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Fixed rounding of floating point values in snprintf

main
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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131
src/stdlib/SDL_string.c
View File

@ -1621,45 +1621,98 @@ 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] = '+';
num[length++] = '+';
}
++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;
}
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;
while (info->precision-- > 0) {
value = (unsigned long)(arg * mult);
length += SDL_PrintUnsignedLong(TEXT_AND_LEN_ARGS, NULL, value);
arg -= (double)value / mult;
mult *= 10;
}
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' : ' ';
size_t width = info->width - length;
@ -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 */

47
test/testautomation_stdlib.c
View File

@ -153,17 +153,46 @@ int stdlib_snprintf(void *arg)
SDLTest_AssertCheck(SDL_strcmp(text, expected) == 0, "Check text, expected: '%s', got: '%s'", expected, text);
SDLTest_AssertCheck(result == 6, "Check result value, expected: 6, got: %d", result);
result = SDL_snprintf(text, sizeof(text), "%g", 100.0);
expected = "100";
SDLTest_AssertPass("Call to SDL_snprintf(\"%%g\", 100.0)");
SDLTest_AssertCheck(SDL_strcmp(text, expected) == 0, "Check text, expected: '%s', got: '%s'", expected, text);
SDLTest_AssertCheck(result == 3, "Check result value, expected: 3, got: %d", result);
{
static struct
{
float value;
const char *expected_f;
const char *expected_g;
} f_and_g_test_cases[] = {
{ 100.0f, "100.000000", "100" },
{ -100.0f, "-100.000000", "-100" },
{ 100.75f, "100.750000", "100.75" },
{ -100.75f, "-100.750000", "-100.75" },
{ ((100 * 60 * 1000) / 1001) / 100.0f, "59.939999", "59.94" },
{ -((100 * 60 * 1000) / 1001) / 100.0f, "-59.939999", "-59.94" },
{ ((100 * 120 * 1000) / 1001) / 100.0f, "119.879997", "119.88" },
{ -((100 * 120 * 1000) / 1001) / 100.0f, "-119.879997", "-119.88" },
{ 9.9999999f, "10.000000", "10" },
{ -9.9999999f, "-10.000000", "-10" },
};
int i;
result = SDL_snprintf(text, sizeof(text), "%g", 100.75);
expected = "100.75";
SDLTest_AssertPass("Call to SDL_snprintf(\"%%g\", 100.75)");
for (i = 0; i < SDL_arraysize(f_and_g_test_cases); ++i) {
float value = f_and_g_test_cases[i].value;
result = SDL_snprintf(text, sizeof(text), "%f", value);
predicted = SDL_snprintf(NULL, 0, "%f", value);
expected = f_and_g_test_cases[i].expected_f;
SDLTest_AssertPass("Call to SDL_snprintf(\"%%f\", %g)", value);
SDLTest_AssertCheck(SDL_strcmp(text, expected) == 0, "Check text, expected: '%s', got: '%s'", expected, text);
SDLTest_AssertCheck(result == 6, "Check result value, expected: 6, got: %d", result);
SDLTest_AssertCheck(result == SDL_strlen(expected), "Check result value, expected: %d, got: %d", SDL_strlen(expected), result);
SDLTest_AssertCheck(predicted == result, "Check predicted value, expected: %d, got: %d", result, predicted);
result = SDL_snprintf(text, sizeof(text), "%g", value);
predicted = SDL_snprintf(NULL, 0, "%g", value);
expected = f_and_g_test_cases[i].expected_g;
SDLTest_AssertPass("Call to SDL_snprintf(\"%%g\", %g)", value);
SDLTest_AssertCheck(SDL_strcmp(text, expected) == 0, "Check text, expected: '%s', got: '%s'", expected, text);
SDLTest_AssertCheck(result == SDL_strlen(expected), "Check result value, expected: %d, got: %d", SDL_strlen(expected), result);
SDLTest_AssertCheck(predicted == result, "Check predicted value, expected: %d, got: %d", result, predicted);
}
}
size = 64;
result = SDL_snprintf(text, sizeof(text), "%zu %s", size, "test");