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Overview
Comment:Remove unnecessary code to round the size of a memory mapping to 4KB from os_unix.c. Rename SQLITE_IOERR_MREMAP to SQLITE_IOERR_MMAP. Fix other small issues in os_unix.c.
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SHA1: dce35c01a5fe66d2970075b1e3f0376026485e4c
User & Date: dan 2013-03-25 16:28:54
Context
2013-03-25
17:00
Change the signature of the xUnfetch method to "int (*xUnfetch)(sqlite3_file*, sqlite3_int64 iOfst, void *p)". check-in: 115b8305 user: dan tags: experimental-mmap
16:28
Remove unnecessary code to round the size of a memory mapping to 4KB from os_unix.c. Rename SQLITE_IOERR_MREMAP to SQLITE_IOERR_MMAP. Fix other small issues in os_unix.c. check-in: dce35c01 user: dan tags: experimental-mmap
14:31
Do not return SQLITE_IOERR when the user attempts to open a small file that is not a database with mmap enabled. Instead return SQLITE_NOTADB. check-in: bbcaab3e user: dan tags: experimental-mmap
Changes
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Changes to src/os_unix.c.

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# define unixShmMap     0
# define unixShmLock    0
# define unixShmBarrier 0
# define unixShmUnmap   0
#endif /* #ifndef SQLITE_OMIT_WAL */

/*
** Arguments x and y are both integers. Argument y must be a power of 2.
** Round x up to the nearest integer multiple of y. For example:
**
**     ROUNDUP(0,  8) ->  0
**     ROUNDUP(13, 8) -> 16
**     ROUNDUP(32, 8) -> 32
*/
#define ROUNDUP(x,y)     (((x)+y-1)&~(y-1))

static void unixUnmapfile(unixFile *pFd){
  assert( pFd->nFetchOut==0 );
  if( pFd->pMapRegion ){
    munmap(pFd->pMapRegion, pFd->mmapOrigsize);
    pFd->pMapRegion = 0;
    pFd->mmapSize = 0;
    pFd->mmapOrigsize = 0;
  }
}

















static int unixMapfile(unixFile *pFd, i64 nByte){
  i64 nMap = nByte;
  int rc;

  assert( nMap>=0 || pFd->nFetchOut==0 );
  if( pFd->nFetchOut>0 ) return SQLITE_OK;

................................................................................
  if( nMap!=pFd->mmapSize ){
    unixUnmapfile(pFd);

    if( nMap>0 ){
      void *pNew;
      int flags = PROT_READ;
      if( (pFd->ctrlFlags & UNIXFILE_RDONLY)==0 ) flags |= PROT_WRITE;
      pNew = mmap(0, ROUNDUP(nMap, 4096), flags, MAP_SHARED, pFd->h, 0);
      if( pNew==MAP_FAILED ){
        return SQLITE_IOERR_MREMAP;
      }

      pFd->pMapRegion = pNew;
      pFd->mmapOrigsize = pFd->mmapSize = nMap;

    }
  }

  return SQLITE_OK;
}













static int unixFetch(sqlite3_file *fd, i64 iOff, int nAmt, void **pp){
  unixFile *pFd = (unixFile *)fd;   /* The underlying database file */
  *pp = 0;

  if( pFd->mmapLimit>0 ){
    if( pFd->pMapRegion==0 ){
      int rc = unixMapfile(pFd, -1);
................................................................................
      *pp = &((u8 *)pFd->pMapRegion)[iOff];
      pFd->nFetchOut++;
    }
  }
  return SQLITE_OK;
}








static int unixUnfetch(sqlite3_file *fd, void *p){
  unixFile *pFd = (unixFile *)fd;   /* The underlying database file */




  assert( (p==0)==(pFd->nFetchOut==0) );

  if( p ){
    pFd->nFetchOut--;
  }else{
    unixUnmapfile(pFd);
  }







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# define unixShmMap     0
# define unixShmLock    0
# define unixShmBarrier 0
# define unixShmUnmap   0
#endif /* #ifndef SQLITE_OMIT_WAL */

/*
** If it is currently memory mapped, unmap file pFd.





*/


static void unixUnmapfile(unixFile *pFd){
  assert( pFd->nFetchOut==0 );
  if( pFd->pMapRegion ){
    munmap(pFd->pMapRegion, pFd->mmapOrigsize);
    pFd->pMapRegion = 0;
    pFd->mmapSize = 0;
    pFd->mmapOrigsize = 0;
  }
}

/*
** Memory map or remap the file opened by file-descriptor pFd (if the file
** is already mapped, the existing mapping is replaced by the new). Or, if 
** there already exists a mapping for this file, and there are still 
** outstanding xFetch() references to it, this function is a no-op.
**
** If parameter nByte is non-negative, then it is the requested size of 
** the mapping to create. Otherwise, if nByte is less than zero, then the 
** requested size is the size of the file on disk. The actual size of the
** created mapping is either the requested size or the value configured 
** using SQLITE_FCNTL_MMAP_SIZE, whichever is smaller.
**
** SQLITE_OK is returned if no error occurs (even if the mapping is not
** recreated as a result of outstanding references) or an SQLite error
** code otherwise.
*/
static int unixMapfile(unixFile *pFd, i64 nByte){
  i64 nMap = nByte;
  int rc;

  assert( nMap>=0 || pFd->nFetchOut==0 );
  if( pFd->nFetchOut>0 ) return SQLITE_OK;

................................................................................
  if( nMap!=pFd->mmapSize ){
    unixUnmapfile(pFd);

    if( nMap>0 ){
      void *pNew;
      int flags = PROT_READ;
      if( (pFd->ctrlFlags & UNIXFILE_RDONLY)==0 ) flags |= PROT_WRITE;
      pNew = mmap(0, nMap, flags, MAP_SHARED, pFd->h, 0);
      if( pNew==MAP_FAILED ){
        return SQLITE_IOERR_MMAP;
      }

      pFd->pMapRegion = pNew;
      pFd->mmapSize = nMap;
      pFd->mmapOrigsize = nMap;
    }
  }

  return SQLITE_OK;
}

/*
** If possible, return a pointer to a mapping of file fd starting at offset
** iOff. The mapping must be valid for at least nAmt bytes.
**
** If such a pointer can be obtained, store it in *pp and return SQLITE_OK.
** Or, if one cannot but no error occurs, set *pp to 0 and return SQLITE_OK.
** Finally, if an error does occur, return an SQLite error code. The final
** value of *pp is undefined in this case.
**
** If this function does return a pointer, the caller must eventually 
** release the reference by calling unixUnfetch().
*/
static int unixFetch(sqlite3_file *fd, i64 iOff, int nAmt, void **pp){
  unixFile *pFd = (unixFile *)fd;   /* The underlying database file */
  *pp = 0;

  if( pFd->mmapLimit>0 ){
    if( pFd->pMapRegion==0 ){
      int rc = unixMapfile(pFd, -1);
................................................................................
      *pp = &((u8 *)pFd->pMapRegion)[iOff];
      pFd->nFetchOut++;
    }
  }
  return SQLITE_OK;
}

/*
** If the second argument is non-NULL, then this function releases a 
** reference obtained by an earlier call to unixFetch(). Or, if the second
** argument is NULL, then this function is being called to inform the VFS
** layer that, according to POSIX, any existing mapping may now be invalid
** and should be unmapped.
*/
static int unixUnfetch(sqlite3_file *fd, void *p){
  unixFile *pFd = (unixFile *)fd;   /* The underlying database file */

  /* If p==0 (unmap the entire file) then there must be no outstanding 
  ** xFetch references. Or, if p!=0 (meaning it is an xFetch reference),
  ** then there must be at least one outstanding.  */
  assert( (p==0)==(pFd->nFetchOut==0) );

  if( p ){
    pFd->nFetchOut--;
  }else{
    unixUnmapfile(pFd);
  }

Changes to src/sqlite.h.in.

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#define SQLITE_IOERR_DIR_CLOSE         (SQLITE_IOERR | (17<<8))
#define SQLITE_IOERR_SHMOPEN           (SQLITE_IOERR | (18<<8))
#define SQLITE_IOERR_SHMSIZE           (SQLITE_IOERR | (19<<8))
#define SQLITE_IOERR_SHMLOCK           (SQLITE_IOERR | (20<<8))
#define SQLITE_IOERR_SHMMAP            (SQLITE_IOERR | (21<<8))
#define SQLITE_IOERR_SEEK              (SQLITE_IOERR | (22<<8))
#define SQLITE_IOERR_DELETE_NOENT      (SQLITE_IOERR | (23<<8))
#define SQLITE_IOERR_MREMAP            (SQLITE_IOERR | (24<<8))
#define SQLITE_LOCKED_SHAREDCACHE      (SQLITE_LOCKED |  (1<<8))
#define SQLITE_BUSY_RECOVERY           (SQLITE_BUSY   |  (1<<8))
#define SQLITE_CANTOPEN_NOTEMPDIR      (SQLITE_CANTOPEN | (1<<8))
#define SQLITE_CANTOPEN_ISDIR          (SQLITE_CANTOPEN | (2<<8))
#define SQLITE_CANTOPEN_FULLPATH       (SQLITE_CANTOPEN | (3<<8))
#define SQLITE_CORRUPT_VTAB            (SQLITE_CORRUPT | (1<<8))
#define SQLITE_READONLY_RECOVERY       (SQLITE_READONLY | (1<<8))







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#define SQLITE_IOERR_DIR_CLOSE         (SQLITE_IOERR | (17<<8))
#define SQLITE_IOERR_SHMOPEN           (SQLITE_IOERR | (18<<8))
#define SQLITE_IOERR_SHMSIZE           (SQLITE_IOERR | (19<<8))
#define SQLITE_IOERR_SHMLOCK           (SQLITE_IOERR | (20<<8))
#define SQLITE_IOERR_SHMMAP            (SQLITE_IOERR | (21<<8))
#define SQLITE_IOERR_SEEK              (SQLITE_IOERR | (22<<8))
#define SQLITE_IOERR_DELETE_NOENT      (SQLITE_IOERR | (23<<8))
#define SQLITE_IOERR_MMAP              (SQLITE_IOERR | (24<<8))
#define SQLITE_LOCKED_SHAREDCACHE      (SQLITE_LOCKED |  (1<<8))
#define SQLITE_BUSY_RECOVERY           (SQLITE_BUSY   |  (1<<8))
#define SQLITE_CANTOPEN_NOTEMPDIR      (SQLITE_CANTOPEN | (1<<8))
#define SQLITE_CANTOPEN_ISDIR          (SQLITE_CANTOPEN | (2<<8))
#define SQLITE_CANTOPEN_FULLPATH       (SQLITE_CANTOPEN | (3<<8))
#define SQLITE_CORRUPT_VTAB            (SQLITE_CORRUPT | (1<<8))
#define SQLITE_READONLY_RECOVERY       (SQLITE_READONLY | (1<<8))