From e130ed9b3a982b36b75d4fbb225ad1fe8e16a7de Mon Sep 17 00:00:00 2001
From: P. J. McDermott <pj@pehjota.net>
Date: Tue, 31 Aug 2021 20:54:28 -0400
Subject: Add option to list supported formats

---
(limited to 'src/datetime.c')

diff --git a/src/datetime.c b/src/datetime.c
index 0056017..1a3bbba 100644
--- a/src/datetime.c
+++ b/src/datetime.c
@@ -19,8 +19,10 @@
 
 #define _XOPEN_SOURCE
 
+#include <ctype.h>
 #include <errno.h>
 #include <limits.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -87,16 +89,16 @@ static const char *DATETIME_TIME_FMTS_[] = {
 };
 static const char *DATETIME_MISC_FMTS_[] = {
 	/* ISO 8601: 1969-12-31 delimited by "T" */
-	" %Y-%m-%dT%H:%M:%S ",
-	" %Y-%m-%dT%H:%M    ",
+	" %Y-%m-%dT%H:%M:%S    ",
+	" %Y-%m-%dT%H:%M       ",
 	/* ISO 8601: 19691231 delimited by "T" */
-	" %Y%m%dT%H%M%S ",
-	" %Y%m%dT%H%M   ",
+	" %Y%m%dT%H%M%S        ",
+	" %Y%m%dT%H%M          ",
 	/* 19691231 */
-	" %Y%m%d  %I%M%S %p ",
-	" %Y%m%d  %H%M%S    ",
-	" %Y%m%d  %I%M %p   ",
-	" %Y%m%d  %H%M      ",
+	" %Y%m%d  %I%M%S %p    ",
+	" %Y%m%d  %H%M%S       ",
+	" %Y%m%d  %I%M %p      ",
+	" %Y%m%d  %H%M         ",
 	/* Wed Dec 31 19:00:01 1969 */
 	" %a %b %d %H:%M:%S %Y ",
 };
@@ -244,3 +246,109 @@ datetime_parse(const char *input, time_t *arg_sec)
 	fputs("Unknown date format\n", stderr);
 	return -1;
 }
+
+static void
+_datetime_copy_trim_fmt(char *buf, const char *fmt)
+{
+	int  buf_i;
+	int  l;
+	bool was_space;
+	int  i;
+
+	buf_i = 0;
+	l = strlen(fmt);
+	was_space = true;
+	for (i = 0; i < l; ++i) {
+		if (isspace(fmt[i]) != 0) {
+			if (was_space == false) {
+				buf[buf_i++] = ' ';
+				was_space = true;
+			}
+		} else {
+			buf[buf_i++] = fmt[i];
+			was_space = false;
+		}
+	}
+	if (buf_i > 0) {
+		buf[buf_i - 1] = '\0';
+	} else {
+		buf[0] = '\0';
+	}
+}
+
+static int
+_datetime_strftime(const char *fmts[], const struct tm *tm, char **out,
+		size_t *out_sz, char **buf, size_t *i)
+{
+	if (*buf == NULL) {
+		*buf = calloc(strlen(fmts[0]), sizeof(**buf));
+		if (*buf == NULL) {
+			fprintf(stderr, "Failed to allocate buffer: %s\n",
+					strerror(errno));
+			return -1;
+		}
+	}
+	if (*out == NULL) {
+		*out_sz = strlen(fmts[0]);
+		*out = calloc(*out_sz, sizeof(**out));
+		if (*out == NULL) {
+			fprintf(stderr, "Failed to allocate buffer: %s\n",
+					strerror(errno));
+			return -1;
+		}
+	}
+
+	*buf[0] = '\0';
+	while (*buf[0] == '\0') {
+		_datetime_copy_trim_fmt(*buf, fmts[*i]);
+		++*i;
+	}
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wformat-nonliteral"
+	while (strftime(*out, *out_sz, *buf, tm) == 0) {
+#pragma GCC diagnostic pop
+		++*out_sz;
+		*out = realloc(*out, *out_sz * sizeof(**out));
+		if (*out == NULL) {
+			fprintf(stderr, "Failed to allocate buffer: %s\n",
+					strerror(errno));
+			return -1;
+		}
+	}
+
+	return 1;
+}
+
+int
+datetime_strftime_date(const struct tm *tm, char **out, size_t *out_sz,
+		char **buf, size_t *i)
+{
+	if (*i >= sizeof(DATETIME_DATE_FMTS_) / sizeof(DATETIME_DATE_FMTS_[0])){
+		return 0;
+	}
+
+	return _datetime_strftime(DATETIME_DATE_FMTS_, tm, out, out_sz, buf, i);
+}
+
+int
+datetime_strftime_time(const struct tm *tm, char **out, size_t *out_sz,
+		char **buf, size_t *i)
+{
+	if (*i >= sizeof(DATETIME_TIME_FMTS_) / sizeof(DATETIME_TIME_FMTS_[0])){
+		return 0;
+	}
+
+	return _datetime_strftime(DATETIME_TIME_FMTS_, tm, out, out_sz, buf, i);
+}
+
+int
+datetime_strftime_misc(const struct tm *tm, char **out, size_t *out_sz,
+		char **buf, size_t *i)
+{
+	if (*i >= sizeof(DATETIME_MISC_FMTS_) / sizeof(DATETIME_MISC_FMTS_[0])){
+		return 0;
+	}
+
+	return _datetime_strftime(DATETIME_MISC_FMTS_, tm, out, out_sz, buf, i);
+}
--
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