/*
** 2001 September 15
**
** 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.
**
*************************************************************************
** Utility functions used throughout sqlite.
**
** This file contains functions for allocating memory, comparing
** strings, and stuff like that.
**
** $Id: util.c,v 1.116 2004/09/06 17:24:13 drh Exp $
*/
#include "sqliteInt.h"
#include <stdarg.h>
#include <ctype.h>

#if SQLITE_DEBUG>2 && defined(__GLIBC__)
#include <execinfo.h>
void print_stack_trace(){
  void *bt[30];
  int i;
  int n = backtrace(bt, 30);

  fprintf(stderr, "STACK: ");
  for(i=0; i<n;i++){
    fprintf(stderr, "%p ", bt[i]);
  }
  fprintf(stderr, "\n");
}
#else
#define print_stack_trace()
#endif

/*
** If malloc() ever fails, this global variable gets set to 1.
** This causes the library to abort and never again function.
*/
int sqlite3_malloc_failed = 0;

/*
** If SQLITE_DEBUG is defined, then use versions of malloc() and
** free() that track memory usage and check for buffer overruns.
*/
#ifdef SQLITE_DEBUG

/*
** For keeping track of the number of mallocs and frees.   This
** is used to check for memory leaks.
*/
int sqlite3_nMalloc;         /* Number of sqliteMalloc() calls */
int sqlite3_nFree;           /* Number of sqliteFree() calls */
int sqlite3_iMallocFail;     /* Fail sqliteMalloc() after this many calls */
#if SQLITE_DEBUG>1
static int memcnt = 0;
#endif

/*
** Number of 32-bit guard words
*/
#define N_GUARD 1

/*
** Allocate new memory and set it to zero.  Return NULL if
** no memory is available.
*/
void *sqlite3Malloc_(int n, int bZero, char *zFile, int line){
  void *p;
  int *pi;
  int i, k;
  if( sqlite3_iMallocFail>=0 ){
    sqlite3_iMallocFail--;
    if( sqlite3_iMallocFail==0 ){
      sqlite3_malloc_failed++;
#if SQLITE_DEBUG>1
      fprintf(stderr,"**** failed to allocate %d bytes at %s:%d\n",
              n, zFile,line);
#endif
      sqlite3_iMallocFail--;
      return 0;
    }
  }
  if( n==0 ) return 0;
  k = (n+sizeof(int)-1)/sizeof(int);
  pi = malloc( (N_GUARD*2+1+k)*sizeof(int));
  if( pi==0 ){
    sqlite3_malloc_failed++;
    return 0;
  }
  sqlite3_nMalloc++;
  for(i=0; i<N_GUARD; i++) pi[i] = 0xdead1122;
  pi[N_GUARD] = n;
  for(i=0; i<N_GUARD; i++) pi[k+1+N_GUARD+i] = 0xdead3344;
  p = &pi[N_GUARD+1];
  memset(p, bZero==0, n);
#if SQLITE_DEBUG>1
  print_stack_trace();
  fprintf(stderr,"%06d malloc %d bytes at 0x%x from %s:%d\n",
      ++memcnt, n, (int)p, zFile,line);
#endif
  return p;
}

/*
** Check to see if the given pointer was obtained from sqliteMalloc()
** and is able to hold at least N bytes.  Raise an exception if this
** is not the case.
**
** This routine is used for testing purposes only.
*/
void sqlite3CheckMemory(void *p, int N){
  int *pi = p;
  int n, i, k;
  pi -= N_GUARD+1;
  for(i=0; i<N_GUARD; i++){
    assert( pi[i]==0xdead1122 );
  }
  n = pi[N_GUARD];
  assert( N>=0 && N<n );
  k = (n+sizeof(int)-1)/sizeof(int);
  for(i=0; i<N_GUARD; i++){
    assert( pi[k+N_GUARD+1+i]==0xdead3344 );
  }
}

/*
** Free memory previously obtained from sqliteMalloc()
*/
void sqlite3Free_(void *p, char *zFile, int line){
  if( p ){
    int *pi, i, k, n;
    pi = p;
    pi -= N_GUARD+1;
    sqlite3_nFree++;
    for(i=0; i<N_GUARD; i++){
      if( pi[i]!=0xdead1122 ){
        fprintf(stderr,"Low-end memory corruption at 0x%x\n", (int)p);
        return;
      }
    }
    n = pi[N_GUARD];
    k = (n+sizeof(int)-1)/sizeof(int);
    for(i=0; i<N_GUARD; i++){
      if( pi[k+N_GUARD+1+i]!=0xdead3344 ){
        fprintf(stderr,"High-end memory corruption at 0x%x\n", (int)p);
        return;
      }
    }
    memset(pi, 0xff, (k+N_GUARD*2+1)*sizeof(int));
#if SQLITE_DEBUG>1
    fprintf(stderr,"%06d free %d bytes at 0x%x from %s:%d\n",
         ++memcnt, n, (int)p, zFile,line);
#endif
    free(pi);
  }
}

/*
** Resize a prior allocation.  If p==0, then this routine
** works just like sqliteMalloc().  If n==0, then this routine
** works just like sqliteFree().
*/
void *sqlite3Realloc_(void *oldP, int n, char *zFile, int line){
  int *oldPi, *pi, i, k, oldN, oldK;
  void *p;
  if( oldP==0 ){
    return sqlite3Malloc_(n,1,zFile,line);
  }
  if( n==0 ){
    sqlite3Free_(oldP,zFile,line);
    return 0;
  }
  oldPi = oldP;
  oldPi -= N_GUARD+1;
  if( oldPi[0]!=0xdead1122 ){
    fprintf(stderr,"Low-end memory corruption in realloc at 0x%x\n", (int)oldP);
    return 0;
  }
  oldN = oldPi[N_GUARD];
  oldK = (oldN+sizeof(int)-1)/sizeof(int);
  for(i=0; i<N_GUARD; i++){
    if( oldPi[oldK+N_GUARD+1+i]!=0xdead3344 ){
      fprintf(stderr,"High-end memory corruption in realloc at 0x%x\n",
              (int)oldP);
      return 0;
    }
  }
  k = (n + sizeof(int) - 1)/sizeof(int);
  pi = malloc( (k+N_GUARD*2+1)*sizeof(int) );
  if( pi==0 ){
    sqlite3_malloc_failed++;
    return 0;
  }
  for(i=0; i<N_GUARD; i++) pi[i] = 0xdead1122;
  pi[N_GUARD] = n;
  for(i=0; i<N_GUARD; i++) pi[k+N_GUARD+1+i] = 0xdead3344;
  p = &pi[N_GUARD+1];
  memcpy(p, oldP, n>oldN ? oldN : n);
  if( n>oldN ){
    memset(&((char*)p)[oldN], 0x55, n-oldN);
  }
  memset(oldPi, 0xab, (oldK+N_GUARD+2)*sizeof(int));
  free(oldPi);
#if SQLITE_DEBUG>1
  print_stack_trace();
  fprintf(stderr,"%06d realloc %d to %d bytes at 0x%x to 0x%x at %s:%d\n",
    ++memcnt, oldN, n, (int)oldP, (int)p, zFile, line);
#endif
  return p;
}

/*
** Make a duplicate of a string into memory obtained from malloc()
** Free the original string using sqliteFree().
**
** This routine is called on all strings that are passed outside of
** the SQLite library.  That way clients can free the string using free()
** rather than having to call sqliteFree().
*/
void sqlite3StrRealloc(char **pz){
  char *zNew;
  if( pz==0 || *pz==0 ) return;
  zNew = malloc( strlen(*pz) + 1 );
  if( zNew==0 ){
    sqlite3_malloc_failed++;
    sqliteFree(*pz);
    *pz = 0;
  }
  strcpy(zNew, *pz);
  sqliteFree(*pz);
  *pz = zNew;
}

/*
** Make a copy of a string in memory obtained from sqliteMalloc()
*/
char *sqlite3StrDup_(const char *z, char *zFile, int line){
  char *zNew;
  if( z==0 ) return 0;
  zNew = sqlite3Malloc_(strlen(z)+1, 0, zFile, line);
  if( zNew ) strcpy(zNew, z);
  return zNew;
}
char *sqlite3StrNDup_(const char *z, int n, char *zFile, int line){
  char *zNew;
  if( z==0 ) return 0;
  zNew = sqlite3Malloc_(n+1, 0, zFile, line);
  if( zNew ){
    memcpy(zNew, z, n);
    zNew[n] = 0;
  }
  return zNew;
}

/*
** A version of sqliteFree that is always a function, not a macro.
*/
void sqlite3FreeX(void *p){
  sqliteFree(p);
}
#endif /* SQLITE_DEBUG */

/*
** The following versions of malloc() and free() are for use in a
** normal build.
*/
#if !defined(SQLITE_DEBUG)

/*
** Allocate new memory and set it to zero.  Return NULL if
** no memory is available.  See also sqliteMallocRaw().
*/
void *sqlite3Malloc(int n){
  void *p;
  if( (p = malloc(n))==0 ){
    if( n>0 ) sqlite3_malloc_failed++;
  }else{
    memset(p, 0, n);
  }
  return p;
}

/*
** Allocate new memory but do not set it to zero.  Return NULL if
** no memory is available.  See also sqliteMalloc().
*/
void *sqlite3MallocRaw(int n){
  void *p;
  if( (p = malloc(n))==0 ){
    if( n>0 ) sqlite3_malloc_failed++;
  }
  return p;
}

/*
** Free memory previously obtained from sqliteMalloc()
*/
void sqlite3FreeX(void *p){
  if( p ){
    free(p);
  }
}

/*
** Resize a prior allocation.  If p==0, then this routine
** works just like sqliteMalloc().  If n==0, then this routine
** works just like sqliteFree().
*/
void *sqlite3Realloc(void *p, int n){
  void *p2;
  if( p==0 ){
    return sqliteMalloc(n);
  }
  if( n==0 ){
    sqliteFree(p);
    return 0;
  }
  p2 = realloc(p, n);
  if( p2==0 ){
    sqlite3_malloc_failed++;
  }
  return p2;
}

/*
** Make a copy of a string in memory obtained from sqliteMalloc()
*/
char *sqlite3StrDup(const char *z){
  char *zNew;
  if( z==0 ) return 0;
  zNew = sqliteMallocRaw(strlen(z)+1);
  if( zNew ) strcpy(zNew, z);
  return zNew;
}
char *sqlite3StrNDup(const char *z, int n){
  char *zNew;
  if( z==0 ) return 0;
  zNew = sqliteMallocRaw(n+1);
  if( zNew ){
    memcpy(zNew, z, n);
    zNew[n] = 0;
  }
  return zNew;
}
#endif /* !defined(SQLITE_DEBUG) */

/*
** Create a string from the 2nd and subsequent arguments (up to the
** first NULL argument), store the string in memory obtained from
** sqliteMalloc() and make the pointer indicated by the 1st argument
** point to that string.  The 1st argument must either be NULL or 
** point to memory obtained from sqliteMalloc().
*/
void sqlite3SetString(char **pz, const char *zFirst, ...){
  va_list ap;
  int nByte;
  const char *z;
  char *zResult;

  if( pz==0 ) return;
  nByte = strlen(zFirst) + 1;
  va_start(ap, zFirst);
  while( (z = va_arg(ap, const char*))!=0 ){
    nByte += strlen(z);
  }
  va_end(ap);
  sqliteFree(*pz);
  *pz = zResult = sqliteMallocRaw( nByte );
  if( zResult==0 ){
    return;
  }
  strcpy(zResult, zFirst);
  zResult += strlen(zResult);
  va_start(ap, zFirst);
  while( (z = va_arg(ap, const char*))!=0 ){
    strcpy(zResult, z);
    zResult += strlen(zResult);
  }
  va_end(ap);
#ifdef SQLITE_DEBUG
#if SQLITE_DEBUG>1
  fprintf(stderr,"string at 0x%x is %s\n", (int)*pz, *pz);
#endif
#endif
}

/*
** Works like sqlite3SetString, but each string is now followed by
** a length integer which specifies how much of the source string 
** to copy (in bytes).  -1 means use the whole string.  The 1st 
** argument must either be NULL or point to memory obtained from 
** sqliteMalloc().
*/
void sqlite3SetNString(char **pz, ...){
  va_list ap;
  int nByte;
  const char *z;
  char *zResult;
  int n;

  if( pz==0 ) return;
  nByte = 0;
  va_start(ap, pz);
  while( (z = va_arg(ap, const char*))!=0 ){
    n = va_arg(ap, int);
    if( n<=0 ) n = strlen(z);
    nByte += n;
  }
  va_end(ap);
  sqliteFree(*pz);
  *pz = zResult = sqliteMallocRaw( nByte + 1 );
  if( zResult==0 ) return;
  va_start(ap, pz);
  while( (z = va_arg(ap, const char*))!=0 ){
    n = va_arg(ap, int);
    if( n<=0 ) n = strlen(z);
    memcpy(zResult, z, n);
    zResult += n;
  }
  *zResult = 0;
#ifdef SQLITE_DEBUG
#if SQLITE_DEBUG>1
  fprintf(stderr,"string at 0x%x is %s\n", (int)*pz, *pz);
#endif
#endif
  va_end(ap);
}

/*
** Set the most recent error code and error string for the sqlite
** handle "db". The error code is set to "err_code".
**
** If it is not NULL, string zFormat specifies the format of the
** error string in the style of the printf functions: The following
** format characters are allowed:
**
**      %s      Insert a string
**      %z      A string that should be freed after use
**      %d      Insert an integer
**      %T      Insert a token
**      %S      Insert the first element of a SrcList
**
** zFormat and any string tokens that follow it are assumed to be
** encoded in UTF-8.
**
** To clear the most recent error for slqite handle "db", sqlite3Error
** should be called with err_code set to SQLITE_OK and zFormat set
** to NULL.
*/
void sqlite3Error(sqlite3 *db, int err_code, const char *zFormat, ...){
  if( db && (db->pErr || (db->pErr = sqlite3ValueNew())) ){
    db->errCode = err_code;
    if( zFormat ){
      char *z;
      va_list ap;
      va_start(ap, zFormat);
      z = sqlite3VMPrintf(zFormat, ap);
      va_end(ap);
      sqlite3ValueSetStr(db->pErr, -1, z, SQLITE_UTF8, sqlite3FreeX);
    }else{
      sqlite3ValueSetStr(db->pErr, 0, 0, SQLITE_UTF8, SQLITE_STATIC);
    }
  }
}

/*
** Add an error message to pParse->zErrMsg and increment pParse->nErr.
** The following formatting characters are allowed:
**
**      %s      Insert a string
**      %z      A string that should be freed after use
**      %d      Insert an integer
**      %T      Insert a token
**      %S      Insert the first element of a SrcList
**
** This function should be used to report any error that occurs whilst
** compiling an SQL statement (i.e. within sqlite3_prepare()). The
** last thing the sqlite3_prepare() function does is copy the error
** stored by this function into the database handle using sqlite3Error().
** Function sqlite3Error() should be used during statement execution
** (sqlite3_step() etc.).
*/
void sqlite3ErrorMsg(Parse *pParse, const char *zFormat, ...){
  va_list ap;
  pParse->nErr++;
  sqliteFree(pParse->zErrMsg);
  va_start(ap, zFormat);
  pParse->zErrMsg = sqlite3VMPrintf(zFormat, ap);
  va_end(ap);
}

/*
** Convert an SQL-style quoted string into a normal string by removing
** the quote characters.  The conversion is done in-place.  If the
** input does not begin with a quote character, then this routine
** is a no-op.
**
** 2002-Feb-14: This routine is extended to remove MS-Access style
** brackets from around identifers.  For example:  "[a-b-c]" becomes
** "a-b-c".
*/
void sqlite3Dequote(char *z){
  int quote;
  int i, j;
  if( z==0 ) return;
  quote = z[0];
  switch( quote ){
    case '\'':  break;
    case '"':   break;
    case '[':   quote = ']';  break;
    default:    return;
  }
  for(i=1, j=0; z[i]; i++){
    if( z[i]==quote ){
      if( z[i+1]==quote ){
        z[j++] = quote;
        i++;
      }else{
        z[j++] = 0;
        break;
      }
    }else{
      z[j++] = z[i];
    }
  }
}

/* An array to map all upper-case characters into their corresponding
** lower-case character. 
*/
const unsigned char sqlite3UpperToLower[] = {
      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16, 17,
     18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,
     36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53,
     54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 97, 98, 99,100,101,102,103,
    104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,
    122, 91, 92, 93, 94, 95, 96, 97, 98, 99,100,101,102,103,104,105,106,107,
    108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,
    126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,
    144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,
    162,163,164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,
    180,181,182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,
    198,199,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,
    216,217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,
    234,235,236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251,
    252,253,254,255
};
#define UpperToLower sqlite3UpperToLower

/*
** This function computes a hash on the name of a keyword.
** Case is not significant.
*/
int sqlite3HashNoCase(const char *z, int n){
  int h = 0;
  if( n<=0 ) n = strlen(z);
  while( n > 0  ){
    h = (h<<3) ^ h ^ UpperToLower[(unsigned char)*z++];
    n--;
  }
  return h & 0x7fffffff;
}

/*
** Some systems have stricmp().  Others have strcasecmp().  Because
** there is no consistency, we will define our own.
*/
int sqlite3StrICmp(const char *zLeft, const char *zRight){
  register unsigned char *a, *b;
  a = (unsigned char *)zLeft;
  b = (unsigned char *)zRight;
  while( *a!=0 && UpperToLower[*a]==UpperToLower[*b]){ a++; b++; }
  return UpperToLower[*a] - UpperToLower[*b];
}
int sqlite3StrNICmp(const char *zLeft, const char *zRight, int N){
  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 : UpperToLower[*a] - UpperToLower[*b];
}

/*
** Return TRUE if z is a pure numeric string.  Return FALSE if the
** string contains any character which is not part of a number. If
** the string is numeric and contains the '.' character, set *realnum
** to TRUE (otherwise FALSE).
**
** An empty string is considered non-numeric.
*/
int sqlite3IsNumber(const char *z, int *realnum, u8 enc){
  int incr = (enc==SQLITE_UTF8?1:2);
  if( enc==SQLITE_UTF16BE ) z++;
  if( *z=='-' || *z=='+' ) z += incr;
  if( !isdigit(*(u8*)z) ){
    return 0;
  }
  z += incr;
  if( realnum ) *realnum = 0;
  while( isdigit(*(u8*)z) ){ z += incr; }
  if( *z=='.' ){
    z += incr;
    if( !isdigit(*(u8*)z) ) return 0;
    while( isdigit(*(u8*)z) ){ z += incr; }
    if( realnum ) *realnum = 1;
  }
  if( *z=='e' || *z=='E' ){
    z += incr;
    if( *z=='+' || *z=='-' ) z += incr;
    if( !isdigit(*(u8*)z) ) return 0;
    while( isdigit(*(u8*)z) ){ z += incr; }
    if( realnum ) *realnum = 1;
  }
  return *z==0;
}

/*
** The string z[] is an ascii representation of a real number.
** Convert this string to a double.
**
** This routine assumes that z[] really is a valid number.  If it
** is not, the result is undefined.
**
** This routine is used instead of the library atof() function because
** the library atof() might want to use "," as the decimal point instead
** of "." depending on how locale is set.  But that would cause problems
** for SQL.  So this routine always uses "." regardless of locale.
*/
double sqlite3AtoF(const char *z, const char **pzEnd){
  int sign = 1;
  LONGDOUBLE_TYPE v1 = 0.0;
  if( *z=='-' ){
    sign = -1;
    z++;
  }else if( *z=='+' ){
    z++;
  }
  while( isdigit(*(u8*)z) ){
    v1 = v1*10.0 + (*z - '0');
    z++;
  }
  if( *z=='.' ){
    LONGDOUBLE_TYPE divisor = 1.0;
    z++;
    while( isdigit(*(u8*)z) ){
      v1 = v1*10.0 + (*z - '0');
      divisor *= 10.0;
      z++;
    }
    v1 /= divisor;
  }
  if( *z=='e' || *z=='E' ){
    int esign = 1;
    int eval = 0;
    LONGDOUBLE_TYPE scale = 1.0;
    z++;
    if( *z=='-' ){
      esign = -1;
      z++;
    }else if( *z=='+' ){
      z++;
    }
    while( isdigit(*(u8*)z) ){
      eval = eval*10 + *z - '0';
      z++;
    }
    while( eval>=64 ){ scale *= 1.0e+64; eval -= 64; }
    while( eval>=16 ){ scale *= 1.0e+16; eval -= 16; }
    while( eval>=4 ){ scale *= 1.0e+4; eval -= 4; }
    while( eval>=1 ){ scale *= 1.0e+1; eval -= 1; }
    if( esign<0 ){
      v1 /= scale;
    }else{
      v1 *= scale;
    }
  }
  if( pzEnd ) *pzEnd = z;
  return sign<0 ? -v1 : v1;
}

/*
** Return TRUE if zNum is a 64-bit signed integer and write
** the value of the integer into *pNum.  If zNum is not an integer
** or is an integer that is too large to be expressed with 64 bits,
** then return false.  If n>0 and the integer is string is not
** exactly n bytes long, return false.
**
** When this routine was originally written it dealt with only
** 32-bit numbers.  At that time, it was much faster than the
** atoi() library routine in RedHat 7.2.
*/
int sqlite3atoi64(const char *zNum, i64 *pNum){
  i64 v = 0;
  int neg;
  int i, c;
  if( *zNum=='-' ){
    neg = 1;
    zNum++;
  }else if( *zNum=='+' ){
    neg = 0;
    zNum++;
  }else{
    neg = 0;
  }
  for(i=0; (c=zNum[i])>='0' && c<='9'; i++){
    v = v*10 + c - '0';
  }
  *pNum = neg ? -v : v;
  return c==0 && i>0 && 
      (i<19 || (i==19 && memcmp(zNum,"9223372036854775807",19)<=0));
}

/*
** The string zNum represents an integer.  There might be some other
** information following the integer too, but that part is ignored.
** If the integer that the prefix of zNum represents will fit in a
** 32-bit signed integer, return TRUE.  Otherwise return FALSE.
**
** This routine returns FALSE for the string -2147483648 even that
** that number will in fact fit in a 32-bit integer.  But positive
** 2147483648 will not fit in 32 bits.  So it seems safer to return
** false.
*/
static int sqlite3FitsIn32Bits(const char *zNum){
  int i, c;
  if( *zNum=='-' || *zNum=='+' ) zNum++;
  for(i=0; (c=zNum[i])>='0' && c<='9'; i++){}
  return i<10 || (i==10 && memcmp(zNum,"2147483647",10)<=0);
}

/*
** If zNum represents an integer that will fit in 32-bits, then set
** *pValue to that integer and return true.  Otherwise return false.
*/
int sqlite3GetInt32(const char *zNum, int *pValue){
  if( sqlite3FitsIn32Bits(zNum) ){
    *pValue = atoi(zNum);
    return 1;
  }
  return 0;
}

/*
** The string zNum represents an integer.  There might be some other
** information following the integer too, but that part is ignored.
** If the integer that the prefix of zNum represents will fit in a
** 64-bit signed integer, return TRUE.  Otherwise return FALSE.
**
** This routine returns FALSE for the string -9223372036854775808 even that
** that number will, in theory fit in a 64-bit integer.  Positive
** 9223373036854775808 will not fit in 64 bits.  So it seems safer to return
** false.
*/
int sqlite3FitsIn64Bits(const char *zNum){
  int i, c;
  if( *zNum=='-' || *zNum=='+' ) zNum++;
  for(i=0; (c=zNum[i])>='0' && c<='9'; i++){}
  return i<19 || (i==19 && memcmp(zNum,"9223372036854775807",19)<=0);
}


/*
** Change the sqlite.magic from SQLITE_MAGIC_OPEN to SQLITE_MAGIC_BUSY.
** Return an error (non-zero) if the magic was not SQLITE_MAGIC_OPEN
** when this routine is called.
**
** This routine is a attempt to detect if two threads use the
** same sqlite* pointer at the same time.  There is a race 
** condition so it is possible that the error is not detected.
** But usually the problem will be seen.  The result will be an
** error which can be used to debug the application that is
** using SQLite incorrectly.
**
** Ticket #202:  If db->magic is not a valid open value, take care not
** to modify the db structure at all.  It could be that db is a stale
** pointer.  In other words, it could be that there has been a prior
** call to sqlite3_close(db) and db has been deallocated.  And we do
** not want to write into deallocated memory.
*/
int sqlite3SafetyOn(sqlite3 *db){
  if( db->magic==SQLITE_MAGIC_OPEN ){
    db->magic = SQLITE_MAGIC_BUSY;
    return 0;
  }else if( db->magic==SQLITE_MAGIC_BUSY || db->magic==SQLITE_MAGIC_ERROR ){
    db->magic = SQLITE_MAGIC_ERROR;
    db->flags |= SQLITE_Interrupt;
  }
  return 1;
}

/*
** Change the magic from SQLITE_MAGIC_BUSY to SQLITE_MAGIC_OPEN.
** Return an error (non-zero) if the magic was not SQLITE_MAGIC_BUSY
** when this routine is called.
*/
int sqlite3SafetyOff(sqlite3 *db){
  if( db->magic==SQLITE_MAGIC_BUSY ){
    db->magic = SQLITE_MAGIC_OPEN;
    return 0;
  }else if( db->magic==SQLITE_MAGIC_OPEN || db->magic==SQLITE_MAGIC_ERROR ){
    db->magic = SQLITE_MAGIC_ERROR;
    db->flags |= SQLITE_Interrupt;
  }
  return 1;
}

/*
** Check to make sure we are not currently executing an sqlite3_exec().
** If we are currently in an sqlite3_exec(), return true and set
** sqlite.magic to SQLITE_MAGIC_ERROR.  This will cause a complete
** shutdown of the database.
**
** This routine is used to try to detect when API routines are called
** at the wrong time or in the wrong sequence.
*/
int sqlite3SafetyCheck(sqlite3 *db){
  if( db->pVdbe!=0 ){
    db->magic = SQLITE_MAGIC_ERROR;
    return 1;
  }
  return 0;
}

/*
** The variable-length integer encoding is as follows:
**
** KEY:
**         A = 0xxxxxxx    7 bits of data and one flag bit
**         B = 1xxxxxxx    7 bits of data and one flag bit
**         C = xxxxxxxx    8 bits of data
**
**  7 bits - A
** 14 bits - BA
** 21 bits - BBA
** 28 bits - BBBA
** 35 bits - BBBBA
** 42 bits - BBBBBA
** 49 bits - BBBBBBA
** 56 bits - BBBBBBBA
** 64 bits - BBBBBBBBC
*/

/*
** Write a 64-bit variable-length integer to memory starting at p[0].
** The length of data write will be between 1 and 9 bytes.  The number
** of bytes written is returned.
**
** A variable-length integer consists of the lower 7 bits of each byte
** for all bytes that have the 8th bit set and one byte with the 8th
** bit clear.  Except, if we get to the 9th byte, it stores the full
** 8 bits and is the last byte.
*/
int sqlite3PutVarint(unsigned char *p, u64 v){
  int i, j, n;
  u8 buf[10];
  if( v & 0xff00000000000000 ){
    p[8] = v;
    v >>= 8;
    for(i=7; i>=0; i--){
      p[i] = (v & 0x7f) | 0x80;
      v >>= 7;
    }
    return 9;
  }    
  n = 0;
  do{
    buf[n++] = (v & 0x7f) | 0x80;
    v >>= 7;
  }while( v!=0 );
  buf[0] &= 0x7f;
  assert( n<=9 );
  for(i=0, j=n-1; j>=0; j--, i++){
    p[i] = buf[j];
  }
  return n;
}

/*
** Read a 64-bit variable-length integer from memory starting at p[0].
** Return the number of bytes read.  The value is stored in *v.
*/
int sqlite3GetVarint(const unsigned char *p, u64 *v){
  u32 x;
  u64 x64;
  int n;
  unsigned char c;
  if( ((c = p[0]) & 0x80)==0 ){
    *v = c;
    return 1;
  }
  x = c & 0x7f;
  if( ((c = p[1]) & 0x80)==0 ){
    *v = (x<<7) | c;
    return 2;
  }
  x = (x<<7) | (c&0x7f);
  if( ((c = p[2]) & 0x80)==0 ){
    *v = (x<<7) | c;
    return 3;
  }
  x = (x<<7) | (c&0x7f);
  if( ((c = p[3]) & 0x80)==0 ){
    *v = (x<<7) | c;
    return 4;
  }
  x64 = (x<<7) | (c&0x7f);
  n = 4;
  do{
    c = p[n++];
    if( n==9 ){
      x64 = (x64<<8) | c;
      break;
    }
    x64 = (x64<<7) | (c&0x7f);
  }while( (c & 0x80)!=0 );
  *v = x64;
  return n;
}

/*
** Read a 32-bit variable-length integer from memory starting at p[0].
** Return the number of bytes read.  The value is stored in *v.
*/
int sqlite3GetVarint32(const unsigned char *p, u32 *v){
  u32 x;
  int n;
  unsigned char c;
  if( ((c = p[0]) & 0x80)==0 ){
    *v = c;
    return 1;
  }
  x = c & 0x7f;
  if( ((c = p[1]) & 0x80)==0 ){
    *v = (x<<7) | c;
    return 2;
  }
  x = (x<<7) | (c & 0x7f);
  n = 2;
  do{
    x = (x<<7) | ((c = p[n++])&0x7f);
  }while( (c & 0x80)!=0 && n<9 );
  *v = x;
  return n;
}

/*
** Return the number of bytes that will be needed to store the given
** 64-bit integer.
*/
int sqlite3VarintLen(u64 v){
  int i = 0;
  do{
    i++;
    v >>= 7;
  }while( v!=0 && i<9 );
  return i;
}

/*
** Translate a single byte of Hex into an integer.
*/
static int hexToInt(int h){
  if( h>='0' && h<='9' ){
    return h - '0';
  }else if( h>='a' && h<='f' ){
    return h - 'a' + 10;
  }else if( h>='A' && h<='F' ){
    return h - 'A' + 10;
  }else{
    return 0;
  }
}

/*
** Convert a BLOB literal of the form "x'hhhhhh'" into its binary
** value.  Return a pointer to its binary value.  Space to hold the
** binary value has been obtained from malloc and must be freed by
** the calling routine.
*/
void *sqlite3HexToBlob(const char *z){
  char *zBlob;
  int i;
  int n = strlen(z);
  if( n%2 ) return 0;

  zBlob = (char *)sqliteMalloc(n/2);
  for(i=0; i<n; i+=2){
    zBlob[i/2] = (hexToInt(z[i])<<4) | hexToInt(z[i+1]);
  }
  return zBlob;
}