Example #1
0
/*
** Move data out of a btree key or data field and into a Mem structure.
** The data or key is taken from the entry that pCur is currently pointing
** to.  offset and amt determine what portion of the data or key to retrieve.
** key is true to get the key or false to get data.  The result is written
** into the pMem element.
**
** The pMem structure is assumed to be uninitialized.  Any prior content
** is overwritten without being freed.
**
** If this routine fails for any reason (malloc returns NULL or unable
** to read from the disk) then the pMem is left in an inconsistent state.
*/
int sqlite3VdbeMemFromBtree(
  BtCursor *pCur,   /* Cursor pointing at record to retrieve. */
  int offset,       /* Offset from the start of data to return bytes from. */
  int amt,          /* Number of bytes to return. */
  int key,          /* If true, retrieve from the btree key, not data. */
  Mem *pMem         /* OUT: Return data in this Mem structure. */
){
  char *zData;       /* Data from the btree layer */
  int available = 0; /* Number of bytes available on the local btree page */
  sqlite3 *db;       /* Database connection */
  int rc = SQLITE_OK;

  db = sqlite3BtreeCursorDb(pCur);
  assert( sqlite3_mutex_held(db->mutex) );
  assert( (pMem->flags & MEM_RowSet)==0 );
  if( key ){
    zData = (char *)sqlite3BtreeKeyFetch(pCur, &available);
  }else{
    zData = (char *)sqlite3BtreeDataFetch(pCur, &available);
  }
  assert( zData!=0 );

  if( offset+amt<=available && ((pMem->flags&MEM_Dyn)==0 || pMem->xDel) ){
    sqlite3VdbeMemRelease(pMem);
    pMem->z = &zData[offset];
    pMem->flags = MEM_Blob|MEM_Ephem;
  }else if( SQLITE_OK==(rc = sqlite3VdbeMemGrow(pMem, amt+2, 0)) ){
    pMem->flags = MEM_Blob|MEM_Dyn|MEM_Term;
    pMem->enc = 0;
    pMem->type = SQLITE_BLOB;
    if( key ){
      rc = sqlite3BtreeKey(pCur, offset, amt, pMem->z);
    }else{
      rc = sqlite3BtreeData(pCur, offset, amt, pMem->z);
    }
    pMem->z[amt] = 0;
    pMem->z[amt+1] = 0;
    if( rc!=SQLITE_OK ){
      sqlite3VdbeMemRelease(pMem);
    }
  }
  pMem->n = amt;

  return rc;
}
Example #2
0
/*
** Move data out of a btree key or data field and into a Mem structure.
** The data or key is taken from the entry that pCur is currently pointing
** to.  offset and amt determine what portion of the data or key to retrieve.
** key is true to get the key or false to get data.  The result is written
** into the pMem element.
**
** The pMem structure is assumed to be uninitialized.  Any prior content
** is overwritten without being freed.
**
** If this routine fails for any reason (malloc returns NULL or unable
** to read from the disk) then the pMem is left in an inconsistent state.
*/
int sqlite3VdbeMemFromBtree(
  BtCursor *pCur,   /* Cursor pointing at record to retrieve. */
  int offset,       /* Offset from the start of data to return bytes from. */
  int amt,          /* Number of bytes to return. */
  int key,          /* If true, retrieve from the btree key, not data. */
  Mem *pMem         /* OUT: Return data in this Mem structure. */
){
  char *zData;       /* Data from the btree layer */
  int available = 0; /* Number of bytes available on the local btree page */
  sqlite3 *db;       /* Database connection */

  db = sqlite3BtreeCursorDb(pCur);
  assert( sqlite3_mutex_held(db->mutex) );
  if( key ){
    zData = (char *)sqlite3BtreeKeyFetch(pCur, &available);
  }else{
    zData = (char *)sqlite3BtreeDataFetch(pCur, &available);
  }
  assert( zData!=0 );

  pMem->db = db;
  pMem->n = amt;
  if( offset+amt<=available ){
    pMem->z = &zData[offset];
    pMem->flags = MEM_Blob|MEM_Ephem;
  }else{
    int rc;
    if( amt>NBFS-2 ){
      zData = (char *)sqlite3DbMallocRaw(db, amt+2);
      if( !zData ){
        return SQLITE_NOMEM;
      }
      pMem->flags = MEM_Blob|MEM_Dyn|MEM_Term;
      pMem->xDel = 0;
    }else{
      zData = &(pMem->zShort[0]);
      pMem->flags = MEM_Blob|MEM_Short|MEM_Term;
    }
    pMem->z = zData;
    pMem->enc = 0;
    pMem->type = SQLITE_BLOB;

    if( key ){
      rc = sqlite3BtreeKey(pCur, offset, amt, zData);
    }else{
      rc = sqlite3BtreeData(pCur, offset, amt, zData);
    }
    zData[amt] = 0;
    zData[amt+1] = 0;
    if( rc!=SQLITE_OK ){
      if( amt>NBFS-2 ){
        assert( zData!=pMem->zShort );
        assert( pMem->flags & MEM_Dyn );
        sqlite3_free(zData);
      } else {
        assert( zData==pMem->zShort );
        assert( pMem->flags & MEM_Short );
      }
      return rc;
    }
  }

  return SQLITE_OK;
}