Test: Add fuzzer for zip_writer.

Change-Id: I081a23a20479a7e68a0b3a30a1d53d3f78efae2f
diff --git a/libziparchive_writer_fuzzer.cpp b/libziparchive_writer_fuzzer.cpp
new file mode 100644
index 0000000..853a768
--- /dev/null
+++ b/libziparchive_writer_fuzzer.cpp
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: Apache-2.0
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <ziparchive/zip_writer.h>
+#include "fuzzer/FuzzedDataProvider.h"
+
+// See current fuzz coverage here:
+// https://android-coverage.googleplex.com/fuzz_targets/libziparchive_writer_fuzzer/index.html
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  FuzzedDataProvider provider(data, size);
+
+  std::unique_ptr<std::FILE, decltype(&fclose)> fp(fopen("fuzz", "wb"),
+                                                   &fclose);
+  if (!fp) {
+    return 0;
+  }
+  ZipWriter writer(fp.get());
+  for (int i = 0; i < 2; i++) {
+    if (provider.remaining_bytes() == 0) {
+      break;
+    }
+    auto path = provider.ConsumeRandomLengthString();
+    if (writer.StartEntry(path, path.size()) == 0) {
+      for (int j = 0; j < 2; j++) {
+        if (provider.remaining_bytes() == 0) {
+          break;
+        }
+        const size_t next_size = provider.ConsumeIntegralInRange<size_t>(
+            0, provider.remaining_bytes());
+        auto next_buf = provider.ConsumeBytes<uint8_t>(next_size);
+        writer.WriteBytes(next_buf.data(), next_buf.size());
+      }
+      writer.FinishEntry();
+    }
+  }
+  writer.Finish();
+  return 0;
+}