Initial basic static delta code drop

This has a very basic level of functionality (deltas can be generated,
and applied offline).  There is only some stubbed out pull code to
fetch them via HTTP.

But, better to commit this now and improve it from a known starting
point, rather than have it languish in a branch.

src/libostree/ostree-repo-static-delta-private.h

@@ -0,0 +1,96 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2013 Colin Walters <walters@verbum.org>
+ *
+ * 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.
+ */
+
+#pragma once
+
+#include "ostree-core.h"
+
+G_BEGIN_DECLS
+
+/* Arbitrarily chosen */
+#define OSTREE_STATIC_DELTA_PART_MAX_SIZE_BYTES (16*1024*1024)
+/* 1 byte for object type, 32 bytes for checksum */
+#define OSTREE_STATIC_DELTA_OBJTYPE_CSUM_LEN 33
+
+/**
+ * OSTREE_STATIC_DELTA_PART_PAYLOAD_FORMAT:
+ *
+ *   ay data source
+ *   ay operations
+ */
+#define OSTREE_STATIC_DELTA_PART_PAYLOAD_FORMAT "(ayay)"
+
+/**
+ * OSTREE_STATIC_DELTA_META_ENTRY_FORMAT:
+ *
+ *   ay checksum
+ *   guint64 size:   Total size of delta (sum of parts)
+ *   guint64 usize:   Uncompressed size of resulting objects on disk
+ *   ARRAY[(guint8 objtype, csum object)]
+ *
+ * The checksum is of the delta payload, and each entry in the array
+ * represents an OSTree object which will be created by the deltapart.
+ */
+
+#define OSTREE_STATIC_DELTA_META_ENTRY_FORMAT "(ayttay)"
+
+/**
+ * OSTREE_STATIC_DELTA_META_FORMAT:
+ *
+ * A .delta object is a custom binary format.  It has the following high
+ * level form:
+ *
+ * delta-descriptor:
+ *   metadata: a{sv}
+ *   ARRAY[(csum from, csum to)]: ay
+ *   ARRAY[delta-part-header]
+ *
+ * The metadata would include things like a version number, as well as
+ * extended verification data like a GPG signature.
+ * 
+ * The second array is an array of delta objects that should be
+ * fetched and applied before this one.  This is a fairly generic
+ * recursion mechanism that would potentially allow saving significant
+ * storage space on the server.
+ */ 
+#define OSTREE_STATIC_DELTA_META_FORMAT "(a{sv}aya" OSTREE_STATIC_DELTA_META_ENTRY_FORMAT ")"
+
+gboolean _ostree_static_delta_part_execute (OstreeRepo      *repo,
+                                            GVariant        *header,
+                                            GVariant        *part,
+                                            GCancellable    *cancellable,
+                                            GError         **error);
+
+typedef enum {
+  OSTREE_STATIC_DELTA_OP_FETCH = 1,
+  OSTREE_STATIC_DELTA_OP_WRITE = 2,
+  OSTREE_STATIC_DELTA_OP_GUNZIP = 3,
+  OSTREE_STATIC_DELTA_OP_CLOSE = 4,
+  OSTREE_STATIC_DELTA_OP_READOBJECT = 5,
+  OSTREE_STATIC_DELTA_OP_READPAYLOAD = 6
+} OstreeStaticDeltaOpCode;
+
+gboolean
+_ostree_static_delta_parse_checksum_array (GVariant      *array,
+                                           guint8       **out_checksums_array,
+                                           guint         *out_n_checksums,
+                                           GError       **error);
+G_END_DECLS
+