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[AROS-Contrib.git] / sqlite3 / util.c

/*
 * 2005 July 4, Markku Sukanen
 *  - modifying the code for AROS.
 *
 * 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.
 * */
/**
 * @file util.c
 * @brief Utility functions used throughout sqlite.
 *
 * This file contains functions for allocating memory, comparing strings, and
 * stuff like that.
 * */
/* $Id$ */
#include "sqliteInt.h"
#include <stdarg.h>
#include <ctype.h>
#include <exec/memory.h>
#include <proto/exec.h>

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

/*
 * For keeping track of the number of mallocs and frees.  This is used to check
 * for memory leaks.  The iMallocFail and iMallocReset values are used to
 * simulate malloc() failures during testing in order to verify that the
 * library correctly handles an out-of-memory condition.
 * */
int sqlite3_nMalloc;         /* Number of sqliteMalloc() calls */
int sqlite3_nFree;           /* Number of sqliteFree() calls */
int sqlite3_iMallocFail;     /* Fail sqliteMalloc() after this many calls */
int sqlite3_iMallocReset = -1; /* When iMallocFail reaches 0, set to this */
#if SQLITE_MEMDEBUG>1
static int memcnt = 0;
#endif

/*
 * Number of 32-bit guard words.  This should probably be a multiple of 2 since
 * on 64-bit machines we want the value returned by sqliteMalloc() to be 8-byte
 * aligned.
 * */
#define N_GUARD 2

/*
 * 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_MEMDEBUG>1
                        fprintf( stderr, "**** failed to allocate %d bytes at %s:%d\n",
                                        n, zFile,line);
#endif
                        sqlite3_iMallocFail = sqlite3_iMallocReset;
                        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 )
        {
                if( n>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_MEMDEBUG>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;
}


/*
 * This version of malloc is always a real function, never a macro
 * */
void *sqlite3MallocX(int n)
{
        return sqlite3Malloc_(n, 0, __FILE__, __LINE__);
}


/*
 * 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_MEMDEBUG>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 )
                return sqlite3Malloc_(n,1,zFile,line);
        if( !n )
        {
                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 )
        {
                if( n>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_MEMDEBUG>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 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_MEMDEBUG */


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

/*
 * 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)))
        {
                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)))
                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 ) return sqliteMalloc(n);
        if( !n )
        {
                sqliteFree( p );
                return 0;
        }
        p2 = realloc(p, n);
        if( !p2 && n>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 ) return NULL;
        zNew = sqliteMallocRaw(strlen(z)+1);
        if( zNew ) strcpy(zNew, z);
        return zNew;
}
char *sqlite3StrNDup(const char *z, int n)
{
        char *zNew;
        if( !z ) return NULL;
        zNew = sqliteMallocRaw(n+1);
        if( zNew )
        {
                memcpy(zNew, z, n);
                zNew[n] = '\0';
        }
        return zNew;
}
#endif /* !defined(SQLITE_MEMDEBUG) */


/*
 * 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(STRPTR *pz, ...)
{
        va_list ap;
        int nByte;
        const char *z;
        char *zResult;

        if( !pz ) return;
        nByte = 1;
        va_start(ap, pz);
        while( (z = va_arg(ap, const char*))!=0 )
                nByte += strlen(z);
        va_end(ap);
        sqliteFree(*pz);
        *pz = zResult = sqliteMallocRaw( nByte );
        if( !zResult )
                return;
        
        *zResult = '\0';
        va_start(ap, pz);
        while( (z = va_arg(ap, const char*)))
        {
                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
}


/*
 * 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->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 ) return;

        switch( (quote = z[0]))
        {
                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

/*
 * 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.
 * */
BOOL 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 BOOL 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.
 * */
BOOL sqlite3GetInt32(const char *zNum, int *pValue)
{
        if( sqlite3FitsIn32Bits(zNum) )
        {
                *pValue = atoi(zNum);
                return TRUE;
        }
        return FALSE;
}


/*
 * 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.
 * */
BOOL 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.
 * */
BOOL sqlite3SafetyOn(sqlite3 *db)
{
        if( db->magic==SQLITE_MAGIC_OPEN )
        {
                db->magic = SQLITE_MAGIC_BUSY;
                return FALSE;
        }
        else if( db->magic==SQLITE_MAGIC_BUSY || db->magic==SQLITE_MAGIC_ERROR )
        {
                db->magic = SQLITE_MAGIC_ERROR;
                db->flags |= SQLITE_Interrupt;
        }
        return TRUE;
}


/*
 * 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.
 * */
BOOL sqlite3SafetyOff(sqlite3 *db)
{
        if( db->magic==SQLITE_MAGIC_BUSY )
        {
                db->magic = SQLITE_MAGIC_OPEN;
                return FALSE;
        }
        else if( db->magic==SQLITE_MAGIC_OPEN || db->magic==SQLITE_MAGIC_ERROR )
        {
                db->magic = SQLITE_MAGIC_ERROR;
                db->flags |= SQLITE_Interrupt;
        }
        return TRUE;
}


/*
 * 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.
 * */
BOOL sqlite3SafetyCheck(sqlite3 *db)
{
        int magic;
        if( !db ) return TRUE;
        magic = db->magic;
        if( magic != SQLITE_MAGIC_CLOSED
                        && magic != SQLITE_MAGIC_OPEN
                        && magic != SQLITE_MAGIC_BUSY ) return TRUE;
        return FALSE;
}


/*
 * 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 );
        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))
        {
                *v = c;
                return 1;
        }
        x = c & 0x7f;
        if( ! ((c = p[1]) & 0x80))
        {
                *v = (x<<7) | c;
                return 2;
        }
        x = (x<<7) | (c&0x7f);
        if( ! ((c = p[2]) & 0x80))
        {
                *v = (x<<7) | c;
                return 3;
        }
        x = (x<<7) | (c&0x7f);
        if( ! ((c = p[3]) & 0x80))
        {
                *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 );
        *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) && 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 && i<9 );
        return i;
}


#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(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;
}
#endif /* !SQLITE_OMIT_BLOB_LITERAL || SQLITE_HAS_CODEC */


#if defined(SQLITE_TEST)
/*
 * Convert text generated by the "%p" conversion format back into a pointer.
 * */
void *sqlite3TextToPtr(const char *z)
{
        void *p;
        u64 v;
        u32 v2;
        if( z[0]=='0' && z[1]=='x' )
                z += 2;
        v = 0;
        while( *z )
        {
                v = (v<<4) + hexToInt(*z);
                z++;
        }
        if( sizeof(p)==sizeof(v) )
                p = *(void**)&v;
        else {
                assert( sizeof(p)==sizeof(v2) );
                v2 = (u32)v;
                p = *(void**)&v2;
        }
        return p;
}
#endif