SQLite

*/
int sqlite3OsSeek(OsFile *id, off_t offset){
  assert( id->isOpen );
  SEEK(offset/1024 + 1);
  lseek(id->h, offset, SEEK_SET);
  return SQLITE_OK;
}

/*
** The fsync() system call does not work as advertised on many
** unix systems.  The following procedure is an attempt to make
** it work better.
*/
static int full_fsync(int fd){
  int rc;
#ifdef F_FULLFSYNC
  rc = fcntl(fd, F_FULLFSYNC, 0);
  if( rc ) rc = fsync(fd);
#else
  rc = fsync(fd);
#endif
  return rc;
}

/*
** 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 sqlite3OsSync(OsFile *id){
  assert( id->isOpen );
  SimulateIOError(SQLITE_IOERR);
  TRACE2("SYNC    %-3d\n", id->h);
  if( full_fsync(id->h) ){
    return SQLITE_IOERR;
  }
  if( id->dirfd>=0 ){
    TRACE2("DIRSYNC %-3d\n", id->dirfd);
    full_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;
}

/*

}

/*
** Close a file.
*/
int sqlite3OsClose(OsFile *id){
  if( !id->isOpen ) return SQLITE_OK;
  id->zFilename = 0;
  sqlite3OsUnlock(id, NO_LOCK);
  if( id->dirfd>=0 ) close(id->dirfd);
  id->dirfd = -1;
  sqlite3OsEnterMutex();
  if( id->pOpen->nLock ){
    /* If there are outstanding locks, do not actually close the file just
    ** yet because that would clear those locks.  Instead, add the file

** PENDING_LOCK or EXCLUSIVE_LOCK.
*/
typedef struct OsFile OsFile;
struct OsFile {
  struct openCnt *pOpen;    /* Info about all open fd's on this inode */
  struct lockInfo *pLock;   /* Info about locks on this inode */
  int h;                    /* The file descriptor */
  const char *zFilename;    /* Name passed to open() */
  unsigned char locktype;   /* The type of lock held on this fd */
  unsigned char isOpen;     /* True if needs to be closed */
  int dirfd;                /* File descriptor for the directory */
};

/*
** Maximum number of characters in a temporary file name