free-list leaf page at the start of the transaction. In that case
  ** the database file is not really being modified, so it is Ok to write
  ** to it in CACHEMOD state.
  */
  assert( !pagerUseWal(pPager) );
  assert( pPager->eState==PAGER_WRITER_DBMOD
       || pPager->eState==PAGER_WRITER_CACHEMOD 
  );
  assert( pPager->eState==PAGER_WRITER_DBMOD 
       || (pList->pDirty==0 && pList->pgno<=pPager->dbFileSize)
  );

  /* At this point there may be either a RESERVED or EXCLUSIVE lock on the
  ** database file. If there is already an EXCLUSIVE lock, the following
  ** call is a no-op.
  **
  ** Moving the lock from RESERVED to EXCLUSIVE actually involves going
  ** through an intermediate state PENDING.   A PENDING lock prevents new
  ** readers from attaching to the database but is unsufficient for us to
  ** write.  The idea of a PENDING lock is to prevent new readers from
  ** coming in while we wait for existing readers to clear.
  **
  ** While the pager is in the RESERVED state, the original database file
  ** is unchanged and we can rollback without having to playback the
  ** journal into the original database file.  Once we transition to
  ** EXCLUSIVE, it means the database file has been changed and any rollback
  ** will require a journal playback.
  */

















  rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);

  /* If the file is a temp-file has not yet been opened, open it now. It
  ** is not possible for rc to be other than SQLITE_OK if this branch
  ** is taken, as pager_wait_on_lock() is a no-op for temp-files.
  */
  if( !isOpen(pPager->fd) ){
4314
4315
4316
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
  sqlite3_vfs * const pVfs = pPager->pVfs;
  int rc = SQLITE_OK;           /* Return code */
  int exists = 1;               /* True if a journal file is present */
  int jrnlOpen = !!isOpen(pPager->jfd);

  assert( pPager->useJournal );
  assert( isOpen(pPager->fd) );
  assert( pPager->eState==PAGER_NONE );

  assert( jrnlOpen==0 || ( sqlite3OsDeviceCharacteristics(pPager->jfd) &
    SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN
  ));

  *pExists = 0;
  if( !jrnlOpen ){







|







4374
4375
4376
4377
4378
4379
4380
4381
4382
4383
4384
4385
4386
4387
4388
  sqlite3_vfs * const pVfs = pPager->pVfs;
  int rc = SQLITE_OK;           /* Return code */
  int exists = 1;               /* True if a journal file is present */
  int jrnlOpen = !!isOpen(pPager->jfd);

  assert( pPager->useJournal );
  assert( isOpen(pPager->fd) );
  assert( pPager->eState==PAGER_OPEN );

  assert( jrnlOpen==0 || ( sqlite3OsDeviceCharacteristics(pPager->jfd) &
    SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN
  ));

  *pExists = 0;
  if( !jrnlOpen ){
4433
4434
4435
4436
4437
4438
4439
4440
4441
4442
4443
4444
4445
4446
4447
4448
4449
4450
4451
4452
4453
4454
4455
** file or rolling back a journal file, the IO error code is returned.
*/
int sqlite3PagerSharedLock(Pager *pPager){
  int rc = SQLITE_OK;                /* Return code */

  /* This routine is only called from b-tree and only when there are no
  ** outstanding pages. This implies that the pager state should either
  ** be NONE or READER. READER is only possible if the pager is or was in 
  ** exclusive access mode.
  */
  assert( sqlite3PcacheRefCount(pPager->pPCache)==0 );
  assert( assert_pager_state(pPager) );
  assert( pPager->eState==PAGER_NONE || pPager->eState==PAGER_READER );
  if( NEVER(MEMDB && pPager->errCode) ){ return pPager->errCode; }

  if( !pagerUseWal(pPager) && pPager->eState==PAGER_NONE ){
    int bHotJournal = 1;          /* True if there exists a hot journal-file */

    assert( !MEMDB );
    assert( pPager->noReadlock==0 || pPager->readOnly );

    if( pPager->noReadlock==0 ){
      rc = pager_wait_on_lock(pPager, SHARED_LOCK);







|




|


|







4493
4494
4495
4496
4497
4498
4499
4500
4501
4502
4503
4504
4505
4506
4507
4508
4509
4510
4511
4512
4513
4514
4515
** file or rolling back a journal file, the IO error code is returned.
*/
int sqlite3PagerSharedLock(Pager *pPager){
  int rc = SQLITE_OK;                /* Return code */

  /* This routine is only called from b-tree and only when there are no
  ** outstanding pages. This implies that the pager state should either
  ** be OPEN or READER. READER is only possible if the pager is or was in 
  ** exclusive access mode.
  */
  assert( sqlite3PcacheRefCount(pPager->pPCache)==0 );
  assert( assert_pager_state(pPager) );
  assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );
  if( NEVER(MEMDB && pPager->errCode) ){ return pPager->errCode; }

  if( !pagerUseWal(pPager) && pPager->eState==PAGER_OPEN ){
    int bHotJournal = 1;          /* True if there exists a hot journal-file */

    assert( !MEMDB );
    assert( pPager->noReadlock==0 || pPager->readOnly );

    if( pPager->noReadlock==0 ){
      rc = pager_wait_on_lock(pPager, SHARED_LOCK);
4529
4530
4531
4532
4533
4534
4535
4536
4537
4538
4539
4540
4541
4542
















4543
4544
4545
4546
4547
4548
4549
4550
4551
4552
4553
4554
      ** the journal before playing it back.
      */
      if( isOpen(pPager->jfd) ){
        assert( rc==SQLITE_OK );
        rc = pagerSyncHotJournal(pPager);
        if( rc==SQLITE_OK ){
          rc = pager_playback(pPager, 1);
          pPager->eState = PAGER_NONE;
        }
      }else if( !pPager->exclusiveMode ){
        pagerUnlockDb(pPager, SHARED_LOCK);
      }

      if( rc!=SQLITE_OK ){
















        pager_error(pPager, rc);
        goto failed;
      }

      assert( pPager->eState==PAGER_NONE );
      assert( (pPager->eLock==SHARED_LOCK)
           || (pPager->exclusiveMode && pPager->eLock>SHARED_LOCK)
      );
    }

    if( !pPager->tempFile 
     && (pPager->pBackup || sqlite3PcachePagecount(pPager->pPCache)>0) 







|






>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>




|







4589
4590
4591
4592
4593
4594
4595
4596
4597
4598
4599
4600
4601
4602
4603
4604
4605
4606
4607
4608
4609
4610
4611
4612
4613
4614
4615
4616
4617
4618
4619
4620
4621
4622
4623
4624
4625
4626
4627
4628
4629
4630
      ** the journal before playing it back.
      */
      if( isOpen(pPager->jfd) ){
        assert( rc==SQLITE_OK );
        rc = pagerSyncHotJournal(pPager);
        if( rc==SQLITE_OK ){
          rc = pager_playback(pPager, 1);
          pPager->eState = PAGER_OPEN;
        }
      }else if( !pPager->exclusiveMode ){
        pagerUnlockDb(pPager, SHARED_LOCK);
      }

      if( rc!=SQLITE_OK ){
        /* This branch is taken if an error occurs while trying to open
        ** or roll back a hot-journal while holding an EXCLUSIVE lock. The
        ** pager_unlock() routine will be called before returning to unlock
        ** the file. If the unlock attempt fails, then Pager.eLock must be
        ** set to UNKNOWN_LOCK (see the comment above the #define for 
        ** UNKNOWN_LOCK above for an explanation). 
        **
        ** In order to get pager_unlock() to do this, set Pager.eState to
        ** PAGER_ERROR now. This is not actually counted as a transition
        ** to ERROR state in the state diagram at the top of this file,
        ** since we know that the same call to pager_unlock() will very
        ** shortly transition the pager object to the OPEN state. Calling
        ** assert_pager_state() would fail now, as it should not be possible
        ** to be in ERROR state when there are zero outstanding page 
        ** references.
        */
        pager_error(pPager, rc);
        goto failed;
      }

      assert( pPager->eState==PAGER_OPEN );
      assert( (pPager->eLock==SHARED_LOCK)
           || (pPager->exclusiveMode && pPager->eLock>SHARED_LOCK)
      );
    }

    if( !pPager->tempFile 
     && (pPager->pBackup || sqlite3PcachePagecount(pPager->pPCache)>0) 
4596
4597
4598
4599
4600
4601
4602
4603
4604
4605
4606
4607
4608
4609
4610
4611
4612
4613
4614
4615
4616
4617
    rc = pagerOpenWalIfPresent(pPager);
  }

  if( pagerUseWal(pPager) && rc==SQLITE_OK ){
    rc = pagerBeginReadTransaction(pPager);
  }

  if( pPager->eState==PAGER_NONE && rc==SQLITE_OK ){
    rc = pagerPagecount(pPager, &pPager->dbSize);
  }

 failed:
  if( rc!=SQLITE_OK ){
    pager_unlock(pPager);
    assert( pPager->eState==PAGER_NONE );
  }else{
    pPager->eState = PAGER_READER;
  }
  return rc;
}

/*







|






|







4672
4673
4674
4675
4676
4677
4678
4679
4680
4681
4682
4683
4684
4685
4686
4687
4688
4689
4690
4691
4692
4693
    rc = pagerOpenWalIfPresent(pPager);
  }

  if( pagerUseWal(pPager) && rc==SQLITE_OK ){
    rc = pagerBeginReadTransaction(pPager);
  }

  if( pPager->eState==PAGER_OPEN && rc==SQLITE_OK ){
    rc = pagerPagecount(pPager, &pPager->dbSize);
  }

 failed:
  if( rc!=SQLITE_OK ){
    pager_unlock(pPager);
    assert( pPager->eState==PAGER_OPEN );
  }else{
    pPager->eState = PAGER_READER;
  }
  return rc;
}

/*
4843
4844
4845
4846
4847
4848
4849
4850
4851
4852
4853
4854
4855
4856
4857
** SQLITE_NOMEM if the attempt to allocate Pager.pInJournal fails, or 
** an IO error code if opening or writing the journal file fails.
*/
static int pager_open_journal(Pager *pPager){
  int rc = SQLITE_OK;                        /* Return code */
  sqlite3_vfs * const pVfs = pPager->pVfs;   /* Local cache of vfs pointer */

  assert( pPager->eState==PAGER_WRITER_INITIAL );
  assert( assert_pager_state(pPager) );
  assert( pPager->pInJournal==0 );
  
  /* If already in the error state, this function is a no-op.  But on
  ** the other hand, this routine is never called if we are already in
  ** an error state. */
  if( NEVER(pPager->errCode) ) return pPager->errCode;







|







4919
4920
4921
4922
4923
4924
4925
4926
4927
4928
4929
4930
4931
4932
4933
** SQLITE_NOMEM if the attempt to allocate Pager.pInJournal fails, or 
** an IO error code if opening or writing the journal file fails.
*/
static int pager_open_journal(Pager *pPager){
  int rc = SQLITE_OK;                        /* Return code */
  sqlite3_vfs * const pVfs = pPager->pVfs;   /* Local cache of vfs pointer */

  assert( pPager->eState==PAGER_WRITER_LOCKED );
  assert( assert_pager_state(pPager) );
  assert( pPager->pInJournal==0 );
  
  /* If already in the error state, this function is a no-op.  But on
  ** the other hand, this routine is never called if we are already in
  ** an error state. */
  if( NEVER(pPager->errCode) ) return pPager->errCode;
4898
4899
4900
4901
4902
4903
4904
4905
4906
4907
4908
4909
4910
4911
4912
    }
  }

  if( rc!=SQLITE_OK ){
    sqlite3BitvecDestroy(pPager->pInJournal);
    pPager->pInJournal = 0;
  }else{
    assert( pPager->eState==PAGER_WRITER_INITIAL );
    pPager->eState = PAGER_WRITER_CACHEMOD;
  }

  return rc;
}

/*







|







4974
4975
4976
4977
4978
4979
4980
4981
4982
4983
4984
4985
4986
4987
4988
    }
  }

  if( rc!=SQLITE_OK ){
    sqlite3BitvecDestroy(pPager->pInJournal);
    pPager->pInJournal = 0;
  }else{
    assert( pPager->eState==PAGER_WRITER_LOCKED );
    pPager->eState = PAGER_WRITER_CACHEMOD;
  }

  return rc;
}

/*
4970
4971
4972
4973
4974
4975
4976
4977
4978
4979
4980
4981
4982
4983
4984
4985
4986
4987
4988
4989
4990
4991
4992
4993
4994
4995
4996
4997
4998
4999
5000
5001
5002
5003
5004
5005
5006
      if( rc==SQLITE_OK && exFlag ){
        rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
      }
    }


    if( rc==SQLITE_OK ){
      /* Change to WRITER_INITIAL state.
      **
      ** WAL mode sets Pager.eState to PAGER_WRITER_INITIAL or CACHEMOD
      ** when it has an open transaction, but never to DBMOD or FINISHED.
      ** This is because in those states the code to roll back savepoint 
      ** transactions may copy data from the sub-journal into the database 
      ** file as well as into the page cache. Which would be incorrect in 
      ** WAL mode.
      */
      pPager->eState = PAGER_WRITER_INITIAL;
      pPager->dbFileSize = pPager->dbOrigSize = pPager->dbSize;
      pPager->journalOff = 0;
    }else{
      /* Ignore any IO error that occurs within pager_end_transaction(). The
      ** purpose of this call is to reset the internal state of the pager
      ** sub-system. It doesn't matter if the journal-file is not properly
      ** finalized at this point (since it is not a valid journal file anyway).
      */
      pager_end_transaction(pPager, 0);
    }

    assert( rc==SQLITE_OK || pPager->eState==PAGER_READER );
    assert( rc!=SQLITE_OK || pPager->eState==PAGER_WRITER_INITIAL );
    assert( assert_pager_state(pPager) );
  }

  PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
  return rc;
}








|

|






|


<
<
<
<
<
<
<



|







5046
5047
5048
5049
5050
5051
5052
5053
5054
5055
5056
5057
5058
5059
5060
5061
5062
5063
5064







5065
5066
5067
5068
5069
5070
5071
5072
5073
5074
5075
      if( rc==SQLITE_OK && exFlag ){
        rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
      }
    }


    if( rc==SQLITE_OK ){
      /* Change to WRITER_LOCKED state.
      **
      ** WAL mode sets Pager.eState to PAGER_WRITER_LOCKED or CACHEMOD
      ** when it has an open transaction, but never to DBMOD or FINISHED.
      ** This is because in those states the code to roll back savepoint 
      ** transactions may copy data from the sub-journal into the database 
      ** file as well as into the page cache. Which would be incorrect in 
      ** WAL mode.
      */
      pPager->eState = PAGER_WRITER_LOCKED;
      pPager->dbFileSize = pPager->dbOrigSize = pPager->dbSize;
      pPager->journalOff = 0;







    }

    assert( rc==SQLITE_OK || pPager->eState==PAGER_READER );
    assert( rc!=SQLITE_OK || pPager->eState==PAGER_WRITER_LOCKED );
    assert( assert_pager_state(pPager) );
  }

  PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
  return rc;
}

5016
5017
5018
5019
5020
5021
5022
5023
5024
5025
5026
5027
5028
5029
5030
  Pager *pPager = pPg->pPager;
  int rc = SQLITE_OK;

  /* This routine is not called unless a write-transaction has already 
  ** been started. The journal file may or may not be open at this point.
  ** It is never called in the ERROR state.
  */
  assert( pPager->eState==PAGER_WRITER_INITIAL
       || pPager->eState==PAGER_WRITER_CACHEMOD
       || pPager->eState==PAGER_WRITER_DBMOD
  );
  assert( assert_pager_state(pPager) );

  /* If an error has been previously detected, report the same error
  ** again. This should not happen, but the check provides robustness. */







|







5085
5086
5087
5088
5089
5090
5091
5092
5093
5094
5095
5096
5097
5098
5099
  Pager *pPager = pPg->pPager;
  int rc = SQLITE_OK;

  /* This routine is not called unless a write-transaction has already 
  ** been started. The journal file may or may not be open at this point.
  ** It is never called in the ERROR state.
  */
  assert( pPager->eState==PAGER_WRITER_LOCKED
       || pPager->eState==PAGER_WRITER_CACHEMOD
       || pPager->eState==PAGER_WRITER_DBMOD
  );
  assert( assert_pager_state(pPager) );

  /* If an error has been previously detected, report the same error
  ** again. This should not happen, but the check provides robustness. */
5049
5050
5051
5052
5053
5054
5055
5056
5057
5058
5059
5060
5061
5062
5063
    ** written to the transaction journal or the checkpoint journal
    ** or both.
    **
    ** Higher level routines have already obtained the necessary locks
    ** to begin the write-transaction, but the rollback journal might not 
    ** yet be open. Open it now if this is the case.
    */
    if( pPager->eState==PAGER_WRITER_INITIAL ){
      rc = pager_open_journal(pPager);
      if( rc!=SQLITE_OK ) return rc;
    }
    assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
    assert( assert_pager_state(pPager) );
  
    /* The transaction journal now exists and we have a RESERVED or an







|







5118
5119
5120
5121
5122
5123
5124
5125
5126
5127
5128
5129
5130
5131
5132
    ** written to the transaction journal or the checkpoint journal
    ** or both.
    **
    ** Higher level routines have already obtained the necessary locks
    ** to begin the write-transaction, but the rollback journal might not 
    ** yet be open. Open it now if this is the case.
    */
    if( pPager->eState==PAGER_WRITER_LOCKED ){
      rc = pager_open_journal(pPager);
      if( rc!=SQLITE_OK ) return rc;
    }
    assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
    assert( assert_pager_state(pPager) );
  
    /* The transaction journal now exists and we have a RESERVED or an
5166
5167
5168
5169
5170
5171
5172
5173
5174
5175
5176
5177
5178
5179
5180
int sqlite3PagerWrite(DbPage *pDbPage){
  int rc = SQLITE_OK;

  PgHdr *pPg = pDbPage;
  Pager *pPager = pPg->pPager;
  Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize);

  assert( pPager->eState>=PAGER_WRITER_INITIAL );
  assert( pPager->eState!=PAGER_ERROR );
  assert( assert_pager_state(pPager) );

  if( nPagePerSector>1 ){
    Pgno nPageCount;          /* Total number of pages in database file */
    Pgno pg1;                 /* First page of the sector pPg is located on. */
    int nPage = 0;            /* Number of pages starting at pg1 to journal */







|







5235
5236
5237
5238
5239
5240
5241
5242
5243
5244
5245
5246
5247
5248
5249
int sqlite3PagerWrite(DbPage *pDbPage){
  int rc = SQLITE_OK;

  PgHdr *pPg = pDbPage;
  Pager *pPager = pPg->pPager;
  Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize);

  assert( pPager->eState>=PAGER_WRITER_LOCKED );
  assert( pPager->eState!=PAGER_ERROR );
  assert( assert_pager_state(pPager) );

  if( nPagePerSector>1 ){
    Pgno nPageCount;          /* Total number of pages in database file */
    Pgno pg1;                 /* First page of the sector pPg is located on. */
    int nPage = 0;            /* Number of pages starting at pg1 to journal */
5415
5416
5417
5418
5419
5420
5421
5422
5423
5424
5425
5426
5427
5428
5429
** Otherwise, either SQLITE_BUSY or an SQLITE_IOERR_XXX error code is 
** returned.
*/
int sqlite3PagerExclusiveLock(Pager *pPager){
  int rc = SQLITE_OK;
  assert( pPager->eState==PAGER_WRITER_CACHEMOD 
       || pPager->eState==PAGER_WRITER_DBMOD 
       || pPager->eState==PAGER_WRITER_INITIAL 
  );
  assert( assert_pager_state(pPager) );
  if( 0==pagerUseWal(pPager) ){
    rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
  }
  return rc;
}







|







5484
5485
5486
5487
5488
5489
5490
5491
5492
5493
5494
5495
5496
5497
5498
** Otherwise, either SQLITE_BUSY or an SQLITE_IOERR_XXX error code is 
** returned.
*/
int sqlite3PagerExclusiveLock(Pager *pPager){
  int rc = SQLITE_OK;
  assert( pPager->eState==PAGER_WRITER_CACHEMOD 
       || pPager->eState==PAGER_WRITER_DBMOD 
       || pPager->eState==PAGER_WRITER_LOCKED 
  );
  assert( assert_pager_state(pPager) );
  if( 0==pagerUseWal(pPager) ){
    rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
  }
  return rc;
}
5457
5458
5459
5460
5461
5462
5463
5464
5465
5466

5467
5468
5469
5470
5471
5472
5473
int sqlite3PagerCommitPhaseOne(
  Pager *pPager,                  /* Pager object */
  const char *zMaster,            /* If not NULL, the master journal name */
  int noSync                      /* True to omit the xSync on the db file */
){
  int rc = SQLITE_OK;             /* Return code */

  assert( pPager->eState==PAGER_WRITER_INITIAL
       || pPager->eState==PAGER_WRITER_CACHEMOD
       || pPager->eState==PAGER_WRITER_DBMOD

  );
  assert( assert_pager_state(pPager) );

  /* If a prior error occurred, report that error again. */
  if( pPager->errCode ) return pPager->errCode;

  PAGERTRACE(("DATABASE SYNC: File=%s zMaster=%s nSize=%d\n", 







|


>







5526
5527
5528
5529
5530
5531
5532
5533
5534
5535
5536
5537
5538
5539
5540
5541
5542
5543
int sqlite3PagerCommitPhaseOne(
  Pager *pPager,                  /* Pager object */
  const char *zMaster,            /* If not NULL, the master journal name */
  int noSync                      /* True to omit the xSync on the db file */
){
  int rc = SQLITE_OK;             /* Return code */

  assert( pPager->eState==PAGER_WRITER_LOCKED
       || pPager->eState==PAGER_WRITER_CACHEMOD
       || pPager->eState==PAGER_WRITER_DBMOD
       || pPager->eState==PAGER_WRITER_ERROR
  );
  assert( assert_pager_state(pPager) );

  /* If a prior error occurred, report that error again. */
  if( pPager->errCode ) return pPager->errCode;

  PAGERTRACE(("DATABASE SYNC: File=%s zMaster=%s nSize=%d\n", 
5654
5655
5656
5657
5658
5659
5660
5661
5662
5663
5664
5665
5666
5667
5668
5669
5670
5671
5672
5673
5674
5675
5676
5677
5678
5679
5680
5681
5682
5683
5684
5685
  int rc = SQLITE_OK;                  /* Return code */

  /* This routine should not be called if a prior error has occurred.
  ** But if (due to a coding error elsewhere in the system) it does get
  ** called, just return the same error code without doing anything. */
  if( NEVER(pPager->errCode) ) return pPager->errCode;

  assert( pPager->eState==PAGER_WRITER_INITIAL
       || pPager->eState==PAGER_WRITER_FINISHED
       || (pagerUseWal(pPager) && pPager->eState==PAGER_WRITER_CACHEMOD)
  );
  assert( assert_pager_state(pPager) );

  /* An optimization. If the database was not actually modified during
  ** this transaction, the pager is running in exclusive-mode and is
  ** using persistent journals, then this function is a no-op.
  **
  ** The start of the journal file currently contains a single journal 
  ** header with the nRec field set to 0. If such a journal is used as
  ** a hot-journal during hot-journal rollback, 0 changes will be made
  ** to the database file. So there is no need to zero the journal 
  ** header. Since the pager is in exclusive mode, there is no need
  ** to drop any locks either.
  */
  if( pPager->eState==PAGER_WRITER_INITIAL 
   && pPager->exclusiveMode 
   && pPager->journalMode==PAGER_JOURNALMODE_PERSIST
  ){
    assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) || !pPager->journalOff );
    pPager->eState = PAGER_READER;
    return SQLITE_OK;
  }







|
















|







5724
5725
5726
5727
5728
5729
5730
5731
5732
5733
5734
5735
5736
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5742
5743
5744
5745
5746
5747
5748
5749
5750
5751
5752
5753
5754
5755
  int rc = SQLITE_OK;                  /* Return code */

  /* This routine should not be called if a prior error has occurred.
  ** But if (due to a coding error elsewhere in the system) it does get
  ** called, just return the same error code without doing anything. */
  if( NEVER(pPager->errCode) ) return pPager->errCode;

  assert( pPager->eState==PAGER_WRITER_LOCKED
       || pPager->eState==PAGER_WRITER_FINISHED
       || (pagerUseWal(pPager) && pPager->eState==PAGER_WRITER_CACHEMOD)
  );
  assert( assert_pager_state(pPager) );

  /* An optimization. If the database was not actually modified during
  ** this transaction, the pager is running in exclusive-mode and is
  ** using persistent journals, then this function is a no-op.
  **
  ** The start of the journal file currently contains a single journal 
  ** header with the nRec field set to 0. If such a journal is used as
  ** a hot-journal during hot-journal rollback, 0 changes will be made
  ** to the database file. So there is no need to zero the journal 
  ** header. Since the pager is in exclusive mode, there is no need
  ** to drop any locks either.
  */
  if( pPager->eState==PAGER_WRITER_LOCKED 
   && pPager->exclusiveMode 
   && pPager->journalMode==PAGER_JOURNALMODE_PERSIST
  ){
    assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) || !pPager->journalOff );
    pPager->eState = PAGER_READER;
    return SQLITE_OK;
  }
5732
5733
5734
5735
5736
5737
5738
5739
5740
5741
5742
5743
5744
5745
5746
**   some other process can use it to restore the database state (by
**   hot-journal rollback).
*/
int sqlite3PagerRollback(Pager *pPager){
  int rc = SQLITE_OK;                  /* Return code */
  PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager)));

  /* PagerRollback() is a no-op if called in READER or NONE state. If
  ** the pager is already in the ERROR state, the rollback is not 
  ** attempted here. Instead, the error code is returned to the caller.
  */
  assert( assert_pager_state(pPager) );
  if( pPager->eState==PAGER_ERROR ) return pPager->errCode;
  if( pPager->eState<=PAGER_READER ) return SQLITE_OK;








|







5802
5803
5804
5805
5806
5807
5808
5809
5810
5811
5812
5813
5814
5815
5816
**   some other process can use it to restore the database state (by
**   hot-journal rollback).
*/
int sqlite3PagerRollback(Pager *pPager){
  int rc = SQLITE_OK;                  /* Return code */
  PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager)));

  /* PagerRollback() is a no-op if called in READER or OPEN state. If
  ** the pager is already in the ERROR state, the rollback is not 
  ** attempted here. Instead, the error code is returned to the caller.
  */
  assert( assert_pager_state(pPager) );
  if( pPager->eState==PAGER_ERROR ) return pPager->errCode;
  if( pPager->eState<=PAGER_READER ) return SQLITE_OK;

5802
5803
5804
5805
5806
5807
5808
5809
5810
5811
5812
5813
5814
5815
5816
** This routine is used for testing and analysis only.
*/
int *sqlite3PagerStats(Pager *pPager){
  static int a[11];
  a[0] = sqlite3PcacheRefCount(pPager->pPCache);
  a[1] = sqlite3PcachePagecount(pPager->pPCache);
  a[2] = sqlite3PcacheGetCachesize(pPager->pPCache);
  a[3] = pPager->eState==PAGER_NONE ? -1 : (int) pPager->dbSize;
  a[4] = pPager->eState;
  a[5] = pPager->errCode;
  a[6] = pPager->nHit;
  a[7] = pPager->nMiss;
  a[8] = 0;  /* Used to be pPager->nOvfl */
  a[9] = pPager->nRead;
  a[10] = pPager->nWrite;







|







5872
5873
5874
5875
5876
5877
5878
5879
5880
5881
5882
5883
5884
5885
5886
** This routine is used for testing and analysis only.
*/
int *sqlite3PagerStats(Pager *pPager){
  static int a[11];
  a[0] = sqlite3PcacheRefCount(pPager->pPCache);
  a[1] = sqlite3PcachePagecount(pPager->pPCache);
  a[2] = sqlite3PcacheGetCachesize(pPager->pPCache);
  a[3] = pPager->eState==PAGER_OPEN ? -1 : (int) pPager->dbSize;
  a[4] = pPager->eState;
  a[5] = pPager->errCode;
  a[6] = pPager->nHit;
  a[7] = pPager->nMiss;
  a[8] = 0;  /* Used to be pPager->nOvfl */
  a[9] = pPager->nRead;
  a[10] = pPager->nWrite;
5835
5836
5837
5838
5839
5840
5841
5842
5843
5844
5845
5846
5847
5848
5849
** occurs while opening the sub-journal file, then an IO error code is
** returned. Otherwise, SQLITE_OK.
*/
int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
  int rc = SQLITE_OK;                       /* Return code */
  int nCurrent = pPager->nSavepoint;        /* Current number of savepoints */

  assert( pPager->eState>=PAGER_WRITER_INITIAL );
  assert( assert_pager_state(pPager) );

  if( nSavepoint>nCurrent && pPager->useJournal ){
    int ii;                                 /* Iterator variable */
    PagerSavepoint *aNew;                   /* New Pager.aSavepoint array */

    /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM







|







5905
5906
5907
5908
5909
5910
5911
5912
5913
5914
5915
5916
5917
5918
5919
** occurs while opening the sub-journal file, then an IO error code is
** returned. Otherwise, SQLITE_OK.
*/
int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
  int rc = SQLITE_OK;                       /* Return code */
  int nCurrent = pPager->nSavepoint;        /* Current number of savepoints */

  assert( pPager->eState>=PAGER_WRITER_LOCKED );
  assert( assert_pager_state(pPager) );

  if( nSavepoint>nCurrent && pPager->useJournal ){
    int ii;                                 /* Iterator variable */
    PagerSavepoint *aNew;                   /* New Pager.aSavepoint array */

    /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
6288
6289
6290
6291
6292
6293
6294
6295
6296
6297
6298
6299
6300
6301
6302
6303
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6305
6306
6307
6308
6309
6310
6311
6312
6313
6314
      **
      ** Before deleting the journal file, obtain a RESERVED lock on the
      ** database file. This ensures that the journal file is not deleted
      ** while it is in use by some other client.
      */
      int rc = SQLITE_OK;
      int state = pPager->eState;
      if( state==PAGER_NONE ){
        rc = sqlite3PagerSharedLock(pPager);
      }
      if( pPager->eState==PAGER_READER ){
        assert( rc==SQLITE_OK );
        rc = pagerLockDb(pPager, RESERVED_LOCK);
      }
      if( rc==SQLITE_OK ){
        sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
      }
      if( rc==SQLITE_OK && state==PAGER_READER ){
        pagerUnlockDb(pPager, SHARED_LOCK);
      }else if( state==PAGER_NONE ){
        pager_unlock(pPager);
      }
      assert( state==pPager->eState );
    }
  }

  /* Return the new journal mode */







|











|







6358
6359
6360
6361
6362
6363
6364
6365
6366
6367
6368
6369
6370
6371
6372
6373
6374
6375
6376
6377
6378
6379
6380
6381
6382
6383
6384
      **
      ** Before deleting the journal file, obtain a RESERVED lock on the
      ** database file. This ensures that the journal file is not deleted
      ** while it is in use by some other client.
      */
      int rc = SQLITE_OK;
      int state = pPager->eState;
      if( state==PAGER_OPEN ){
        rc = sqlite3PagerSharedLock(pPager);
      }
      if( pPager->eState==PAGER_READER ){
        assert( rc==SQLITE_OK );
        rc = pagerLockDb(pPager, RESERVED_LOCK);
      }
      if( rc==SQLITE_OK ){
        sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
      }
      if( rc==SQLITE_OK && state==PAGER_READER ){
        pagerUnlockDb(pPager, SHARED_LOCK);
      }else if( state==PAGER_OPEN ){
        pager_unlock(pPager);
      }
      assert( state==pPager->eState );
    }
  }

  /* Return the new journal mode */
6404
6405
6406
6407
6408
6409
6410
6411
6412
6413
6414
6415
6416
6417
6418
6419
6420
6421
6422
6423
6424
6425
6426
6427
6428
6429
6430
6431
6432
6433
6434
6435
6436
6437
int sqlite3PagerOpenWal(
  Pager *pPager,                  /* Pager object */
  int *pbOpen                     /* OUT: Set to true if call is a no-op */
){
  int rc = SQLITE_OK;             /* Return code */

  assert( assert_pager_state(pPager) );
  assert( pPager->eState==PAGER_NONE   || pbOpen );
  assert( pPager->eState==PAGER_READER || !pbOpen );
  assert( pbOpen==0 || *pbOpen==0 );
  assert( pbOpen!=0 || (!pPager->tempFile && !pPager->pWal) );

  if( !pPager->tempFile && !pPager->pWal ){
    if( !sqlite3PagerWalSupported(pPager) ) return SQLITE_CANTOPEN;

    if( isOpen(pPager->jfd) ){
      sqlite3OsClose(pPager->jfd);
    }

    /* Open the connection to the log file. If this operation fails, 
    ** (e.g. due to malloc() failure), unlock the database file and 
    ** return an error code.
    */
    rc = sqlite3WalOpen(pPager->pVfs, pPager->fd, pPager->zWal, &pPager->pWal);
    if( rc==SQLITE_OK ){
      pPager->journalMode = PAGER_JOURNALMODE_WAL;
      pPager->eState = PAGER_NONE;
    }
  }else{
    *pbOpen = 1;
  }

  return rc;
}







|


















|







6474
6475
6476
6477
6478
6479
6480
6481
6482
6483
6484
6485
6486
6487
6488
6489
6490
6491
6492
6493
6494
6495
6496
6497
6498
6499
6500
6501
6502
6503
6504
6505
6506
6507
int sqlite3PagerOpenWal(
  Pager *pPager,                  /* Pager object */
  int *pbOpen                     /* OUT: Set to true if call is a no-op */
){
  int rc = SQLITE_OK;             /* Return code */

  assert( assert_pager_state(pPager) );
  assert( pPager->eState==PAGER_OPEN   || pbOpen );
  assert( pPager->eState==PAGER_READER || !pbOpen );
  assert( pbOpen==0 || *pbOpen==0 );
  assert( pbOpen!=0 || (!pPager->tempFile && !pPager->pWal) );

  if( !pPager->tempFile && !pPager->pWal ){
    if( !sqlite3PagerWalSupported(pPager) ) return SQLITE_CANTOPEN;

    if( isOpen(pPager->jfd) ){
      sqlite3OsClose(pPager->jfd);
    }

    /* Open the connection to the log file. If this operation fails, 
    ** (e.g. due to malloc() failure), unlock the database file and 
    ** return an error code.
    */
    rc = sqlite3WalOpen(pPager->pVfs, pPager->fd, pPager->zWal, &pPager->pWal);
    if( rc==SQLITE_OK ){
      pPager->journalMode = PAGER_JOURNALMODE_WAL;
      pPager->eState = PAGER_OPEN;
    }
  }else{
    *pbOpen = 1;
  }

  return rc;
}