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LibC: Implemented atof()

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`atof()` has now been implemented as part of the standard C library.
It supports scientific notation such as `1.2e-3` etc, ala the version
found as part of `glibc`.

It's a bit chunky, so there's probably room for optimisations here
and there, however, for now it works as intended (and allows Quake
to run).
This commit is contained in:
Jesse Buhagiar 2019-11-04 01:56:41 +11:00 committed by Andreas Kling
parent c538648465
commit 70fb92fa0e
Notes: sideshowbarker 2024-07-19 11:25:54 +09:00 
Author: https://github.com/Quaker762
Commit: https://github.com/SerenityOS/serenity/commit/70fb92fa0e4
Pull-request: https://github.com/SerenityOS/serenity/pull/730
Reviewed-by: https://github.com/awesomekling
1 changed files with 70 additions and 8 deletions
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78
Libraries/LibC/stdlib.cpp
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@ -1,7 +1,7 @@
#include <AK/String.h>
#include <AK/Assertions.h>
#include <AK/HashMap.h>
#include <AK/StdLibExtras.h>
#include <AK/String.h>
#include <AK/Types.h>
#include <Kernel/Syscall.h>
#include <alloca.h>
@ -166,7 +166,6 @@ int putenv(char* new_var)
environ = new_environ;
return 0;
}
}
double strtod(const char* str, char** endptr)
@ -185,7 +184,6 @@ long double strtold(const char* str, char** endptr)
ASSERT_NOT_REACHED();
}
float strtof(const char* str, char** endptr)
{
(void)str;
@ -196,8 +194,72 @@ float strtof(const char* str, char** endptr)
double atof(const char* str)
{
dbgprintf("LibC: atof: '%s'\n", str);
ASSERT_NOT_REACHED();
size_t len = strlen(str);
size_t weight = 1;
int exp_val = 0;
double value = 0.0f;
double fraction = 0.0f;
bool has_sign = false;
bool is_negative = false;
bool is_fractional = false;
bool is_scientific = false;
if (str[0] == '-') {
is_negative = true;
has_sign = true;
}
if (str[0] == '+') {
has_sign = true;
}
for (size_t i = has_sign; i < len; i++) {
// Looks like we're about to start working on the fractional part
if (str[i] == '.') {
is_fractional = true;
continue;
}
if (str[i] == 'e' || str[i] == 'E') {
if (str[i + 1] == '-' || str[i + 1] == '+')
exp_val = atoi(str + i + 2);
else
exp_val = atoi(str + i + 1);
is_scientific = true;
continue;
}
if (str[i] < '0' || str[i] > '9' || exp_val != 0)
continue;
if (is_fractional) {
fraction *= 10;
fraction += str[i] - '0';
weight *= 10;
} else {
value = value * 10;
value += str[i] - '0';
}
}
fraction /= weight;
value += fraction;
if (is_scientific) {
bool divide = exp_val < 0;
if (divide)
exp_val *= -1;
for (int i = 0; i < exp_val; i++) {
if (divide)
value /= 10;
else
value *= 10;
}
}
return is_negative ? -value : value;
}
int atoi(const char* str)
@ -338,10 +400,10 @@ char* mkdtemp(char* pattern)
struct stat st;
int rc = lstat(pattern, &st);
if (rc < 0 && errno == ENOENT) {
if (mkdir(pattern, 0700) < 0)
if (mkdir(pattern, 0700) < 0)
return nullptr;
return pattern;
}
return pattern;
}
}
errno = EEXIST;