[Qemu-devel] [PATCH] qemu-img: sort block formats in help message

[Mike Day <ncmike@ncultra.org>]

The help message for qemu-img lists the supported block formats, of
which there are 27 as of version 2.0.50. The formats are printed in
the order of their driver's position in a linked list, which appears
random. This patch prints the formats in sorted order, making it
easier to read and to find a specific format in the list.

Signed-off-by: Mike Day <ncmike@ncultra.org>
---
 qemu-img.c | 33 ++++++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

 diff --git a/qemu-img.c b/qemu-img.c
 index 96f4463..d8b7ef4 100644
 --- a/qemu-img.c
 +++ b/qemu-img.c
 @@ -32,6 +32,7 @@
 #include "block/block_int.h"
 #include "block/qapi.h"
 #include <getopt.h>
 +#include <glib.h>
 
 #define QEMU_IMG_VERSION "qemu-img version " QEMU_VERSION \
 ", Copyright (c) 2004-2008 Fabrice Bellard\n"
 @@ -60,6 +61,32 @@ static void format_print(void *opaque, const char *name)
 printf(" %s", name);
 }
 
 +static gint compare_data(gconstpointer a, gconstpointer b, gpointer user)
 +{
 +    return g_strcmp0((const char *)a, (const char *)b);
 +}
 +
 +static void GFunc_print_format(gpointer data, gpointer user)
 +{
 +    format_print(user, data);
 +}
 +
 +static GSequence *init_sequence(void)
 +{
 +    return g_sequence_new(NULL);
 +}
 +
 +static void add_format_to_seq(void *opaque, const char *fmt_name)
 +{
 +    GSequence *seq = (GSequence *)opaque;
 +
 +    if (!g_sequence_lookup(seq, (gpointer)fmt_name,
 +                          compare_data, NULL)) {
 +        g_sequence_insert_sorted(seq, (gpointer)fmt_name,
 +                                 compare_data, NULL);
 +    }
 +}
 +
 static void QEMU_NORETURN GCC_FMT_ATTR(1, 2) error_exit(const char *fmt, ...)
 {
 va_list ap;
 @@ -144,8 +171,12 @@ static void QEMU_NORETURN help(void)
 "  '-s' run in Strict mode - fail on different image size or sector allocation\n";
 
 printf("%s\nSupported formats:", help_msg);
 -    bdrv_iterate_format(format_print, NULL);
 +    GSequence *seq = init_sequence();
 +    bdrv_iterate_format(add_format_to_seq, seq);
 +    g_sequence_foreach(seq, GFunc_print_format, NULL);
 printf("\n");
 +    g_sequence_free(seq);
 +
 exit(EXIT_SUCCESS);
 }
 
 -- 
 1.9.0