Implement XzExtentWriter.
The new XzExtentWriter class is an ExtentWriter that uses xz-embedded
to decompress an xz stream and write it to the underlying extent
writer. This will be used to implement REPLACE_XZ in a follow up CL.
Bug: 23604708
Test: Added unittests.
Change-Id: Ifd2ba0c917b66ab33e5cff1d6069da833ad54882
diff --git a/xz_extent_writer.h b/xz_extent_writer.h
new file mode 100644
index 0000000..0b9ee17
--- /dev/null
+++ b/xz_extent_writer.h
@@ -0,0 +1,60 @@
+//
+// Copyright (C) 2015 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.
+//
+
+#ifndef UPDATE_ENGINE_XZ_EXTENT_WRITER_H_
+#define UPDATE_ENGINE_XZ_EXTENT_WRITER_H_
+
+#include <xz.h>
+
+#include <memory>
+#include <vector>
+
+#include <chromeos/secure_blob.h>
+
+#include "update_engine/extent_writer.h"
+
+// XzExtentWriter is a concrete ExtentWriter subclass that xz-decompresses
+// what it's given in Write using xz-embedded. Note that xz-embedded only
+// supports files with either no CRC or CRC-32. It passes the decompressed data
+// to an underlying ExtentWriter.
+
+namespace chromeos_update_engine {
+
+class XzExtentWriter : public ExtentWriter {
+ public:
+ explicit XzExtentWriter(std::unique_ptr<ExtentWriter> underlying_writer)
+ : underlying_writer_(std::move(underlying_writer)) {}
+ ~XzExtentWriter() override;
+
+ bool Init(FileDescriptorPtr fd,
+ const std::vector<Extent>& extents,
+ uint32_t block_size) override;
+ bool Write(const void* bytes, size_t count) override;
+ bool EndImpl() override;
+
+ private:
+ // The underlying ExtentWriter.
+ std::unique_ptr<ExtentWriter> underlying_writer_;
+ // The opaque xz decompressor struct.
+ xz_dec* stream_{nullptr};
+ chromeos::Blob input_buffer_;
+
+ DISALLOW_COPY_AND_ASSIGN(XzExtentWriter);
+};
+
+} // namespace chromeos_update_engine
+
+#endif // UPDATE_ENGINE_XZ_EXTENT_WRITER_H_