ini file parsing

ini.c

#include <string.h>
#include <stdio.h>

enum ini_parts {
	ini_section, ini_key, ini_value,
	ini_section_start = '[', ini_section_end=']',
	ini_key_value = '=',
	ini_comment = ';'
};

static char valid_token(const char token[])
{
	return strchr(token, ini_section_start) == NULL
		&& strchr(token, ini_section_end) == NULL
		&& strchr(token, ini_comment) == NULL;
}

// find the start and length of the next section title
char *ini_next_section(char * const file, int * const length)
{
char * start, * end;
	start = strchr(file, ini_section_start);
	if (start == NULL) return NULL;
	end = strchr(++start, ini_section_end);
	if (end == NULL) return NULL;
	*length = end - start;
	return start;
}

int ini_find_value(const char file[], const char section[], const char key[], char * const value)
{
size_t _sl = strlen(section) + 2, _kl = strlen(key) + 1, _end;
char _section[_sl], _key[_kl];
const char * _start, * _next, * _value;
	if (!valid_token(section) || !valid_token(key))
		return -1;
	sprintf(_section, "%c%s%c", ini_section_start, section, ini_section_end);
	sprintf(_key, "%s%c", key, ini_key_value);
	_start = strstr(file, _section);
	if (_start == NULL)	return -2;	// no '[section]'
	_value = strstr(_start + _sl, _key);
	if (_value == NULL) return -3;	// no 'key='
	_value += _kl;
	_next = strchr(_start + _sl, ini_section_start);
	if (_next == NULL) _next = file + strlen(file);
	if (_value > _next) return -4;	// 'key=' is after the next '[section]'
	_end = strcspn(_value, "\n\r;");
	memcpy(value, _value, _end);
	value[_end] = 0;
	return _end;
}

test.c

/* test ini.c */
#include <stdio.h>
#include <stdlib.h>

size_t fsize(FILE * const file)
{
size_t size = -1;
	fseek(file, 0, SEEK_END);
	size = ftell(file);
	rewind(file);
	return size;
}

char * fgeta(FILE * const file)
{
char * buffer = NULL;
size_t string_size, read_size;
	if (file)
	{
		string_size = fsize(file);
		buffer = (char*) malloc(sizeof(char) * (string_size + 1));
		read_size = fread(buffer, sizeof(char), string_size, file);
		buffer[string_size + 1] = '\0';
		if (string_size != read_size)
		{
			free(buffer);
			buffer = NULL;
		}
	}
	return buffer;
}

extern int ini_find_value(const char file[], const char section[], const char key[], char * const value);

void test_ini(const char file[], const char section[], const char key[])
{
static char value[200];
	if (ini_find_value(file, section, key, value) < 0)
		fprintf(stderr, "![%s]%s not found\n", section, key);
	else
		printf("[%s]%s=%s\n", section, key, value);
}

int main(int argc, char **argv)
{
char * file = fgeta(fopen(argv[1], "r"));
	test_ini(file, "section","key");
	test_ini(file, "section","key2");
	test_ini(file, "section","key3");
	test_ini(file, "section","bcde");
	test_ini(file, "section","prev");
	test_ini(file, "next","prev");
	test_ini(file, "next","test");
	test_ini(file, "test","test");
	test_ini(file, "test=0","test");
}

test.ini

[section]
key=1
key2=3;comment
bcde=fghi
[next];section comment
prev=four;comment;with;comments
[test]
[test=0]
test=3
;end comment