Add repository "summary" file and metalink support

For Fedora and potentially other distributions which use globally
distributed mirrors, metalink is a popular solution to redirect
clients to a dynamic set of mirrors.

In order to make metalink work though, it needs *one* file which can
be checksummed.  (Well, potentially we could explode all refs into the
metalink.xml, but that would be a lot more invasive, and a bit weird
as we'd end up checksumming the checksum file).

This commit adds a new command:

$ ostree summary -u

To regenerate the summary file.  Can only be run by one process at a
time.

After that's done, the metalink can be generated based on it, and the
client fetch code will parse and load it.

https://bugzilla.gnome.org/show_bug.cgi?id=729585

src/libotutil/ot-checksum-utils.c

@@ -139,6 +139,32 @@ ot_gio_checksum_stream (GInputStream   *in,
   return ot_gio_splice_get_checksum (NULL, in, out_csum, cancellable, error);
 }
 
+char *
+ot_checksum_file (GFile          *file,
+                  GChecksumType   checksum_type,
+                  GCancellable   *cancellable,
+                  GError        **error)
+{
+  GChecksum *checksum = NULL;
+  char *ret = NULL;
+  gs_unref_object GInputStream *in = NULL;
+
+  in = (GInputStream*)g_file_read (file, cancellable, error);
+  if (!in)
+    goto out;
+
+  checksum = g_checksum_new (checksum_type);
+
+  if (!ot_gio_splice_update_checksum (NULL, in, checksum, cancellable, error))
+    goto out;
+
+  ret = g_strdup (g_checksum_get_string (checksum));
+ out:
+  g_clear_pointer (&checksum, (GDestroyNotify) g_checksum_free);
+  return ret;
+
+}
+
 static void
 checksum_stream_thread (GSimpleAsyncResult   *result,
                         GObject              *object,

src/libotutil/ot-checksum-utils.h

@@ -53,6 +53,11 @@ gboolean ot_gio_checksum_stream (GInputStream   *in,
                                  GCancellable   *cancellable,
                                  GError        **error);
 
+char * ot_checksum_file (GFile          *file,
+                         GChecksumType   checksum_type,
+                         GCancellable   *cancellable,
+                         GError        **error);
+
 void ot_gio_checksum_stream_async (GInputStream         *in,
                                    int                   io_priority,
                                    GCancellable         *cancellable,

src/libotutil/ot-variant-utils.c

@@ -30,6 +30,12 @@
 
 #include "otutil.h"
 
+GVariant *
+ot_gvariant_new_empty_string_dict (void)
+{
+  return g_variant_builder_end (g_variant_builder_new (G_VARIANT_TYPE ("a{sv}")));
+}
+
 GVariant *
 ot_gvariant_new_bytearray (const guchar   *data,
                            gsize           len)
@@ -282,3 +288,61 @@ ot_variant_new_from_bytes (const GVariantType  *type,
                                   (GDestroyNotify)g_bytes_unref, bytes);
 #endif
 }
+
+/**
+ * ot_variant_bsearch_str:
+ * @array: A GVariant array whose first element must be a string
+ * @str: Search for this string
+ * @out_pos: Output position
+ *
+ *
+ * Binary search in a GVariant array, which must be of the form 'a(s...)',
+ * where '...' may be anything.  The array elements must be sorted.
+ *
+ * Returns: %TRUE if found, %FALSE otherwise
+ */
+gboolean
+ot_variant_bsearch_str (GVariant   *array,
+                        const char *str,
+                        int        *out_pos)
+{
+  gsize imax, imin;
+  gsize imid;
+  gsize n;
+
+  n = g_variant_n_children (array);
+  if (n == 0)
+    return FALSE;
+
+  imax = n - 1;
+  imin = 0;
+  while (imax >= imin)
+    {
+      gs_unref_variant GVariant *child = NULL;
+      const char *cur;
+      int cmp;
+
+      imid = (imin + imax) / 2;
+
+      child = g_variant_get_child_value (array, imid);
+      g_variant_get_child (child, 0, "&s", &cur, NULL);      
+
+      cmp = strcmp (cur, str);
+      if (cmp < 0)
+        imin = imid + 1;
+      else if (cmp > 0)
+        {
+          if (imid == 0)
+            break;
+          imax = imid - 1;
+        }
+      else
+        {
+          *out_pos = imid;
+          return TRUE;
+        }
+    }
+
+  *out_pos = imid;
+  return FALSE;
+}

src/libotutil/ot-variant-utils.h

@@ -31,6 +31,8 @@ GVariant *ot_gvariant_new_bytearray (const guchar   *data,
 
 GVariant *ot_gvariant_new_ay_bytes (GBytes *bytes);
 
+GVariant *ot_gvariant_new_empty_string_dict (void);
+
 GHashTable *ot_util_variant_asv_to_hash_table (GVariant *variant);
 
 GVariant * ot_util_variant_take_ref (GVariant *variant);
@@ -70,5 +72,10 @@ ot_variant_new_from_bytes (const GVariantType  *type,
                            GBytes        *bytes,
                            gboolean       trusted);
 
+gboolean
+ot_variant_bsearch_str (GVariant   *array,
+                        const char *str,
+                        int        *out_pos);
+
 G_END_DECLS