avifinfo: Fuzz target

Change-Id: Ia147c689a12060e8717af18a64976aaef221747c

tests/avifinfo_fuzz.cc

diff --git a/tests/avifinfo_fuzz.cc b/tests/avifinfo_fuzz.cc
new file mode 100644
index 0000000..6e9cf27
--- /dev/null
+++ b/tests/avifinfo_fuzz.cc
@@ -0,0 +1,57 @@
+// Copyright (c) 2021, Alliance for Open Media. All rights reserved
+//
+// This source code is subject to the terms of the BSD 2 Clause License and
+// the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
+// was not distributed with this source code in the LICENSE file, you can
+// obtain it at www.aomedia.org/license/software. If the Alliance for Open
+// Media Patent License 1.0 was not distributed with this source code in the
+// PATENTS file, you can obtain it at www.aomedia.org/license/patent.
+
+#include <cstddef>
+#include <cstdint>
+#include <cstdlib>
+
+#include "avifinfo.h"
+
+// Test a random bitstream of random size, whether it is valid or not.
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t data_size) {
+  AvifInfoStatus previous_status = kAvifInfoNotEnoughData;
+  AvifInfoFeatures previous_features = {0};
+
+  // Check the consistency of the returned status and features:
+  // for a given size and a status that is not kAvifInfoNotEnoughData, any
+  // bigger size (of the same data) should return the same status and features.
+  for (size_t size = 0; size < data_size; ++size) {
+    AvifInfoFeatures features;
+    const AvifInfoStatus status =
+        AvifInfoGetWithSize(data, size, &features, data_size);
+
+    if (previous_status != kAvifInfoNotEnoughData &&
+        status != previous_status) {
+      std::abort();
+    }
+
+    if (status == previous_status) {
+      if (features.width != previous_features.width ||
+          features.height != previous_features.height ||
+          features.bit_depth != previous_features.bit_depth ||
+          features.num_channels != previous_features.num_channels) {
+        std::abort();
+      }
+    } else if (status == kAvifInfoOk) {
+      if (features.width == 0u || features.height == 0u ||
+          features.bit_depth == 0u || features.num_channels == 0u) {
+        std::abort();
+      }
+    } else {
+      if (features.width != 0u || features.height != 0u ||
+          features.bit_depth != 0u || features.num_channels != 0u) {
+        std::abort();
+      }
+    }
+
+    previous_status = status;
+    previous_features = features;
+  }
+  return 0;
+}