/*
** 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;
}
/*
** 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;
}