xref: /sqlite-3.40.0/src/printf.c (revision 72b3fbc7)

/*
** The "printf" code that follows dates from the 1980's.  It is in
** the public domain.  The original comments are included here for
** completeness.  They are very out-of-date but might be useful as
** an historical reference.  Most of the "enhancements" have been backed
** out so that the functionality is now the same as standard printf().
**
**************************************************************************
**
** This file contains code for a set of "printf"-like routines.  These
** routines format strings much like the printf() from the standard C
** library, though the implementation here has enhancements to support
** SQLlite.
*/
#include "sqliteInt.h"

/*
** Conversion types fall into various categories as defined by the
** following enumeration.
*/
#define etRADIX       1 /* Integer types.  %d, %x, %o, and so forth */
#define etFLOAT       2 /* Floating point.  %f */
#define etEXP         3 /* Exponentional notation. %e and %E */
#define etGENERIC     4 /* Floating or exponential, depending on exponent. %g */
#define etSIZE        5 /* Return number of characters processed so far. %n */
#define etSTRING      6 /* Strings. %s */
#define etDYNSTRING   7 /* Dynamically allocated strings. %z */
#define etPERCENT     8 /* Percent symbol. %% */
#define etCHARX       9 /* Characters. %c */
/* The rest are extensions, not normally found in printf() */
#define etSQLESCAPE  10 /* Strings with '\'' doubled.  %q */
#define etSQLESCAPE2 11 /* Strings with '\'' doubled and enclosed in '',
                          NULL pointers replaced by SQL NULL.  %Q */
#define etTOKEN      12 /* a pointer to a Token structure */
#define etSRCLIST    13 /* a pointer to a SrcList */
#define etPOINTER    14 /* The %p conversion */
#define etSQLESCAPE3 15 /* %w -> Strings with '\"' doubled */
#define etORDINAL    16 /* %r -> 1st, 2nd, 3rd, 4th, etc.  English only */

#define etINVALID     0 /* Any unrecognized conversion type */


/*
** An "etByte" is an 8-bit unsigned value.
*/
typedef unsigned char etByte;

/*
** Each builtin conversion character (ex: the 'd' in "%d") is described
** by an instance of the following structure
*/
typedef struct et_info {   /* Information about each format field */
  char fmttype;            /* The format field code letter */
  etByte base;             /* The base for radix conversion */
  etByte flags;            /* One or more of FLAG_ constants below */
  etByte type;             /* Conversion paradigm */
  etByte charset;          /* Offset into aDigits[] of the digits string */
  etByte prefix;           /* Offset into aPrefix[] of the prefix string */
} et_info;

/*
** Allowed values for et_info.flags
*/
#define FLAG_SIGNED  1     /* True if the value to convert is signed */
#define FLAG_INTERN  2     /* True if for internal use only */
#define FLAG_STRING  4     /* Allow infinity precision */


/*
** The following table is searched linearly, so it is good to put the
** most frequently used conversion types first.
*/
static const char aDigits[] = "0123456789ABCDEF0123456789abcdef";
static const char aPrefix[] = "-x0\000X0";
static const et_info fmtinfo[] = {
  {  'd', 10, 1, etRADIX,      0,  0 },
  {  's',  0, 4, etSTRING,     0,  0 },
  {  'g',  0, 1, etGENERIC,    30, 0 },
  {  'z',  0, 4, etDYNSTRING,  0,  0 },
  {  'q',  0, 4, etSQLESCAPE,  0,  0 },
  {  'Q',  0, 4, etSQLESCAPE2, 0,  0 },
  {  'w',  0, 4, etSQLESCAPE3, 0,  0 },
  {  'c',  0, 0, etCHARX,      0,  0 },
  {  'o',  8, 0, etRADIX,      0,  2 },
  {  'u', 10, 0, etRADIX,      0,  0 },
  {  'x', 16, 0, etRADIX,      16, 1 },
  {  'X', 16, 0, etRADIX,      0,  4 },
#ifndef SQLITE_OMIT_FLOATING_POINT
  {  'f',  0, 1, etFLOAT,      0,  0 },
  {  'e',  0, 1, etEXP,        30, 0 },
  {  'E',  0, 1, etEXP,        14, 0 },
  {  'G',  0, 1, etGENERIC,    14, 0 },
#endif
  {  'i', 10, 1, etRADIX,      0,  0 },
  {  'n',  0, 0, etSIZE,       0,  0 },
  {  '%',  0, 0, etPERCENT,    0,  0 },
  {  'p', 16, 0, etPOINTER,    0,  1 },

/* All the rest have the FLAG_INTERN bit set and are thus for internal
** use only */
  {  'T',  0, 2, etTOKEN,      0,  0 },
  {  'S',  0, 2, etSRCLIST,    0,  0 },
  {  'r', 10, 3, etORDINAL,    0,  0 },
};

/*
** If SQLITE_OMIT_FLOATING_POINT is defined, then none of the floating point
** conversions will work.
*/
#ifndef SQLITE_OMIT_FLOATING_POINT
/*
** "*val" is a double such that 0.1 <= *val < 10.0
** Return the ascii code for the leading digit of *val, then
** multiply "*val" by 10.0 to renormalize.
**
** Example:
**     input:     *val = 3.14159
**     output:    *val = 1.4159    function return = '3'
**
** The counter *cnt is incremented each time.  After counter exceeds
** 16 (the number of significant digits in a 64-bit float) '0' is
** always returned.
*/
static char et_getdigit(LONGDOUBLE_TYPE *val, int *cnt){
  int digit;
  LONGDOUBLE_TYPE d;
  if( (*cnt)<=0 ) return '0';
  (*cnt)--;
  digit = (int)*val;
  d = digit;
  digit += '0';
  *val = (*val - d)*10.0;
  return (char)digit;
}
#endif /* SQLITE_OMIT_FLOATING_POINT */

/*
** Append N space characters to the given string buffer.
*/
void sqlite3AppendSpace(StrAccum *pAccum, int N){
  static const char zSpaces[] = "                             ";
  while( N>=(int)sizeof(zSpaces)-1 ){
    sqlite3StrAccumAppend(pAccum, zSpaces, sizeof(zSpaces)-1);
    N -= sizeof(zSpaces)-1;
  }
  if( N>0 ){
    sqlite3StrAccumAppend(pAccum, zSpaces, N);
  }
}

/*
** On machines with a small stack size, you can redefine the
** SQLITE_PRINT_BUF_SIZE to be something smaller, if desired.
*/
#ifndef SQLITE_PRINT_BUF_SIZE
# define SQLITE_PRINT_BUF_SIZE 70
#endif
#define etBUFSIZE SQLITE_PRINT_BUF_SIZE  /* Size of the output buffer */

/*
** Render a string given by "fmt" into the StrAccum object.
*/
void sqlite3VXPrintf(
  StrAccum *pAccum,                  /* Accumulate results here */
  int useExtended,                   /* Allow extended %-conversions */
  const char *fmt,                   /* Format string */
  va_list ap                         /* arguments */
){
  int c;                     /* Next character in the format string */
  char *bufpt;               /* Pointer to the conversion buffer */
  int precision;             /* Precision of the current field */
  int length;                /* Length of the field */
  int idx;                   /* A general purpose loop counter */
  int width;                 /* Width of the current field */
  etByte flag_leftjustify;   /* True if "-" flag is present */
  etByte flag_plussign;      /* True if "+" flag is present */
  etByte flag_blanksign;     /* True if " " flag is present */
  etByte flag_alternateform; /* True if "#" flag is present */
  etByte flag_altform2;      /* True if "!" flag is present */
  etByte flag_zeropad;       /* True if field width constant starts with zero */
  etByte flag_long;          /* True if "l" flag is present */
  etByte flag_longlong;      /* True if the "ll" flag is present */
  etByte done;               /* Loop termination flag */
  etByte xtype = 0;          /* Conversion paradigm */
  char prefix;               /* Prefix character.  "+" or "-" or " " or '\0'. */
  sqlite_uint64 longvalue;   /* Value for integer types */
  LONGDOUBLE_TYPE realvalue; /* Value for real types */
  const et_info *infop;      /* Pointer to the appropriate info structure */
  char *zOut;                /* Rendering buffer */
  int nOut;                  /* Size of the rendering buffer */
  char *zExtra;              /* Malloced memory used by some conversion */
#ifndef SQLITE_OMIT_FLOATING_POINT
  int  exp, e2;              /* exponent of real numbers */
  int nsd;                   /* Number of significant digits returned */
  double rounder;            /* Used for rounding floating point values */
  etByte flag_dp;            /* True if decimal point should be shown */
  etByte flag_rtz;           /* True if trailing zeros should be removed */
#endif
  char buf[etBUFSIZE];       /* Conversion buffer */

  bufpt = 0;
  for(; (c=(*fmt))!=0; ++fmt){
    if( c!='%' ){
      int amt;
      bufpt = (char *)fmt;
      amt = 1;
      while( (c=(*++fmt))!='%' && c!=0 ) amt++;
      sqlite3StrAccumAppend(pAccum, bufpt, amt);
      if( c==0 ) break;
    }
    if( (c=(*++fmt))==0 ){
      sqlite3StrAccumAppend(pAccum, "%", 1);
      break;
    }
    /* Find out what flags are present */
    flag_leftjustify = flag_plussign = flag_blanksign =
     flag_alternateform = flag_altform2 = flag_zeropad = 0;
    done = 0;
    do{
      switch( c ){
        case '-':   flag_leftjustify = 1;     break;
        case '+':   flag_plussign = 1;        break;
        case ' ':   flag_blanksign = 1;       break;
        case '#':   flag_alternateform = 1;   break;
        case '!':   flag_altform2 = 1;        break;
        case '0':   flag_zeropad = 1;         break;
        default:    done = 1;                 break;
      }
    }while( !done && (c=(*++fmt))!=0 );
    /* Get the field width */
    width = 0;
    if( c=='*' ){
      width = va_arg(ap,int);
      if( width<0 ){
        flag_leftjustify = 1;
        width = -width;
      }
      c = *++fmt;
    }else{
      while( c>='0' && c<='9' ){
        width = width*10 + c - '0';
        c = *++fmt;
      }
    }
    /* Get the precision */
    if( c=='.' ){
      precision = 0;
      c = *++fmt;
      if( c=='*' ){
        precision = va_arg(ap,int);
        if( precision<0 ) precision = -precision;
        c = *++fmt;
      }else{
        while( c>='0' && c<='9' ){
          precision = precision*10 + c - '0';
          c = *++fmt;
        }
      }
    }else{
      precision = -1;
    }
    /* Get the conversion type modifier */
    if( c=='l' ){
      flag_long = 1;
      c = *++fmt;
      if( c=='l' ){
        flag_longlong = 1;
        c = *++fmt;
      }else{
        flag_longlong = 0;
      }
    }else{
      flag_long = flag_longlong = 0;
    }
    /* Fetch the info entry for the field */
    infop = &fmtinfo[0];
    xtype = etINVALID;
    for(idx=0; idx<ArraySize(fmtinfo); idx++){
      if( c==fmtinfo[idx].fmttype ){
        infop = &fmtinfo[idx];
        if( useExtended || (infop->flags & FLAG_INTERN)==0 ){
          xtype = infop->type;
        }else{
          return;
        }
        break;
      }
    }
    zExtra = 0;

    /*
    ** At this point, variables are initialized as follows:
    **
    **   flag_alternateform          TRUE if a '#' is present.
    **   flag_altform2               TRUE if a '!' is present.
    **   flag_plussign               TRUE if a '+' is present.
    **   flag_leftjustify            TRUE if a '-' is present or if the
    **                               field width was negative.
    **   flag_zeropad                TRUE if the width began with 0.
    **   flag_long                   TRUE if the letter 'l' (ell) prefixed
    **                               the conversion character.
    **   flag_longlong               TRUE if the letter 'll' (ell ell) prefixed
    **                               the conversion character.
    **   flag_blanksign              TRUE if a ' ' is present.
    **   width                       The specified field width.  This is
    **                               always non-negative.  Zero is the default.
    **   precision                   The specified precision.  The default
    **                               is -1.
    **   xtype                       The class of the conversion.
    **   infop                       Pointer to the appropriate info struct.
    */
    switch( xtype ){
      case etPOINTER:
        flag_longlong = sizeof(char*)==sizeof(i64);
        flag_long = sizeof(char*)==sizeof(long int);
        /* Fall through into the next case */
      case etORDINAL:
      case etRADIX:
        if( infop->flags & FLAG_SIGNED ){
          i64 v;
          if( flag_longlong ){
            v = va_arg(ap,i64);
          }else if( flag_long ){
            v = va_arg(ap,long int);
          }else{
            v = va_arg(ap,int);
          }
          if( v<0 ){
            if( v==SMALLEST_INT64 ){
              longvalue = ((u64)1)<<63;
            }else{
              longvalue = -v;
            }
            prefix = '-';
          }else{
            longvalue = v;
            if( flag_plussign )        prefix = '+';
            else if( flag_blanksign )  prefix = ' ';
            else                       prefix = 0;
          }
        }else{
          if( flag_longlong ){
            longvalue = va_arg(ap,u64);
          }else if( flag_long ){
            longvalue = va_arg(ap,unsigned long int);
          }else{
            longvalue = va_arg(ap,unsigned int);
          }
          prefix = 0;
        }
        if( longvalue==0 ) flag_alternateform = 0;
        if( flag_zeropad && precision<width-(prefix!=0) ){
          precision = width-(prefix!=0);
        }
        if( precision<etBUFSIZE-10 ){
          nOut = etBUFSIZE;
          zOut = buf;
        }else{
          nOut = precision + 10;
          zOut = zExtra = sqlite3Malloc( nOut );
          if( zOut==0 ){
            pAccum->mallocFailed = 1;
            return;
          }
        }
        bufpt = &zOut[nOut-1];
        if( xtype==etORDINAL ){
          static const char zOrd[] = "thstndrd";
          int x = (int)(longvalue % 10);
          if( x>=4 || (longvalue/10)%10==1 ){
            x = 0;
          }
          *(--bufpt) = zOrd[x*2+1];
          *(--bufpt) = zOrd[x*2];
        }
        {
          register const char *cset;      /* Use registers for speed */
          register int base;
          cset = &aDigits[infop->charset];
          base = infop->base;
          do{                                           /* Convert to ascii */
            *(--bufpt) = cset[longvalue%base];
            longvalue = longvalue/base;
          }while( longvalue>0 );
        }
        length = (int)(&zOut[nOut-1]-bufpt);
        for(idx=precision-length; idx>0; idx--){
          *(--bufpt) = '0';                             /* Zero pad */
        }
        if( prefix ) *(--bufpt) = prefix;               /* Add sign */
        if( flag_alternateform && infop->prefix ){      /* Add "0" or "0x" */
          const char *pre;
          char x;
          pre = &aPrefix[infop->prefix];
          for(; (x=(*pre))!=0; pre++) *(--bufpt) = x;
        }
        length = (int)(&zOut[nOut-1]-bufpt);
        break;
      case etFLOAT:
      case etEXP:
      case etGENERIC:
        realvalue = va_arg(ap,double);
#ifdef SQLITE_OMIT_FLOATING_POINT
        length = 0;
#else
        if( precision<0 ) precision = 6;         /* Set default precision */
        if( realvalue<0.0 ){
          realvalue = -realvalue;
          prefix = '-';
        }else{
          if( flag_plussign )          prefix = '+';
          else if( flag_blanksign )    prefix = ' ';
          else                         prefix = 0;
        }
        if( xtype==etGENERIC && precision>0 ) precision--;
#if 0
        /* Rounding works like BSD when the constant 0.4999 is used.  Wierd! */
        for(idx=precision, rounder=0.4999; idx>0; idx--, rounder*=0.1);
#else
        /* It makes more sense to use 0.5 */
        for(idx=precision, rounder=0.5; idx>0; idx--, rounder*=0.1){}
#endif
        if( xtype==etFLOAT ) realvalue += rounder;
        /* Normalize realvalue to within 10.0 > realvalue >= 1.0 */
        exp = 0;
        if( sqlite3IsNaN((double)realvalue) ){
          bufpt = "NaN";
          length = 3;
          break;
        }
        if( realvalue>0.0 ){
          LONGDOUBLE_TYPE scale = 1.0;
          while( realvalue>=1e64*scale && exp<=350 ){ scale *= 1e64; exp+=64; }
          while( realvalue>=1e8*scale && exp<=350 ){ scale *= 1e8; exp+=8; }
          while( realvalue>=10.0*scale && exp<=350 ){ scale *= 10.0; exp++; }
          realvalue /= scale;
          while( realvalue<1e-8 ){ realvalue *= 1e8; exp-=8; }
          while( realvalue<1.0 ){ realvalue *= 10.0; exp--; }
          if( exp>350 ){
            if( prefix=='-' ){
              bufpt = "-Inf";
            }else if( prefix=='+' ){
              bufpt = "+Inf";
            }else{
              bufpt = "Inf";
            }
            length = sqlite3Strlen30(bufpt);
            break;
          }
        }
        bufpt = buf;
        /*
        ** If the field type is etGENERIC, then convert to either etEXP
        ** or etFLOAT, as appropriate.
        */
        if( xtype!=etFLOAT ){
          realvalue += rounder;
          if( realvalue>=10.0 ){ realvalue *= 0.1; exp++; }
        }
        if( xtype==etGENERIC ){
          flag_rtz = !flag_alternateform;
          if( exp<-4 || exp>precision ){
            xtype = etEXP;
          }else{
            precision = precision - exp;
            xtype = etFLOAT;
          }
        }else{
          flag_rtz = flag_altform2;
        }
        if( xtype==etEXP ){
          e2 = 0;
        }else{
          e2 = exp;
        }
        if( e2+precision+width > etBUFSIZE - 15 ){
          bufpt = zExtra = sqlite3Malloc( e2+precision+width+15 );
          if( bufpt==0 ){
            pAccum->mallocFailed = 1;
            return;
          }
        }
        zOut = bufpt;
        nsd = 16 + flag_altform2*10;
        flag_dp = (precision>0 ?1:0) | flag_alternateform | flag_altform2;
        /* The sign in front of the number */
        if( prefix ){
          *(bufpt++) = prefix;
        }
        /* Digits prior to the decimal point */
        if( e2<0 ){
          *(bufpt++) = '0';
        }else{
          for(; e2>=0; e2--){
            *(bufpt++) = et_getdigit(&realvalue,&nsd);
          }
        }
        /* The decimal point */
        if( flag_dp ){
          *(bufpt++) = '.';
        }
        /* "0" digits after the decimal point but before the first
        ** significant digit of the number */
        for(e2++; e2<0; precision--, e2++){
          assert( precision>0 );
          *(bufpt++) = '0';
        }
        /* Significant digits after the decimal point */
        while( (precision--)>0 ){
          *(bufpt++) = et_getdigit(&realvalue,&nsd);
        }
        /* Remove trailing zeros and the "." if no digits follow the "." */
        if( flag_rtz && flag_dp ){
          while( bufpt[-1]=='0' ) *(--bufpt) = 0;
          assert( bufpt>zOut );
          if( bufpt[-1]=='.' ){
            if( flag_altform2 ){
              *(bufpt++) = '0';
            }else{
              *(--bufpt) = 0;
            }
          }
        }
        /* Add the "eNNN" suffix */
        if( xtype==etEXP ){
          *(bufpt++) = aDigits[infop->charset];
          if( exp<0 ){
            *(bufpt++) = '-'; exp = -exp;
          }else{
            *(bufpt++) = '+';
          }
          if( exp>=100 ){
            *(bufpt++) = (char)((exp/100)+'0');        /* 100's digit */
            exp %= 100;
          }
          *(bufpt++) = (char)(exp/10+'0');             /* 10's digit */
          *(bufpt++) = (char)(exp%10+'0');             /* 1's digit */
        }
        *bufpt = 0;

        /* The converted number is in buf[] and zero terminated. Output it.
        ** Note that the number is in the usual order, not reversed as with
        ** integer conversions. */
        length = (int)(bufpt-zOut);
        bufpt = zOut;

        /* Special case:  Add leading zeros if the flag_zeropad flag is
        ** set and we are not left justified */
        if( flag_zeropad && !flag_leftjustify && length < width){
          int i;
          int nPad = width - length;
          for(i=width; i>=nPad; i--){
            bufpt[i] = bufpt[i-nPad];
          }
          i = prefix!=0;
          while( nPad-- ) bufpt[i++] = '0';
          length = width;
        }
#endif /* !defined(SQLITE_OMIT_FLOATING_POINT) */
        break;
      case etSIZE:
        *(va_arg(ap,int*)) = pAccum->nChar;
        length = width = 0;
        break;
      case etPERCENT:
        buf[0] = '%';
        bufpt = buf;
        length = 1;
        break;
      case etCHARX:
        c = va_arg(ap,int);
        buf[0] = (char)c;
        if( precision>=0 ){
          for(idx=1; idx<precision; idx++) buf[idx] = (char)c;
          length = precision;
        }else{
          length =1;
        }
        bufpt = buf;
        break;
      case etSTRING:
      case etDYNSTRING:
        bufpt = va_arg(ap,char*);
        if( bufpt==0 ){
          bufpt = "";
        }else if( xtype==etDYNSTRING ){
          zExtra = bufpt;
        }
        if( precision>=0 ){
          for(length=0; length<precision && bufpt[length]; length++){}
        }else{
          length = sqlite3Strlen30(bufpt);
        }
        break;
      case etSQLESCAPE:
      case etSQLESCAPE2:
      case etSQLESCAPE3: {
        int i, j, k, n, isnull;
        int needQuote;
        char ch;
        char q = ((xtype==etSQLESCAPE3)?'"':'\'');   /* Quote character */
        char *escarg = va_arg(ap,char*);
        isnull = escarg==0;
        if( isnull ) escarg = (xtype==etSQLESCAPE2 ? "NULL" : "(NULL)");
        k = precision;
        for(i=n=0; k!=0 && (ch=escarg[i])!=0; i++, k--){
          if( ch==q )  n++;
        }
        needQuote = !isnull && xtype==etSQLESCAPE2;
        n += i + 1 + needQuote*2;
        if( n>etBUFSIZE ){
          bufpt = zExtra = sqlite3Malloc( n );
          if( bufpt==0 ){
            pAccum->mallocFailed = 1;
            return;
          }
        }else{
          bufpt = buf;
        }
        j = 0;
        if( needQuote ) bufpt[j++] = q;
        k = i;
        for(i=0; i<k; i++){
          bufpt[j++] = ch = escarg[i];
          if( ch==q ) bufpt[j++] = ch;
        }
        if( needQuote ) bufpt[j++] = q;
        bufpt[j] = 0;
        length = j;
        /* The precision in %q and %Q means how many input characters to
        ** consume, not the length of the output...
        ** if( precision>=0 && precision<length ) length = precision; */
        break;
      }
      case etTOKEN: {
        Token *pToken = va_arg(ap, Token*);
        if( pToken ){
          sqlite3StrAccumAppend(pAccum, (const char*)pToken->z, pToken->n);
        }
        length = width = 0;
        break;
      }
      case etSRCLIST: {
        SrcList *pSrc = va_arg(ap, SrcList*);
        int k = va_arg(ap, int);
        struct SrcList_item *pItem = &pSrc->a[k];
        assert( k>=0 && k<pSrc->nSrc );
        if( pItem->zDatabase ){
          sqlite3StrAccumAppend(pAccum, pItem->zDatabase, -1);
          sqlite3StrAccumAppend(pAccum, ".", 1);
        }
        sqlite3StrAccumAppend(pAccum, pItem->zName, -1);
        length = width = 0;
        break;
      }
      default: {
        assert( xtype==etINVALID );
        return;
      }
    }/* End switch over the format type */
    /*
    ** The text of the conversion is pointed to by "bufpt" and is
    ** "length" characters long.  The field width is "width".  Do
    ** the output.
    */
    if( !flag_leftjustify ){
      register int nspace;
      nspace = width-length;
      if( nspace>0 ){
        sqlite3AppendSpace(pAccum, nspace);
      }
    }
    if( length>0 ){
      sqlite3StrAccumAppend(pAccum, bufpt, length);
    }
    if( flag_leftjustify ){
      register int nspace;
      nspace = width-length;
      if( nspace>0 ){
        sqlite3AppendSpace(pAccum, nspace);
      }
    }
    sqlite3_free(zExtra);
  }/* End for loop over the format string */
} /* End of function */

/*
** Append N bytes of text from z to the StrAccum object.
*/
void sqlite3StrAccumAppend(StrAccum *p, const char *z, int N){
  assert( z!=0 || N==0 );
  if( p->tooBig | p->mallocFailed ){
    testcase(p->tooBig);
    testcase(p->mallocFailed);
    return;
  }
  assert( p->zText!=0 || p->nChar==0 );
  if( N<0 ){
    N = sqlite3Strlen30(z);
  }
  if( N==0 || NEVER(z==0) ){
    return;
  }
  if( p->nChar+N >= p->nAlloc ){
    char *zNew;
    if( !p->useMalloc ){
      p->tooBig = 1;
      N = p->nAlloc - p->nChar - 1;
      if( N<=0 ){
        return;
      }
    }else{
      char *zOld = (p->zText==p->zBase ? 0 : p->zText);
      i64 szNew = p->nChar;
      szNew += N + 1;
      if( szNew > p->mxAlloc ){
        sqlite3StrAccumReset(p);
        p->tooBig = 1;
        return;
      }else{
        p->nAlloc = (int)szNew;
      }
      if( p->useMalloc==1 ){
        zNew = sqlite3DbRealloc(p->db, zOld, p->nAlloc);
      }else{
        zNew = sqlite3_realloc(zOld, p->nAlloc);
      }
      if( zNew ){
        if( zOld==0 && p->nChar>0 ) memcpy(zNew, p->zText, p->nChar);
        p->zText = zNew;
      }else{
        p->mallocFailed = 1;
        sqlite3StrAccumReset(p);
        return;
      }
    }
  }
  assert( p->zText );
  memcpy(&p->zText[p->nChar], z, N);
  p->nChar += N;
}

/*
** Finish off a string by making sure it is zero-terminated.
** Return a pointer to the resulting string.  Return a NULL
** pointer if any kind of error was encountered.
*/
char *sqlite3StrAccumFinish(StrAccum *p){
  if( p->zText ){
    p->zText[p->nChar] = 0;
    if( p->useMalloc && p->zText==p->zBase ){
      if( p->useMalloc==1 ){
        p->zText = sqlite3DbMallocRaw(p->db, p->nChar+1 );
      }else{
        p->zText = sqlite3_malloc(p->nChar+1);
      }
      if( p->zText ){
        memcpy(p->zText, p->zBase, p->nChar+1);
      }else{
        p->mallocFailed = 1;
      }
    }
  }
  return p->zText;
}

/*
** Reset an StrAccum string.  Reclaim all malloced memory.
*/
void sqlite3StrAccumReset(StrAccum *p){
  if( p->zText!=p->zBase ){
    if( p->useMalloc==1 ){
      sqlite3DbFree(p->db, p->zText);
    }else{
      sqlite3_free(p->zText);
    }
  }
  p->zText = 0;
}

/*
** Initialize a string accumulator
*/
void sqlite3StrAccumInit(StrAccum *p, char *zBase, int n, int mx){
  p->zText = p->zBase = zBase;
  p->db = 0;
  p->nChar = 0;
  p->nAlloc = n;
  p->mxAlloc = mx;
  p->useMalloc = 1;
  p->tooBig = 0;
  p->mallocFailed = 0;
}

/*
** Print into memory obtained from sqliteMalloc().  Use the internal
** %-conversion extensions.
*/
char *sqlite3VMPrintf(sqlite3 *db, const char *zFormat, va_list ap){
  char *z;
  char zBase[SQLITE_PRINT_BUF_SIZE];
  StrAccum acc;
  assert( db!=0 );
  sqlite3StrAccumInit(&acc, zBase, sizeof(zBase),
                      db->aLimit[SQLITE_LIMIT_LENGTH]);
  acc.db = db;
  sqlite3VXPrintf(&acc, 1, zFormat, ap);
  z = sqlite3StrAccumFinish(&acc);
  if( acc.mallocFailed ){
    db->mallocFailed = 1;
  }
  return z;
}

/*
** Print into memory obtained from sqliteMalloc().  Use the internal
** %-conversion extensions.
*/
char *sqlite3MPrintf(sqlite3 *db, const char *zFormat, ...){
  va_list ap;
  char *z;
  va_start(ap, zFormat);
  z = sqlite3VMPrintf(db, zFormat, ap);
  va_end(ap);
  return z;
}

/*
** Like sqlite3MPrintf(), but call sqlite3DbFree() on zStr after formatting
** the string and before returnning.  This routine is intended to be used
** to modify an existing string.  For example:
**
**       x = sqlite3MPrintf(db, x, "prefix %s suffix", x);
**
*/
char *sqlite3MAppendf(sqlite3 *db, char *zStr, const char *zFormat, ...){
  va_list ap;
  char *z;
  va_start(ap, zFormat);
  z = sqlite3VMPrintf(db, zFormat, ap);
  va_end(ap);
  sqlite3DbFree(db, zStr);
  return z;
}

/*
** Print into memory obtained from sqlite3_malloc().  Omit the internal
** %-conversion extensions.
*/
char *sqlite3_vmprintf(const char *zFormat, va_list ap){
  char *z;
  char zBase[SQLITE_PRINT_BUF_SIZE];
  StrAccum acc;
#ifndef SQLITE_OMIT_AUTOINIT
  if( sqlite3_initialize() ) return 0;
#endif
  sqlite3StrAccumInit(&acc, zBase, sizeof(zBase), SQLITE_MAX_LENGTH);
  acc.useMalloc = 2;
  sqlite3VXPrintf(&acc, 0, zFormat, ap);
  z = sqlite3StrAccumFinish(&acc);
  return z;
}

/*
** Print into memory obtained from sqlite3_malloc()().  Omit the internal
** %-conversion extensions.
*/
char *sqlite3_mprintf(const char *zFormat, ...){
  va_list ap;
  char *z;
#ifndef SQLITE_OMIT_AUTOINIT
  if( sqlite3_initialize() ) return 0;
#endif
  va_start(ap, zFormat);
  z = sqlite3_vmprintf(zFormat, ap);
  va_end(ap);
  return z;
}

/*
** sqlite3_snprintf() works like snprintf() except that it ignores the
** current locale settings.  This is important for SQLite because we
** are not able to use a "," as the decimal point in place of "." as
** specified by some locales.
**
** Oops:  The first two arguments of sqlite3_snprintf() are backwards
** from the snprintf() standard.  Unfortunately, it is too late to change
** this without breaking compatibility, so we just have to live with the
** mistake.
**
** sqlite3_vsnprintf() is the varargs version.
*/
char *sqlite3_vsnprintf(int n, char *zBuf, const char *zFormat, va_list ap){
  StrAccum acc;
  if( n<=0 ) return zBuf;
  sqlite3StrAccumInit(&acc, zBuf, n, 0);
  acc.useMalloc = 0;
  sqlite3VXPrintf(&acc, 0, zFormat, ap);
  return sqlite3StrAccumFinish(&acc);
}
char *sqlite3_snprintf(int n, char *zBuf, const char *zFormat, ...){
  char *z;
  va_list ap;
  va_start(ap,zFormat);
  z = sqlite3_vsnprintf(n, zBuf, zFormat, ap);
  va_end(ap);
  return z;
}

/*
** This is the routine that actually formats the sqlite3_log() message.
** We house it in a separate routine from sqlite3_log() to avoid using
** stack space on small-stack systems when logging is disabled.
**
** sqlite3_log() must render into a static buffer.  It cannot dynamically
** allocate memory because it might be called while the memory allocator
** mutex is held.
*/
static void renderLogMsg(int iErrCode, const char *zFormat, va_list ap){
  StrAccum acc;                          /* String accumulator */
  char zMsg[SQLITE_PRINT_BUF_SIZE*3];    /* Complete log message */

  sqlite3StrAccumInit(&acc, zMsg, sizeof(zMsg), 0);
  acc.useMalloc = 0;
  sqlite3VXPrintf(&acc, 0, zFormat, ap);
  sqlite3GlobalConfig.xLog(sqlite3GlobalConfig.pLogArg, iErrCode,
                           sqlite3StrAccumFinish(&acc));
}

/*
** Format and write a message to the log if logging is enabled.
*/
void sqlite3_log(int iErrCode, const char *zFormat, ...){
  va_list ap;                             /* Vararg list */
  if( sqlite3GlobalConfig.xLog ){
    va_start(ap, zFormat);
    renderLogMsg(iErrCode, zFormat, ap);
    va_end(ap);
  }
}

#if defined(SQLITE_DEBUG)
/*
** A version of printf() that understands %lld.  Used for debugging.
** The printf() built into some versions of windows does not understand %lld
** and segfaults if you give it a long long int.
*/
void sqlite3DebugPrintf(const char *zFormat, ...){
  va_list ap;
  StrAccum acc;
  char zBuf[500];
  sqlite3StrAccumInit(&acc, zBuf, sizeof(zBuf), 0);
  acc.useMalloc = 0;
  va_start(ap,zFormat);
  sqlite3VXPrintf(&acc, 0, zFormat, ap);
  va_end(ap);
  sqlite3StrAccumFinish(&acc);
  fprintf(stdout,"%s", zBuf);
  fflush(stdout);
}
#endif

#ifndef SQLITE_OMIT_TRACE
/*
** variable-argument wrapper around sqlite3VXPrintf().
*/
void sqlite3XPrintf(StrAccum *p, const char *zFormat, ...){
  va_list ap;
  va_start(ap,zFormat);
  sqlite3VXPrintf(p, 1, zFormat, ap);
  va_end(ap);
}
#endif