[ostree] core: Add API to convert checksum -> csum in place

[Colin Walters <walters src gnome org>]

commit d9f59c6fd5529fd517d680d9929bf7409e3d49f7
Author: Colin Walters <walters verbum org>
Date:   Wed Aug 14 18:17:09 2013 -0400

    core: Add API to convert checksum -> csum in place
    
    We already have the opposite, and this will be used in some
    places to avoid a malloc.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=706031

 src/libostree/ostree-core.c |   18 +++++++++++++-----
 src/libostree/ostree-core.h |    3 +++
 2 files changed, 16 insertions(+), 5 deletions(-)
---
diff --git a/src/libostree/ostree-core.c b/src/libostree/ostree-core.c
index f1e1fc9..9231141 100644
--- a/src/libostree/ostree-core.c
+++ b/src/libostree/ostree-core.c
@@ -972,9 +972,17 @@ ostree_object_name_deserialize (GVariant         *variant,
   *out_objtype = (OstreeObjectType)objtype_u32;
 }
 
-static void
-checksum_to_bytes (const char *checksum,
-                   guchar     *buf)
+/**
+ * ostree_checksum_inplace_to_bytes:
+ * @checksum: a SHA256 string
+ * @buf: Output buffer with at least 32 bytes of space
+ *
+ * Convert @checksum from a string to binary in-place, without
+ * allocating memory.  Use this function in hot code paths.
+ */
+void
+ostree_checksum_inplace_to_bytes (const char *checksum,
+                                  guchar     *buf)
 {
   guint i;
   guint j;
@@ -1000,7 +1008,7 @@ guchar *
 ostree_checksum_to_bytes (const char *checksum)
 {
   guchar *ret = g_malloc (32);
-  checksum_to_bytes (checksum, ret);
+  ostree_checksum_inplace_to_bytes (checksum, ret);
   return ret;
 }
 
@@ -1008,7 +1016,7 @@ GVariant *
 ostree_checksum_to_bytes_v (const char *checksum)
 {
   guchar result[32];
-  checksum_to_bytes (checksum, result);
+  ostree_checksum_inplace_to_bytes (checksum, result);
   return ot_gvariant_new_bytearray ((guchar*)result, 32);
 }
 
diff --git a/src/libostree/ostree-core.h b/src/libostree/ostree-core.h
index 6f89265..a28b0ca 100644
--- a/src/libostree/ostree-core.h
+++ b/src/libostree/ostree-core.h
@@ -132,6 +132,9 @@ char * ostree_checksum_from_bytes_v (GVariant *bytes);
 void ostree_checksum_inplace_from_bytes (const guchar *bytes,
                                          char         *buf);
 
+void ostree_checksum_inplace_to_bytes (const char *checksum,
+                                       guchar     *buf);
+
 const guchar *ostree_checksum_bytes_peek (GVariant *bytes);
 
 int ostree_cmp_checksum_bytes (const guchar *a, const guchar *b);