--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/engine/sqlite/src/vdbeblob.cpp Thu Feb 25 14:29:19 2010 +0000
@@ -0,0 +1,340 @@
+/*
+** 2007 May 1
+**
+** The author disclaims copyright to this source code. In place of
+** a legal notice, here is a blessing:
+**
+** May you do good and not evil.
+** May you find forgiveness for yourself and forgive others.
+** May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code used to implement incremental BLOB I/O.
+**
+** $Id: vdbeblob.cpp 1282 2008-11-13 09:31:33Z LarsPson $
+*/
+
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+#ifndef SQLITE_OMIT_INCRBLOB
+
+/*
+** Valid sqlite3_blob* handles point to Incrblob structures.
+*/
+typedef struct Incrblob Incrblob;
+struct Incrblob {
+ int flags; /* Copy of "flags" passed to sqlite3_blob_open() */
+ int nByte; /* Size of open blob, in bytes */
+ int iOffset; /* Byte offset of blob in cursor data */
+ BtCursor *pCsr; /* Cursor pointing at blob row */
+ sqlite3_stmt *pStmt; /* Statement holding cursor open */
+ sqlite3 *db; /* The associated database */
+};
+
+/*
+** Open a blob handle.
+*/
+EXPORT_C 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_Callback.
+ ** 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_Integer, 0, 0, 0}, /* 2: Database number */
+
+ /* One of the following two instructions is replaced by an
+ ** OP_Noop before exection.
+ */
+ {OP_OpenRead, 0, 0, 0}, /* 3: Open cursor 0 for reading */
+ {OP_OpenWrite, 0, 0, 0}, /* 4: Open cursor 0 for read/write */
+ {OP_SetNumColumns, 0, 0, 0}, /* 5: Num cols for cursor */
+
+ {OP_Variable, 1, 0, 0}, /* 6: Push the rowid to the stack */
+ {OP_NotExists, 0, 10, 0}, /* 7: Seek the cursor */
+ {OP_Column, 0, 0, 0}, /* 8 */
+ {OP_Callback, 0, 0, 0}, /* 9 */
+ {OP_Close, 0, 0, 0}, /* 10 */
+ {OP_Halt, 0, 0, 0}, /* 11 */
+ };
+
+ Vdbe *v = 0;
+ int rc = SQLITE_OK;
+ char zErr[128];
+
+ zErr[0] = 0;
+ sqlite3_mutex_enter(db->mutex);
+ do {
+ Parse sParse;
+ Table *pTab;
+
+ memset(&sParse, 0, sizeof(Parse));
+ sParse.db = db;
+
+ rc = sqlite3SafetyOn(db);
+ if( rc!=SQLITE_OK ){
+ sqlite3_mutex_leave(db->mutex);
+ return rc;
+ }
+
+ sqlite3BtreeEnterAll(db);
+ pTab = sqlite3LocateTable(&sParse, zTable, zDb);
+ if( !pTab ){
+ if( sParse.zErrMsg ){
+ sqlite3_snprintf(sizeof(zErr), zErr, "%s", sParse.zErrMsg);
+ }
+ sqlite3_free(sParse.zErrMsg);
+ rc = SQLITE_ERROR;
+ 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 ){
+ sqlite3_snprintf(sizeof(zErr), zErr, "no such column: \"%s\"", zColumn);
+ rc = SQLITE_ERROR;
+ 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 ){
+ sqlite3_snprintf(sizeof(zErr), zErr,
+ "cannot open indexed column for writing");
+ rc = SQLITE_ERROR;
+ 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);
+
+ /* Configure the OP_Transaction */
+ sqlite3VdbeChangeP1(v, 0, iDb);
+ sqlite3VdbeChangeP2(v, 0, (flags ? 1 : 0));
+
+ /* 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 db number pushed onto the stack */
+ sqlite3VdbeChangeP1(v, 2, iDb);
+
+ /* Remove either the OP_OpenWrite or OpenRead. Set the P2
+ ** parameter of the other to pTab->tnum.
+ */
+ sqlite3VdbeChangeToNoop(v, (flags ? 3 : 4), 1);
+ sqlite3VdbeChangeP2(v, (flags ? 4 : 3), pTab->tnum);
+
+ /* Configure the OP_SetNumColumns. 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.
+ */
+ sqlite3VdbeChangeP2(v, 5, pTab->nCol+1);
+ if( !db->mallocFailed ){
+ sqlite3VdbeMakeReady(v, 1, 0, 1, 0);
+ }
+ }
+
+ sqlite3BtreeLeaveAll(db);
+ rc = sqlite3SafetyOff(db);
+ if( 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);
+ sqlite3_snprintf(sizeof(zErr), zErr, 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 ){
+ sqlite3_snprintf(sizeof(zErr), zErr, "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 ){
+ sqlite3_free(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 ){
+ sqlite3_snprintf(sizeof(zErr), zErr, "no such rowid: %lld", iRow);
+ rc = SQLITE_ERROR;
+ }
+
+blob_open_out:
+ zErr[sizeof(zErr)-1] = '\0';
+ if( rc!=SQLITE_OK || db->mallocFailed ){
+ sqlite3_finalize((sqlite3_stmt *)v);
+ }
+ sqlite3Error(db, rc, (rc==SQLITE_OK?0:zErr));
+ rc = sqlite3ApiExit(db, rc);
+ sqlite3_mutex_leave(db->mutex);
+ return rc;
+}
+
+/*
+** Close a blob handle that was previously created using
+** sqlite3_blob_open().
+*/
+EXPORT_C int sqlite3_blob_close(sqlite3_blob *pBlob){
+ Incrblob *p = (Incrblob *)pBlob;
+ int rc;
+
+ rc = sqlite3_finalize(p->pStmt);
+ sqlite3_free(p);
+ 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 = p->db;
+
+ /* Request is out of range. Return a transient error. */
+ if( (iOffset+n)>p->nByte ){
+ return SQLITE_ERROR;
+ }
+ sqlite3_mutex_enter(db->mutex);
+
+ /* If there is no statement handle, then the blob-handle has
+ ** already been invalidated. Return SQLITE_ABORT in this case.
+ */
+ v = (Vdbe*)p->pStmt;
+ if( v==0 ){
+ 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;
+}
+
+/*
+** Read data from a blob handle.
+*/
+EXPORT_C int sqlite3_blob_read(sqlite3_blob *pBlob, void *z, int n, int iOffset){
+ return blobReadWrite(pBlob, z, n, iOffset, sqlite3BtreeData);
+}
+
+/*
+** Write data to a blob handle.
+*/
+EXPORT_C int sqlite3_blob_write(sqlite3_blob *pBlob, const void *z, int n, int iOffset){
+ return blobReadWrite(pBlob, (void *)z, n, iOffset, sqlite3BtreePutData);
+}
+
+/*
+** Query a blob handle for the size of the data.
+**
+** The Incrblob.nByte field is fixed for the lifetime of the Incrblob
+** so no mutex is required for access.
+*/
+EXPORT_C int sqlite3_blob_bytes(sqlite3_blob *pBlob){
+ Incrblob *p = (Incrblob *)pBlob;
+ return p->nByte;
+}
+
+#endif /* #ifndef SQLITE_OMIT_INCRBLOB */