SQLite

**
*************************************************************************
** Utility functions used throughout sqlite.
**
** This file contains functions for allocating memory, comparing
** strings, and stuff like that.
**
** $Id: util.c,v 1.64 2003/06/02 06:17:10 jplyon Exp $
*/
#include "sqliteInt.h"
#include <stdarg.h>
#include <ctype.h>

/*
** If malloc() ever fails, this global variable gets set to 1.

  register unsigned char *a, *b;
  a = (unsigned char *)zLeft;
  b = (unsigned char *)zRight;
  while( N-- > 0 && *a!=0 && UpperToLower[*a]==UpperToLower[*b]){ a++; b++; }
  return N<0 ? 0 : *a - *b;
}

#if 0  /* NOT USED */
/* 
** The sortStrCmp() function below is used to order elements according
** to the ORDER BY clause of a SELECT.  The sort order is a little different
** from what one might expect.  This note attempts to describe what is
** going on.
**
** We want the main string comparision function used for sorting to
** sort both numbers and alphanumeric words into the correct sequence.
** The same routine should do both without prior knowledge of which
** type of text the input represents.  It should even work for strings
** which are a mixture of text and numbers.  (It does not work for
** numeric substrings in exponential notation, however.)
**
** To accomplish this, we keep track of a state number while scanning
** the two strings.  The states are as follows:
**
**    1      Beginning of word
**    2      Arbitrary text
**    3      Integer
**    4      Negative integer
**    5      Real number
**    6      Negative real
**
** The scan begins in state 1, beginning of word.  Transitions to other
** states are determined by characters seen, as shown in the following
** chart:
**
**      Current State         Character Seen  New State
**      --------------------  --------------  -------------------
**      0 Beginning of word   "-"             3 Negative integer
**                            digit           2 Integer
**                            space           0 Beginning of word
**                            otherwise       1 Arbitrary text
**
**      1 Arbitrary text      space           0 Beginning of word
**                            digit           2 Integer
**                            otherwise       1 Arbitrary text
**
**      2 Integer             space           0 Beginning of word
**                            "."             4 Real number
**                            digit           2 Integer
**                            otherwise       1 Arbitrary text
**
**      3 Negative integer    space           0 Beginning of word
**                            "."             5 Negative Real num
**                            digit           3 Negative integer
**                            otherwise       1 Arbitrary text
**
**      4 Real number         space           0 Beginning of word
**                            digit           4 Real number
**                            otherwise       1 Arbitrary text
**
**      5 Negative real num   space           0 Beginning of word
**                            digit           5 Negative real num
**                            otherwise       1 Arbitrary text
**
** To implement this state machine, we first classify each character
** into on of the following categories:
**
**      0  Text
**      1  Space
**      2  Digit
**      3  "-"
**      4  "."
**
** Given an arbitrary character, the array charClass[] maps that character
** into one of the atove categories.
*/
static const unsigned char charClass[] = {
        /* x0 x1 x2 x3 x4 x5 x6 x7 x8 x9 xA xB xC xD xE xF */
/* 0x */   0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0,
/* 1x */   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 2x */   1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 4, 0,
/* 3x */   2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 0, 0, 0, 0, 0, 0,
/* 4x */   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 5x */   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 6x */   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 7x */   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 8x */   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 9x */   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* Ax */   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* Bx */   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* Cx */   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* Dx */   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* Ex */   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* Fx */   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
};
#define N_CHAR_CLASS 5

/*
** Given the current state number (0 thru 5), this array figures
** the new state number given the character class.
*/
static const unsigned char stateMachine[] = {
 /* Text,  Space, Digit, "-", "." */
      1,      0,    2,    3,   1,      /* State 0: Beginning of word */
      1,      0,    2,    1,   1,      /* State 1: Arbitrary text */
      1,      0,    2,    1,   4,      /* State 2: Integer */
      1,      0,    3,    1,   5,      /* State 3: Negative integer */
      1,      0,    4,    1,   1,      /* State 4: Real number */
      1,      0,    5,    1,   1,      /* State 5: Negative real num */
};

/* This routine does a comparison of two strings.  Case is used only
** if useCase!=0.  Numeric substrings compare in numerical order for the
** most part but this routine does not understand exponential notation.
*/
static int sortStrCmp(const char *atext, const char *btext, int useCase){
  register unsigned char *a, *b, *map, ca, cb;
  int result;
  register int cclass = 0;

  a = (unsigned char *)atext;
  b = (unsigned char *)btext;
  if( useCase ){
    do{
      if( (ca= *a++)!=(cb= *b++) ) break;
      cclass = stateMachine[cclass*N_CHAR_CLASS + charClass[ca]];
    }while( ca!=0 );
  }else{
    map = UpperToLower;
    do{
      if( (ca=map[*a++])!=(cb=map[*b++]) ) break;
      cclass = stateMachine[cclass*N_CHAR_CLASS + charClass[ca]];
    }while( ca!=0 );
    if( ca>='[' && ca<='`' ) cb = b[-1];
    if( cb>='[' && cb<='`' ) ca = a[-1];
  }
  switch( cclass ){
    case 0:
    case 1: {
      if( isdigit(ca) && isdigit(cb) ){
        cclass = 2;
      }
      break;
    }
    default: {
      break;
    }
  }
  switch( cclass ){
    case 2:
    case 3: {
      if( isdigit(ca) ){
        if( isdigit(cb) ){
          int acnt, bcnt;
          acnt = bcnt = 0;
          while( isdigit(*a++) ) acnt++;
          while( isdigit(*b++) ) bcnt++;
          result = acnt - bcnt;
          if( result==0 ) result = ca-cb;
        }else{
          result = 1;
        }
      }else if( isdigit(cb) ){
        result = -1;
      }else if( ca=='.' ){
        result = 1;
      }else if( cb=='.' ){
        result = -1;
      }else{
        result = ca - cb;
        cclass = 2;
      }
      if( cclass==3 ) result = -result;
      break;
    }
    case 0:
    case 1:
    case 4: {
      result = ca - cb;
      break;
    }
    case 5: {
      result = cb - ca;
    };
  }
  return result;
}
#endif /* NOT USED */

/*
** Return TRUE if z is a pure numeric string.  Return FALSE if the
** string contains any character which is not part of a number.
**
** Am empty string is considered non-numeric.
*/
int sqliteIsNumber(const char *z){