ladybird/Userland/Libraries/LibC/getsubopt.cpp
Liav A e02da2ed41 LibC: Implement the getsubopt function
This is a LibC function that POSIX defines to help userspace programs
to get suboptions. An example of a suboption is the token "pixclk" from
a Shell command running "edid-decode --gtf w=1024,h=768,pixclk=48".
The function should be run in a while loop to acquire all suboptions
until the last one.
2022-06-25 12:10:04 +01:00

51 lines
1.7 KiB
C++

/*
* Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/ScopeGuard.h>
#include <AK/StringView.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
// https://pubs.opengroup.org/onlinepubs/9699919799/functions/getsubopt.html
int getsubopt(char** option_array, char* const* tokens, char** option_value)
{
if (**option_array == '\0')
return -1;
auto option_string = StringView(*option_array);
auto possible_comma_location = option_string.find(',');
char* option_end = const_cast<char*>(option_string.characters_without_null_termination()) + possible_comma_location.value_or(option_string.length());
auto possible_equals_char_location = option_string.find('=');
char* value_start = option_end;
if (possible_equals_char_location.has_value()) {
value_start = const_cast<char*>(option_string.characters_without_null_termination()) + possible_equals_char_location.value();
}
ScopeGuard ensure_end_array_contains_null_char([&]() {
if (*option_end != '\0')
*option_end++ = '\0';
*option_array = option_end;
});
for (int count = 0; tokens[count] != NULL; ++count) {
auto token_stringview = StringView(tokens[count]);
if (!option_string.starts_with(token_stringview))
continue;
if (tokens[count][value_start - *option_array] != '\0')
continue;
*option_value = value_start != option_end ? value_start + 1 : nullptr;
return count;
}
// Note: The current sub-option does not match any option, so prepare to tell this
// to the application.
*option_value = *option_array;
return -1;
}