/*
** This function is used by both blob_open() and blob_reopen(). It seeks
** the b-tree cursor associated with blob handle p to point to row iRow.
** If successful, SQLITE_OK is returned and subsequent calls to
** sqlite3_blob_read() or sqlite3_blob_write() access the specified row.
**
** If an error occurs, or if the specified row does not exist or does not
** contain a value of type TEXT or BLOB in the column nominated when the
** blob handle was opened, then an error code is returned and *pzErr may
** be set to point to a buffer containing an error message. It is the
** responsibility of the caller to free the error message buffer using
** sqlite3DbFree().
**
** If an error does occur, then the b-tree cursor is closed. All subsequent
** calls to sqlite3_blob_read(), blob_write() or blob_reopen() will
** immediately return SQLITE_ABORT.
*/
static int blobSeekToRow(Incrblob *p, sqlite3_int64 iRow, char **pzErr){
int rc; /* Error code */
char *zErr = 0; /* Error message */
Vdbe *v = (Vdbe *)p->pStmt;
/* Set the value of the SQL statements only variable to integer iRow.
** This is done directly instead of using sqlite3_bind_int64() to avoid
** triggering asserts related to mutexes.
*/
assert( v->aVar[0].flags&MEM_Int );
v->aVar[0].u.i = iRow;
rc = sqlite3_step(p->pStmt);
if( rc==SQLITE_ROW ){
u32 type = v->apCsr[0]->aType[p->iCol];
if( type<12 ){
zErr = sqlite3MPrintf(p->db, "cannot open value of type %s",
type==0?"null": type==7?"real": "integer"
);
rc = SQLITE_ERROR;
sqlite3_finalize(p->pStmt);
p->pStmt = 0;
}else{
p->iOffset = v->apCsr[0]->aOffset[p->iCol];
p->nByte = sqlite3VdbeSerialTypeLen(type);
p->pCsr = v->apCsr[0]->pCursor;
sqlite3BtreeEnterCursor(p->pCsr);
sqlite3BtreeCacheOverflow(p->pCsr);
sqlite3BtreeLeaveCursor(p->pCsr);
}
}
if( rc==SQLITE_ROW ){
rc = SQLITE_OK;
}else if( p->pStmt ){
rc = sqlite3_finalize(p->pStmt);
p->pStmt = 0;
if( rc==SQLITE_OK ){
zErr = sqlite3MPrintf(p->db, "no such rowid: %lld", iRow);
rc = SQLITE_ERROR;
}else{
zErr = sqlite3MPrintf(p->db, "%s", sqlite3_errmsg(p->db));
}
}
assert( rc!=SQLITE_OK || zErr==0 );
assert( rc!=SQLITE_ROW && rc!=SQLITE_DONE );
*pzErr = zErr;
return rc;
}
/*
** Perform a read or write operation on a blob
*/
static int blobReadWrite(
sqlite3_blob *pBlob,
void *z,
int n,
int iOffset,
int (*xCall)(BtCursor*, u32, u32, void*)
){
int rc;
Incrblob *p = (Incrblob *)pBlob;
Vdbe *v;
sqlite3 *db;
if( p==0 ) return SQLITE_MISUSE;
db = p->db;
sqlite3_mutex_enter(db->mutex);
v = (Vdbe*)p->pStmt;
if( n<0 || iOffset<0 || (iOffset+n)>p->nByte ){
/* Request is out of range. Return a transient error. */
rc = SQLITE_ERROR;
sqlite3Error(db, SQLITE_ERROR, 0);
} else if( v==0 ){
/* If there is no statement handle, then the blob-handle has
** already been invalidated. Return SQLITE_ABORT in this case.
*/
rc = SQLITE_ABORT;
}else{
/* Call either BtreeData() or BtreePutData(). If SQLITE_ABORT is
** returned, clean-up the statement handle.
*/
assert( db == v->db );
sqlite3BtreeEnterCursor(p->pCsr);
rc = xCall(p->pCsr, iOffset+p->iOffset, n, z);
sqlite3BtreeLeaveCursor(p->pCsr);
if( rc==SQLITE_ABORT ){
sqlite3VdbeFinalize(v);
p->pStmt = 0;
}else{
db->errCode = rc;
v->rc = rc;
}
}
rc = sqlite3ApiExit(db, rc);
sqlite3_mutex_leave(db->mutex);
return rc;
}
/*
** Open a blob handle.
*/
int sqlite3_blob_open(
sqlite3* db, /* The database connection */
const char *zDb, /* The attached database containing the blob */
const char *zTable, /* The table containing the blob */
const char *zColumn, /* The column containing the blob */
sqlite_int64 iRow, /* The row containing the glob */
int flags, /* True -> read/write access, false -> read-only */
sqlite3_blob **ppBlob /* Handle for accessing the blob returned here */
){
int nAttempt = 0;
int iCol; /* Index of zColumn in row-record */
/* This VDBE program seeks a btree cursor to the identified
** db/table/row entry. The reason for using a vdbe program instead
** of writing code to use the b-tree layer directly is that the
** vdbe program will take advantage of the various transaction,
** locking and error handling infrastructure built into the vdbe.
**
** After seeking the cursor, the vdbe executes an OP_ResultRow.
** Code external to the Vdbe then "borrows" the b-tree cursor and
** uses it to implement the blob_read(), blob_write() and
** blob_bytes() functions.
**
** The sqlite3_blob_close() function finalizes the vdbe program,
** which closes the b-tree cursor and (possibly) commits the
** transaction.
*/
static const VdbeOpList openBlob[] = {
{OP_Transaction, 0, 0, 0}, /* 0: Start a transaction */
{OP_VerifyCookie, 0, 0, 0}, /* 1: Check the schema cookie */
{OP_TableLock, 0, 0, 0}, /* 2: Acquire a read or write lock */
/* One of the following two instructions is replaced by an OP_Noop. */
{OP_OpenRead, 0, 0, 0}, /* 3: Open cursor 0 for reading */
{OP_OpenWrite, 0, 0, 0}, /* 4: Open cursor 0 for read/write */
{OP_Variable, 1, 1, 1}, /* 5: Push the rowid to the stack */
{OP_NotExists, 0, 9, 1}, /* 6: Seek the cursor */
{OP_Column, 0, 0, 1}, /* 7 */
{OP_ResultRow, 1, 0, 0}, /* 8 */
{OP_Close, 0, 0, 0}, /* 9 */
{OP_Halt, 0, 0, 0}, /* 10 */
};
Vdbe *v = 0;
int rc = SQLITE_OK;
char *zErr = 0;
Table *pTab;
Parse *pParse;
*ppBlob = 0;
sqlite3_mutex_enter(db->mutex);
pParse = sqlite3StackAllocRaw(db, sizeof(*pParse));
if( pParse==0 ){
rc = SQLITE_NOMEM;
goto blob_open_out;
}
do {
memset(pParse, 0, sizeof(Parse));
pParse->db = db;
if( sqlite3SafetyOn(db) ){
sqlite3DbFree(db, zErr);
sqlite3StackFree(db, pParse);
sqlite3_mutex_leave(db->mutex);
return SQLITE_MISUSE;
}
sqlite3BtreeEnterAll(db);
pTab = sqlite3LocateTable(pParse, 0, zTable, zDb);
if( pTab && IsVirtual(pTab) ){
pTab = 0;
sqlite3ErrorMsg(pParse, "cannot open virtual table: %s", zTable);
}
#ifndef SQLITE_OMIT_VIEW
if( pTab && pTab->pSelect ){
pTab = 0;
sqlite3ErrorMsg(pParse, "cannot open view: %s", zTable);
}
#endif
if( !pTab ){
if( pParse->zErrMsg ){
sqlite3DbFree(db, zErr);
zErr = pParse->zErrMsg;
pParse->zErrMsg = 0;
}
rc = SQLITE_ERROR;
(void)sqlite3SafetyOff(db);
sqlite3BtreeLeaveAll(db);
goto blob_open_out;
}
/* Now search pTab for the exact column. */
for(iCol=0; iCol < pTab->nCol; iCol++) {
if( sqlite3StrICmp(pTab->aCol[iCol].zName, zColumn)==0 ){
break;
}
}
if( iCol==pTab->nCol ){
sqlite3DbFree(db, zErr);
zErr = sqlite3MPrintf(db, "no such column: \"%s\"", zColumn);
rc = SQLITE_ERROR;
(void)sqlite3SafetyOff(db);
sqlite3BtreeLeaveAll(db);
goto blob_open_out;
}
/* If the value is being opened for writing, check that the
** column is not indexed. It is against the rules to open an
** indexed column for writing.
*/
if( flags ){
Index *pIdx;
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
int j;
for(j=0; j<pIdx->nColumn; j++){
if( pIdx->aiColumn[j]==iCol ){
sqlite3DbFree(db, zErr);
zErr = sqlite3MPrintf(db,
"cannot open indexed column for writing");
rc = SQLITE_ERROR;
(void)sqlite3SafetyOff(db);
sqlite3BtreeLeaveAll(db);
goto blob_open_out;
}
}
}
}
v = sqlite3VdbeCreate(db);
if( v ){
int iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
sqlite3VdbeAddOpList(v, sizeof(openBlob)/sizeof(VdbeOpList), openBlob);
flags = !!flags; /* flags = (flags ? 1 : 0); */
/* Configure the OP_Transaction */
sqlite3VdbeChangeP1(v, 0, iDb);
sqlite3VdbeChangeP2(v, 0, flags);
/* Configure the OP_VerifyCookie */
sqlite3VdbeChangeP1(v, 1, iDb);
sqlite3VdbeChangeP2(v, 1, pTab->pSchema->schema_cookie);
/* Make sure a mutex is held on the table to be accessed */
sqlite3VdbeUsesBtree(v, iDb);
/* Configure the OP_TableLock instruction */
sqlite3VdbeChangeP1(v, 2, iDb);
sqlite3VdbeChangeP2(v, 2, pTab->tnum);
sqlite3VdbeChangeP3(v, 2, flags);
sqlite3VdbeChangeP4(v, 2, pTab->zName, P4_TRANSIENT);
/* Remove either the OP_OpenWrite or OpenRead. Set the P2
** parameter of the other to pTab->tnum. */
sqlite3VdbeChangeToNoop(v, 4 - flags, 1);
sqlite3VdbeChangeP2(v, 3 + flags, pTab->tnum);
sqlite3VdbeChangeP3(v, 3 + flags, iDb);
/* Configure the number of columns. Configure the cursor to
** think that the table has one more column than it really
** does. An OP_Column to retrieve this imaginary column will
** always return an SQL NULL. This is useful because it means
** we can invoke OP_Column to fill in the vdbe cursors type
** and offset cache without causing any IO.
*/
sqlite3VdbeChangeP4(v, 3+flags, SQLITE_INT_TO_PTR(pTab->nCol+1),P4_INT32);
sqlite3VdbeChangeP2(v, 7, pTab->nCol);
if( !db->mallocFailed ){
sqlite3VdbeMakeReady(v, 1, 1, 1, 0);
}
}
sqlite3BtreeLeaveAll(db);
rc = sqlite3SafetyOff(db);
if( NEVER(rc!=SQLITE_OK) || db->mallocFailed ){
goto blob_open_out;
}
sqlite3_bind_int64((sqlite3_stmt *)v, 1, iRow);
rc = sqlite3_step((sqlite3_stmt *)v);
if( rc!=SQLITE_ROW ){
nAttempt++;
rc = sqlite3_finalize((sqlite3_stmt *)v);
sqlite3DbFree(db, zErr);
zErr = sqlite3MPrintf(db, sqlite3_errmsg(db));
v = 0;
}
} while( nAttempt<5 && rc==SQLITE_SCHEMA );
if( rc==SQLITE_ROW ){
/* The row-record has been opened successfully. Check that the
** column in question contains text or a blob. If it contains
** text, it is up to the caller to get the encoding right.
*/
Incrblob *pBlob;
u32 type = v->apCsr[0]->aType[iCol];
if( type<12 ){
sqlite3DbFree(db, zErr);
zErr = sqlite3MPrintf(db, "cannot open value of type %s",
type==0?"null": type==7?"real": "integer"
);
rc = SQLITE_ERROR;
goto blob_open_out;
}
pBlob = (Incrblob *)sqlite3DbMallocZero(db, sizeof(Incrblob));
if( db->mallocFailed ){
sqlite3DbFree(db, pBlob);
goto blob_open_out;
}
pBlob->flags = flags;
pBlob->pCsr = v->apCsr[0]->pCursor;
sqlite3BtreeEnterCursor(pBlob->pCsr);
sqlite3BtreeCacheOverflow(pBlob->pCsr);
sqlite3BtreeLeaveCursor(pBlob->pCsr);
pBlob->pStmt = (sqlite3_stmt *)v;
pBlob->iOffset = v->apCsr[0]->aOffset[iCol];
pBlob->nByte = sqlite3VdbeSerialTypeLen(type);
pBlob->db = db;
*ppBlob = (sqlite3_blob *)pBlob;
rc = SQLITE_OK;
}else if( rc==SQLITE_OK ){
sqlite3DbFree(db, zErr);
zErr = sqlite3MPrintf(db, "no such rowid: %lld", iRow);
rc = SQLITE_ERROR;
}
blob_open_out:
if( v && (rc!=SQLITE_OK || db->mallocFailed) ){
sqlite3VdbeFinalize(v);
}
sqlite3Error(db, rc, zErr);
sqlite3DbFree(db, zErr);
sqlite3StackFree(db, pParse);
rc = sqlite3ApiExit(db, rc);
sqlite3_mutex_leave(db->mutex);
return rc;
}
