vdbe.c

一个小型的嵌入式数据库

  if( pTos->flags & MEM_Int ){
    v = pTos->i + (pOp->p1!=0);
  }else{
    Realify(pTos);
    v = (int)pTos->r;
    if( pTos->r>(double)v ) v++;
    if( pOp->p1 && pTos->r==(double)v ) v++;
  }
  Release(pTos);
  pTos->i = v;
  pTos->flags = MEM_Int;
  break;
}

/* Opcode: MustBeInt P1 P2 *
** 
** Force the top of the stack to be an integer.  If the top of the
** stack is not an integer and cannot be converted into an integer
** with out data loss, then jump immediately to P2, or if P2==0
** raise an SQLITE_MISMATCH exception.
**
** If the top of the stack is not an integer and P2 is not zero and
** P1 is 1, then the stack is popped.  In all other cases, the depth
** of the stack is unchanged.
*/
case OP_MustBeInt: {
  assert( pTos>=p->aStack );
  applyAffinity(pTos, SQLITE_AFF_INTEGER, db->enc);
  if( (pTos->flags & MEM_Int)==0 ){
    if( pOp->p2==0 ){
      rc = SQLITE_MISMATCH;
      goto abort_due_to_error;
    }else{
      if( pOp->p1 ) popStack(&pTos, 1);
      pc = pOp->p2 - 1;
    }
  }else{
    Release(pTos);
    pTos->flags = MEM_Int;
  }
  break;
}

/* Opcode: Eq P1 P2 P3
**
** Pop the top two elements from the stack.  If they are equal, then
** jump to instruction P2.  Otherwise, continue to the next instruction.
**
** The least significant byte of P1 may be either 0x00 or 0x01. If either
** operand is NULL (and thus if the result is unknown) then take the jump
** only if the least significant byte of P1 is 0x01.
**
** The second least significant byte of P1 must be an affinity character -
** 'n', 't', 'i' or 'o' - or 0x00. An attempt is made to coerce both values
** according to the affinity before the comparison is made. If the byte is
** 0x00, then numeric affinity is used.
**
** Once any conversions have taken place, and neither value is NULL, 
** the values are compared. If both values are blobs, or both are text,
** then memcmp() is used to determine the results of the comparison. If
** both values are numeric, then a numeric comparison is used. If the
** two values are of different types, then they are inequal.
**
** If P2 is zero, do not jump.  Instead, push an integer 1 onto the
** stack if the jump would have been taken, or a 0 if not.  Push a
** NULL if either operand was NULL.
**
** If P3 is not NULL it is a pointer to a collating sequence (a CollSeq
** structure) that defines how to compare text.
*/
/* Opcode: Ne P1 P2 P3
**
** This works just like the Eq opcode except that the jump is taken if
** the operands from the stack are not equal.  See the Eq opcode for
** additional information.
*/
/* Opcode: Lt P1 P2 P3
**
** This works just like the Eq opcode except that the jump is taken if
** the 2nd element down on the stack is less than the top of the stack.
** See the Eq opcode for additional information.
*/
/* Opcode: Le P1 P2 P3
**
** This works just like the Eq opcode except that the jump is taken if
** the 2nd element down on the stack is less than or equal to the
** top of the stack.  See the Eq opcode for additional information.
*/
/* Opcode: Gt P1 P2 P3
**
** This works just like the Eq opcode except that the jump is taken if
** the 2nd element down on the stack is greater than the top of the stack.
** See the Eq opcode for additional information.
*/
/* Opcode: Ge P1 P2 P3
**
** This works just like the Eq opcode except that the jump is taken if
** the 2nd element down on the stack is greater than or equal to the
** top of the stack.  See the Eq opcode for additional information.
*/
case OP_Eq:               /* same as TK_EQ */
case OP_Ne:               /* same as TK_NE */
case OP_Lt:               /* same as TK_LT */
case OP_Le:               /* same as TK_LE */
case OP_Gt:               /* same as TK_GT */
case OP_Ge: {             /* same as TK_GE */
  Mem *pNos;
  int flags;
  int res;
  char affinity;

  pNos = &pTos[-1];
  flags = pTos->flags|pNos->flags;

  /* If either value is a NULL P2 is not zero, take the jump if the least
  ** significant byte of P1 is true. If P2 is zero, then push a NULL onto
  ** the stack.
  */
  if( flags&MEM_Null ){
    popStack(&pTos, 2);
    if( pOp->p2 ){
      if( (pOp->p1&0xFF) ) pc = pOp->p2-1;
    }else{
      pTos++;
      pTos->flags = MEM_Null;
    }
    break;
  }

  affinity = (pOp->p1>>8)&0xFF;
  if( affinity ){
    applyAffinity(pNos, affinity, db->enc);
    applyAffinity(pTos, affinity, db->enc);
  }

  assert( pOp->p3type==P3_COLLSEQ || pOp->p3==0 );
  res = sqlite3MemCompare(pNos, pTos, (CollSeq*)pOp->p3);
  switch( pOp->opcode ){
    case OP_Eq:    res = res==0;     break;
    case OP_Ne:    res = res!=0;     break;
    case OP_Lt:    res = res<0;      break;
    case OP_Le:    res = res<=0;     break;
    case OP_Gt:    res = res>0;      break;
    default:       res = res>=0;     break;
  }

  popStack(&pTos, 2);
  if( pOp->p2 ){
    if( res ){
      pc = pOp->p2-1;
    }
  }else{
    pTos++;
    pTos->flags = MEM_Int;
    pTos->i = res;
  }
  break;
}

/* Opcode: And * * *
**
** Pop two values off the stack.  Take the logical AND of the
** two values and push the resulting boolean value back onto the
** stack. 
*/
/* Opcode: Or * * *
**
** Pop two values off the stack.  Take the logical OR of the
** two values and push the resulting boolean value back onto the
** stack. 
*/
case OP_And:              /* same as TK_AND */
case OP_Or: {             /* same as TK_OR */
  Mem *pNos = &pTos[-1];
  int v1, v2;    /* 0==TRUE, 1==FALSE, 2==UNKNOWN or NULL */

  assert( pNos>=p->aStack );
  if( pTos->flags & MEM_Null ){
    v1 = 2;
  }else{
    Integerify(pTos);
    v1 = pTos->i==0;
  }
  if( pNos->flags & MEM_Null ){
    v2 = 2;
  }else{
    Integerify(pNos);
    v2 = pNos->i==0;
  }
  if( pOp->opcode==OP_And ){
    static const unsigned char and_logic[] = { 0, 1, 2, 1, 1, 1, 2, 1, 2 };
    v1 = and_logic[v1*3+v2];
  }else{
    static const unsigned char or_logic[] = { 0, 0, 0, 0, 1, 2, 0, 2, 2 };
    v1 = or_logic[v1*3+v2];
  }
  popStack(&pTos, 2);
  pTos++;
  if( v1==2 ){
    pTos->flags = MEM_Null;
  }else{
    pTos->i = v1==0;
    pTos->flags = MEM_Int;
  }
  break;
}

/* Opcode: Negative * * *
**
** Treat the top of the stack as a numeric quantity.  Replace it
** with its additive inverse.  If the top of the stack is NULL
** its value is unchanged.
*/
/* Opcode: AbsValue * * *
**
** Treat the top of the stack as a numeric quantity.  Replace it
** with its absolute value. If the top of the stack is NULL
** its value is unchanged.
*/
case OP_Negative:              /* same as TK_UMINUS */
case OP_AbsValue: {
  assert( pTos>=p->aStack );
  if( pTos->flags & MEM_Real ){
    Release(pTos);
    if( pOp->opcode==OP_Negative || pTos->r<0.0 ){
      pTos->r = -pTos->r;
    }
    pTos->flags = MEM_Real;
  }else if( pTos->flags & MEM_Int ){
    Release(pTos);
    if( pOp->opcode==OP_Negative || pTos->i<0 ){
      pTos->i = -pTos->i;
    }
    pTos->flags = MEM_Int;
  }else if( pTos->flags & MEM_Null ){
    /* Do nothing */
  }else{
    Realify(pTos);
    if( pOp->opcode==OP_Negative || pTos->r<0.0 ){
      pTos->r = -pTos->r;
    }
    pTos->flags = MEM_Real;
  }
  break;
}

/* Opcode: Not * * *
**
** Interpret the top of the stack as a boolean value.  Replace it
** with its complement.  If the top of the stack is NULL its value
** is unchanged.
*/
case OP_Not: {                /* same as TK_NOT */
  assert( pTos>=p->aStack );
  if( pTos->flags & MEM_Null ) break;  /* Do nothing to NULLs */
  Integerify(pTos);
  assert( (pTos->flags & MEM_Dyn)==0 );
  pTos->i = !pTos->i;
  pTos->flags = MEM_Int;
  break;
}

/* Opcode: BitNot * * *
**
** Interpret the top of the stack as an value.  Replace it
** with its ones-complement.  If the top of the stack is NULL its
** value is unchanged.
*/
case OP_BitNot: {             /* same as TK_BITNOT */
  assert( pTos>=p->aStack );
  if( pTos->flags & MEM_Null ) break;  /* Do nothing to NULLs */
  Integerify(pTos);
  assert( (pTos->flags & MEM_Dyn)==0 );
  pTos->i = ~pTos->i;
  pTos->flags = MEM_Int;
  break;
}

/* Opcode: Noop * * *
**
** Do nothing.  This instruction is often useful as a jump
** destination.
*/
case OP_Noop: {
  break;
}

/* Opcode: If P1 P2 *
**
** Pop a single boolean from the stack.  If the boolean popped is
** true, 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.
*/
/* 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:
case OP_IfNot: {
  int c;
  assert( pTos>=p->aStack );
  if( pTos->flags & MEM_Null ){
    c = pOp->p1;
  }else{
    c = sqlite3VdbeIntValue(pTos);
    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 */
  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 */
  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: {
  Cursor *pC;
  assert( (pOp->p1)<p->nCursor );
  assert( p->apCsr[pOp->p1]!=0 );
  pC = p->apCsr[pOp->p1];
  pC->nField = pOp->p2;
  if( (!pC->keyAsData && pC->zeroData) || (pC->keyAsData && pC->intKey) ){
    rc = SQLITE_CORRUPT;
    goto abort_due_to_error;
  }
  break;
}

/* Opcode: Column P1 P2 *
**
** 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.
*/
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.