vdbe.c

SQLite 2.8.6 源代码,用来在Linux/Unix/Windows上编译安装.它是一个小型的数据库,但是非常好用,速度也快,一般的数据库查询之类的操作据统计比MySQL,PostgreSQL

      p->rc = SQLITE_MISUSE;
    }
  }
  return p->rc==SQLITE_OK ? SQLITE_DONE : SQLITE_ERROR;
}

/*
** The parameters are pointers to the head of two sorted lists
** of Sorter structures.  Merge these two lists together and return
** a single sorted list.  This routine forms the core of the merge-sort
** algorithm.
**
** In the case of a tie, left sorts in front of right.
*/
static Sorter *Merge(Sorter *pLeft, Sorter *pRight){
  Sorter sHead;
  Sorter *pTail;
  pTail = &sHead;
  pTail->pNext = 0;
  while( pLeft && pRight ){
    int c = sqliteSortCompare(pLeft->zKey, pRight->zKey);
    if( c<=0 ){
      pTail->pNext = pLeft;
      pLeft = pLeft->pNext;
    }else{
      pTail->pNext = pRight;
      pRight = pRight->pNext;
    }
    pTail = pTail->pNext;
  }
  if( pLeft ){
    pTail->pNext = pLeft;
  }else if( pRight ){
    pTail->pNext = pRight;
  }
  return sHead.pNext;
}

/*
** Convert an integer in between the native integer format and
** the bigEndian format used as the record number for tables.
**
** The bigEndian format (most significant byte first) is used for
** record numbers so that records will sort into the correct order
** even though memcmp() is used to compare the keys.  On machines
** whose native integer format is little endian (ex: i486) the
** order of bytes is reversed.  On native big-endian machines
** (ex: Alpha, Sparc, Motorola) the byte order is the same.
**
** This function is its own inverse.  In other words
**
**         X == byteSwap(byteSwap(X))
*/
static int byteSwap(int x){
  union {
     char zBuf[sizeof(int)];
     int i;
  } ux;
  ux.zBuf[3] = x&0xff;
  ux.zBuf[2] = (x>>8)&0xff;
  ux.zBuf[1] = (x>>16)&0xff;
  ux.zBuf[0] = (x>>24)&0xff;
  return ux.i;
}

/*
** When converting from the native format to the key format and back
** again, in addition to changing the byte order we invert the high-order
** bit of the most significant byte.  This causes negative numbers to
** sort before positive numbers in the memcmp() function.
*/
#define keyToInt(X)   (byteSwap(X) ^ 0x80000000)
#define intToKey(X)   (byteSwap((X) ^ 0x80000000))

/*
** Code contained within the VERIFY() macro is not needed for correct
** execution.  It is there only to catch errors.  So when we compile
** with NDEBUG=1, the VERIFY() code is omitted.
*/
#ifdef NDEBUG
# define VERIFY(X)
#else
# define VERIFY(X) X
#endif

/*
** The following routine works like a replacement for the standard
** library routine fgets().  The difference is in how end-of-line (EOL)
** is handled.  Standard fgets() uses LF for EOL under unix, CRLF
** under windows, and CR under mac.  This routine accepts any of these
** character sequences as an EOL mark.  The EOL mark is replaced by
** a single LF character in zBuf.
*/
static char *vdbe_fgets(char *zBuf, int nBuf, FILE *in){
  int i, c;
  for(i=0; i<nBuf-1 && (c=getc(in))!=EOF; i++){
    zBuf[i] = c;
    if( c=='\r' || c=='\n' ){
      if( c=='\r' ){
        zBuf[i] = '\n';
        c = getc(in);
        if( c!=EOF && c!='\n' ) ungetc(c, in);
      }
      i++;
      break;
    }
  }
  zBuf[i]  = 0;
  return i>0 ? zBuf : 0;
}

#if !defined(NDEBUG) || defined(VDBE_PROFILE)
/*
** Print a single opcode.  This routine is used for debugging only.
*/
static void vdbePrintOp(FILE *pOut, int pc, Op *pOp){
  char *zP3;
  char zPtr[40];
  if( pOp->p3type==P3_POINTER ){
    sprintf(zPtr, "ptr(%#x)", (int)pOp->p3);
    zP3 = zPtr;
  }else{
    zP3 = pOp->p3;
  }
  if( pOut==0 ) pOut = stdout;
  fprintf(pOut,"%4d %-12s %4d %4d %s\n",
      pc, sqliteOpcodeNames[pOp->opcode], pOp->p1, pOp->p2, zP3 ? zP3 : "");
  fflush(pOut);
}
#endif

/*
** Make sure there is space in the Vdbe structure to hold at least
** mxCursor cursors.  If there is not currently enough space, then
** allocate more.
**
** If a memory allocation error occurs, return 1.  Return 0 if
** everything works.
*/
static int expandCursorArraySize(Vdbe *p, int mxCursor){
  if( mxCursor>=p->nCursor ){
    Cursor *aCsr = sqliteRealloc( p->aCsr, (mxCursor+1)*sizeof(Cursor) );
    if( aCsr==0 ) return 1;
    p->aCsr = aCsr;
    memset(&p->aCsr[p->nCursor], 0, sizeof(Cursor)*(mxCursor+1-p->nCursor));
    p->nCursor = mxCursor+1;
  }
  return 0;
}

#ifdef VDBE_PROFILE
/*
** The following routine only works on pentium-class processors.
** It uses the RDTSC opcode to read cycle count value out of the
** processor and returns that value.  This can be used for high-res
** profiling.
*/
__inline__ unsigned long long int hwtime(void){
  unsigned long long int x;
  __asm__("rdtsc\n\t"
          "mov %%edx, %%ecx\n\t"
          :"=A" (x));
  return x;
}
#endif

/*
** The CHECK_FOR_INTERRUPT macro defined here looks to see if the
** sqlite_interrupt() routine has been called.  If it has been, then
** processing of the VDBE program is interrupted.
**
** This macro added to every instruction that does a jump in order to
** implement a loop.  This test used to be on every single instruction,
** but that meant we more testing that we needed.  By only testing the
** flag on jump instructions, we get a (small) speed improvement.
*/
#define CHECK_FOR_INTERRUPT \
   if( db->flags & SQLITE_Interrupt ) goto abort_due_to_interrupt;


/*
** Prepare a virtual machine for execution.  This involves things such
** as allocating stack space and initializing the program counter.
** After the VDBE has be prepped, it can be executed by one or more
** calls to sqliteVdbeExec().  
**
** The behavior of sqliteVdbeExec() is influenced by the parameters to
** this routine.  If xCallback is NULL, then sqliteVdbeExec() will return
** with SQLITE_ROW whenever there is a row of the result set ready
** to be delivered.  p->azResColumn will point to the row and 
** p->nResColumn gives the number of columns in the row.  If xCallback
** is not NULL, then the xCallback() routine is invoked to process each
** row in the result set.
*/
void sqliteVdbeMakeReady(
  Vdbe *p,                       /* The VDBE */
  sqlite_callback xCallback,     /* Result callback */
  void *pCallbackArg,            /* 1st argument to xCallback() */
  int isExplain                  /* True if the EXPLAIN keywords is present */
){
  int n;

  assert( p!=0 );
  assert( p->aStack==0 );
  assert( p->magic==VDBE_MAGIC_INIT );

  /* Add a HALT instruction to the very end of the program.
  */
  sqliteVdbeAddOp(p, OP_Halt, 0, 0);

  /* No instruction ever pushes more than a single element onto the
  ** stack.  And the stack never grows on successive executions of the
  ** same loop.  So the total number of instructions is an upper bound
  ** on the maximum stack depth required.
  **
  ** Allocation all the stack space we will ever need.
  */
  n = isExplain ? 10 : p->nOp;
  p->aStack = sqliteMalloc( n*(sizeof(p->aStack[0]) + 2*sizeof(char*)) );
  p->zStack = (char**)&p->aStack[n];
  p->azColName = (char**)&p->zStack[n];

  sqliteHashInit(&p->agg.hash, SQLITE_HASH_BINARY, 0);
  p->agg.pSearch = 0;
#ifdef MEMORY_DEBUG
  if( sqliteOsFileExists("vdbe_trace") ){
    p->trace = stdout;
  }
#endif
  p->tos = -1;
  p->pc = 0;
  p->rc = SQLITE_OK;
  p->uniqueCnt = 0;
  p->returnDepth = 0;
  p->errorAction = OE_Abort;
  p->undoTransOnError = 0;
  p->xCallback = xCallback;
  p->pCbArg = pCallbackArg;
  p->popStack =  0;
  p->explain = isExplain;
  p->magic = VDBE_MAGIC_RUN;
#ifdef VDBE_PROFILE
  for(i=0; i<p->nOp; i++){
    p->aOp[i].cnt = 0;
    p->aOp[i].cycles = 0;
  }
#endif
}

/*
** Execute as much of a VDBE program as we can then return.
**
** sqliteVdbeMakeReady() must be called before this routine in order to
** close the program with a final OP_Halt and to set up the callbacks
** and the error message pointer.
**
** Whenever a row or result data is available, this routine will either
** invoke the result callback (if there is one) or return with
** SQLITE_ROW.
**
** If an attempt is made to open a locked database, then this routine
** will either invoke the busy callback (if there is one) or it will
** return SQLITE_BUSY.
**
** If an error occurs, an error message is written to memory obtained
** from sqliteMalloc() and p->zErrMsg is made to point to that memory.
** The error code is stored in p->rc and this routine returns SQLITE_ERROR.
**
** If the callback ever returns non-zero, then the program exits
** immediately.  There will be no error message but the p->rc field is
** set to SQLITE_ABORT and this routine will return SQLITE_ERROR.
**
** A memory allocation error causes p->rc to be set to SQLITE_NOMEM and this
** routine to return SQLITE_ERROR.
**
** Other fatal errors return SQLITE_ERROR.
**
** After this routine has finished, sqliteVdbeFinalize() should be
** used to clean up the mess that was left behind.
*/
int sqliteVdbeExec(
  Vdbe *p                    /* The VDBE */
){
  int pc;                    /* The program counter */
  Op *pOp;                   /* Current operation */
  int rc = SQLITE_OK;        /* Value to return */
  sqlite *db = p->db;        /* The database */
  char **zStack = p->zStack; /* Text stack */
  Stack *aStack = p->aStack; /* Additional stack information */
  char zBuf[100];            /* Space to sprintf() an integer */
#ifdef VDBE_PROFILE
  unsigned long long start;  /* CPU clock count at start of opcode */
  int origPc;                /* Program counter at start of opcode */
#endif

  if( p->magic!=VDBE_MAGIC_RUN ) return SQLITE_MISUSE;
  assert( db->magic==SQLITE_MAGIC_BUSY );
  assert( p->rc==SQLITE_OK || p->rc==SQLITE_BUSY );
  p->rc = SQLITE_OK;
  assert( p->explain==0 );
  if( sqlite_malloc_failed ) goto no_mem;
  if( p->popStack ){
    PopStack(p, p->popStack);
    p->popStack = 0;
  }
  for(pc=p->pc; rc==SQLITE_OK; pc++){
    assert( pc>=0 && pc<p->nOp );
#ifdef VDBE_PROFILE
    origPc = pc;
    start = hwtime();
#endif
    pOp = &p->aOp[pc];

    /* Only allow tracing if NDEBUG is not defined.
    */
#ifndef NDEBUG
    if( p->trace ){
      vdbePrintOp(p->trace, pc, pOp);
    }
#endif

    switch( pOp->opcode ){

/*****************************************************************************
** What follows is a massive switch statement where each case implements a
** separate instruction in the virtual machine.  If we follow the usual
** indentation conventions, each case should be indented by 6 spaces.  But
** that is a lot of wasted space on the left margin.  So the code within
** the switch statement will break with convention and be flush-left. Another
** big comment (similar to this one) will mark the point in the code where
** we transition back to normal indentation.
**
** The formatting of each case is important.  The makefile for SQLite
** generates two C files "opcodes.h" and "opcodes.c" by scanning this
** file looking for lines that begin with "case OP_".  The opcodes.h files
** will be filled with #defines that give unique integer values to each
** opcode and the opcodes.c file is filled with an array of strings where
** each string is the symbolic name for the corresponding opcode.
**
** Documentation about VDBE opcodes is generated by scanning this file
** for lines of that contain "Opcode:".  That line and all subsequent
** comment lines are used in the generation of the opcode.html documentation
** file.
**
** SUMMARY:
**
**     Formatting is important to scripts that scan this file.
**     Do not deviate from the formatting style currently in use.
**
*****************************************************************************/

/* Opcode:  Goto * P2 *
**
** An unconditional jump to address P2.
** The next instruction executed will be 
** the one at index P2 from the beginning of
** the program.
*/
case OP_Goto: {
  CHECK_FOR_INTERRUPT;
  pc = pOp->p2 - 1;
  break;
}

/* Opcode:  Gosub * P2 *
**
** Push the current address plus 1 onto the return address stack
** and then jump to address P2.
**
** The return address stack is of limited depth.  If too many
** OP_Gosub operations occur without intervening OP_Returns, then
** the return address stack will fill up and processing will abort
** with a fatal error.
*/
case OP_Gosub: {
  if( p->returnDepth>=sizeof(p->returnStack)/sizeof(p->returnStack[0]) ){
    sqliteSetString(&p->zErrMsg, "return address stack overflow", 0);
    p->rc = SQLITE_INTERNAL;
    return SQLITE_ERROR;
  }
  p->returnStack[p->returnDepth++] = pc+1;
  pc = pOp->p2 - 1;
  break;
}

/* Opcode:  Return * * *
**
** Jump immediately to the next instruction after the last unreturned
** OP_Gosub.  If an OP_Return has occurred for all OP_Gosubs, then
** processing aborts with a fatal error.
*/
case OP_Return: {
  if( p->returnDepth<=0 ){
    sqliteSetString(&p->zErrMsg, "return address stack underflow", 0);
    p->rc = SQLITE_INTERNAL;
    return SQLITE_ERROR;
  }
  p->returnDepth--;
  pc = p->returnStack[p->returnDepth] - 1;
  break;
}

/* Opcode:  Halt P1 P2 *
**
** Exit immediately.  All open cursors, Lists, Sorts, etc are closed
** automatically.
**
** P1 is the result code returned by sqlite_exec().  For a normal
** halt, this should be SQLITE_OK (0).  For errors, it can be some
** other value.  If P1!=0 then P2 will determine whether or not to
** rollback the current transaction.  Do not rollback if P2==OE_Fail.
** Do the rollback if P2==OE_Rollback.  If P2==OE_Abort, then back
** out all changes that have occurred during this execution of the
** VDBE, but do not rollback the transaction. 
**
** There is an implied "Halt 0 0 0" instruction inserted at the very end of
** every program.  So a jump past the last instruction of the program
** is the same as executing Halt.
*/
case OP_Halt: {
  p->magic = VDBE_MAGIC_HALT;
  if( pOp->p1!=SQLITE_OK ){
    p->rc = pOp->p1;
    p->errorAction = pOp->p2;
    if( pOp->p3 ){
      sqliteSetString(&p->zErrMsg, pOp->p3, 0);
    }
    return SQLITE_ERROR;
  }else{
    p->rc = SQLITE_OK;
    return SQLITE_DONE;
  }
}