diff -r 5f8e5adbbed9 -r 29cda98b007e engine/sqlite/src/util.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/engine/sqlite/src/util.cpp	Thu Feb 25 14:29:19 2010 +0000
@@ -0,0 +1,707 @@
+/*
+** 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.cpp 1282 2008-11-13 09:31:33Z LarsPson $
+*/
+#include "sqliteInt.h"
+#include <stdarg.h>
+#include <ctype.h>
+
+
+/*
+** 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 sqlite 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))!=0) ){
+    db->errCode = err_code;
+    if( zFormat ){
+      char *z;
+      va_list ap;
+      va_start(ap, zFormat);
+      z = sqlite3VMPrintf(db, zFormat, ap);
+      va_end(ap);
+      sqlite3ValueSetStr(db->pErr, -1, z, SQLITE_UTF8, sqlite3_free);
+    }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++;
+  sqlite3_free(pParse->zErrMsg);
+  va_start(ap, zFormat);
+  pParse->zErrMsg = sqlite3VMPrintf(pParse->db, zFormat, ap);
+  va_end(ap);
+  if( pParse->rc==SQLITE_OK ){
+    pParse->rc = SQLITE_ERROR;
+  }
+}
+
+/*
+** Clear the error message in pParse, if any
+*/
+void sqlite3ErrorClear(Parse *pParse){
+  sqlite3_free(pParse->zErrMsg);
+  pParse->zErrMsg = 0;
+  pParse->nErr = 0;
+}
+
+/*
+** 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 '`':   break;                /* For MySQL compatibility */
+    case '[':   quote = ']';  break;  /* For MS SqlServer compatibility */
+    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[] = {
+#ifdef SQLITE_ASCII
+      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
+#endif
+#ifdef SQLITE_EBCDIC
+      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, /* 0x */
+     16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, /* 1x */
+     32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, /* 2x */
+     48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, /* 3x */
+     64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, /* 4x */
+     80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, /* 5x */
+     96, 97, 66, 67, 68, 69, 70, 71, 72, 73,106,107,108,109,110,111, /* 6x */
+    112, 81, 82, 83, 84, 85, 86, 87, 88, 89,122,123,124,125,126,127, /* 7x */
+    128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143, /* 8x */
+    144,145,146,147,148,149,150,151,152,153,154,155,156,157,156,159, /* 9x */
+    160,161,162,163,164,165,166,167,168,169,170,171,140,141,142,175, /* Ax */
+    176,177,178,179,180,181,182,183,184,185,186,187,188,189,190,191, /* Bx */
+    192,129,130,131,132,133,134,135,136,137,202,203,204,205,206,207, /* Cx */
+    208,145,146,147,148,149,150,151,152,153,218,219,220,221,222,223, /* Dx */
+    224,225,162,163,164,165,166,167,168,169,232,203,204,205,206,207, /* Ex */
+    239,240,241,242,243,244,245,246,247,248,249,219,220,221,222,255, /* Fx */
+#endif
+};
+#define UpperToLower sqlite3UpperToLower
+
+/*
+** 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.
+*/
+int sqlite3AtoF(const char *z, double *pResult){
+#ifndef SQLITE_OMIT_FLOATING_POINT
+  int sign = 1;
+  const char *zBegin = z;
+  LONGDOUBLE_TYPE v1 = 0.0;
+  while( isspace(*(u8*)z) ) z++;
+  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;
+    }
+  }
+  *pResult = sign<0 ? -v1 : v1;
+  return z - zBegin;
+#else
+  return sqlite3Atoi64(z, pResult);
+#endif /* SQLITE_OMIT_FLOATING_POINT */
+}
+
+/*
+** Compare the 19-character string zNum against the text representation
+** value 2^63:  9223372036854775808.  Return negative, zero, or positive
+** if zNum is less than, equal to, or greater than the string.
+**
+** Unlike memcmp() this routine is guaranteed to return the difference
+** in the values of the last digit if the only difference is in the
+** last digit.  So, for example,
+**
+**      compare2pow63("9223372036854775800")
+**
+** will return -8.
+*/
+static int compare2pow63(const char *zNum){
+  int c;
+  c = memcmp(zNum,"922337203685477580",18);
+  if( c==0 ){
+    c = zNum[18] - '8';
+  }
+  return c;
+}
+
+
+/*
+** 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.
+**
+** 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;
+  while( isspace(*(u8*)zNum) ) zNum++;
+  if( *zNum=='-' ){
+    neg = 1;
+    zNum++;
+  }else if( *zNum=='+' ){
+    neg = 0;
+    zNum++;
+  }else{
+    neg = 0;
+  }
+  while( zNum[0]=='0' ){ zNum++; } /* Skip over leading zeros. Ticket #2454 */
+  for(i=0; (c=zNum[i])>='0' && c<='9'; i++){
+    v = v*10 + c - '0';
+  }
+  *pNum = neg ? -v : v;
+  if( c!=0 || i==0 || i>19 ){
+    /* zNum is empty or contains non-numeric text or is longer
+    ** than 19 digits (thus guaranting that it is too large) */
+    return 0;
+  }else if( i<19 ){
+    /* Less than 19 digits, so we know that it fits in 64 bits */
+    return 1;
+  }else{
+    /* 19-digit numbers must be no larger than 9223372036854775807 if positive
+    ** or 9223372036854775808 if negative.  Note that 9223372036854665808
+    ** is 2^63. */
+    return compare2pow63(zNum)<neg;
+  }
+}
+
+/*
+** 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 negFlag){
+  int i, c;
+  int neg = 0;
+  if( *zNum=='-' ){
+    neg = 1;
+    zNum++;
+  }else if( *zNum=='+' ){
+    zNum++;
+  }
+  if( negFlag ) neg = 1-neg;
+  while( *zNum=='0' ){
+    zNum++;   /* Skip leading zeros.  Ticket #2454 */
+  }
+  for(i=0; (c=zNum[i])>='0' && c<='9'; i++){}
+  if( i<19 ){
+    /* Guaranteed to fit if less than 19 digits */
+    return 1;
+  }else if( i>19 ){
+    /* Guaranteed to be too big if greater than 19 digits */
+    return 0;
+  }else{
+    /* Compare against 2^63. */
+    return compare2pow63(zNum)<neg;
+  }
+}
+
+/*
+** If zNum represents an integer that will fit in 32-bits, then set
+** *pValue to that integer and return true.  Otherwise return false.
+**
+** Any non-numeric characters that following zNum are ignored.
+** This is different from sqlite3Atoi64() which requires the
+** input number to be zero-terminated.
+*/
+int sqlite3GetInt32(const char *zNum, int *pValue){
+  sqlite_int64 v = 0;
+  int i, c;
+  int neg = 0;
+  if( zNum[0]=='-' ){
+    neg = 1;
+    zNum++;
+  }else if( zNum[0]=='+' ){
+    zNum++;
+  }
+  while( zNum[0]=='0' ) zNum++;
+  for(i=0; i<11 && (c = zNum[i] - '0')>=0 && c<=9; i++){
+    v = v*10 + c;
+  }
+
+  /* The longest decimal representation of a 32 bit integer is 10 digits:
+  **
+  **             1234567890
+  **     2^31 -> 2147483648
+  */
+  if( i>10 ){
+    return 0;
+  }
+  if( v-neg>2147483647 ){
+    return 0;
+  }
+  if( neg ){
+    v = -v;
+  }
+  *pValue = (int)v;
+  return 1;
+}
+
+/*
+** Check to make sure we have a valid db pointer.  This test is not
+** foolproof but it does provide some measure of protection against
+** misuse of the interface such as passing in db pointers that are
+** NULL or which have been previously closed.  If this routine returns
+** TRUE it means that the db pointer is invalid and should not be
+** dereferenced for any reason.  The calling function should invoke
+** SQLITE_MISUSE immediately.
+*/
+int sqlite3SafetyCheck(sqlite3 *db){
+  int magic;
+  if( db==0 ) return 1;
+  magic = db->magic;
+  if( magic!=SQLITE_MAGIC_CLOSED &&
+         magic!=SQLITE_MAGIC_OPEN &&
+         magic!=SQLITE_MAGIC_BUSY ) 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 & (((u64)0xff000000)<<32) ){
+    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( ((signed char*)p)[0]>=0 ){
+    *v = p[0];
+    return 1;
+  }
+  x = p[0] & 0x7f;
+  if( ((signed char*)p)[1]>=0 ){
+    *v = (x<<7) | p[1];
+    return 2;
+  }
+  x = (x<<7) | (p[1] & 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;
+}
+
+
+/*
+** Read or write a four-byte big-endian integer value.
+*/
+u32 sqlite3Get4byte(const u8 *p){
+  return (p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];
+}
+void sqlite3Put4byte(unsigned char *p, u32 v){
+  p[0] = v>>24;
+  p[1] = v>>16;
+  p[2] = v>>8;
+  p[3] = v;
+}
+
+
+
+#if !defined(SQLITE_OMIT_BLOB_LITERAL) || defined(SQLITE_HAS_CODEC) \
+    || defined(SQLITE_TEST)
+/*
+** 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{
+    assert( h>='A' && h<='F' );
+    return h - 'A' + 10;
+  }
+}
+#endif /* !SQLITE_OMIT_BLOB_LITERAL || SQLITE_HAS_CODEC || SQLITE_TEST */
+
+#if !defined(SQLITE_OMIT_BLOB_LITERAL) || defined(SQLITE_HAS_CODEC)
+/*
+** 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(sqlite3 *db, const char *z){
+  char *zBlob;
+  int i;
+  int n = strlen(z);
+  if( n%2 ) return 0;
+
+  zBlob = (char *)sqlite3DbMallocRaw(db, n/2);
+  if( zBlob ){
+    for(i=0; i<n; i+=2){
+      zBlob[i/2] = (hexToInt(z[i])<<4) | hexToInt(z[i+1]);
+    }
+  }
+  return zBlob;
+}
+#endif /* !SQLITE_OMIT_BLOB_LITERAL || SQLITE_HAS_CODEC */
+
+
+/*
+** 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 called when entering an SQLite API.  The SQLITE_MAGIC_OPEN
+** value indicates that the database connection passed into the API is
+** open and is not being used by another thread.  By changing the value
+** to SQLITE_MAGIC_BUSY we indicate that the connection is in use.
+** sqlite3SafetyOff() below will change the value back to SQLITE_MAGIC_OPEN
+** when the API exits. 
+**
+** 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->u1.isInterrupted = 1;
+  }
+  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 {
+    db->magic = SQLITE_MAGIC_ERROR;
+    db->u1.isInterrupted = 1;
+    return 1;
+  }
+}