vdbe.c

sqlite-3.4.1,嵌入式数据库.是一个功能强大的开源数据库,给学习和研发以及小型公司的发展带来了全所未有的好处.

case OP_Blob: {
  pTos++;
  assert( pOp->p1 < SQLITE_MAX_LENGTH ); /* Due to SQLITE_MAX_SQL_LENGTH */
  sqlite3VdbeMemSetStr(pTos, pOp->p3, pOp->p1, 0, 0);
  pTos->enc = encoding;
  break;
}
#endif /* SQLITE_OMIT_BLOB_LITERAL */

/* Opcode: Variable P1 * *
**
** Push the value of variable P1 onto the stack.  A variable is
** an unknown in the original SQL string as handed to sqlite3_compile().
** Any occurance of the '?' character in the original SQL is considered
** a variable.  Variables in the SQL string are number from left to
** right beginning with 1.  The values of variables are set using the
** sqlite3_bind() API.
*/
case OP_Variable: {
  int j = pOp->p1 - 1;
  Mem *pVar;
  assert( j>=0 && j<p->nVar );

  pVar = &p->aVar[j];
  if( sqlite3VdbeMemTooBig(pVar) ){
    goto too_big;
  }
  pTos++;
  sqlite3VdbeMemShallowCopy(pTos, &p->aVar[j], MEM_Static);
  break;
}

/* Opcode: Pop P1 * *
**
** P1 elements are popped off of the top of stack and discarded.
*/
case OP_Pop: {            /* no-push */
  assert( pOp->p1>=0 );
  popStack(&pTos, pOp->p1);
  assert( pTos>=&p->aStack[-1] );
  break;
}

/* Opcode: Dup P1 P2 *
**
** A copy of the P1-th element of the stack 
** is made and pushed onto the top of the stack.
** The top of the stack is element 0.  So the
** instruction "Dup 0 0 0" will make a copy of the
** top of the stack.
**
** If the content of the P1-th element is a dynamically
** allocated string, then a new copy of that string
** is made if P2==0.  If P2!=0, then just a pointer
** to the string is copied.
**
** Also see the Pull instruction.
*/
case OP_Dup: {
  Mem *pFrom = &pTos[-pOp->p1];
  assert( pFrom<=pTos && pFrom>=p->aStack );
  pTos++;
  sqlite3VdbeMemShallowCopy(pTos, pFrom, MEM_Ephem);
  if( pOp->p2 ){
    Deephemeralize(pTos);
  }
  break;
}

/* Opcode: Pull P1 * *
**
** The P1-th element is removed from its current location on 
** the stack and pushed back on top of the stack.  The
** top of the stack is element 0, so "Pull 0 0 0" is
** a no-op.  "Pull 1 0 0" swaps the top two elements of
** the stack.
**
** See also the Dup instruction.
*/
case OP_Pull: {            /* no-push */
  Mem *pFrom = &pTos[-pOp->p1];
  int i;
  Mem ts;

  ts = *pFrom;
  Deephemeralize(pTos);
  for(i=0; i<pOp->p1; i++, pFrom++){
    Deephemeralize(&pFrom[1]);
    assert( (pFrom[1].flags & MEM_Ephem)==0 );
    *pFrom = pFrom[1];
    if( pFrom->flags & MEM_Short ){
      assert( pFrom->flags & (MEM_Str|MEM_Blob) );
      assert( pFrom->z==pFrom[1].zShort );
      pFrom->z = pFrom->zShort;
    }
  }
  *pTos = ts;
  if( pTos->flags & MEM_Short ){
    assert( pTos->flags & (MEM_Str|MEM_Blob) );
    assert( pTos->z==pTos[-pOp->p1].zShort );
    pTos->z = pTos->zShort;
  }
  break;
}

/* Opcode: Push P1 * *
**
** Overwrite the value of the P1-th element down on the
** stack (P1==0 is the top of the stack) with the value
** of the top of the stack.  Then pop the top of the stack.
*/
case OP_Push: {            /* no-push */
  Mem *pTo = &pTos[-pOp->p1];

  assert( pTo>=p->aStack );
  sqlite3VdbeMemMove(pTo, pTos);
  pTos--;
  break;
}

/* Opcode: Callback P1 * *
**
** The top P1 values on the stack represent a single result row from
** a query.  This opcode causes the sqlite3_step() call to terminate
** with an SQLITE_ROW return code and it sets up the sqlite3_stmt
** structure to provide access to the top P1 values as the result
** row.  When the sqlite3_step() function is run again, the top P1
** values will be automatically popped from the stack before the next
** instruction executes.
*/
case OP_Callback: {            /* no-push */
  Mem *pMem;
  Mem *pFirstColumn;
  assert( p->nResColumn==pOp->p1 );

  /* Data in the pager might be moved or changed out from under us
  ** in between the return from this sqlite3_step() call and the
  ** next call to sqlite3_step().  So deephermeralize everything on 
  ** the stack.  Note that ephemeral data is never stored in memory 
  ** cells so we do not have to worry about them.
  */
  pFirstColumn = &pTos[0-pOp->p1];
  for(pMem = p->aStack; pMem<pFirstColumn; pMem++){
    Deephemeralize(pMem);
  }

  /* Invalidate all ephemeral cursor row caches */
  p->cacheCtr = (p->cacheCtr + 2)|1;

  /* Make sure the results of the current row are \000 terminated
  ** and have an assigned type.  The results are deephemeralized as
  ** as side effect.
  */
  for(; pMem<=pTos; pMem++ ){
    sqlite3VdbeMemNulTerminate(pMem);
    storeTypeInfo(pMem, encoding);
  }

  /* Set up the statement structure so that it will pop the current
  ** results from the stack when the statement returns.
  */
  p->resOnStack = 1;
  p->nCallback++;
  p->popStack = pOp->p1;
  p->pc = pc + 1;
  p->pTos = pTos;
  return SQLITE_ROW;
}

/* Opcode: Concat P1 P2 *
**
** Look at the first P1+2 elements of the stack.  Append them all 
** together with the lowest element first.  The original P1+2 elements
** are popped from the stack if P2==0 and retained if P2==1.  If
** any element of the stack is NULL, then the result is NULL.
**
** When P1==1, this routine makes a copy of the top stack element
** into memory obtained from sqliteMalloc().
*/
case OP_Concat: {           /* same as TK_CONCAT */
  char *zNew;
  i64 nByte;
  int nField;
  int i, j;
  Mem *pTerm;

  /* Loop through the stack elements to see how long the result will be. */
  nField = pOp->p1 + 2;
  pTerm = &pTos[1-nField];
  nByte = 0;
  for(i=0; i<nField; i++, pTerm++){
    assert( pOp->p2==0 || (pTerm->flags&MEM_Str) );
    if( pTerm->flags&MEM_Null ){
      nByte = -1;
      break;
    }
    ExpandBlob(pTerm);
    Stringify(pTerm, encoding);
    nByte += pTerm->n;
  }

  if( nByte<0 ){
    /* If nByte is less than zero, then there is a NULL value on the stack.
    ** In this case just pop the values off the stack (if required) and
    ** push on a NULL.
    */
    if( pOp->p2==0 ){
      popStack(&pTos, nField);
    }
    pTos++;
    pTos->flags = MEM_Null;
  }else{
    /* Otherwise malloc() space for the result and concatenate all the
    ** stack values.
    */
    if( nByte+2>SQLITE_MAX_LENGTH ){
      goto too_big;
    }
    zNew = sqliteMallocRaw( nByte+2 );
    if( zNew==0 ) goto no_mem;
    j = 0;
    pTerm = &pTos[1-nField];
    for(i=j=0; i<nField; i++, pTerm++){
      int n = pTerm->n;
      assert( pTerm->flags & (MEM_Str|MEM_Blob) );
      memcpy(&zNew[j], pTerm->z, n);
      j += n;
    }
    zNew[j] = 0;
    zNew[j+1] = 0;
    assert( j==nByte );

    if( pOp->p2==0 ){
      popStack(&pTos, nField);
    }
    pTos++;
    pTos->n = j;
    pTos->flags = MEM_Str|MEM_Dyn|MEM_Term;
    pTos->xDel = 0;
    pTos->enc = encoding;
    pTos->z = zNew;
  }
  break;
}

/* Opcode: Add * * *
**
** Pop the top two elements from the stack, add them together,
** and push the result back onto the stack.  If either element
** is a string then it is converted to a double using the atof()
** function before the addition.
** If either operand is NULL, the result is NULL.
*/
/* Opcode: Multiply * * *
**
** Pop the top two elements from the stack, multiply them together,
** and push the result back onto the stack.  If either element
** is a string then it is converted to a double using the atof()
** function before the multiplication.
** If either operand is NULL, the result is NULL.
*/
/* Opcode: Subtract * * *
**
** Pop the top two elements from the stack, subtract the
** first (what was on top of the stack) from the second (the
** next on stack)
** and push the result back onto the stack.  If either element
** is a string then it is converted to a double using the atof()
** function before the subtraction.
** If either operand is NULL, the result is NULL.
*/
/* Opcode: Divide * * *
**
** Pop the top two elements from the stack, divide the
** first (what was on top of the stack) from the second (the
** next on stack)
** and push the result back onto the stack.  If either element
** is a string then it is converted to a double using the atof()
** function before the division.  Division by zero returns NULL.
** If either operand is NULL, the result is NULL.
*/
/* Opcode: Remainder * * *
**
** Pop the top two elements from the stack, divide the
** first (what was on top of the stack) from the second (the
** next on stack)
** and push the remainder after division onto the stack.  If either element
** is a string then it is converted to a double using the atof()
** function before the division.  Division by zero returns NULL.
** If either operand is NULL, the result is NULL.
*/
case OP_Add:                   /* same as TK_PLUS, no-push */
case OP_Subtract:              /* same as TK_MINUS, no-push */
case OP_Multiply:              /* same as TK_STAR, no-push */
case OP_Divide:                /* same as TK_SLASH, no-push */
case OP_Remainder: {           /* same as TK_REM, no-push */
  Mem *pNos = &pTos[-1];
  int flags;
  assert( pNos>=p->aStack );
  flags = pTos->flags | pNos->flags;
  if( (flags & MEM_Null)!=0 ){
    Release(pTos);
    pTos--;
    Release(pTos);
    pTos->flags = MEM_Null;
  }else if( (pTos->flags & pNos->flags & MEM_Int)==MEM_Int ){
    i64 a, b;
    a = pTos->u.i;
    b = pNos->u.i;
    switch( pOp->opcode ){
      case OP_Add:         b += a;       break;
      case OP_Subtract:    b -= a;       break;
      case OP_Multiply:    b *= a;       break;
      case OP_Divide: {
        if( a==0 ) goto divide_by_zero;
        /* Dividing the largest possible negative 64-bit integer (1<<63) by 
        ** -1 returns an integer to large to store in a 64-bit data-type. On
        ** some architectures, the value overflows to (1<<63). On others,
        ** a SIGFPE is issued. The following statement normalizes this
        ** behaviour so that all architectures behave as if integer 
        ** overflow occured.
        */
        if( a==-1 && b==(((i64)1)<<63) ) a = 1;
        b /= a;
        break;
      }
      default: {
        if( a==0 ) goto divide_by_zero;
        if( a==-1 ) a = 1;
        b %= a;
        break;
      }
    }
    Release(pTos);
    pTos--;
    Release(pTos);
    pTos->u.i = b;
    pTos->flags = MEM_Int;
  }else{
    double a, b;
    a = sqlite3VdbeRealValue(pTos);
    b = sqlite3VdbeRealValue(pNos);
    switch( pOp->opcode ){
      case OP_Add:         b += a;       break;
      case OP_Subtract:    b -= a;       break;
      case OP_Multiply:    b *= a;       break;
      case OP_Divide: {
        if( a==0.0 ) goto divide_by_zero;
        b /= a;
        break;
      }
      default: {
        i64 ia = (i64)a;
        i64 ib = (i64)b;
        if( ia==0 ) goto divide_by_zero;
        if( ia==-1 ) ia = 1;
        b = ib % ia;
        break;
      }
    }
    if( sqlite3_isnan(b) ){
      goto divide_by_zero;
    }
    Release(pTos);
    pTos--;
    Release(pTos);
    pTos->r = b;
    pTos->flags = MEM_Real;
    if( (flags & MEM_Real)==0 ){
      sqlite3VdbeIntegerAffinity(pTos);
    }
  }
  break;

divide_by_zero:
  Release(pTos);
  pTos--;
  Release(pTos);
  pTos->flags = MEM_Null;
  break;
}

/* Opcode: CollSeq * * P3
**
** P3 is a pointer to a CollSeq struct. If the next call to a user function
** or aggregate calls sqlite3GetFuncCollSeq(), this collation sequence will
** be returned. This is used by the built-in min(), max() and nullif()
** functions.
**
** The interface used by the implementation of the aforementioned functions
** to retrieve the collation sequence set by this opcode is not available
** publicly, only to user functions defined in func.c.
*/
case OP_CollSeq: {             /* no-push */
  assert( pOp->p3type==P3_COLLSEQ );
  break;
}

/* Opcode: Function P1 P2 P3
**
** Invoke a user function (P3 is a pointer to a Function structure that
** defines the function) with P2 arguments taken from the stack.  Pop all
** arguments from the stack and push back the result.
**
** P1 is a 32-bit bitmask indicating whether or not each argument to the 
** function was determined to be constant at compile time. If the first
** argument was constant then bit 0 of P1 is set. This is used to determine
** whether meta data associated with a user function argument using the
** sqlite3_set_auxdata() API may be safely retained until the next
** invocation of this opcode.
**
** See also: AggStep and AggFinal
*/
case OP_Function: {
  int i;
  Mem *pArg;
  sqlite3_context ctx;
  sqlite3_value **apVal;
  int n = pOp->p2;