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

1 files changed, 64 insertions, 0 deletions

diff --git a/src/libotutil/ot-variant-utils.c b/src/libotutil/ot-variant-utils.c
index ffc2defa..aa3dff56 100644
--- a/src/libotutil/ot-variant-utils.c
+++ b/src/libotutil/ot-variant-utils.c
@@ -31,6 +31,12 @@
 #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;
+}