Add option to list supported formats

4 files changed, 204 insertions, 14 deletions

diff --git a/configure.ac b/configure.ac
index cb2f4da..131540e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -38,8 +38,8 @@ test -d "${srcdir}/.git" || CFLAGS="${save_CFLAGS}"
 funcs_missing=false
 AC_CHECK_FUNCS(
 	[\
-		calloc fprintf fputs free localtime mktime printf setvbuf \
-		sleep strerror strlen strptime time
+		calloc fprintf fputs free isspace localtime mktime printf \
+		realloc setvbuf sleep strerror strlen strftime strptime time
 	],
 	[],
 	[funcs_missing=true])
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);
+}
diff --git a/src/datetime.h b/src/datetime.h
index 49a86a5..edff8f7 100644
--- a/src/datetime.h
+++ b/src/datetime.h
@@ -25,4 +25,16 @@
 int
 datetime_parse(const char *input, time_t *arg_sec);
 
+int
+datetime_strftime_date(const struct tm *tm, char **out, size_t *out_sz,
+		char **buf, size_t *i);
+
+int
+datetime_strftime_time(const struct tm *tm, char **out, size_t *out_sz,
+		char **buf, size_t *i);
+
+int
+datetime_strftime_misc(const struct tm *tm, char **out, size_t *out_sz,
+		char **buf, size_t *i);
+
 #endif  /* DATETIME_H_ */
diff --git a/src/main.c b/src/main.c
index 81096a5..f450281 100644
--- a/src/main.c
+++ b/src/main.c
@@ -36,6 +36,12 @@ extern const char *PACKAGE_VERSION_GIT;
 #if defined(HAVE_GETOPT_LONG) && HAVE_GETOPT_LONG
 struct option LONGOPTS_[] = {
 	{
+		.name    = "list-formats",
+		.has_arg = 0,
+		.flag    = NULL,
+		.val     = 'F',
+	},
+	{
 		.name    = "help",
 		.has_arg = 0,
 		.flag    = NULL,
@@ -62,15 +68,76 @@ _print_help(const char *program_name)
 	_print_usage(stdout, program_name);
 	puts("Options:");
 #if defined(HAVE_GETOPT_LONG) && HAVE_GETOPT_LONG
-	puts("\t-h, --help     Show this help information");
-	puts("\t-V, --version  Show version information");
+	puts("\t-F, --list-formats  List all supported date and time formats");
+	puts("\t-h, --help          Show this help information");
+	puts("\t-V, --version       Show version information");
 #else
+	puts("\t-F  List all supported date and time formats");
 	puts("\t-h  Show this help information");
 	puts("\t-V  Show version information");
 #endif
 }
 
 static void
+_list_formats(void)
+{
+	time_t     tim;
+	struct tm *tm;
+	char      *out;
+	size_t     out_sz;
+	char      *buf;
+	size_t     i;
+
+	tim = time(NULL);
+	tm  = localtime(&tim);
+
+	puts("Time formats:");
+	out    = NULL;
+	out_sz = 0;
+	buf    = NULL;
+	i      = 0;
+	while (datetime_strftime_time(tm, &out, &out_sz, &buf, &i) > 0) {
+		printf("  * %s\n", out);
+	}
+	if (out != NULL) {
+		free(out);
+	}
+	if (buf != NULL) {
+		free(buf);
+	}
+
+	puts("Date formats:");
+	out    = NULL;
+	out_sz = 0;
+	buf    = NULL;
+	i      = 0;
+	while (datetime_strftime_date(tm, &out, &out_sz, &buf, &i) > 0) {
+		printf("  * %s\n", out);
+	}
+	if (out != NULL) {
+		free(out);
+	}
+	if (buf != NULL) {
+		free(buf);
+	}
+
+	puts("Additional formats:");
+	out    = NULL;
+	out_sz = 0;
+	buf    = NULL;
+	i      = 0;
+	while (datetime_strftime_misc(tm, &out, &out_sz, &buf, &i) > 0) {
+		printf("  * %s\n", out);
+	}
+	if (out != NULL) {
+		free(out);
+	}
+	if (buf != NULL) {
+		free(buf);
+	}
+}
+
+static void
 _print_version(void)
 {
 	printf("@ (atsign) %s%s\n", PACKAGE_VERSION, PACKAGE_VERSION_GIT);
@@ -128,11 +195,14 @@ main(int argc, char * const argv[])
 	optind = 1;
 	opterr = 0;
 #if defined(HAVE_GETOPT_LONG) && HAVE_GETOPT_LONG
-	while ((opt = getopt_long(argc, argv, "hV", LONGOPTS_, NULL)) > 0) {
+	while ((opt = getopt_long(argc, argv, "FhV", LONGOPTS_, NULL)) > 0) {
 #else
-	while ((opt = getopt(argc, argv, "hV")) > 0) {
+	while ((opt = getopt(argc, argv, "FhV")) > 0) {
 #endif
 		switch (opt) {
+			case 'F':
+				_list_formats();
+				return EXIT_SUCCESS;
 			case 'h':
 				_print_help(argv[0]);
 				return EXIT_SUCCESS;