[ostree] core: Add API to convert csum -> checksum without malloc()

[Colin Walters <walters src gnome org>]

commit a821420711279415a41e17f559b1db8cab4fa275
Author: Colin Walters <walters verbum org>
Date:   Sat Feb 23 11:02:56 2013 -0500

    core: Add API to convert csum -> checksum without malloc()
    
    Just doing some profiling, this was in the top malloc() callers.

 src/libostree/ostree-core.c      |   20 ++++++++++++--------
 src/libostree/ostree-core.h      |    3 +++
 src/libostree/ostree-repo-file.c |   10 +++++-----
 3 files changed, 20 insertions(+), 13 deletions(-)
---
diff --git a/src/libostree/ostree-core.c b/src/libostree/ostree-core.c
index 09ce530..9a90da5 100644
--- a/src/libostree/ostree-core.c
+++ b/src/libostree/ostree-core.c
@@ -948,23 +948,27 @@ ostree_checksum_to_bytes_v (const char *checksum)
   return ot_gvariant_new_bytearray ((guchar*)result, 32);
 }
 
-char *
-ostree_checksum_from_bytes (const guchar *csum)
+void
+ostree_checksum_inplace_from_bytes (const guchar *csum,
+                                    char         *buf)
 {
   static const gchar hexchars[] = "0123456789abcdef";
-  char *ret;
   guint i, j;
 
-  ret = g_malloc (65);
-  
   for (i = 0, j = 0; i < 32; i++, j += 2)
     {
       guchar byte = csum[i];
-      ret[j] = hexchars[byte >> 4];
-      ret[j+1] = hexchars[byte & 0xF];
+      buf[j] = hexchars[byte >> 4];
+      buf[j+1] = hexchars[byte & 0xF];
     }
-  ret[j] = '\0';
+  buf[j] = '\0';
+}
 
+char *
+ostree_checksum_from_bytes (const guchar *csum)
+{
+  char *ret = g_malloc (65);
+  ostree_checksum_inplace_from_bytes (csum, ret);
   return ret;
 }
 
diff --git a/src/libostree/ostree-core.h b/src/libostree/ostree-core.h
index 83f688b..b3f761e 100644
--- a/src/libostree/ostree-core.h
+++ b/src/libostree/ostree-core.h
@@ -113,6 +113,9 @@ GVariant *ostree_checksum_to_bytes_v (const char *checksum);
 char * ostree_checksum_from_bytes (const guchar *bytes);
 char * ostree_checksum_from_bytes_v (GVariant *bytes);
 
+void ostree_checksum_inplace_from_bytes (const guchar *bytes,
+                                         char         *buf);
+
 const guchar *ostree_checksum_bytes_peek (GVariant *bytes);
 
 int ostree_cmp_checksum_bytes (const guchar *a, const guchar *b);
diff --git a/src/libostree/ostree-repo-file.c b/src/libostree/ostree-repo-file.c
index 5a95afc..0fb3a63 100644
--- a/src/libostree/ostree-repo-file.c
+++ b/src/libostree/ostree-repo-file.c
@@ -816,7 +816,7 @@ ostree_repo_file_tree_query_child (OstreeRepoFile  *self,
   ot_lvariant GVariant *tree_child_metadata = NULL;
   ot_lvariant GVariant *content_csum_v = NULL;
   ot_lvariant GVariant *meta_csum_v = NULL;
-  ot_lfree char *tmp_checksum = NULL;
+  char tmp_checksum[65];
   GFileAttributeMatcher *matcher = NULL;
 
   if (!ostree_repo_file_ensure_resolved (self, error))
@@ -833,8 +833,8 @@ ostree_repo_file_tree_query_child (OstreeRepoFile  *self,
   if (n < c)
     {
       g_variant_get_child (files_variant, n, "(&s ay)", &name, &content_csum_v);
-      g_free (tmp_checksum);
-      tmp_checksum = ostree_checksum_from_bytes_v (content_csum_v);
+      ostree_checksum_inplace_from_bytes (ostree_checksum_bytes_peek (content_csum_v),
+                                          tmp_checksum);
 
       if (!ostree_repo_load_file (self->repo, tmp_checksum, NULL, &ret_info, NULL,
                                   cancellable, error))
@@ -850,8 +850,8 @@ ostree_repo_file_tree_query_child (OstreeRepoFile  *self,
         {
           g_variant_get_child (dirs_variant, n, "(&s ay@ay)",
                                &name, NULL, &meta_csum_v);
-          g_free (tmp_checksum);
-          tmp_checksum = ostree_checksum_from_bytes_v (meta_csum_v);
+          ostree_checksum_inplace_from_bytes (ostree_checksum_bytes_peek (meta_csum_v),
+                                              tmp_checksum);
 
           if (!query_child_info_dir (self->repo, tmp_checksum,
                                      matcher, flags, &ret_info,