test that xof_many doesn't write more blocks than requested

1 files changed, 4 insertions, 0 deletions

diff --git a/c/blake3_dispatch.c b/c/blake3_dispatch.c
index a90c757..cf5bad7 100644
--- a/c/blake3_dispatch.c
+++ b/c/blake3_dispatch.c
@@ -228,6 +228,10 @@ void blake3_xof_many(const uint32_t cv[8],
                      const uint8_t block[BLAKE3_BLOCK_LEN],
                      uint8_t block_len, uint64_t counter, uint8_t flags,
                      uint8_t out[64], size_t outblocks) {
+  if (outblocks == 0) {
+    // The current assembly implementation always outputs at least 1 block.
+    return;
+  }
 #if defined(IS_X86)
   const enum cpu_feature features = get_cpu_features();
 #if defined(__unix__) && !defined(BLAKE3_NO_AVX512)