SQLite

/*
** 2004 April 6
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.161 2004/06/07 16:27:46 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.

** is currently pointing to.
*/
int sqlite3BtreeFlags(BtCursor *pCur){
  MemPage *pPage = pCur->pPage;
  return pPage ? pPage->aData[pPage->hdrOffset] : 0;
}







/*
** Print a disassembly of the given page on standard output.  This routine
** is used for debugging and testing only.
*/
#ifdef SQLITE_TEST
int sqlite3BtreePageDump(Btree *pBt, int pgno, int recursive){
  int rc;

** sqlite3OsLock().
*/
#define NO_LOCK         0
#define SHARED_LOCK     1
#define RESERVED_LOCK   2
#define PENDING_LOCK    3
#define EXCLUSIVE_LOCK  4

/*
** Windows file locking notes:
**
** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because
** those functions are not available.  So we use only LockFile() and
** UnlockFile().
**
** LockFile() prevents not just writing but also reading by other processes.
** (This is a design error on the part of Windows, but there is nothing
** we can do about that.)  So the region used for locking is at the
** end of the file where it is unlikely to ever interfere with an
** actual read attempt.
**
** A SHARED_LOCK is obtained by locking a single randomly-chosen 
** byte out of a specific range of bytes. The lock byte is obtained at 
** random so two separate readers can probably access the file at the 
** same time, unless they are unlucky and choose the same lock byte.
** An EXCLUSIVE_LOCK is obtained by locking all bytes in the range.
** There can only be one writer.  A RESERVED_LOCK is obtained by locking
** a single byte of the file that is designated as the reserved lock byte.
** A PENDING_LOCK is obtained by locking a designated byte different from
** the RESERVED_LOCK byte.
**
** On WinNT/2K/XP systems, LockFileEx() and UnlockFileEx() are available,
** which means we can use reader/writer locks.  When reader/writer locks
** are used, the lock is placed on the same range of bytes that is used
** for probabilistic locking in Win95/98/ME.  Hence, the locking scheme
** will support two or more Win95 readers or two or more WinNT readers.
** But a single Win95 reader will lock out all WinNT readers and a single
** WinNT reader will lock out all other Win95 readers.
**
** The following #defines specify the range of bytes used for locking.
** SHARED_SIZE is the number of bytes available in the pool from which
** a random byte is selected for a shared lock.  The pool of bytes for
** shared locks begins at SHARED_FIRST. 
**
** These #defines are available in os.h so that Unix can use the same
** byte ranges for locking.  This leaves open the possiblity of having
** clients on win95, winNT, and unix all talking to the same shared file
** and all locking correctly.
**
** Locking in windows is manditory.  For this reason, we cannot store
** actual data in the bytes used for locking.  The pager never allocates
** the pages involved in locking therefore.
*/
#define SHARED_SIZE       10238
#define SHARED_FIRST      (0x3fffffff - (SHARED_SIZE - 1))
#define RESERVED_BYTE     (SHARED_FIRST - 1)
#define PENDING_BYTE      (RESERVED_BYTE - 1)


int sqlite3OsDelete(const char*);
int sqlite3OsFileExists(const char*);
int sqliteOsFileRename(const char*, const char*);
int sqlite3OsOpenReadWrite(const char*, OsFile*, int*);
int sqlite3OsOpenExclusive(const char*, OsFile*, int);
int sqlite3OsOpenReadOnly(const char*, OsFile*);

*/


/*
** Macros for performance tracing.  Normally turned off.  Only works
** on i486 hardware.
*/
int sqlite3_os_trace = 0;
#if 1
static int last_page = 0;
__inline__ unsigned long long int hwtime(void){
  unsigned long long int x;
  __asm__("rdtsc\n\t"
          "mov %%edx, %%ecx\n\t"
          :"=A" (x));
  return x;
}
static unsigned long long int g_start;
static unsigned int elapse;
#define TIMER_START       g_start=hwtime()
#define TIMER_END         elapse=hwtime()-g_start
#define SEEK(X)           last_page=(X)
#define TRACE1(X)         if( sqlite3_os_trace ) sqlite3DebugPrintf(X)
#define TRACE2(X,Y)       if( sqlite3_os_trace ) sqlite3DebugPrintf(X,Y)
#define TRACE3(X,Y,Z)     if( sqlite3_os_trace ) sqlite3DebugPrintf(X,Y,Z)
#define TRACE4(X,Y,Z,A)   if( sqlite3_os_trace ) sqlite3DebugPrintf(X,Y,Z,A)
#define TRACE5(X,Y,Z,A,B) if( sqlite3_os_trace ) sqlite3DebugPrintf(X,Y,Z,A,B)
#else
#define TIMER_START
#define TIMER_END
#define SEEK(X)
#define TRACE1(X)
#define TRACE2(X,Y)
#define TRACE3(X,Y,Z)

**
** A single inode can have multiple file descriptors, so each OsFile
** structure contains a pointer to an instance of this object and this
** object keeps a count of the number of OsFiles pointing to it.
*/
struct lockInfo {
  struct lockKey key;  /* The lookup key */
  int cnt;             /* Number of SHARED locks held */
  int locktype;        /* One of SHARED_LOCK, RESERVED_LOCK etc. */
  int nRef;            /* Number of pointers to this structure */
};

/*
** An instance of the following structure serves as the key used
** to locate a particular openCnt structure given its inode.  This

  *pSize = buf.st_size;
  return SQLITE_OK;
}

/*
** This routine checks if there is a RESERVED lock held on the specified
** file by this or any other process. If such a lock is held, return
** non-zero.  If the file is unlocked or holds only SHARED locks, then
** return zero.
*/
int sqlite3OsCheckWriteLock(OsFile *id){
  int r = 0;

  sqlite3OsEnterMutex(); /* Needed because id->pLock is shared across threads */

  /* Check if a thread in this process holds such a lock */
  if( id->pLock->locktype>SHARED_LOCK ){
    r = 1;
  }

  /* Otherwise see if some other process holds it.

  */
  if( !r ){
    struct flock lock;
    lock.l_whence = SEEK_SET;
    lock.l_start = RESERVED_BYTE;
    lock.l_len = 1;
    lock.l_type = F_WRLCK;
    fcntl(id->fd, F_GETLK, &lock);
    if( lock.l_type!=F_UNLCK ){
      r = 1;
    }
  }
  
  sqlite3OsLeaveMutex();
  TRACE3("TEST WR-LOCK %d %d\n", id->fd, r);

  return r;
}

/*
** Lock the file with the lock specified by parameter locktype - one
** of the following:
**
**     (1) SHARED_LOCK
**     (2) RESERVED_LOCK
**     (3) PENDING_LOCK
**     (4) EXCLUSIVE_LOCK
**
** Locks are are hierarchical.  Getting a lock N implies getting all locks
** N-1, N-2, N-3, ....  So, for example, getting a PENDING lock
** implies a SHARED and a RESERVED lock.  This routine adds locks one
** at a time until the desired lock is acheived.  A locking failure might
** occur at any point.  When a failure occurs intermediate locks are
** retained.  For example, if a SHARED lock is held and this routine
** is called with EXCLUSIVE, it might obtain a RESERVED and PENDING lock
** but fail to get the EXCLUSIVE lock.  In that case, the file would be
** left in the PENDING lock state - it does not revert to SHARED.
**
** This routine will only increase a lock.  The sqlite3OsUnlock() routine
** erases all locks at once and returns us immediately to locking level 0.
** It is not possible to lower the locking level one step at a time.  You
** must go straight to locking level 0.
*/
int sqlite3OsLock(OsFile *id, int locktype){
  int rc = SQLITE_OK;
  struct lockInfo *pLock = id->pLock;
  struct flock lock;
  int s;


  TRACE5("LOCK %d %d was %d(%d)\n",



          id->fd, locktype, id->locktype, pLock->locktype);

  /* If there is already a lock of this type or more restrictive on the
  ** OsFile, do nothing. Don't use the end_lock: exit path, as
  ** sqlite3OsEnterMutex() hasn't been called yet.
  */
  if( id->locktype>=locktype ){
    return SQLITE_OK;
  }

  /* Make sure locking is sequential.  In other words, make sure we have
  ** SHARED before trying for RESERVED, and that we have RESERVED before
  ** trying for PENDING, and that we have PENDING before trying for
  ** EXCLUSIVE.
  */
  while( locktype>id->locktype+1 ){
    rc = sqlite3OsLock(id, id->locktype+1);
    if( rc!=SQLITE_OK ){
      return rc;
    }
  }
  assert( locktype==id->locktype+1 );

  sqlite3OsEnterMutex();  /* Needed because pLock is shared across threads */

  /* If some thread using this PID has a lock via a different OsFile*
  ** handle that precludes the requested lock, return BUSY.
  */
  if( (id->locktype!=pLock->locktype && 
          (pLock->locktype>=PENDING_LOCK || locktype>SHARED_LOCK))
   || (locktype==EXCLUSIVE_LOCK && pLock->cnt>1)
  ){
    rc = SQLITE_BUSY;
    goto end_lock;
  }

  /* If a SHARED lock is requested, and some thread using this PID already
  ** has a SHARED or RESERVED lock, then increment reference counts and

  /* If control gets to this point, then actually go ahead and make
  ** operating system calls for the specified lock.
  */
  if( locktype==SHARED_LOCK ){
    assert( pLock->cnt==0 );
    assert( pLock->locktype==0 );
  
    /* Temporarily grab a PENDING lock.  This prevents new SHARED locks from
    ** being formed if a PENDING lock is already held.
    */
    lock.l_type = F_RDLCK;
    lock.l_start = PENDING_BYTE;
    s = fcntl(id->fd, F_SETLK, &lock);
    if( s ){
      rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
      goto end_lock;
    }

    /* Now get the read-lock */
    lock.l_start = SHARED_FIRST;
    lock.l_len = SHARED_SIZE;
    s = fcntl(id->fd, F_SETLK, &lock);

    /* Drop the temporary PENDING lock */
    lock.l_start = PENDING_BYTE;
    lock.l_len = 1L;
    lock.l_type = F_UNLCK;
    fcntl(id->fd, F_SETLK, &lock);
    if( s ){
      rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
    }else{
      id->locktype = SHARED_LOCK;
      id->pOpen->nLock++;
      pLock->cnt = 1;
    }
  }else{
    /* The request was for a RESERVED, PENDING or EXCLUSIVE lock.  It is
    ** assumed that there is a SHARED or greater lock on the file
    ** already.
    */
    assert( 0!=id->locktype );
    lock.l_type = F_WRLCK;
    switch( locktype ){
      case RESERVED_LOCK:
        lock.l_start = RESERVED_BYTE;
        break;
      case PENDING_LOCK:
        lock.l_start = PENDING_BYTE;
        break;
      case EXCLUSIVE_LOCK:
        lock.l_start = SHARED_FIRST;
        lock.l_len = SHARED_SIZE;
        break;
      default:
        assert(0);
    }
    s = fcntl(id->fd, F_SETLK, &lock);
    if( s ){
      rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
    }
  }
  
  if( rc==SQLITE_OK ){
    id->locktype = locktype;
    pLock->locktype = locktype;

  }

end_lock:
  sqlite3OsLeaveMutex();
  TRACE4("LOCK %d %d %s\n", id->fd, locktype, rc==SQLITE_OK ? "ok" : "failed");
  return rc;
}

/*
** Unlock the given file descriptor.  If the file descriptor was
** not previously locked, then this routine is a no-op.  If this
** library was compiled with large file support (LFS) but LFS is not

  DWORD upperBits, lowerBits;
  SimulateIOError(SQLITE_IOERR);
  lowerBits = GetFileSize(id->h, &upperBits);
  *pSize = (((off_t)upperBits)<<32) + lowerBits;
  return SQLITE_OK;
}










































/*
** Return true (non-zero) if we are running under WinNT, Win2K or WinXP.
** Return false (zero) for Win95, Win98, or WinME.
**
** Here is an interesting observation:  Win95, Win98, and WinME lack
** the LockFileEx() API.  But we can still statically link against that
** API as long as we don't call it win running Win95/98/ME.  A call to

** file by this or any other process. If such a lock is held, return
** non-zero, otherwise zero.
*/
int sqlite3OsCheckWriteLock(OsFile *id){
  int rc;
  if( id->locktype>=RESERVED_LOCK ){
    rc = 1;
    TRACE3("TEST WR-LOCK %d %d (local)\n", id->h, rc);
  }else{
    rc = LockFile(id->h, RESERVED_BYTE, 0, 1, 0);
    if( rc ){
      UnlockFile(id->h, RESERVED_BYTE, 0, 1, 0);
    }
    rc = !rc;
    TRACE3("TEST WR-LOCK %d %d (remote)\n", id->h, rc);
  }
  return rc;
}

/*
** Unlock the given file descriptor.  If the file descriptor was
** not previously locked, then this routine is a no-op.  If this
** library was compiled with large file support (LFS) but LFS is not
** available on the host, then an SQLITE_NOLFS is returned.

** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.113 2004/06/07 16:27:46 drh Exp $
*/
#include "os.h"         /* Must be first to enable large file support */
#include "sqliteInt.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

  if( pList==0 ) return SQLITE_OK;
  pPager = pList->pPager;

  /* 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
  ** calls to sqlite3OsLock() are no-ops.
  **
  ** The upgrade from a RESERVED to PENDING might return SQLITE_BUSY on
  ** windows because the windows locking mechanism acquires a transient
  ** PENDING lock during its attempts to get a SHARED lock.  So if another
  ** process were trying to get a SHARED lock at the same time this process
  ** is upgrading from RESERVED to PENDING, the two could collide.
  **
  ** The upgrade from PENDING to EXCLUSIVE can return SQLITE_BUSY if there

  ** are still active readers that were created before the PENDING lock
  ** was acquired.
  */







  do {
    rc = sqlite3OsLock(&pPager->fd, EXCLUSIVE_LOCK);
  }while( rc==SQLITE_BUSY && 
      pPager->pBusyHandler && 
      pPager->pBusyHandler->xFunc && 
      pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, "", busy++)
  );

*/
void sqlite3DebugPrintf(const char *zFormat, ...){
  va_list ap;
  char zBuf[500];
  va_start(ap, zFormat);
  base_vprintf(0, 0, zBuf, sizeof(zBuf), zFormat, ap);
  va_end(ap);
  fprintf(stdout,"%s", zBuf);
  fflush(stdout);
}
#endif

/*
** The following four routines implement the varargs versions of the
** sqlite3_exec() and sqlite3_get_table() interfaces.  See the sqlite.h
** header files for a more detailed description of how these interfaces

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the printf() interface to SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test1.c,v 1.70 2004/06/07 16:27:46 drh Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include "os.h"
#include <stdlib.h>
#include <string.h>

     { "sqlite3OsOpenReadWrite",test_sqlite3OsOpenReadWrite, 0 },
     { "sqlite3OsClose",        test_sqlite3OsClose, 0 },
     { "sqlite3OsLock",         test_sqlite3OsLock, 0 },
     { "sqlite3OsUnlock",       test_sqlite3OsUnlock, 0 },

  };
  int i;
  extern int sqlite3_os_trace;

  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
  }
  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
  }
  Tcl_LinkVar(interp, "sqlite_search_count", 
      (char*)&sqlite3_search_count, TCL_LINK_INT);
  Tcl_LinkVar(interp, "sqlite_interrupt_count", 
      (char*)&sqlite3_interrupt_count, TCL_LINK_INT);
  Tcl_LinkVar(interp, "sqlite_open_file_count", 
      (char*)&sqlite3_open_file_count, TCL_LINK_INT);
  Tcl_LinkVar(interp, "sqlite_current_time", 
      (char*)&sqlite3_current_time, TCL_LINK_INT);
  Tcl_LinkVar(interp, "sqlite_os_trace",
      (char*)&sqlite3_os_trace, TCL_LINK_INT);
  Tcl_LinkVar(interp, "sqlite_static_bind_value",
      (char*)&sqlite_static_bind_value, TCL_LINK_STRING);
  return TCL_OK;
}

  /* If there are any write-transactions at all, invoke the commit hook */
  if( needXcommit && db->xCommitCallback ){
    if( db->xCommitCallback(db->pCommitArg) ){
      return SQLITE_CONSTRAINT;
    }
  }

  /* The simple case - no more than one database file (not counting the TEMP
  ** database) has a transaction active.   There is no need for the
  ** master-journal.
  */
  if( nTrans<=1 ){
    for(i=0; rc==SQLITE_OK && i<db->nDb; i++){ 
      Btree *pBt = db->aDb[i].pBt;
      if( pBt ){
        rc = sqlite3BtreeSync(pBt, 0);
      }
    }

    /* Do the commit only if all databases successfully synced */
    if( rc==SQLITE_OK ){
      for(i=0; i<db->nDb; i++){
        Btree *pBt = db->aDb[i].pBt;
        if( pBt ){
          sqlite3BtreeCommit(pBt);
        }
      }
    }
  }

  /* The complex case - There is a multi-file write-transaction active.
  ** This requires a master journal file to ensure the transaction is
  ** committed atomicly.

    for(i=0; i<db->nDb; i++){ 
      Btree *pBt = db->aDb[i].pBt;
      if( pBt ){
        sqlite3BtreeCommit(pBt);
      }
    }
  }
  return rc;
}

/* 
** This routine checks that the sqlite3.activeVdbeCnt count variable
** matches the number of vdbe's in the list sqlite3.pVdbe that are
** currently active. An assertion fails if the two counts do not match.
**

#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is testing the ATTACH and DETACH commands
# and related functionality.
#
# $Id: attach2.test,v 1.12 2004/06/07 16:27:47 drh Exp $
#
set sqlite_os_trace 0

set testdir [file dirname $argv0]
source $testdir/tester.tcl


# Ticket #354
#
# Databases test.db and test2.db contain identical schemas.  Make
# sure we can attach test2.db from test.db.
#
do_test attach2-1.1 {
  db eval {
    CREATE TABLE t1(a,b);
    CREATE INDEX x1 ON t1(a);
  }
  file delete -force test2.db

  foreach {idx name file} [execsql {PRAGMA database_list} $db] {
    lappend list $idx $name
  }
  return $list
}
db eval {DETACH t2}
do_test attach2-2.1 {
  # lock test2.db then try to attach it.  This is no longer an error because
  # db2 just RESERVES the database.  It does not obtain a write-lock until
  # we COMMIT.
  db2 eval {BEGIN}
  db2 eval {UPDATE t1 SET a = 0 WHERE 0}
  catchsql {
    ATTACH 'test2.db' AS t2;
  }
} {0 {}}
do_test attach2-2.2 {
  # make sure test2.db did get attached.
  db_list db
} {0 main 1 temp 2 t2}


db2 eval {COMMIT}







do_test attach2-2.5 {
  # Make sure we can read test2.db from db
  catchsql {
    SELECT name FROM t2.sqlite_master;
  }
} {0 {t1 x1}}
do_test attach2-2.6 {
  # lock test2.db and try to read from it.  This should still work because
  # the lock is only a RESERVED lock which does not prevent reading.
  #
  db2 eval BEGIN
  db2 eval {UPDATE t1 SET a = 0 WHERE 0}
  catchsql {
    SELECT name FROM t2.sqlite_master;
  }
} {0 {t1 x1}}
do_test attach2-2.7 {
  # but we can still read from test1.db even though test2.db is locked.
  catchsql {
    SELECT name FROM main.sqlite_master;
  }
} {0 {t1 x1}}
do_test attach2-2.8 {

} {}
do_test attach2-2.12 {
  catchsql {
    COMMIT
  }
} {1 {cannot commit - no transaction is active}}

# Ticket #574:  Make sure it works using the non-callback API
#
do_test attach2-3.1 {
  db close
  set DB [sqlite db test.db]
  set rc [catch {sqlite3_prepare $DB "ATTACH 'test2.db' AS t2" -1 TAIL} VM]
  if {$rc} {lappend rc $VM}
  sqlite3_finalize $VM
  set rc
} {0}
do_test attach2-3.2 {
  set rc [catch {sqlite3_prepare $DB "DETACH t2" -1 TAIL} VM]
  if {$rc} {lappend rc $VM}
  sqlite3_finalize $VM
  set rc
} {0}

db close
for {set i 2} {$i<=15} {incr i} {
  catch {db$i close}
}
set sqlite_os_trace 0

# Tests attach2-4.* test that read-locks work correctly with attached
# databases.
do_test attach2-4.1 {
  sqlite db test.db
  sqlite db2 test.db
  execsql {ATTACH 'test2.db' as file2}
  execsql {ATTACH 'test2.db' as file2} db2
} {}

do_test attach2-4.2 {
  # Handle 'db' read-locks test.db
  execsql {BEGIN}
  execsql {SELECT * FROM t1}
} {}
do_test attach2-4.3 {
  # The read lock held by db does not prevent db2 from reading test.db
  execsql {SELECT * FROM t1} db2
} {}
do_test attach2-4.4 {
  # db is only holding a read lock on test.db, so we should not be able
  # to commit a write to test.db from db2
  set r [catch { 
    execsql {
      INSERT INTO t1 VALUES(1, 2)
    } db2 
  } msg]
  list $r $msg
} {1 {database is locked}}
do_test attach2-4.5 {
  # Handle 'db2' reserves file2.
  execsql {BEGIN} db2
  execsql {INSERT INTO file2.t1 VALUES(1, 2)} db2
} {}
do_test attach2-4.6.1 {
  # Reads are allowed against a reserved database.
  catchsql {
    SELECT * FROM file2.t1;
  }
} {0 {}}
do_test attach2-4.6.2 {
  # Writes against a reserved database are not allowed.
  catchsql {
    UPDATE file2.t1 SET a=0;
  }
} {1 {database is locked}}
do_test attach2-4.7 {
  # Ensure handle 'db' retains the lock on the main file after
  # failing to obtain a write-lock on file2.

  catchsql {
    INSERT INTO t1 VALUES(1, 2)
  } db2 


} {1 {database is locked}}
do_test attach2-4.8 {
  # Read lock the main file with db2. Now both db and db2 have a read lock
  # on the main file, db2 has a write-lock on file2.
  execsql {SELECT * FROM t1} db2
} {}
do_test attach2-4.9 {
  # Try to upgrade the handle 'db' lock.

  catchsql {
    INSERT INTO t1 VALUES(1, 2)
  }

  list $r $msg
} {1 {database is locked}}
do_test attach2-4.10 {
  # Release the locks held by handle 'db2'
  execsql {COMMIT} db2
} {}
do_test attach2-4.11 {

} {}

db close
db2 close
file delete -force test2.db

finish_test