AAPT2: Separate out the various steps

An early refactor. Some ideas became clearer as
development continued. Now the various phases are much
clearer and more easily reusable.

Also added a ton of tests!

Change-Id: Ic8f0a70c8222370352e63533b329c40457c0903e
diff --git a/tools/aapt2/flatten/ChunkWriter.h b/tools/aapt2/flatten/ChunkWriter.h
new file mode 100644
index 0000000..de1d87a
--- /dev/null
+++ b/tools/aapt2/flatten/ChunkWriter.h
@@ -0,0 +1,87 @@
+/*
+ * 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 AAPT_FLATTEN_CHUNKWRITER_H
+#define AAPT_FLATTEN_CHUNKWRITER_H
+
+#include "util/BigBuffer.h"
+#include "util/Util.h"
+
+#include <androidfw/ResourceTypes.h>
+
+namespace aapt {
+
+class ChunkWriter {
+private:
+    BigBuffer* mBuffer;
+    size_t mStartSize = 0;
+    android::ResChunk_header* mHeader = nullptr;
+
+public:
+    explicit inline ChunkWriter(BigBuffer* buffer) : mBuffer(buffer) {
+    }
+
+    ChunkWriter(const ChunkWriter&) = delete;
+    ChunkWriter& operator=(const ChunkWriter&) = delete;
+    ChunkWriter(ChunkWriter&&) = default;
+    ChunkWriter& operator=(ChunkWriter&&) = default;
+
+    template <typename T>
+    inline T* startChunk(uint16_t type) {
+        mStartSize = mBuffer->size();
+        T* chunk = mBuffer->nextBlock<T>();
+        mHeader = &chunk->header;
+        mHeader->type = util::hostToDevice16(type);
+        mHeader->headerSize = util::hostToDevice16(sizeof(T));
+        return chunk;
+    }
+
+    template <typename T>
+    inline T* nextBlock(size_t count = 1) {
+        return mBuffer->nextBlock<T>(count);
+    }
+
+    inline BigBuffer* getBuffer() {
+        return mBuffer;
+    }
+
+    inline android::ResChunk_header* getChunkHeader() {
+        return mHeader;
+    }
+
+    inline size_t size() {
+        return mBuffer->size() - mStartSize;
+    }
+
+    inline android::ResChunk_header* finish() {
+        mBuffer->align4();
+        mHeader->size = util::hostToDevice32(mBuffer->size() - mStartSize);
+        return mHeader;
+    }
+};
+
+template <>
+inline android::ResChunk_header* ChunkWriter::startChunk(uint16_t type) {
+    mStartSize = mBuffer->size();
+    mHeader = mBuffer->nextBlock<android::ResChunk_header>();
+    mHeader->type = util::hostToDevice16(type);
+    mHeader->headerSize = util::hostToDevice16(sizeof(android::ResChunk_header));
+    return mHeader;
+}
+
+} // namespace aapt
+
+#endif /* AAPT_FLATTEN_CHUNKWRITER_H */