vdbeaux.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.

/*
** 2003 September 6
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains code used for creating, destroying, and populating
** a VDBE (or an "sqlite3_stmt" as it is known to the outside world.)  Prior
** to version 2.8.7, all this code was combined into the vdbe.c source file.
** But that file was getting too big so this subroutines were split out.
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"


/*
** When debugging the code generator in a symbolic debugger, one can
** set the sqlite3_vdbe_addop_trace to 1 and all opcodes will be printed
** as they are added to the instruction stream.
*/
#ifdef SQLITE_DEBUG
int sqlite3_vdbe_addop_trace = 0;
#endif


/*
** Create a new virtual database engine.
*/
Vdbe *sqlite3VdbeCreate(sqlite3 *db){
  Vdbe *p;
  p = sqliteMalloc( sizeof(Vdbe) );
  if( p==0 ) return 0;
  p->db = db;
  if( db->pVdbe ){
    db->pVdbe->pPrev = p;
  }
  p->pNext = db->pVdbe;
  p->pPrev = 0;
  db->pVdbe = p;
  p->magic = VDBE_MAGIC_INIT;
  return p;
}

/*
** Remember the SQL string for a prepared statement.
*/
void sqlite3VdbeSetSql(Vdbe *p, const char *z, int n){
  if( p==0 ) return;
  assert( p->zSql==0 );
  p->zSql = sqlite3StrNDup(z, n);
}

/*
** Return the SQL associated with a prepared statement
*/
const char *sqlite3VdbeGetSql(Vdbe *p){
  return p->zSql;
}

/*
** Swap all content between two VDBE structures.
*/
void sqlite3VdbeSwap(Vdbe *pA, Vdbe *pB){
  Vdbe tmp, *pTmp;
  char *zTmp;
  int nTmp;
  tmp = *pA;
  *pA = *pB;
  *pB = tmp;
  pTmp = pA->pNext;
  pA->pNext = pB->pNext;
  pB->pNext = pTmp;
  pTmp = pA->pPrev;
  pA->pPrev = pB->pPrev;
  pB->pPrev = pTmp;
  zTmp = pA->zSql;
  pA->zSql = pB->zSql;
  pB->zSql = zTmp;
  nTmp = pA->nSql;
  pA->nSql = pB->nSql;
  pB->nSql = nTmp;
}

#ifdef SQLITE_DEBUG
/*
** Turn tracing on or off
*/
void sqlite3VdbeTrace(Vdbe *p, FILE *trace){
  p->trace = trace;
}
#endif

/*
** Resize the Vdbe.aOp array so that it contains at least N
** elements. If the Vdbe is in VDBE_MAGIC_RUN state, then
** the Vdbe.aOp array will be sized to contain exactly N
** elements. Vdbe.nOpAlloc is set to reflect the new size of
** the array.
**
** If an out-of-memory error occurs while resizing the array,
** Vdbe.aOp and Vdbe.nOpAlloc remain unchanged (this is so that
** any opcodes already allocated can be correctly deallocated
** along with the rest of the Vdbe).
*/
static void resizeOpArray(Vdbe *p, int N){
  int runMode = p->magic==VDBE_MAGIC_RUN;
  if( runMode || p->nOpAlloc<N ){
    VdbeOp *pNew;
    int nNew = N + 100*(!runMode);
    int oldSize = p->nOpAlloc;
    pNew = sqliteRealloc(p->aOp, nNew*sizeof(Op));
    if( pNew ){
      p->nOpAlloc = nNew;
      p->aOp = pNew;
      if( nNew>oldSize ){
        memset(&p->aOp[oldSize], 0, (nNew-oldSize)*sizeof(Op));
      }
    }
  }
}

/*
** Add a new instruction to the list of instructions current in the
** VDBE.  Return the address of the new instruction.
**
** Parameters:
**
**    p               Pointer to the VDBE
**
**    op              The opcode for this instruction
**
**    p1, p2          First two of the three possible operands.
**
** Use the sqlite3VdbeResolveLabel() function to fix an address and
** the sqlite3VdbeChangeP3() function to change the value of the P3
** operand.
*/
int sqlite3VdbeAddOp(Vdbe *p, int op, int p1, int p2){
  int i;
  VdbeOp *pOp;

  i = p->nOp;
  assert( p->magic==VDBE_MAGIC_INIT );
  if( p->nOpAlloc<=i ){
    resizeOpArray(p, i+1);
    if( sqlite3MallocFailed() ){
      return 0;
    }
  }
  p->nOp++;
  pOp = &p->aOp[i];
  pOp->opcode = op;
  pOp->p1 = p1;
  pOp->p2 = p2;
  pOp->p3 = 0;
  pOp->p3type = P3_NOTUSED;
  p->expired = 0;
#ifdef SQLITE_DEBUG
  if( sqlite3_vdbe_addop_trace ) sqlite3VdbePrintOp(0, i, &p->aOp[i]);
#endif
  return i;
}

/*
** Add an opcode that includes the p3 value.
*/
int sqlite3VdbeOp3(Vdbe *p, int op, int p1, int p2, const char *zP3,int p3type){
  int addr = sqlite3VdbeAddOp(p, op, p1, p2);
  sqlite3VdbeChangeP3(p, addr, zP3, p3type);
  return addr;
}

/*
** Create a new symbolic label for an instruction that has yet to be
** coded.  The symbolic label is really just a negative number.  The
** label can be used as the P2 value of an operation.  Later, when
** the label is resolved to a specific address, the VDBE will scan
** through its operation list and change all values of P2 which match
** the label into the resolved address.
**
** The VDBE knows that a P2 value is a label because labels are
** always negative and P2 values are suppose to be non-negative.
** Hence, a negative P2 value is a label that has yet to be resolved.
**
** Zero is returned if a malloc() fails.
*/
int sqlite3VdbeMakeLabel(Vdbe *p){
  int i;
  i = p->nLabel++;
  assert( p->magic==VDBE_MAGIC_INIT );
  if( i>=p->nLabelAlloc ){
    p->nLabelAlloc = p->nLabelAlloc*2 + 10;
    p->aLabel = sqliteReallocOrFree(p->aLabel,
                                    p->nLabelAlloc*sizeof(p->aLabel[0]));
  }
  if( p->aLabel ){
    p->aLabel[i] = -1;
  }
  return -1-i;
}

/*
** Resolve label "x" to be the address of the next instruction to
** be inserted.  The parameter "x" must have been obtained from
** a prior call to sqlite3VdbeMakeLabel().
*/
void sqlite3VdbeResolveLabel(Vdbe *p, int x){
  int j = -1-x;
  assert( p->magic==VDBE_MAGIC_INIT );
  assert( j>=0 && j<p->nLabel );
  if( p->aLabel ){
    p->aLabel[j] = p->nOp;
  }
}

/*
** Return non-zero if opcode 'op' is guarenteed not to push more values
** onto the VDBE stack than it pops off.
*/
static int opcodeNoPush(u8 op){
  /* The 10 NOPUSH_MASK_n constants are defined in the automatically
  ** generated header file opcodes.h. Each is a 16-bit bitmask, one
  ** bit corresponding to each opcode implemented by the virtual
  ** machine in vdbe.c. The bit is true if the word "no-push" appears
  ** in a comment on the same line as the "case OP_XXX:" in 
  ** sqlite3VdbeExec() in vdbe.c.
  **
  ** If the bit is true, then the corresponding opcode is guarenteed not
  ** to grow the stack when it is executed. Otherwise, it may grow the
  ** stack by at most one entry.
  **
  ** NOPUSH_MASK_0 corresponds to opcodes 0 to 15. NOPUSH_MASK_1 contains
  ** one bit for opcodes 16 to 31, and so on.
  **
  ** 16-bit bitmasks (rather than 32-bit) are specified in opcodes.h 
  ** because the file is generated by an awk program. Awk manipulates
  ** all numbers as floating-point and we don't want to risk a rounding
  ** error if someone builds with an awk that uses (for example) 32-bit 
  ** IEEE floats.
  */ 
  static const u32 masks[5] = {
    NOPUSH_MASK_0 + (((unsigned)NOPUSH_MASK_1)<<16),
    NOPUSH_MASK_2 + (((unsigned)NOPUSH_MASK_3)<<16),
    NOPUSH_MASK_4 + (((unsigned)NOPUSH_MASK_5)<<16),
    NOPUSH_MASK_6 + (((unsigned)NOPUSH_MASK_7)<<16),
    NOPUSH_MASK_8 + (((unsigned)NOPUSH_MASK_9)<<16)
  };
  assert( op<32*5 );
  return (masks[op>>5] & (1<<(op&0x1F)));
}

#ifndef NDEBUG
int sqlite3VdbeOpcodeNoPush(u8 op){
  return opcodeNoPush(op);
}
#endif

/*
** Loop through the program looking for P2 values that are negative.
** Each such value is a label.  Resolve the label by setting the P2
** value to its correct non-zero value.
**
** This routine is called once after all opcodes have been inserted.
**
** Variable *pMaxFuncArgs is set to the maximum value of any P2 argument 
** to an OP_Function, OP_AggStep or OP_VFilter opcode. This is used by 
** sqlite3VdbeMakeReady() to size the Vdbe.apArg[] array.
**
** The integer *pMaxStack is set to the maximum number of vdbe stack
** entries that static analysis reveals this program might need.
**
** This routine also does the following optimization:  It scans for
** Halt instructions where P1==SQLITE_CONSTRAINT or P2==OE_Abort or for
** IdxInsert instructions where P2!=0.  If no such instruction is
** found, then every Statement instruction is changed to a Noop.  In
** this way, we avoid creating the statement journal file unnecessarily.
*/
static void resolveP2Values(Vdbe *p, int *pMaxFuncArgs, int *pMaxStack){
  int i;
  int nMaxArgs = 0;
  int nMaxStack = p->nOp;
  Op *pOp;
  int *aLabel = p->aLabel;
  int doesStatementRollback = 0;
  int hasStatementBegin = 0;
  for(pOp=p->aOp, i=p->nOp-1; i>=0; i--, pOp++){
    u8 opcode = pOp->opcode;

    if( opcode==OP_Function || opcode==OP_AggStep 
#ifndef SQLITE_OMIT_VIRTUALTABLE
        || opcode==OP_VUpdate
#endif
    ){
      if( pOp->p2>nMaxArgs ) nMaxArgs = pOp->p2;
    }
    if( opcode==OP_Halt ){
      if( pOp->p1==SQLITE_CONSTRAINT && pOp->p2==OE_Abort ){
        doesStatementRollback = 1;
      }
    }else if( opcode==OP_Statement ){
      hasStatementBegin = 1;
#ifndef SQLITE_OMIT_VIRTUALTABLE
    }else if( opcode==OP_VUpdate || opcode==OP_VRename ){
      doesStatementRollback = 1;
    }else if( opcode==OP_VFilter ){
      int n;
      assert( p->nOp - i >= 3 );
      assert( pOp[-2].opcode==OP_Integer );
      n = pOp[-2].p1;
      if( n>nMaxArgs ) nMaxArgs = n;
#endif
    }
    if( opcodeNoPush(opcode) ){
      nMaxStack--;
    }

    if( pOp->p2>=0 ) continue;
    assert( -1-pOp->p2<p->nLabel );
    pOp->p2 = aLabel[-1-pOp->p2];
  }
  sqliteFree(p->aLabel);
  p->aLabel = 0;

  *pMaxFuncArgs = nMaxArgs;
  *pMaxStack = nMaxStack;

  /* If we never rollback a statement transaction, then statement
  ** transactions are not needed.  So change every OP_Statement
  ** opcode into an OP_Noop.  This avoid a call to sqlite3OsOpenExclusive()
  ** which can be expensive on some platforms.
  */
  if( hasStatementBegin && !doesStatementRollback ){
    for(pOp=p->aOp, i=p->nOp-1; i>=0; i--, pOp++){
      if( pOp->opcode==OP_Statement ){
        pOp->opcode = OP_Noop;
      }
    }
  }
}

/*
** Return the address of the next instruction to be inserted.
*/
int sqlite3VdbeCurrentAddr(Vdbe *p){
  assert( p->magic==VDBE_MAGIC_INIT );
  return p->nOp;
}

/*
** Add a whole list of operations to the operation stack.  Return the
** address of the first operation added.
*/
int sqlite3VdbeAddOpList(Vdbe *p, int nOp, VdbeOpList const *aOp){
  int addr;
  assert( p->magic==VDBE_MAGIC_INIT );
  resizeOpArray(p, p->nOp + nOp);
  if( sqlite3MallocFailed() ){
    return 0;
  }
  addr = p->nOp;
  if( nOp>0 ){
    int i;
    VdbeOpList const *pIn = aOp;
    for(i=0; i<nOp; i++, pIn++){
      int p2 = pIn->p2;
      VdbeOp *pOut = &p->aOp[i+addr];
      pOut->opcode = pIn->opcode;
      pOut->p1 = pIn->p1;
      pOut->p2 = p2<0 ? addr + ADDR(p2) : p2;
      pOut->p3 = pIn->p3;
      pOut->p3type = pIn->p3 ? P3_STATIC : P3_NOTUSED;
#ifdef SQLITE_DEBUG
      if( sqlite3_vdbe_addop_trace ){
        sqlite3VdbePrintOp(0, i+addr, &p->aOp[i+addr]);
      }
#endif
    }
    p->nOp += nOp;
  }
  return addr;
}

/*
** Change the value of the P1 operand for a specific instruction.
** This routine is useful when a large program is loaded from a
** static array using sqlite3VdbeAddOpList but we want to make a
** few minor changes to the program.
*/
void sqlite3VdbeChangeP1(Vdbe *p, int addr, int val){
  assert( p==0 || p->magic==VDBE_MAGIC_INIT );
  if( p && addr>=0 && p->nOp>addr && p->aOp ){
    p->aOp[addr].p1 = val;
  }
}

/*
** Change the value of the P2 operand for a specific instruction.
** This routine is useful for setting a jump destination.
*/
void sqlite3VdbeChangeP2(Vdbe *p, int addr, int val){
  assert( val>=0 );
  assert( p==0 || p->magic==VDBE_MAGIC_INIT );
  if( p && addr>=0 && p->nOp>addr && p->aOp ){
    p->aOp[addr].p2 = val;
  }
}

/*
** Change the P2 operand of instruction addr so that it points to
** the address of the next instruction to be coded.
*/
void sqlite3VdbeJumpHere(Vdbe *p, int addr){
  sqlite3VdbeChangeP2(p, addr, p->nOp);
}


/*
** If the input FuncDef structure is ephemeral, then free it.  If
** the FuncDef is not ephermal, then do nothing.
*/
static void freeEphemeralFunction(FuncDef *pDef){
  if( pDef && (pDef->flags & SQLITE_FUNC_EPHEM)!=0 ){
    sqliteFree(pDef);
  }
}

/*
** Delete a P3 value if necessary.
*/
static void freeP3(int p3type, void *p3){
  if( p3 ){