vdbe.c

调用sqlite开源数据的小程序

** false if it has zero length and true otherwise.
**
** If the value popped of the stack is NULL, then take the jump if P1
** is true and fall through if P1 is false.
*/
/* Opcode: IfNot P1 P2 *
**
** Pop a single boolean from the stack.  If the boolean popped is
** false, then jump to p2.  Otherwise continue to the next instruction.
** An integer is false if zero and true otherwise.  A string is
** false if it has zero length and true otherwise.
**
** If the value popped of the stack is NULL, then take the jump if P1
** is true and fall through if P1 is false.
*/
case OP_If:                 /* no-push */
case OP_IfNot: {            /* no-push */
  int c;
  assert( pTos>=p->aStack );
  if( pTos->flags & MEM_Null ){
    c = pOp->p1;
  }else{
#ifdef SQLITE_OMIT_FLOATING_POINT
    c = sqlite3VdbeIntValue(pTos);
#else
    c = sqlite3VdbeRealValue(pTos)!=0.0;
#endif
    if( pOp->opcode==OP_IfNot ) c = !c;
  }
  Release(pTos);
  pTos--;
  if( c ) pc = pOp->p2-1;
  break;
}

/* Opcode: IsNull P1 P2 *
**
** If any of the top abs(P1) values on the stack are NULL, then jump
** to P2.  Pop the stack P1 times if P1>0.   If P1<0 leave the stack
** unchanged.
*/
case OP_IsNull: {            /* same as TK_ISNULL, no-push */
  int i, cnt;
  Mem *pTerm;
  cnt = pOp->p1;
  if( cnt<0 ) cnt = -cnt;
  pTerm = &pTos[1-cnt];
  assert( pTerm>=p->aStack );
  for(i=0; i<cnt; i++, pTerm++){
    if( pTerm->flags & MEM_Null ){
      pc = pOp->p2-1;
      break;
    }
  }
  if( pOp->p1>0 ) popStack(&pTos, cnt);
  break;
}

/* Opcode: NotNull P1 P2 *
**
** Jump to P2 if the top P1 values on the stack are all not NULL.  Pop the
** stack if P1 times if P1 is greater than zero.  If P1 is less than
** zero then leave the stack unchanged.
*/
case OP_NotNull: {            /* same as TK_NOTNULL, no-push */
  int i, cnt;
  cnt = pOp->p1;
  if( cnt<0 ) cnt = -cnt;
  assert( &pTos[1-cnt] >= p->aStack );
  for(i=0; i<cnt && (pTos[1+i-cnt].flags & MEM_Null)==0; i++){}
  if( i>=cnt ) pc = pOp->p2-1;
  if( pOp->p1>0 ) popStack(&pTos, cnt);
  break;
}

/* Opcode: SetNumColumns P1 P2 *
**
** Before the OP_Column opcode can be executed on a cursor, this
** opcode must be called to set the number of fields in the table.
**
** This opcode sets the number of columns for cursor P1 to P2.
**
** If OP_KeyAsData is to be applied to cursor P1, it must be executed
** before this op-code.
*/
case OP_SetNumColumns: {       /* no-push */
  Cursor *pC;
  assert( (pOp->p1)<p->nCursor );
  assert( p->apCsr[pOp->p1]!=0 );
  pC = p->apCsr[pOp->p1];
  pC->nField = pOp->p2;
  break;
}

/* Opcode: Column P1 P2 P3
**
** Interpret the data that cursor P1 points to as a structure built using
** the MakeRecord instruction.  (See the MakeRecord opcode for additional
** information about the format of the data.) Push onto the stack the value
** of the P2-th column contained in the data. If there are less that (P2+1) 
** values in the record, push a NULL onto the stack.
**
** If the KeyAsData opcode has previously executed on this cursor, then the
** field might be extracted from the key rather than the data.
**
** If P1 is negative, then the record is stored on the stack rather than in
** a table.  For P1==-1, the top of the stack is used.  For P1==-2, the
** next on the stack is used.  And so forth.  The value pushed is always
** just a pointer into the record which is stored further down on the
** stack.  The column value is not copied. The number of columns in the
** record is stored on the stack just above the record itself.
**
** If the column contains fewer than P2 fields, then push a NULL.  Or
** if P3 is of type P3_MEM, then push the P3 value.  The P3 value will
** be default value for a column that has been added using the ALTER TABLE
** ADD COLUMN command.  If P3 is an ordinary string, just push a NULL.
** When P3 is a string it is really just a comment describing the value
** to be pushed, not a default value.
*/
case OP_Column: {
  u32 payloadSize;   /* Number of bytes in the record */
  int p1 = pOp->p1;  /* P1 value of the opcode */
  int p2 = pOp->p2;  /* column number to retrieve */
  Cursor *pC = 0;    /* The VDBE cursor */
  char *zRec;        /* Pointer to complete record-data */
  BtCursor *pCrsr;   /* The BTree cursor */
  u32 *aType;        /* aType[i] holds the numeric type of the i-th column */
  u32 *aOffset;      /* aOffset[i] is offset to start of data for i-th column */
  u32 nField;        /* number of fields in the record */
  u32 szHdr;         /* Number of bytes in the record header */
  int len;           /* The length of the serialized data for the column */
  int offset = 0;    /* Offset into the data */
  int idx;           /* Index into the header */
  int i;             /* Loop counter */
  char *zData;       /* Part of the record being decoded */
  Mem sMem;          /* For storing the record being decoded */

  sMem.flags = 0;
  assert( p1<p->nCursor );
  pTos++;
  pTos->flags = MEM_Null;

  /* This block sets the variable payloadSize to be the total number of
  ** bytes in the record.
  **
  ** zRec is set to be the complete text of the record if it is available.
  ** The complete record text is always available for pseudo-tables and
  ** when we are decoded a record from the stack.  If the record is stored
  ** in a cursor, the complete record text might be available in the 
  ** pC->aRow cache.  Or it might not be.  If the data is unavailable,
  ** zRec is set to NULL.
  **
  ** We also compute the number of columns in the record.  For cursors,
  ** the number of columns is stored in the Cursor.nField element.  For
  ** records on the stack, the next entry down on the stack is an integer
  ** which is the number of records.
  */
  assert( p1<0 || p->apCsr[p1]!=0 );
  if( p1<0 ){
    /* Take the record off of the stack */
    Mem *pRec = &pTos[p1];
    Mem *pCnt = &pRec[-1];
    assert( pRec>=p->aStack );
    assert( pRec->flags & MEM_Blob );
    payloadSize = pRec->n;
    zRec = pRec->z;
    assert( pCnt>=p->aStack );
    assert( pCnt->flags & MEM_Int );
    nField = pCnt->i;
    pCrsr = 0;
  }else if( (pC = p->apCsr[p1])->pCursor!=0 ){
    /* The record is stored in a B-Tree */
    rc = sqlite3VdbeCursorMoveto(pC);
    if( rc ) goto abort_due_to_error;
    zRec = 0;
    pCrsr = pC->pCursor;
    if( pC->nullRow ){
      payloadSize = 0;
    }else if( pC->cacheValid ){
      payloadSize = pC->payloadSize;
      zRec = pC->aRow;
    }else if( pC->isIndex ){
      i64 payloadSize64;
      sqlite3BtreeKeySize(pCrsr, &payloadSize64);
      payloadSize = payloadSize64;
    }else{
      sqlite3BtreeDataSize(pCrsr, &payloadSize);
    }
    nField = pC->nField;
#ifndef SQLITE_OMIT_TRIGGER
  }else if( pC->pseudoTable ){
    /* The record is the sole entry of a pseudo-table */
    payloadSize = pC->nData;
    zRec = pC->pData;
    pC->cacheValid = 0;
    assert( payloadSize==0 || zRec!=0 );
    nField = pC->nField;
    pCrsr = 0;
#endif
  }else{
    zRec = 0;
    payloadSize = 0;
    pCrsr = 0;
    nField = 0;
  }

  /* If payloadSize is 0, then just push a NULL onto the stack. */
  if( payloadSize==0 ){
    pTos->flags = MEM_Null;
    break;
  }

  assert( p2<nField );

  /* Read and parse the table header.  Store the results of the parse
  ** into the record header cache fields of the cursor.
  */
  if( pC && pC->cacheValid ){
    aType = pC->aType;
    aOffset = pC->aOffset;
  }else{
    int avail;    /* Number of bytes of available data */
    if( pC && pC->aType ){
      aType = pC->aType;
    }else{
      aType = sqliteMallocRaw( 2*nField*sizeof(aType) );
    }
    aOffset = &aType[nField];
    if( aType==0 ){
      goto no_mem;
    }

    /* Figure out how many bytes are in the header */
    if( zRec ){
      zData = zRec;
    }else{
      if( pC->isIndex ){
        zData = (char*)sqlite3BtreeKeyFetch(pCrsr, &avail);
      }else{
        zData = (char*)sqlite3BtreeDataFetch(pCrsr, &avail);
      }
      /* If KeyFetch()/DataFetch() managed to get the entire payload,
      ** save the payload in the pC->aRow cache.  That will save us from
      ** having to make additional calls to fetch the content portion of
      ** the record.
      */
      if( avail>=payloadSize ){
        zRec = pC->aRow = zData;
      }else{
        pC->aRow = 0;
      }
    }
    idx = sqlite3GetVarint32(zData, &szHdr);


    /* The KeyFetch() or DataFetch() above are fast and will get the entire
    ** record header in most cases.  But they will fail to get the complete
    ** record header if the record header does not fit on a single page
    ** in the B-Tree.  When that happens, use sqlite3VdbeMemFromBtree() to
    ** acquire the complete header text.
    */
    if( !zRec && avail<szHdr ){
      rc = sqlite3VdbeMemFromBtree(pCrsr, 0, szHdr, pC->isIndex, &sMem);
      if( rc!=SQLITE_OK ){
        goto op_column_out;
      }
      zData = sMem.z;
    }

    /* Scan the header and use it to fill in the aType[] and aOffset[]
    ** arrays.  aType[i] will contain the type integer for the i-th
    ** column and aOffset[i] will contain the offset from the beginning
    ** of the record to the start of the data for the i-th column
    */
    offset = szHdr;
    assert( offset>0 );
    i = 0;
    while( idx<szHdr && i<nField && offset<=payloadSize ){
      aOffset[i] = offset;
      idx += sqlite3GetVarint32(&zData[idx], &aType[i]);
      offset += sqlite3VdbeSerialTypeLen(aType[i]);
      i++;
    }
    Release(&sMem);
    sMem.flags = MEM_Null;

    /* If i is less that nField, then there are less fields in this
    ** record than SetNumColumns indicated there are columns in the
    ** table. Set the offset for any extra columns not present in
    ** the record to 0. This tells code below to push a NULL onto the
    ** stack instead of deserializing a value from the record.
    */
    while( i<nField ){
      aOffset[i++] = 0;
    }

    /* The header should end at the start of data and the data should
    ** end at last byte of the record. If this is not the case then
    ** we are dealing with a malformed record.
    */
    if( idx!=szHdr || offset!=payloadSize ){
      rc = SQLITE_CORRUPT_BKPT;
      goto op_column_out;
    }

    /* Remember all aType and aColumn information if we have a cursor
    ** to remember it in. */
    if( pC ){
      pC->payloadSize = payloadSize;
      pC->aType = aType;
      pC->aOffset = aOffset;
      pC->cacheValid = 1;
    }
  }

  /* Get the column information. If aOffset[p2] is non-zero, then 
  ** deserialize the value from the record. If aOffset[p2] is zero,
  ** then there are not enough fields in the record to satisfy the
  ** request.  In this case, set the value NULL or to P3 if P3 is
  ** a pointer to a Mem object.
  */
  if( aOffset[p2] ){
    assert( rc==SQLITE_OK );
    if( zRec ){
      zData = &zRec[aOffset[p2]];
    }else{
      len = sqlite3VdbeSerialTypeLen(aType[p2]);
      rc = sqlite3VdbeMemFromBtree(pCrsr, aOffset[p2], len, pC->isIndex,&sMem);
      if( rc!=SQLITE_OK ){
        goto op_column_out;
      }
      zData = sMem.z;
    }
    sqlite3VdbeSerialGet(zData, aType[p2], pTos);
    pTos->enc = db->enc;
  }else{
    if( pOp->p3type==P3_MEM ){
      sqlite3VdbeMemShallowCopy(pTos, (Mem *)(pOp->p3), MEM_Static);
    }else{
      pTos->flags = MEM_Null;
    }
  }

  /* If we dynamically allocated space to hold the data (in the
  ** sqlite3VdbeMemFromBtree() call above) then transfer control of that
  ** dynamically allocated space over to the pTos structure rather.
  ** This prevents a memory copy.
  */
  if( (sMem.flags & MEM_Dyn)!=0 ){
    assert( pTos->flags & MEM_Ephem );
    assert( pTos->flags & (MEM_Str|MEM_Blob) );
    assert( pTos->z==sMem.z );
    assert( sMem.flags & MEM_Term );
    pTos->flags &= ~MEM_Ephem;
    pTos->flags |= MEM_Dyn|MEM_Term;
  }

  /* pTos->z might be pointing to sMem.zShort[].  Fix that so that we
  ** can abandon sMem */
  rc = sqlite3VdbeMemMakeWriteable(pTos);

op_column_out:
  /* Release the aType[] memory if we are not dealing with cursor */
  if( !pC || !pC->aType ){
    sqliteFree(aType);
  }
  break;
}

/* Opcode: MakeRecord P1 P2 P3
**
** Convert the top abs(P1) entries of the stack into a single entry
** suitable for use as a data record in a database table or as a key
** in an index.  The details of the format are irrelavant as long as
** the OP_Column opcode can decode the record later and as long as the
** sqlite3VdbeRecordCompare function will correctly compare two encoded
** records.  Refer to source code comments for the details of the record
** format.
**
** The original stack entries are popped from the stack if P1>0 but
** remain on the stack if P1<0.
**
** If P2 is not zero and one or more of the entries are NULL, then jump
** to the address given by P2.  This feature can be used to skip a
** uniqueness test on indices.
**
** P3 may be a string that is P1 characters long.  The nth character of the
** string indicates the column affinity that should be used for the nth
** field of the index key (i.e. the first character of P3 corresponds to the
** lowest element on the stack).
**
** The mapping from character to affinity is as follows:
**    'n' = NUMERIC.
**    'i' = INTEGER.
**    't' = TEXT.
**    'o' = NONE.
**
** If P3 is NULL then all index fields have the affinity NONE.
**
** See also OP_MakeIdxRec
*/
/* Opcode: MakeRecordI P1 P2 P3
**
** This opcode works just OP_MakeRecord except that it reads an extra
** integer from the stack (thus reading a total of abs(P1+1) entries)
** and appends that extra integer to the end of the record as a varint.
** This results in an index key.
*/
case OP_MakeIdxRec:
case OP_MakeRecord: {
  /* Assuming the record contains N fields, the record format looks
  ** like this:
  **
  ** ------------------------------------------------------------------------
  ** | hdr-size | type 0 | type 1 | ... | type N-1 | data0 | ... | data N-1 | 
  ** ------------------------------------------------------------------------
  **
  ** Data(0) is taken from the lowest element of the stack and data(N-1) is
  ** the top of the stack.
  **
  ** Each type field is a varint repr