[ostree] deltas: Make apply-offline only read the parts once

[Alexander Larsson <alexl src gnome org>]

commit eaa678eaa4059a666a2c461fddfe7ecb498628e0
Author: Alexander Larsson <alexl redhat com>
Date:   Thu Oct 15 15:54:35 2015 +0200

    deltas: Make apply-offline only read the parts once
    
    No need to read() the file for the checksum if we then directly mmap it.
    Instead we just mmap it initially and checksum from that.

 src/libostree/ostree-repo-static-delta-core.c |   49 ++++++++++---------------
 1 files changed, 19 insertions(+), 30 deletions(-)
---
diff --git a/src/libostree/ostree-repo-static-delta-core.c b/src/libostree/ostree-repo-static-delta-core.c
index 1a96166..f014b61 100644
--- a/src/libostree/ostree-repo-static-delta-core.c
+++ b/src/libostree/ostree-repo-static-delta-core.c
@@ -296,9 +296,7 @@ ostree_repo_static_delta_execute_offline (OstreeRepo                    *self,
       g_autoptr(GVariant) header = NULL;
       g_autoptr(GVariant) csum_v = NULL;
       g_autoptr(GVariant) objects = NULL;
-      g_autoptr(GFile) part_path = NULL;
-      g_autoptr(GInputStream) raw_in = NULL;
-      g_autoptr(GInputStream) in = NULL;
+      g_autoptr(GBytes) bytes = NULL;
       g_autofree char *deltapart_path = NULL;
 
       header = g_variant_get_child_value (headers, i);
@@ -330,17 +328,24 @@ ostree_repo_static_delta_execute_offline (OstreeRepo                    *self,
 
       part_data = g_variant_lookup_value (metadata, deltapart_path, G_VARIANT_TYPE("(yay)"));
       if (part_data)
-        in = ot_variant_read (part_data);
+        {
+          bytes = g_variant_get_data_as_bytes (part_data);
+        }
       else
         {
-          part_path = ot_gfile_resolve_path_printf (dir, "%u", i);
-          in = (GInputStream*)g_file_read (part_path, cancellable, error);
+          g_autoptr(GFile) part_path = ot_gfile_resolve_path_printf (dir, "%u", i);
+          GMappedFile *mfile = gs_file_map_noatime (part_path, cancellable, error);
+          if (!mfile)
+            goto out;
+
+          bytes = g_mapped_file_get_bytes (mfile);
+          g_mapped_file_unref (mfile);
         }
-      if (!in)
-        goto out;
 
       if (!skip_validation)
         {
+          g_autoptr(GInputStream) in = g_memory_input_stream_new_from_bytes (bytes);
+
           g_autofree char *expected_checksum = ostree_checksum_from_bytes (csum);
           if (!_ostree_static_delta_part_validate (self, in, i,
                                                    expected_checksum,
@@ -348,28 +353,12 @@ ostree_repo_static_delta_execute_offline (OstreeRepo                    *self,
             goto out;
         }
 
-      {
-        g_autoptr(GBytes) bytes = NULL;
-
-        if (part_data)
-          bytes = g_variant_get_data_as_bytes (part_data);
-        else
-          {
-            GMappedFile *mfile = gs_file_map_noatime (part_path, cancellable, error);
-            if (!mfile)
-              goto out;
-
-            bytes = g_mapped_file_get_bytes (mfile);
-            g_mapped_file_unref (mfile);
-          }
-        
-        if (!_ostree_static_delta_part_execute (self, objects, bytes,
-                                                cancellable, error))
-          {
-            g_prefix_error (error, "executing delta part %i: ", i);
-            goto out;
-          }
-      }
+      if (!_ostree_static_delta_part_execute (self, objects, bytes,
+                                              cancellable, error))
+        {
+          g_prefix_error (error, "executing delta part %i: ", i);
+          goto out;
+        }
     }
 
   ret = TRUE;