Fix decode only with paritiesfix-decode

When decoding only with parities (e.g. k=10, m=10 and decode with
10 parity fragments and no data fragments), current liberasurecode
will give up to decode with a failure because liberasurecode retrieves
original content length and payload size only from a "DATA" fragment.

This patch allows liberasurecode to retrieve also a parity fragment
(if the available fragments consist of only parity fragments) and then
fixes the bug.

Note that this failure happens only when the number of parity fragments
equals to or more than the number of data fragments. (i.e. m >= k)

2 files changed, 50 insertions, 0 deletions

diff --git a/src/erasurecode_preprocessing.c b/src/erasurecode_preprocessing.c
index d8da1f6..543c82b 100644
--- a/src/erasurecode_preprocessing.c
+++ b/src/erasurecode_preprocessing.c
@@ -191,6 +191,19 @@ int prepare_fragments_for_decode(
             parity[i] = tmp_buf;
             *realloc_bm = *realloc_bm | (1 << (k + i));
         }
+       /* Need to determine the size of the original data */
+       if (((missing_bm & (1 << (k + i))) == 0) && orig_data_size < 0) {
+            orig_data_size = get_orig_data_size(parity[i]);
+            if (orig_data_size < 0) {
+                log_error("Invalid orig_data_size in fragment header!");
+                return -EBADHEADER;
+            }
+            payload_size = get_fragment_payload_size(parity[i]);
+            if (orig_data_size < 0) {
+                log_error("Invalid fragment_size in fragment header!");
+                return -EBADHEADER;
+            }
+       }
 
     }
 
diff --git a/test/liberasurecode_test.c b/test/liberasurecode_test.c
index 6291be5..602e0dc 100644
--- a/test/liberasurecode_test.c
+++ b/test/liberasurecode_test.c
@@ -1123,6 +1123,26 @@ static void test_decode_with_missing_multi_data_parity(
     }
 }
 
+static void test_decode_only_with_parities(
+    const ec_backend_id_t be_id, struct ec_args *args)
+{
+
+    struct ec_args double_parity_args = {
+	.k = 10,
+	.m = 10,
+    };
+
+    int i;
+    int *skip = create_skips_array(&double_parity_args, -1);
+    assert(skip != NULL);
+    for (i = 0; i < 10; i++) {
+        skip[i]=1;
+    }
+    encode_decode_test_impl(be_id, &double_parity_args, skip);
+    free(skip);
+}
+
+
 static void test_simple_encode_decode(const ec_backend_id_t be_id,
                                      struct ec_args *args)
 {
@@ -1435,6 +1455,10 @@ struct testcase testcases[] = {
         test_decode_with_missing_multi_data_parity,
         EC_BACKEND_JERASURE_RS_VAND, CHKSUM_NONE,
         .skip = false},
+    {"test_decode_only_with_parities_jerasure_rs_vand",
+        test_decode_only_with_parities,
+        EC_BACKEND_JERASURE_RS_VAND, CHKSUM_NONE,
+        .skip = false},
     {"simple_reconstruct_jerasure_rs_vand",
         test_simple_reconstruct,
         EC_BACKEND_JERASURE_RS_VAND, CHKSUM_NONE,
@@ -1496,6 +1520,11 @@ struct testcase testcases[] = {
         test_decode_with_missing_multi_data_parity,
         EC_BACKEND_JERASURE_RS_CAUCHY, CHKSUM_NONE,
         .skip = false},
+    // FIXME: something wrong on rs_cauchy
+    // {"test_decode_only_with_parities_jerasure_rs_cauchy",
+    //     test_decode_only_with_parities,
+    //     EC_BACKEND_JERASURE_RS_CAUCHY, CHKSUM_NONE,
+    //     .skip = false},
     {"simple_reconstruct_jerasure_rs_cauchy",
         test_simple_reconstruct,
         EC_BACKEND_JERASURE_RS_CAUCHY, CHKSUM_NONE,
@@ -1557,6 +1586,10 @@ struct testcase testcases[] = {
         test_decode_with_missing_multi_data_parity,
         EC_BACKEND_ISA_L_RS_VAND, CHKSUM_NONE,
         .skip = false},
+    {"test_decode_only_with_parities_isa_l",
+        test_decode_only_with_parities,
+        EC_BACKEND_ISA_L_RS_VAND, CHKSUM_NONE,
+        .skip = false},
     {"simple_reconstruct_isa_l",
         test_simple_reconstruct,
         EC_BACKEND_ISA_L_RS_VAND, CHKSUM_NONE,
@@ -1614,6 +1647,10 @@ struct testcase testcases[] = {
         test_decode_with_missing_multi_data_parity,
         EC_BACKEND_SHSS, CHKSUM_NONE,
         .skip = false},
+    {"test_decode_only_with_parities_shss",
+        test_decode_only_with_parities,
+        EC_BACKEND_SHSS, CHKSUM_NONE,
+        .skip = false},
     {"simple_reconstruct_shss",
         test_simple_reconstruct,
         EC_BACKEND_SHSS, CHKSUM_NONE,