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Fixed rounding of floating point values in snprintf

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This commit is contained in:
Sam Lantinga 2023-01-02 21:57:42 -08:00
parent 72f0056961
commit 38b138cd0a
2 changed files with 118 additions and 64 deletions
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133
src/stdlib/SDL_string.c
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@ -1621,44 +1621,97 @@ SDL_PrintUnsignedLongLong(char *text, size_t maxlen, SDL_FormatInfo *info, Uint6
}
static size_t
SDL_PrintFloat(char *text, size_t maxlen, SDL_FormatInfo *info, double arg)
SDL_PrintFloat(char *text, size_t maxlen, SDL_FormatInfo *info, double arg, SDL_bool g)
{
char num[327];
size_t length = 0;
size_t integer_length;
int precision = info->precision;
/* This isn't especially accurate, but hey, it's easy. :) */
unsigned long value;
Uint64 value;
if (arg < 0) {
if (length < maxlen) {
text[length] = '-';
}
++length;
num[length++] = '-';
arg = -arg;
} else if (info->force_sign) {
if (length < maxlen) {
text[length] = '+';
}
++length;
num[length++] = '+';
}
value = (unsigned long)arg;
length += SDL_PrintUnsignedLong(TEXT_AND_LEN_ARGS, NULL, value);
value = (Uint64)arg;
integer_length = SDL_PrintUnsignedLongLong(&num[length], sizeof(num) - length, NULL, value);
length += integer_length;
arg -= value;
if (info->precision < 0) {
info->precision = 6;
if (precision < 0) {
precision = 6;
}
if (info->force_type || info->precision > 0) {
int mult = 10;
if (length < maxlen) {
text[length] = '.';
if (g) {
/* The precision includes the integer portion */
precision -= SDL_min((int)integer_length, precision);
}
if (info->force_type || precision > 0) {
const char decimal_separator = '.';
double integer_value;
SDL_assert(length < sizeof(num));
num[length++] = decimal_separator;
while (precision > 1) {
arg *= 10.0;
arg = SDL_modf(arg, &integer_value);
SDL_assert(length < sizeof(num));
num[length++] = '0' + (int)integer_value;
--precision;
}
++length;
while (info->precision-- > 0) {
value = (unsigned long)(arg * mult);
length += SDL_PrintUnsignedLong(TEXT_AND_LEN_ARGS, NULL, value);
arg -= (double)value / mult;
mult *= 10;
if (precision == 1) {
arg *= 10.0;
integer_value = SDL_round(arg);
if (integer_value == 10.0) {
/* Carry the one... */
size_t i;
for (i = length; i--; ) {
if (num[i] == decimal_separator) {
continue;
}
if (num[i] == '9') {
num[i] = '0';
} else {
++num[i];
break;
}
}
if (i == 0 || num[i] == '-' || num[i] == '+') {
SDL_memmove(&num[i+1], &num[i], length - i);
num[i] = '1';
++length;
}
SDL_assert(length < sizeof(num));
num[length++] = '0';
} else {
SDL_assert(length < sizeof(num));
num[length++] = '0' + (int)integer_value;
}
}
if (g) {
/* Trim trailing zeroes and decimal separator */
size_t i;
for (i = length - 1; num[i] != decimal_separator; --i) {
if (num[i] == '0') {
--length;
} else {
break;
}
}
if (num[i] == decimal_separator) {
--length;
}
}
}
num[length] = '\0';
info->precision = -1;
length = SDL_PrintString(text, maxlen, info, num);
if (info->width > 0 && (size_t)info->width > length) {
const char fill = info->pad_zeroes ? '0' : ' ';
@ -1671,30 +1724,6 @@ SDL_PrintFloat(char *text, size_t maxlen, SDL_FormatInfo *info, double arg)
SDL_memset(text, fill, filllen);
length += width;
}
return length;
}
static size_t
SDL_TrimTrailingFractionalZeroes(char *text, size_t start, size_t length)
{
size_t i, j;
for (i = start; i < length; ++i) {
if (text[i] == '.' || text[i] == ',') {
for (j = length - 1; j > i; --j) {
if (text[j] == '0') {
--length;
} else {
break;
}
}
if (j == i) {
--length;
}
break;
}
}
return length;
}
@ -1876,17 +1905,13 @@ int SDL_vsnprintf(SDL_OUT_Z_CAP(maxlen) char *text, size_t maxlen, const char *f
done = SDL_TRUE;
break;
case 'f':
length += SDL_PrintFloat(TEXT_AND_LEN_ARGS, &info, va_arg(ap, double));
length += SDL_PrintFloat(TEXT_AND_LEN_ARGS, &info, va_arg(ap, double), SDL_FALSE);
done = SDL_TRUE;
break;
case 'g':
{
size_t starting_length = length;
length += SDL_PrintFloat(TEXT_AND_LEN_ARGS, &info, va_arg(ap, double));
length = SDL_TrimTrailingFractionalZeroes(text, starting_length, length);
length += SDL_PrintFloat(TEXT_AND_LEN_ARGS, &info, va_arg(ap, double), SDL_TRUE);
done = SDL_TRUE;
break;
}
case 'S':
{
/* In practice this is used on Windows for WCHAR strings */