1 files changed, 43 insertions, 0 deletions
diff --git a/third_party/jpeg-xl/lib/jxl/ans_common_test.cc b/third_party/jpeg-xl/lib/jxl/ans_common_test.cc
new file mode 100644
index 0000000000..487b6cf5bd
--- /dev/null
+++ b/third_party/jpeg-xl/lib/jxl/ans_common_test.cc
@@ -0,0 +1,43 @@
+// Copyright (c) the JPEG XL Project Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "lib/jxl/ans_common.h"
+
+#include <vector>
+
+#include "lib/jxl/ans_params.h"
+#include "lib/jxl/testing.h"
+
+namespace jxl {
+namespace {
+
+void VerifyAliasDistribution(const std::vector<int>& distribution,
+                             uint32_t range) {
+  constexpr size_t log_alpha_size = 8;
+  AliasTable::Entry table[1 << log_alpha_size];
+  InitAliasTable(distribution, range, log_alpha_size, table);
+  std::vector<std::vector<uint32_t>> offsets(distribution.size());
+  for (uint32_t i = 0; i < range; i++) {
+    AliasTable::Symbol s = AliasTable::Lookup(
+        table, i, ANS_LOG_TAB_SIZE - 8, (1 << (ANS_LOG_TAB_SIZE - 8)) - 1);
+    offsets[s.value].push_back(s.offset);
+  }
+  for (uint32_t i = 0; i < distribution.size(); i++) {
+    ASSERT_EQ(static_cast<size_t>(distribution[i]), offsets[i].size());
+    std::sort(offsets[i].begin(), offsets[i].end());
+    for (uint32_t j = 0; j < offsets[i].size(); j++) {
+      ASSERT_EQ(offsets[i][j], j);
+    }
+  }
+}
+
+TEST(ANSCommonTest, AliasDistributionSmoke) {
+  VerifyAliasDistribution({ANS_TAB_SIZE / 2, ANS_TAB_SIZE / 2}, ANS_TAB_SIZE);
+  VerifyAliasDistribution({ANS_TAB_SIZE}, ANS_TAB_SIZE);
+  VerifyAliasDistribution({0, 0, 0, ANS_TAB_SIZE, 0}, ANS_TAB_SIZE);
+}
+
+}  // namespace
+}  // namespace jxl