SQLite

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.301 2004/05/19 11:24:26 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*

      pc = pOp->p2-1;
    }
  }else{
    pTos++;
    pTos->flags = MEM_Int;
    pTos->i = res;
  }
  break;
}
/* INSERT NO CODE HERE!
**
** The opcode numbers are extracted from this source file by doing
**
**    grep '^case OP_' vdbe.c | ... >opcodes.h
**
** The opcodes are numbered in the order that they appear in this file.
** But in order for the expression generating code to work right, the
** string comparison operators that follow must be numbered exactly 6
** greater than the numeric comparison opcodes above.  So no other
** cases can appear between the two.
*/
/* Opcode: StrEq P1 P2 *
**
** Pop the top two elements from the stack.  If they are equal, then
** jump to instruction P2.  Otherwise, continue to the next instruction.
**
** If either operand is NULL (and thus if the result is unknown) then
** take the jump if P1 is true.
**
** The strcmp() library routine is used for the comparison.  For a
** numeric comparison, use OP_Eq.
**
** 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.
*/
/* Opcode: StrNe P1 P2 *
**
** Pop the top two elements from the stack.  If they are not equal, then
** jump to instruction P2.  Otherwise, continue to the next instruction.
**
** If either operand is NULL (and thus if the result is unknown) then
** take the jump if P1 is true.
**
** The strcmp() library routine is used for the comparison.  For a
** numeric comparison, use OP_Ne.
**
** 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.
*/
/* Opcode: StrLt P1 P2 *
**
** Pop the top two elements from the stack.  If second element (the
** next on stack) is less than the first (the top of stack), then
** jump to instruction P2.  Otherwise, continue to the next instruction.
** In other words, jump if NOS<TOS.
**
** If either operand is NULL (and thus if the result is unknown) then
** take the jump if P1 is true.
**
** The strcmp() library routine is used for the comparison.  For a
** numeric comparison, use OP_Lt.
**
** 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.
*/
/* Opcode: StrLe P1 P2 *
**
** Pop the top two elements from the stack.  If second element (the
** next on stack) is less than or equal to the first (the top of stack),
** then jump to instruction P2. In other words, jump if NOS<=TOS.
**
** If either operand is NULL (and thus if the result is unknown) then
** take the jump if P1 is true.
**
** The strcmp() library routine is used for the comparison.  For a
** numeric comparison, use OP_Le.
**
** 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.
*/
/* Opcode: StrGt P1 P2 *
**
** Pop the top two elements from the stack.  If second element (the
** next on stack) is greater than the first (the top of stack),
** then jump to instruction P2. In other words, jump if NOS>TOS.
**
** If either operand is NULL (and thus if the result is unknown) then
** take the jump if P1 is true.
**
** The strcmp() library routine is used for the comparison.  For a
** numeric comparison, use OP_Gt.
**
** 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.
*/
/* Opcode: StrGe P1 P2 *
**
** Pop the top two elements from the stack.  If second element (the next
** on stack) is greater than or equal to the first (the top of stack),
** then jump to instruction P2. In other words, jump if NOS>=TOS.
**
** If either operand is NULL (and thus if the result is unknown) then
** take the jump if P1 is true.
**
** The strcmp() library routine is used for the comparison.  For a
** numeric comparison, use OP_Ge.
**
** 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.
*/
case OP_StrEq:
case OP_StrNe:
case OP_StrLt:
case OP_StrLe:
case OP_StrGt:
case OP_StrGe: {
  Mem *pNos = &pTos[-1];
  int c;
  assert( pNos>=p->aStack );
  if( (pNos->flags | pTos->flags) & MEM_Null ){
    popStack(&pTos, 2);
    if( pOp->p2 ){
      if( pOp->p1 ) pc = pOp->p2-1;
    }else{
      pTos++;
      pTos->flags = MEM_Null;
    }
    break;
  }else{
    Stringify(pTos);
    Stringify(pNos);
    c = strcmp(pNos->z, pTos->z);
  }
  /* The asserts on each case of the following switch are there to verify
  ** that string comparison opcodes are always exactly 6 greater than the
  ** corresponding numeric comparison opcodes.  The code generator depends
  ** on this fact.
  */
  switch( pOp->opcode ){
    case OP_StrEq:    c = c==0;    assert( pOp->opcode-6==OP_Eq );   break;
    case OP_StrNe:    c = c!=0;    assert( pOp->opcode-6==OP_Ne );   break;
    case OP_StrLt:    c = c<0;     assert( pOp->opcode-6==OP_Lt );   break;
    case OP_StrLe:    c = c<=0;    assert( pOp->opcode-6==OP_Le );   break;
    case OP_StrGt:    c = c>0;     assert( pOp->opcode-6==OP_Gt );   break;
    default:          c = c>=0;    assert( pOp->opcode-6==OP_Ge );   break;
  }
  popStack(&pTos, 2);
  if( pOp->p2 ){
    if( c ) pc = pOp->p2-1;
  }else{
    pTos++;
    pTos->flags = MEM_Int;
    pTos->i = c;
  }
  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