SQLite

  d = digit;
  digit += '0';
  *val = (*val - d)*10.0;
  return (char)digit;
}
#endif /* SQLITE_OMIT_FLOATING_POINT */

#ifndef SQLITE_OMIT_FLOATING_POINT
/*
** "*val" is a u64.  *msd is a divisor used to extract the
** most significant digit of *val.  Extract that most significant
** digit and return it.
*/
static char et_getdigit_int(u64 *val, u64 *msd){
  u64 x = (*val)/(*msd);
  *val -= x*(*msd);
  if( *msd>=10 ) *msd /= 10;
  return '0' + (char)(x & 15);
}
#endif /* SQLITE_OMIT_FLOATING_POINT */

/*
** Set the StrAccum object to an error mode.
*/
void sqlite3StrAccumSetError(StrAccum *p, u8 eError){
  assert( eError==SQLITE_NOMEM || eError==SQLITE_TOOBIG );
  p->accError = eError;
  if( p->mxAlloc ) sqlite3_str_reset(p);

  etByte done;               /* Loop termination flag */
  etByte cThousand;          /* Thousands separator for %d and %u */
  etByte xtype = etINVALID;  /* Conversion paradigm */
  u8 bArgList;               /* True for SQLITE_PRINTF_SQLFUNC */
  char prefix;               /* Prefix character.  "+" or "-" or " " or '\0'. */
  sqlite_uint64 longvalue;   /* Value for integer types */
  LONGDOUBLE_TYPE realvalue; /* Value for real types */
  sqlite_uint64 msd;         /* Divisor to get most-significant-digit
                             ** of longvalue */
  const et_info *infop;      /* Pointer to the appropriate info structure */
  char *zOut;                /* Rendering buffer */
  int nOut;                  /* Size of the rendering buffer */
  char *zExtra = 0;          /* 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 */

#endif
        if( realvalue<0.0 ){
          realvalue = -realvalue;
          prefix = '-';
        }else{
          prefix = flag_prefix;
        }
        exp = 0;
        if( xtype==etGENERIC && precision>0 ) precision--;
        testcase( precision>0xfff );
        if( realvalue<1.0e+16
         && realvalue==(LONGDOUBLE_TYPE)(longvalue = (u64)realvalue)
        ){
          /* Number is a pure integer that can be represented as u64 */
          for(msd=1; msd*10<=longvalue; msd *= 10, exp++){}
          if( exp>precision && xtype!=etFLOAT ){
            u64 rnd = msd/2;
            int kk = precision;
            while( kk-- > 0 ){  rnd /= 10; }
            longvalue += rnd;
          }
        }else{
          msd = 0;
          longvalue = 0;  /* To prevent a compiler warning */
          idx = precision & 0xfff;
          rounder = arRound[idx%10];
          while( idx>=10 ){ rounder *= 1.0e-10; idx -= 10; }
          if( xtype==etFLOAT ){
            double rx = (double)realvalue;
            sqlite3_uint64 u;
            int ex;
            memcpy(&u, &rx, sizeof(u));
            ex = -1023 + (int)((u>>52)&0x7ff);
            if( precision+(ex/3) < 15 ) rounder += realvalue*3e-16;
            realvalue += rounder;
          }


          if( sqlite3IsNaN((double)realvalue) ){
            bufpt = "NaN";
            length = 3;
            break;
          }

          /* Normalize realvalue to within 10.0 > realvalue >= 1.0 */
          if( ALWAYS(realvalue>0.0) ){
            LONGDOUBLE_TYPE scale = 1.0;
            while( realvalue>=1e100*scale && exp<=350){ scale*=1e100;exp+=100;}
            while( realvalue>=1e10*scale && exp<=350 ){ scale*=1e10; exp+=10; }
            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 ){
              bufpt = buf;
              buf[0] = prefix;
              memcpy(buf+(prefix!=0),"Inf",4);
              length = 3+(prefix!=0);
              break;
            }
            if( xtype!=etFLOAT ){
              realvalue += rounder;
              if( realvalue>=10.0 ){ realvalue *= 0.1; exp++; }
            }
          }
        }

        /*
        ** If the field type is etGENERIC, then convert to either etEXP
        ** or etFLOAT, as appropriate.
        */




        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;
        }
        nsd = 16 + flag_altform2*10;
        bufpt = buf;
        {
          i64 szBufNeeded;           /* Size of a temporary buffer needed */
          szBufNeeded = MAX(e2,0)+(i64)precision+(i64)width+15;
          if( szBufNeeded > etBUFSIZE ){
            bufpt = zExtra = printfTempBuf(pAccum, szBufNeeded);
            if( bufpt==0 ) return;
          }
        }
        zOut = bufpt;

        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 if( msd>0 ){
          for(; e2>=0; e2--){
            *(bufpt++) = et_getdigit_int(&longvalue,&msd);
          }
        }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 */
        if( msd>0 ){
          while( (precision--)>0 ){
            *(bufpt++) = et_getdigit_int(&longvalue,&msd);
          }
        }else{
          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 ){

# 2020-05-23
# ticket 23439ea582241138
#
do_execsql_test printf-16.1 {
  SELECT printf('%.*g',2147483647,0.01);
} {0.01}

# 2023-02-23 https://sqlite.org/forum/forumpost/d1387c3979c7f557
# Loss of precision when doing floating-point to decimal
# conversions on values that have no factional part.
#
do_execsql_test printf-17.1 {
  SELECT format('%!.20g', 13.0);
} 13.0
do_execsql_test printf-17.2 {
  SELECT format('%.3e', 199990000.0);
} 2.000e+08
do_execsql_test printf-17.3 {
  SELECT format('%.3f', 199990000.0);
} 199990000.000
do_execsql_test printf-17.4 {
  SELECT format('%.3g', 199990000.0);
} 2e+08
do_execsql_test printf-17.5 {
  SELECT format('%.4e', 199990000.0);
} 1.9999e+08
do_execsql_test printf-17.6 {
  SELECT format('%.4f', 199990000.0);
} 199990000.0000
do_execsql_test printf-17.7 {
  SELECT format('%.4g', 199990000.0);
} 2e+08
do_execsql_test printf-17.8 {
  SELECT format('%.5e', 199990000.0);
} 1.99990e+08
do_execsql_test printf-17.9 {
  SELECT format('%.5f', 199990000.0);
} 199990000.00000
do_execsql_test printf-17.10 {
  SELECT format('%.5g', 199990000.0);
} 1.9999e+08
do_execsql_test printf-17.11 {
  SELECT format('%.30f',1.0000000000000000076e-50);
} 0.000000000000000000000000000000

finish_test