SQLite

*/
int sqliteOsOpenReadWrite(
  const char *zFilename,
  OsFile *id,
  int *pReadonly
){
#if OS_UNIX
  id->dirfd = -1;
  id->fd = open(zFilename, O_RDWR|O_CREAT|O_LARGEFILE|O_BINARY, 0644);
  if( id->fd<0 ){
    id->fd = open(zFilename, O_RDONLY|O_LARGEFILE|O_BINARY);
    if( id->fd<0 ){
      return SQLITE_CANTOPEN; 
    }
    *pReadonly = 1;

** On failure, return SQLITE_CANTOPEN.
*/
int sqliteOsOpenExclusive(const char *zFilename, OsFile *id, int delFlag){
#if OS_UNIX
  if( access(zFilename, 0)==0 ){
    return SQLITE_CANTOPEN;
  }
  id->dirfd = -1;
  id->fd = open(zFilename,
                O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW|O_LARGEFILE|O_BINARY, 0600);
  if( id->fd<0 ){
    return SQLITE_CANTOPEN;
  }
  sqliteOsEnterMutex();
  id->pLock = findLockInfo(id->fd);

**
** On success, write the file handle into *id and return SQLITE_OK.
**
** On failure, return SQLITE_CANTOPEN.
*/
int sqliteOsOpenReadOnly(const char *zFilename, OsFile *id){
#if OS_UNIX
  id->dirfd = -1;
  id->fd = open(zFilename, O_RDONLY|O_LARGEFILE|O_BINARY);
  if( id->fd<0 ){
    return SQLITE_CANTOPEN;
  }
  sqliteOsEnterMutex();
  id->pLock = findLockInfo(id->fd);
  sqliteOsLeaveMutex();

  }
  id->locked = 0;
  id->delOnClose = 0;
  OpenCounter(+1);
  return SQLITE_OK;
#endif
}

/*
** Attempt to open a file descriptor for the directory that contains a
** file.  This file descriptor can be used to fsync() the directory
** in order to make sure the creation of a new file is actually written
** to disk.
**
** This routine is only meaningful for Unix.  It is a no-op under
** windows since windows does not support hard links.
**
** On success, a handle for a previously open file is at *id is
** updated with the new directory file descriptor and SQLITE_OK is
** returned.
**
** On failure, the function returns SQLITE_CANTOPEN and leaves
** *id unchanged.
*/
int sqliteOsOpenDirectory(
  const char *zDirname,
  OsFile *id
){
#if OS_UNIX
  if( id->fd<0 ){
    /* Do not open the directory if the corresponding file is not already
    ** open. */
    return SQLITE_CANTOPEN;
  }
  assert( id->dirfd<0 );
  id->dirfd = open(zDirname, O_RDONLY|O_BINARY, 0644);
  if( id->dirfd<0 ){
    return SQLITE_CANTOPEN; 
  }
  TRACE3("OPENDIR %-3d %s\n", id->dirfd, zDirname);
#endif
  return SQLITE_OK;
}

/*
** Create a temporary file name in zBuf.  zBuf must be big enough to
** hold at least SQLITE_TEMPNAME_SIZE characters.
*/
int sqliteOsTempFileName(char *zBuf){
#if OS_UNIX

/*
** Close a file
*/
int sqliteOsClose(OsFile *id){
#if OS_UNIX
  close(id->fd);
  if( id->dirfd>=0 ) close(id->dirfd);
  id->dirfd = -1;
  sqliteOsEnterMutex();
  releaseLockInfo(id->pLock);
  sqliteOsLeaveMutex();
  TRACE2("CLOSE   %-3d\n", id->fd);
  OpenCounter(-1);
  return SQLITE_OK;
#endif

    }
  }
#endif
}

/*
** Make sure all writes to a particular file are committed to disk.
**
** Under Unix, also make sure that the directory entry for the file
** has been created by fsync-ing the directory that contains the file.
** If we do not do this and we encounter a power failure, the directory
** entry for the journal might not exist after we reboot.  The next
** SQLite to access the file will not know that the journal exists (because
** the directory entry for the journal was never created) and the transaction
** will not roll back - possibly leading to database corruption.
*/
int sqliteOsSync(OsFile *id){
#if OS_UNIX
  SimulateIOError(SQLITE_IOERR);
  TRACE2("SYNC    %-3d\n", id->fd);
  if( fsync(id->fd) ){
    return SQLITE_IOERR;
  }else{
    if( id->dirfd>=0 ){
      TRACE2("DIRSYNC %-3d\n", id->dirfd);
      fsync(id->dirfd);
      close(id->dirfd);  /* Only need to sync once, so close the directory */
      id->dirfd = -1;    /* when we are done. */
    }
    return SQLITE_OK;
  }
#endif
#if OS_WIN
  if( FlushFileBuffers(id->h) ){
    return SQLITE_OK;
  }else{

# include <fcntl.h>
# include <unistd.h>
  typedef struct OsFile OsFile;
  struct OsFile {
    struct lockInfo *pLock;  /* Information about locks on this inode */
    int fd;                  /* The file descriptor */
    int locked;              /* True if this user holds the lock */
    int dirfd;               /* File descriptor for the directory */
  };
# define SQLITE_TEMPNAME_SIZE 200
# if defined(HAVE_USLEEP) && HAVE_USLEEP
#  define SQLITE_MIN_SLEEP_MS 1
# else
#  define SQLITE_MIN_SLEEP_MS 1000
# endif

int sqliteOsDelete(const char*);
int sqliteOsFileExists(const char*);
int sqliteOsFileRename(const char*, const char*);
int sqliteOsOpenReadWrite(const char*, OsFile*, int*);
int sqliteOsOpenExclusive(const char*, OsFile*, int);
int sqliteOsOpenReadOnly(const char*, OsFile*);
int sqliteOsOpenDirectory(const char*, OsFile*);
int sqliteOsTempFileName(char*);
int sqliteOsClose(OsFile*);
int sqliteOsRead(OsFile*, void*, int amt);
int sqliteOsWrite(OsFile*, const void*, int amt);
int sqliteOsSeek(OsFile*, off_t offset);
int sqliteOsSync(OsFile*);
int sqliteOsTruncate(OsFile*, off_t size);

** 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 1.87 2003/07/27 18:59:43 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>

/*
** A open page cache is an instance of the following structure.
*/
struct Pager {
  char *zFilename;            /* Name of the database file */
  char *zJournal;             /* Name of the journal file */
  char *zDirectory;           /* Directory hold database and journal files */
  OsFile fd, jfd;             /* File descriptors for database and journal */
  OsFile cpfd;                /* File descriptor for the checkpoint journal */
  int dbSize;                 /* Number of pages in the file */
  int origDbSize;             /* dbSize before the current change */
  int ckptSize;               /* Size of database (in pages) at ckpt_begin() */
  off_t ckptJSize;            /* Size of journal at ckpt_begin() */
  int nRec;                   /* Number of pages written to the journal */

  int nExtra,              /* Extra bytes append to each in-memory page */
  int useJournal           /* TRUE to use a rollback journal on this file */
){
  Pager *pPager;
  char *zFullPathname;
  int nameLen;
  OsFile fd;
  int rc, i;
  int tempFile;
  int readOnly = 0;
  char zTemp[SQLITE_TEMPNAME_SIZE];

  *ppPager = 0;
  if( sqlite_malloc_failed ){
    return SQLITE_NOMEM;

    return SQLITE_NOMEM;
  }
  if( rc!=SQLITE_OK ){
    sqliteFree(zFullPathname);
    return SQLITE_CANTOPEN;
  }
  nameLen = strlen(zFullPathname);
  pPager = sqliteMalloc( sizeof(*pPager) + nameLen*3 + 30 );
  if( pPager==0 ){
    sqliteOsClose(&fd);
    sqliteFree(zFullPathname);
    return SQLITE_NOMEM;
  }
  SET_PAGER(pPager);
  pPager->zFilename = (char*)&pPager[1];
  pPager->zDirectory = &pPager->zFilename[nameLen+1];
  pPager->zJournal = &pPager->zDirectory[nameLen+1];
  strcpy(pPager->zFilename, zFullPathname);
  strcpy(pPager->zDirectory, zFullPathname);
  for(i=nameLen; i>0 && pPager->zDirectory[i-1]!='/'; i--){}
  if( i>0 ) pPager->zDirectory[i-1] = 0;
  strcpy(pPager->zJournal, zFullPathname);
  sqliteFree(zFullPathname);
  strcpy(&pPager->zJournal[nameLen], "-journal");
  pPager->fd = fd;
  pPager->journalOpen = 0;
  pPager->useJournal = useJournal;
  pPager->ckptOpen = 0;

  /* Temp files are automatically deleted by the OS
  ** if( pPager->tempFile ){
  **   sqliteOsDelete(pPager->zFilename);
  ** }
  */
  CLR_PAGER(pPager);
  if( pPager->zFilename!=(char*)&pPager[1] ){
    assert( 0 );  /* Cannot happen */
    sqliteFree(pPager->zFilename);
    sqliteFree(pPager->zJournal);
    sqliteFree(pPager->zDirectory);
  }
  sqliteFree(pPager);
  return SQLITE_OK;
}

/*
** Return the page number for the given page data.

  if( rc!=SQLITE_OK ){
    sqliteFree(pPager->aInJournal);
    pPager->aInJournal = 0;
    sqliteOsReadLock(&pPager->fd);
    pPager->state = SQLITE_READLOCK;
    return SQLITE_CANTOPEN;
  }
  sqliteOsOpenDirectory(pPager->zDirectory, &pPager->jfd);
  pPager->journalOpen = 1;
  pPager->journalStarted = 0;
  pPager->needSync = 0;
  pPager->alwaysRollback = 0;
  pPager->nRec = 0;
  if( pPager->errMask!=0 ){
    rc = pager_errcode(pPager);