Add support for custom backend metadatabackend_metadata_adder

A backend may have the need to add custom metadata to the
encoded data/parity fragments, in addition to the
liberasurecode "fragment metadata headers".  This patch
gives the ability to a EC backend writer to specify a
"metadata adder" that is taken into account when allocating
output data/parity fragment buffers.

Signed-off-by: Tushar Gohad <tushar.gohad@intel.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/src/erasurecode_helpers.c b/src/erasurecode_helpers.c
index 6e4c882..42877eb 100644
--- a/src/erasurecode_helpers.c
+++ b/src/erasurecode_helpers.c
@@ -103,14 +103,20 @@ void * check_and_free_buffer(void * buf)
     return NULL;
 }
 
-char *alloc_fragment_buffer(int size)
+char *alloc_fragment_buffer(ec_backend_t instance, int size)
 {
     char *buf;
     fragment_header_t *header = NULL;
 
+    if (NULL != instance) {
+        /* Account for any custom backend metadata in the fragment size */
+         size += instance->common.metadata_adder;
+    }
+
+    /* liberasurecode metadata */
     size += sizeof(fragment_header_t);
-    buf = get_aligned_buffer16(size);
 
+    buf = get_aligned_buffer16(size);
     if (buf) {
         header = (fragment_header_t *) buf;
         header->magic = LIBERASURECODE_FRAG_HEADER_MAGIC;