/* ** 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; }
/* ** Query the database. But instead of invoking a callback for each row, ** malloc() for space to hold the result and return the entire results ** at the conclusion of the call. ** 数据库执行。分配空间来保存结果并在调用结束时返回整个结果,而不是对每行都进行调用 ** The result that is written to ***pazResult is held in memory obtained ** from malloc(). But the caller cannot free this memory directly. ** Instead, the entire table should be passed to sqlite3_free_table() when ** the calling procedure is finished using it. ** 分配空间给pazResult指针所指单元中,并用它来保存结果。 ** 分配的空间不是直接释放的,而是在函数执行结束后调用sqlite3_free_table()函数来进行统一释放。 */ int sqlite3_get_table( sqlite3 *db, /* The database on which the SQL executes 执行查询的数据库*/ const char *zSql, /* The SQL to be executed 执行语句*/ char ***pazResult, /* Write the result table here 需要写入记录的表*/ int *pnRow, /* Write the number of rows in the result here 结果集行数*/ int *pnColumn, /* Write the number of columns of result here 结果集列数*/ char **pzErrMsg /* Write error messages here 错误信息*/ ){ int rc; TabResult res; /*开始分配空间*/ *pazResult = 0; if( pnColumn ) *pnColumn = 0; if( pnRow ) *pnRow = 0; if( pzErrMsg ) *pzErrMsg = 0; res.zErrMsg = 0; res.nRow = 0; res.nColumn = 0; res.nData = 1; res.nAlloc = 20; res.rc = SQLITE_OK; res.azResult = sqlite3_malloc(sizeof(char*)*res.nAlloc ); if( res.azResult==0 ){ db->errCode = SQLITE_NOMEM; return SQLITE_NOMEM; } res.azResult[0] = 0; rc = sqlite3_exec(db, zSql, sqlite3_get_table_cb, &res, pzErrMsg); assert( sizeof(res.azResult[0])>= sizeof(res.nData) ); res.azResult[0] = SQLITE_INT_TO_PTR(res.nData); if( (rc&0xff)==SQLITE_ABORT ){ sqlite3_free_table(&res.azResult[1]); //释放表空间 if( res.zErrMsg ){ if( pzErrMsg ){ sqlite3_free(*pzErrMsg); *pzErrMsg = sqlite3_mprintf("%s",res.zErrMsg); } sqlite3_free(res.zErrMsg); } db->errCode = res.rc; /* Assume 32-bit assignment is atomic */ return res.rc; } sqlite3_free(res.zErrMsg); if( rc!=SQLITE_OK ){ sqlite3_free_table(&res.azResult[1]); return rc; } if( res.nAlloc>res.nData ){ char **azNew; azNew = sqlite3_realloc( res.azResult, sizeof(char*)*res.nData ); if( azNew==0 ){ sqlite3_free_table(&res.azResult[1]); db->errCode = SQLITE_NOMEM; return SQLITE_NOMEM; } res.azResult = azNew; } *pazResult = &res.azResult[1]; if( pnColumn ) *pnColumn = res.nColumn; if( pnRow ) *pnRow = res.nRow; 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, 10, 1}, /* 6: Seek the cursor */ {OP_Column, 0, 0, 1}, /* 7 */ {OP_ResultRow, 1, 0, 0}, /* 8 */ {OP_Goto, 0, 5, 0}, /* 9 */ {OP_Close, 0, 0, 0}, /* 10 */ {OP_Halt, 0, 0, 0}, /* 11 */ }; int rc = SQLITE_OK; char *zErr = 0; Table *pTab; Parse *pParse = 0; Incrblob *pBlob = 0; flags = !!flags; /* flags = (flags ? 1 : 0); */ *ppBlob = 0; sqlite3_mutex_enter(db->mutex); pBlob = (Incrblob *)sqlite3DbMallocZero(db, sizeof(Incrblob)); if( !pBlob ) goto blob_open_out; pParse = sqlite3StackAllocRaw(db, sizeof(*pParse)); if( !pParse ) goto blob_open_out; do { memset(pParse, 0, sizeof(Parse)); pParse->db = db; sqlite3DbFree(db, zErr); zErr = 0; 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; 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; sqlite3BtreeLeaveAll(db); goto blob_open_out; } /* If the value is being opened for writing, check that the ** column is not indexed, and that it is not part of a foreign key. ** It is against the rules to open a column to which either of these ** descriptions applies for writing. */ if( flags ){ const char *zFault = 0; Index *pIdx; #ifndef SQLITE_OMIT_FOREIGN_KEY if( db->flags&SQLITE_ForeignKeys ){ /* Check that the column is not part of an FK child key definition. It ** is not necessary to check if it is part of a parent key, as parent ** key columns must be indexed. The check below will pick up this ** case. */ FKey *pFKey; for(pFKey=pTab->pFKey; pFKey; pFKey=pFKey->pNextFrom){ int j; for(j=0; j<pFKey->nCol; j++){ if( pFKey->aCol[j].iFrom==iCol ){ zFault = "foreign key"; } } } } #endif for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){ int j; for(j=0; j<pIdx->nColumn; j++){ if( pIdx->aiColumn[j]==iCol ){ zFault = "indexed"; } } } if( zFault ){ sqlite3DbFree(db, zErr); zErr = sqlite3MPrintf(db, "cannot open %s column for writing", zFault); rc = SQLITE_ERROR; sqlite3BtreeLeaveAll(db); goto blob_open_out; } } pBlob->pStmt = (sqlite3_stmt *)sqlite3VdbeCreate(db); assert( pBlob->pStmt || db->mallocFailed ); if( pBlob->pStmt ){ Vdbe *v = (Vdbe *)pBlob->pStmt; 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); /* Configure the OP_VerifyCookie */ sqlite3VdbeChangeP1(v, 1, iDb); sqlite3VdbeChangeP2(v, 1, pTab->pSchema->schema_cookie); sqlite3VdbeChangeP3(v, 1, pTab->pSchema->iGeneration); /* Make sure a mutex is held on the table to be accessed */ sqlite3VdbeUsesBtree(v, iDb); /* Configure the OP_TableLock instruction */ #ifdef SQLITE_OMIT_SHARED_CACHE sqlite3VdbeChangeToNoop(v, 2); #else sqlite3VdbeChangeP1(v, 2, iDb); sqlite3VdbeChangeP2(v, 2, pTab->tnum); sqlite3VdbeChangeP3(v, 2, flags); sqlite3VdbeChangeP4(v, 2, pTab->zName, P4_TRANSIENT); #endif /* Remove either the OP_OpenWrite or OpenRead. Set the P2 ** parameter of the other to pTab->tnum. */ sqlite3VdbeChangeToNoop(v, 4 - flags); 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 ){ pParse->nVar = 1; pParse->nMem = 1; pParse->nTab = 1; sqlite3VdbeMakeReady(v, pParse); } } pBlob->flags = flags; pBlob->iCol = iCol; pBlob->db = db; sqlite3BtreeLeaveAll(db); if( db->mallocFailed ){ goto blob_open_out; } sqlite3_bind_int64(pBlob->pStmt, 1, iRow); rc = blobSeekToRow(pBlob, iRow, &zErr); } while( (++nAttempt)<5 && rc==SQLITE_SCHEMA ); blob_open_out: if( rc==SQLITE_OK && db->mallocFailed==0 ){ *ppBlob = (sqlite3_blob *)pBlob; }else{ if( pBlob && pBlob->pStmt ) sqlite3VdbeFinalize((Vdbe *)pBlob->pStmt); sqlite3DbFree(db, pBlob); } sqlite3Error(db, rc, (zErr ? "%s" : 0), zErr); sqlite3DbFree(db, zErr); sqlite3StackFree(db, pParse); rc = sqlite3ApiExit(db, rc); sqlite3_mutex_leave(db->mutex); return rc; }
/* ** Query the database. But instead of invoking a callback for each row, ** malloc() for space to hold the result and return the entire results ** at the conclusion of the call. ** ** The result that is written to ***pazResult is held in memory obtained ** from malloc(). But the caller cannot free this memory directly. ** Instead, the entire table should be passed to sqlite3_free_table() when ** the calling procedure is finished using it. */ int sqlite3_get_table( sqlite3 *db, /* The database on which the SQL executes */ const char *zSql, /* The SQL to be executed */ char ***pazResult, /* Write the result table here */ int *pnRow, /* Write the number of rows in the result here */ int *pnColumn, /* Write the number of columns of result here */ char **pzErrMsg /* Write error messages here */ ){ int rc; TabResult res; #ifdef SQLITE_ENABLE_API_ARMOR if( !sqlite3SafetyCheckOk(db) || pazResult==0 ) return SQLITE_MISUSE_BKPT; #endif *pazResult = 0; if( pnColumn ) *pnColumn = 0; if( pnRow ) *pnRow = 0; if( pzErrMsg ) *pzErrMsg = 0; res.zErrMsg = 0; res.nRow = 0; res.nColumn = 0; res.nData = 1; res.nAlloc = 20; res.rc = SQLITE_OK; res.azResult = sqlite3_malloc64(sizeof(char*)*res.nAlloc ); if( res.azResult==0 ){ db->errCode = SQLITE_NOMEM; return SQLITE_NOMEM_BKPT; } res.azResult[0] = 0; rc = sqlite3_exec(db, zSql, sqlite3_get_table_cb, &res, pzErrMsg); assert( sizeof(res.azResult[0])>= sizeof(res.nData) ); res.azResult[0] = SQLITE_INT_TO_PTR(res.nData); if( (rc&0xff)==SQLITE_ABORT ){ sqlite3_free_table(&res.azResult[1]); if( res.zErrMsg ){ if( pzErrMsg ){ sqlite3_free(*pzErrMsg); *pzErrMsg = sqlite3_mprintf("%s",res.zErrMsg); } sqlite3_free(res.zErrMsg); } db->errCode = res.rc; /* Assume 32-bit assignment is atomic */ return res.rc; } sqlite3_free(res.zErrMsg); if( rc!=SQLITE_OK ){ sqlite3_free_table(&res.azResult[1]); return rc; } if( res.nAlloc>res.nData ){ char **azNew; azNew = sqlite3_realloc64( res.azResult, sizeof(char*)*res.nData ); if( azNew==0 ){ sqlite3_free_table(&res.azResult[1]); db->errCode = SQLITE_NOMEM; return SQLITE_NOMEM_BKPT; } res.azResult = azNew; } *pazResult = &res.azResult[1]; if( pnColumn ) *pnColumn = res.nColumn; if( pnRow ) *pnRow = res.nRow; return rc; }