lib/repo-finder: Add basic support for finding remote URIs by ref name

Add an initial OstreeRepoFinder interface (but no implementations),
which will find remote URIs by ref names and collection IDs, the
combination of which is globally unique.

The new API is used in a new ostree_repo_find_updates() function, which
resolves a list of ref names to update into a set of remote URIs to pull
them from, which can be treated as mirrors. It is an attempt to
generalise resolution of the URIs to pull from, and to generalise
determination of the order and parallelisation which they should be
downloaded from in.

Includes fixes by Krzesimir Nowak <krzesimir@kinvolk.io>.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

Closes: #924
Approved by: cgwalters

1 files changed, 172 insertions, 0 deletions

diff --git a/src/libostree/ostree-repo-finder.h b/src/libostree/ostree-repo-finder.h
new file mode 100644
index 00000000..6b0ce8ca
--- /dev/null
+++ b/src/libostree/ostree-repo-finder.h
@@ -0,0 +1,172 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright © 2017 Endless Mobile, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ *
+ * Authors:
+ *  - Philip Withnall <withnall@endlessm.com>
+ */
+
+#pragma once
+
+#include <gio/gio.h>
+#include <glib.h>
+#include <glib-object.h>
+
+#include "ostree-ref.h"
+#include "ostree-remote.h"
+#include "ostree-types.h"
+
+G_BEGIN_DECLS
+
+#define OSTREE_TYPE_REPO_FINDER (ostree_repo_finder_get_type ())
+
+/* Manually expanded version of the following, omitting autoptr support (for GLib < 2.44):
+_OSTREE_PUBLIC
+G_DECLARE_INTERFACE (OstreeRepoFinder, ostree_repo_finder, OSTREE, REPO_FINDER, GObject) */
+
+_OSTREE_PUBLIC
+GType ostree_repo_finder_get_type (void);
+G_GNUC_BEGIN_IGNORE_DEPRECATIONS
+typedef struct _OstreeRepoFinder OstreeRepoFinder;
+typedef struct _OstreeRepoFinderInterface OstreeRepoFinderInterface;
+
+static inline OstreeRepoFinder *OSTREE_REPO_FINDER (gpointer ptr) { return G_TYPE_CHECK_INSTANCE_CAST (ptr, ostree_repo_finder_get_type (), OstreeRepoFinder); }
+static inline gboolean OSTREE_IS_REPO_FINDER (gpointer ptr) { return G_TYPE_CHECK_INSTANCE_TYPE (ptr, ostree_repo_finder_get_type ()); }
+static inline OstreeRepoFinderInterface *OSTREE_REPO_FINDER_GET_IFACE (gpointer ptr) { return G_TYPE_INSTANCE_GET_INTERFACE (ptr, ostree_repo_finder_get_type (), OstreeRepoFinderInterface); }
+G_GNUC_END_IGNORE_DEPRECATIONS
+
+struct _OstreeRepoFinderInterface
+{
+  GTypeInterface g_iface;
+
+  void (*resolve_async) (OstreeRepoFinder                  *self,
+                         const OstreeCollectionRef * const *refs,
+                         OstreeRepo                        *parent_repo,
+                         GCancellable                      *cancellable,
+                         GAsyncReadyCallback                callback,
+                         gpointer                           user_data);
+  GPtrArray *(*resolve_finish) (OstreeRepoFinder  *self,
+                                GAsyncResult      *result,
+                                GError           **error);
+};
+
+_OSTREE_PUBLIC
+void ostree_repo_finder_resolve_async (OstreeRepoFinder                  *self,
+                                       const OstreeCollectionRef * const *refs,
+                                       OstreeRepo                        *parent_repo,
+                                       GCancellable                      *cancellable,
+                                       GAsyncReadyCallback                callback,
+                                       gpointer                           user_data);
+_OSTREE_PUBLIC
+GPtrArray *ostree_repo_finder_resolve_finish (OstreeRepoFinder  *self,
+                                              GAsyncResult      *result,
+                                              GError           **error);
+
+_OSTREE_PUBLIC
+void ostree_repo_finder_resolve_all_async (OstreeRepoFinder * const          *finders,
+                                           const OstreeCollectionRef * const *refs,
+                                           OstreeRepo                        *parent_repo,
+                                           GCancellable                      *cancellable,
+                                           GAsyncReadyCallback                callback,
+                                           gpointer                           user_data);
+_OSTREE_PUBLIC
+GPtrArray *ostree_repo_finder_resolve_all_finish (GAsyncResult  *result,
+                                                  GError       **error);
+
+/**
+ * OstreeRepoFinderResult:
+ * @remote: #OstreeRemote which contains the transport details for the result,
+ *    such as its URI and GPG key
+ * @finder: the #OstreeRepoFinder instance which produced this result
+ * @priority: static priority of the result, where higher numbers indicate lower
+ *    priority
+ * @ref_to_checksum: (element-type OstreeCollectionRef utf8): map of collection–ref
+ *    pairs to checksums provided by this remote; values may be %NULL to
+ *    indicate this remote doesn’t provide that ref
+ * @summary_last_modified: Unix timestamp (seconds since the epoch, UTC) when
+ *    the summary file on the remote was last modified, or `0` if unknown
+ *
+ * #OstreeRepoFinderResult gives a single result from an
+ * ostree_repo_finder_resolve_async() or ostree_repo_finder_resolve_all_async()
+ * operation. This represents a single remote which provides none, some or all
+ * of the refs being resolved. The structure includes various bits of metadata
+ * which allow ostree_repo_pull_from_remotes_async() (for example) to prioritise
+ * how to pull the refs.
+ *
+ * The @priority is used as one input of many to ordering functions like
+ * ostree_repo_finder_result_compare().
+ *
+ * @ref_to_checksum indicates which refs (out of the ones queried for as inputs
+ * to ostree_repo_finder_resolve_async()) are provided by this remote. The refs
+ * are present as keys (of type #OstreeCollectionRef), and the corresponding values
+ * are the checksums of the commits the remote currently has for those refs. (These
+ * might not be the latest commits available out of all results.) A
+ * checksum may be %NULL if the remote does not advertise the corresponding ref.
+ * After ostree_repo_finder_resolve_async() has been called, the commit metadata
+ * should be available locally, so the details for each checksum can be looked
+ * up using ostree_repo_load_commit().
+ *
+ * Since: 2017.8
+ */
+typedef struct
+{
+  OstreeRemote *remote;
+  OstreeRepoFinder *finder;
+  gint priority;
+  GHashTable *ref_to_checksum;
+  guint64 summary_last_modified;
+
+  /*< private >*/
+  gpointer padding[4];
+} OstreeRepoFinderResult;
+
+_OSTREE_PUBLIC
+GType ostree_repo_finder_result_get_type (void);
+
+_OSTREE_PUBLIC
+OstreeRepoFinderResult *ostree_repo_finder_result_new (OstreeRemote     *remote,
+                                                       OstreeRepoFinder *finder,
+                                                       gint              priority,
+                                                       GHashTable       *ref_to_checksum,
+                                                       guint64           summary_last_modified);
+_OSTREE_PUBLIC
+OstreeRepoFinderResult *ostree_repo_finder_result_dup (OstreeRepoFinderResult *result);
+_OSTREE_PUBLIC
+gint ostree_repo_finder_result_compare (const OstreeRepoFinderResult *a,
+                                        const OstreeRepoFinderResult *b);
+_OSTREE_PUBLIC
+void ostree_repo_finder_result_free (OstreeRepoFinderResult *result);
+
+/**
+ * OstreeRepoFinderResultv:
+ *
+ * A %NULL-terminated array of #OstreeRepoFinderResult instances, designed to
+ * be used with g_auto():
+ *
+ * |[<!-- language="C" -->
+ * g_auto(OstreeRepoFinderResultv) results = NULL;
+ * ]|
+ *
+ * Since: 2017.8
+ */
+typedef OstreeRepoFinderResult** OstreeRepoFinderResultv;
+
+_OSTREE_PUBLIC
+void ostree_repo_finder_result_freev (OstreeRepoFinderResult **results);
+
+G_END_DECLS