Add 'display_icon' example program.

Running this on a disk image displays the guest icon
(using external 'display' program).

.gitignore

@@ -74,6 +74,7 @@ erlang/examples/stamp-guestfs-erlang.pod
 erlang/guestfs.beam
 erlang/guestfs.erl
 examples/create_disk
+examples/display_icon
 examples/guestfs-examples.3
 examples/guestfs-recipes.1
 examples/guestfs-testing.1

examples/Makefile.am

@@ -26,7 +26,7 @@ CLEANFILES = \
 	stamp-guestfs-recipes.pod \
 	stamp-guestfs-testing.pod
 
-noinst_PROGRAMS = create_disk inspect_vm
+noinst_PROGRAMS = create_disk display_icon inspect_vm
 if HAVE_HIVEX
 noinst_PROGRAMS += virt-dhcp-address
 endif
@@ -39,6 +39,14 @@ create_disk_CFLAGS = \
 create_disk_LDADD = \
 	$(top_builddir)/src/libguestfs.la
 
+display_icon_SOURCES = display_icon.c
+display_icon_CFLAGS = \
+	-DGUESTFS_WARN_DEPRECATED=1 \
+	-I$(top_srcdir)/src -I$(top_builddir)/src \
+	$(WARN_CFLAGS) $(WERROR_CFLAGS)
+display_icon_LDADD = \
+	$(top_builddir)/src/libguestfs.la
+
 inspect_vm_SOURCES = inspect_vm.c
 inspect_vm_CFLAGS = \
 	-DGUESTFS_WARN_DEPRECATED=1 \

examples/display_icon.c

@@ -0,0 +1,131 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <guestfs.h>
+
+static int
+compare_keys_len (const void *p1, const void *p2)
+{
+  const char *key1 = * (char * const *) p1;
+  const char *key2 = * (char * const *) p2;
+  return strlen (key1) - strlen (key2);
+}
+
+static size_t
+count_strings (char *const *argv)
+{
+  size_t c;
+
+  for (c = 0; argv[c]; ++c)
+    ;
+  return c;
+}
+
+int
+main (int argc, char *argv[])
+{
+  guestfs_h *g;
+  const char *disk;
+  char **roots, *root, **mountpoints, *icon;
+  size_t i, j, icon_size;
+  FILE *fp;
+
+  if (argc != 2) {
+    fprintf (stderr, "usage: display_icon disk.img\n");
+    exit (EXIT_FAILURE);
+  }
+  disk = argv[1];
+
+  g = guestfs_create ();
+  if (g == NULL) {
+    perror ("failed to create libguestfs handle");
+    exit (EXIT_FAILURE);
+  }
+
+  /* Attach the disk image read-only to libguestfs. */
+  if (guestfs_add_drive_opts (g, disk,
+     /* GUESTFS_ADD_DRIVE_OPTS_FORMAT, "raw", */
+        GUESTFS_ADD_DRIVE_OPTS_READONLY, 1,
+        -1) /* this marks end of optional arguments */
+      == -1)
+    exit (EXIT_FAILURE);
+
+  /* Run the libguestfs back-end. */
+  if (guestfs_launch (g) == -1)
+    exit (EXIT_FAILURE);
+
+  /* Ask libguestfs to inspect for operating systems. */
+  roots = guestfs_inspect_os (g);
+  if (roots == NULL)
+    exit (EXIT_FAILURE);
+  if (roots[0] == NULL) {
+    fprintf (stderr, "display_icon: no operating systems found\n");
+    exit (EXIT_FAILURE);
+  }
+
+  for (j = 0; roots[j] != NULL; ++j) {
+    root = roots[j];
+
+    /* Mount up the disks, like guestfish -i.
+     *
+     * Sort keys by length, shortest first, so that we end up
+     * mounting the filesystems in the correct order.
+     */
+    mountpoints = guestfs_inspect_get_mountpoints (g, root);
+    if (mountpoints == NULL)
+      exit (EXIT_FAILURE);
+
+    qsort (mountpoints, count_strings (mountpoints) / 2, 2 * sizeof (char *),
+           compare_keys_len);
+    for (i = 0; mountpoints[i] != NULL; i += 2) {
+      /* Ignore failures from this call, since bogus entries can
+       * appear in the guest's /etc/fstab.
+       */
+      guestfs_mount_ro (g, mountpoints[i+1], mountpoints[i]);
+      free (mountpoints[i]);
+      free (mountpoints[i+1]);
+    }
+    free (mountpoints);
+
+    /* Get the icon.
+     * This function returns a buffer ('icon').  Normally it is a png
+     * file, returned as a string, but it can also be a zero length
+     * buffer which has a special meaning, or NULL which means there
+     * was an error.
+     */
+    icon = guestfs_inspect_get_icon (g, root, &icon_size, -1);
+    if (!icon)                  /* actual libguestfs error */
+      exit (EXIT_FAILURE);
+    if (icon_size == 0)         /* no icon available */
+      fprintf (stderr, "%s: %s: no icon available for this operating system\n",
+               disk, root);
+    else {
+      /* Display the icon. */
+      fp = popen ("display -", "w");
+      if (fp == NULL) {
+        perror ("display");
+        exit (EXIT_FAILURE);
+      }
+      if (fwrite (icon, 1, icon_size, fp) != icon_size) {
+        perror ("write");
+        exit (EXIT_FAILURE);
+      }
+      if (pclose (fp) == -1) {
+        perror ("pclose");
+        exit (EXIT_FAILURE);
+      }
+    }
+    free (icon);
+
+    /* Unmount everything. */
+    if (guestfs_umount_all (g) == -1)
+      exit (EXIT_FAILURE);
+
+    free (root);
+  }
+  free (roots);
+
+  guestfs_close (g);
+
+  exit (EXIT_SUCCESS);
+}