/* SPDX-License-Identifier: GPL-3.0-or-later */
/* Copyright (C) 2021 KikooDX */

#include "strtoint.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* Attempt to convert a string to integer. */
int strtoint(char *string)
{
	char character;
	int i;
	const size_t string_len = strlen(string);
	int sum = 0;
	int multiplier = 1;
	int negative = string[0] == '-';
	for (i = string_len - 1; i >= negative; i -= 1) {
		character = string[i];
		if (character < '0' || character > '9') {
			fprintf(stderr,
			        "ERROR: flag expected a number "
			        "argument, got \"%s\"\n",
			        string);
			exit(EXIT_FAILURE);
		}
		sum += multiplier * (character - '0');
		multiplier *= 10;
	}
	if (negative)
		return sum * -1;
	else
		return sum;
}