time: Split out time-related functions from util

1 files changed, 247 insertions, 0 deletions

diff --git a/time.c b/time.c
new file mode 100644
index 0000000..3575abd
--- /dev/null
+++ b/time.c
@@ -0,0 +1,247 @@
+/****************************************************************************
+ * bfs                                                                      *
+ * Copyright (C) 2020 Tavian Barnes <tavianator@tavianator.com>             *
+ *                                                                          *
+ * Permission to use, copy, modify, and/or distribute this software for any *
+ * purpose with or without fee is hereby granted.                           *
+ *                                                                          *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES *
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF         *
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR  *
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES   *
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN    *
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF  *
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.           *
+ ****************************************************************************/
+
+#include "time.h"
+#include <errno.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+int xlocaltime(const time_t *timep, struct tm *result) {
+	// Should be called before localtime_r() according to POSIX.1-2004
+	tzset();
+
+	if (localtime_r(timep, result)) {
+		return 0;
+	} else {
+		return -1;
+	}
+}
+
+int xgmtime(const time_t *timep, struct tm *result) {
+	// Should be called before gmtime_r() according to POSIX.1-2004
+	tzset();
+
+	if (gmtime_r(timep, result)) {
+		return 0;
+	} else {
+		return -1;
+	}
+}
+
+int xmktime(struct tm *tm, time_t *timep) {
+	*timep = mktime(tm);
+
+	if (*timep == -1) {
+		int error = errno;
+
+		struct tm tmp;
+		if (xlocaltime(timep, &tmp) != 0) {
+			return -1;
+		}
+
+		if (tm->tm_year != tmp.tm_year || tm->tm_yday != tmp.tm_yday
+		    || tm->tm_hour != tmp.tm_hour || tm->tm_min != tmp.tm_min || tm->tm_sec != tmp.tm_sec) {
+			errno = error;
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
+int xtimegm(struct tm *tm, time_t *timep) {
+	// Some man pages for timegm() recommend this as a portable approach
+	int ret = -1;
+	int error;
+
+	char *old_tz = getenv("TZ");
+	if (old_tz) {
+		old_tz = strdup(old_tz);
+		if (!old_tz) {
+			error = errno;
+			goto fail;
+		}
+	}
+
+	if (setenv("TZ", "UTC0", true) != 0) {
+		error = errno;
+		goto fail;
+	}
+
+	ret = xmktime(tm, timep);
+	error = errno;
+
+	if (old_tz) {
+		if (setenv("TZ", old_tz, true) != 0) {
+			ret = -1;
+			error = errno;
+			goto fail;
+		}
+	} else {
+		if (unsetenv("TZ") != 0) {
+			ret = -1;
+			error = errno;
+			goto fail;
+		}
+	}
+
+	tzset();
+fail:
+	free(old_tz);
+	errno = error;
+	return ret;
+}
+
+/** Parse some digits from a timestamp. */
+static int parse_timestamp_part(const char **str, size_t n, int *result) {
+	char buf[n + 1];
+	for (size_t i = 0; i < n; ++i, ++*str) {
+		char c = **str;
+		if (c < '0' || c > '9') {
+			return -1;
+		}
+		buf[i] = c;
+	}
+	buf[n] = '\0';
+
+	*result = atoi(buf);
+	return 0;
+}
+
+int parse_timestamp(const char *str, struct timespec *result) {
+	struct tm tm = {
+		.tm_isdst = -1,
+	};
+
+	int tz_hour = 0;
+	int tz_min = 0;
+	bool tz_negative = false;
+	bool local = true;
+
+	// YYYY
+	if (parse_timestamp_part(&str, 4, &tm.tm_year) != 0) {
+		goto invalid;
+	}
+	tm.tm_year -= 1900;
+
+	// MM
+	if (*str == '-') {
+		++str;
+	}
+	if (parse_timestamp_part(&str, 2, &tm.tm_mon) != 0) {
+		goto invalid;
+	}
+	tm.tm_mon -= 1;
+
+	// DD
+	if (*str == '-') {
+		++str;
+	}
+	if (parse_timestamp_part(&str, 2, &tm.tm_mday) != 0) {
+		goto invalid;
+	}
+
+	if (!*str) {
+		goto end;
+	} else if (*str == 'T') {
+		++str;
+	}
+
+	// hh
+	if (parse_timestamp_part(&str, 2, &tm.tm_hour) != 0) {
+		goto invalid;
+	}
+
+	// mm
+	if (!*str) {
+		goto end;
+	} else if (*str == ':') {
+		++str;
+	}
+	if (parse_timestamp_part(&str, 2, &tm.tm_min) != 0) {
+		goto invalid;
+	}
+
+	// ss
+	if (!*str) {
+		goto end;
+	} else if (*str == ':') {
+		++str;
+	}
+	if (parse_timestamp_part(&str, 2, &tm.tm_sec) != 0) {
+		goto invalid;
+	}
+
+	if (!*str) {
+		goto end;
+	} else if (*str == 'Z') {
+		local = false;
+		++str;
+	} else if (*str == '+' || *str == '-') {
+		local = false;
+		tz_negative = *str == '-';
+		++str;
+
+		// hh
+		if (parse_timestamp_part(&str, 2, &tz_hour) != 0) {
+			goto invalid;
+		}
+
+		// mm
+		if (!*str) {
+			goto end;
+		} else if (*str == ':') {
+			++str;
+		}
+		if (parse_timestamp_part(&str, 2, &tz_min) != 0) {
+			goto invalid;
+		}
+	} else {
+		goto invalid;
+	}
+
+	if (*str) {
+		goto invalid;
+	}
+
+end:
+	if (local) {
+		if (xmktime(&tm, &result->tv_sec) != 0) {
+			goto error;
+		}
+	} else {
+		if (xtimegm(&tm, &result->tv_sec) != 0) {
+			goto error;
+		}
+
+		int offset = 60*tz_hour + tz_min;
+		if (tz_negative) {
+			result->tv_sec -= offset;
+		} else {
+			result->tv_sec += offset;
+		}
+	}
+
+	result->tv_nsec = 0;
+	return 0;
+
+invalid:
+	errno = EINVAL;
+error:
+	return -1;
+}