diff --git a/aosp/cow_converter.cc b/aosp/cow_converter.cc
new file mode 100644
index 0000000..8c641b8
--- /dev/null
+++ b/aosp/cow_converter.cc
@@ -0,0 +1,131 @@
+//
+// Copyright (C) 2021 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include <stdio.h>
+#include <string.h>
+
+#include <cstdint>
+#include <cstdio>
+#include <memory>
+
+#include <sys/fcntl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+
+#include <base/files/file_path.h>
+#include <libsnapshot/cow_writer.h>
+
+#include "update_engine/common/cow_operation_convert.h"
+#include "update_engine/common/utils.h"
+#include "update_engine/payload_consumer/file_descriptor.h"
+#include "update_engine/payload_consumer/payload_metadata.h"
+#include "update_engine/payload_generator/cow_size_estimator.h"
+#include "update_engine/update_metadata.pb.h"
+
+using android::snapshot::CowWriter;
+
+namespace chromeos_update_engine {
+
+bool ProcessPartition(const chromeos_update_engine::PartitionUpdate& partition,
+                      const char* image_dir,
+                      size_t block_size) {
+  base::FilePath img_dir{image_dir};
+  auto target_img = img_dir.Append(partition.partition_name() + ".img");
+  auto output_cow = img_dir.Append(partition.partition_name() + ".cow");
+  FileDescriptorPtr target_img_fd = std::make_shared<EintrSafeFileDescriptor>();
+  if (!target_img_fd->Open(target_img.value().c_str(), O_RDONLY)) {
+    PLOG(ERROR) << "Failed to open " << target_img.value();
+    return false;
+  }
+  android::base::unique_fd output_fd{
+      open(output_cow.value().c_str(), O_RDWR | O_CREAT, 0744)};
+  if (output_fd < 0) {
+    PLOG(ERROR) << "Failed to open " << output_cow.value();
+    return false;
+  }
+
+  android::snapshot::CowWriter cow_writer{
+      {.block_size = static_cast<uint32_t>(block_size), .compression = "gz"}};
+  TEST_AND_RETURN_FALSE(cow_writer.Initialize(output_fd));
+  TEST_AND_RETURN_FALSE(CowDryRun(target_img_fd,
+                                  partition.operations(),
+                                  partition.merge_operations(),
+                                  block_size,
+                                  &cow_writer));
+  TEST_AND_RETURN_FALSE(cow_writer.Finalize());
+  return true;
+}
+
+}  // namespace chromeos_update_engine
+
+using chromeos_update_engine::MetadataParseResult;
+using chromeos_update_engine::PayloadMetadata;
+
+int main(int argc, const char* argv[]) {
+  if (argc != 3) {
+    printf("Usage: %s <payload.bin> <extracted target_file>\n", argv[0]);
+    return -1;
+  }
+  const char* payload_path = argv[1];
+  const char* images_dir = argv[2];
+  int payload_fd = open(payload_path, O_RDONLY);
+  if (payload_fd < 0) {
+    PLOG(ERROR) << "Failed to open payload file:";
+    return 1;
+  }
+  chromeos_update_engine::ScopedFdCloser closer{&payload_fd};
+  auto payload_size = chromeos_update_engine::utils::FileSize(payload_fd);
+  if (payload_size <= 0) {
+    PLOG(ERROR)
+        << "Couldn't determine size of payload file, or payload file is empty";
+    return 2;
+  }
+
+  PayloadMetadata payload_metadata;
+  auto payload = static_cast<unsigned char*>(
+      mmap(nullptr, payload_size, PROT_READ, MAP_PRIVATE, payload_fd, 0));
+
+  // C++ dark magic to ensure that |payload| is properly deallocated once the
+  // program exits.
+  auto munmap_deleter = [payload_size](auto payload) {
+    munmap(payload, payload_size);
+  };
+  std::unique_ptr<unsigned char, decltype(munmap_deleter)> munmapper{
+      payload, munmap_deleter};
+
+  if (payload == nullptr) {
+    PLOG(ERROR) << "Failed to mmap() payload file";
+    return 3;
+  }
+  if (payload_metadata.ParsePayloadHeader(payload, payload_size, nullptr) !=
+      chromeos_update_engine::MetadataParseResult::kSuccess) {
+    LOG(ERROR) << "Payload header parse failed!";
+    return 4;
+  }
+  chromeos_update_engine::DeltaArchiveManifest manifest;
+  if (!payload_metadata.GetManifest(payload, payload_size, &manifest)) {
+    LOG(ERROR) << "Failed to parse manifest!";
+    return 5;
+  }
+
+  for (const auto& partition : manifest.partitions()) {
+    LOG(INFO) << partition.partition_name();
+    if (!ProcessPartition(partition, images_dir, manifest.block_size())) {
+      return 6;
+    }
+  }
+  return 0;
+}