utils

iso_parse.c (1688B)

// Collection of Unix tools, comparable to coreutils
// SPDX-FileCopyrightText: 2023 Haelwenn (lanodan) Monnier <contact+utils@hacktivis.me>
// SPDX-License-Identifier: MPL-2.0
#define _DEFAULT_SOURCE         // tm_gmtoff/tm_zone
#define _XOPEN_SOURCE 700       // strptime (NetBSD)
#define _POSIX_C_SOURCE 200809L // st_atim/st_mtim
#include <ctype.h>  /* isdigit */
#include <errno.h>  /* errno */
#include <stdio.h>  /* perror, sscanf */
#include <stdlib.h> /* exit */
#include <string.h> /* memset */
#include <time.h>   /* strptime, tm */
// Calls exit() on failure
struct timespec
iso_parse(char *arg)
{
	// YYYY-MM-DD[T ]hh:mm:SS([,\.]frac)?Z?
	// Dammit Unixes why no nanoseconds in `struct tm` nor `strptime`
	struct timespec time = {.tv_sec = 0, .tv_nsec = 0};
	// For Alpine's abuild compatibility
	if(arg[0] == '@')
	{
		arg++;
		errno = 0;
		time.tv_sec = strtol(arg, NULL, 10);
		if(errno != 0)
		{
			perror("strtol");
			exit(EXIT_FAILURE);
		}
		return time;
	}
	struct tm tm;
	memset(&tm, 0, sizeof(tm));
	// No %F in POSIX
	char *s = strptime(arg, "%Y-%m-%d", &tm);
	if(s[0] != 'T' && s[0] != ' ') exit(EXIT_FAILURE);
	s++;
	s = strptime(s, "%H:%M:%S", &tm);
	if(s[0] == ',' || s[0] == '.')
	{
		double fraction = 0.0;
		int parsed      = 0;
		if(s[0] == ',') s[0] = '.';
		if(sscanf(s, "%10lf%n", &fraction, &parsed) < 1) exit(EXIT_FAILURE);
		time.tv_nsec = fraction * 1000000000;
		s += parsed;
		// too many digits
		if(isdigit(s[0])) exit(EXIT_FAILURE);
	}
	if(s[0] == 'Z')
	{
		tm.tm_gmtoff = 0;
		tm.tm_zone   = "UTC";
	}
	time.tv_sec = mktime(&tm);
	if(time.tv_sec == (time_t)-1)
	{
		perror("mktime");
		exit(EXIT_FAILURE);
	}
	return time;
}