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_unittest.cc b/xz_extent_writer_unittest.cc
new file mode 100644
index 0000000..2fd580d
--- /dev/null
+++ b/xz_extent_writer_unittest.cc
@@ -0,0 +1,165 @@
+//
+// 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.
+//
+
+#include "update_engine/xz_extent_writer.h"
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <algorithm>
+#include <string>
+#include <vector>
+
+#include <chromeos/make_unique_ptr.h>
+#include <gtest/gtest.h>
+
+#include "update_engine/fake_extent_writer.h"
+#include "update_engine/test_utils.h"
+#include "update_engine/utils.h"
+
+using std::string;
+using std::vector;
+
+namespace chromeos_update_engine {
+
+namespace {
+
+const char kSampleData[] = "Redundaaaaaaaaaaaaaant\n";
+
+// Compressed data with CRC-32 check, generated with:
+// echo "Redundaaaaaaaaaaaaaant" | xz -9 --check=crc32 |
+// hexdump -v -e '"    " 12/1 "0x%02x, " "\n"'
+const uint8_t kCompressedDataCRC32[] = {
+    0xfd, 0x37, 0x7a, 0x58, 0x5a, 0x00, 0x00, 0x01, 0x69, 0x22, 0xde, 0x36,
+    0x02, 0x00, 0x21, 0x01, 0x1c, 0x00, 0x00, 0x00, 0x10, 0xcf, 0x58, 0xcc,
+    0xe0, 0x00, 0x16, 0x00, 0x10, 0x5d, 0x00, 0x29, 0x19, 0x48, 0x87, 0x88,
+    0xec, 0x49, 0x88, 0x73, 0x8b, 0x5d, 0xa6, 0x46, 0xb4, 0x00, 0x00, 0x00,
+    0x68, 0xfc, 0x7b, 0x25, 0x00, 0x01, 0x28, 0x17, 0x46, 0x9e, 0x08, 0xfe,
+    0x90, 0x42, 0x99, 0x0d, 0x01, 0x00, 0x00, 0x00, 0x00, 0x01, 0x59, 0x5a,
+};
+
+// Compressed data without checksum, generated with:
+// echo "Redundaaaaaaaaaaaaaant" | xz -9 --check=none |
+// hexdump -v -e '"    " 12/1 "0x%02x, " "\n"'
+const uint8_t kCompressedDataNoCheck[] = {
+    0xfd, 0x37, 0x7a, 0x58, 0x5a, 0x00, 0x00, 0x00, 0xff, 0x12, 0xd9, 0x41,
+    0x02, 0x00, 0x21, 0x01, 0x1c, 0x00, 0x00, 0x00, 0x10, 0xcf, 0x58, 0xcc,
+    0xe0, 0x00, 0x16, 0x00, 0x10, 0x5d, 0x00, 0x29, 0x19, 0x48, 0x87, 0x88,
+    0xec, 0x49, 0x88, 0x73, 0x8b, 0x5d, 0xa6, 0x46, 0xb4, 0x00, 0x00, 0x00,
+    0x00, 0x01, 0x24, 0x17, 0x4a, 0xd1, 0xbd, 0x52, 0x06, 0x72, 0x9e, 0x7a,
+    0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x59, 0x5a,
+};
+
+// Highly redundant data bigger than the internal buffer, generated with:
+// dd if=/dev/zero bs=30K count=1 | tr '\0' 'a' | xz -9 --check=crc32 |
+// hexdump -v -e '"    " 12/1 "0x%02x, " "\n"'
+const uint8_t kCompressed30KiBofA[] = {
+    0xfd, 0x37, 0x7a, 0x58, 0x5a, 0x00, 0x00, 0x01, 0x69, 0x22, 0xde, 0x36,
+    0x02, 0x00, 0x21, 0x01, 0x1c, 0x00, 0x00, 0x00, 0x10, 0xcf, 0x58, 0xcc,
+    0xe0, 0x77, 0xff, 0x00, 0x41, 0x5d, 0x00, 0x30, 0xef, 0xfb, 0xbf, 0xfe,
+    0xa3, 0xb1, 0x5e, 0xe5, 0xf8, 0x3f, 0xb2, 0xaa, 0x26, 0x55, 0xf8, 0x68,
+    0x70, 0x41, 0x70, 0x15, 0x0f, 0x8d, 0xfd, 0x1e, 0x4c, 0x1b, 0x8a, 0x42,
+    0xb7, 0x19, 0xf4, 0x69, 0x18, 0x71, 0xae, 0x66, 0x23, 0x8a, 0x8a, 0x4d,
+    0x2f, 0xa3, 0x0d, 0xd9, 0x7f, 0xa6, 0xe3, 0x8c, 0x23, 0x11, 0x53, 0xe0,
+    0x59, 0x18, 0xc5, 0x75, 0x8a, 0xe2, 0x76, 0x4c, 0xee, 0x30, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0xf9, 0x47, 0xb5, 0xee, 0x00, 0x01, 0x59, 0x80,
+    0xf0, 0x01, 0x00, 0x00, 0xe0, 0x41, 0x96, 0xde, 0x3e, 0x30, 0x0d, 0x8b,
+    0x02, 0x00, 0x00, 0x00, 0x00, 0x01, 0x59, 0x5a,
+};
+
+}  // namespace
+
+class XzExtentWriterTest : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    fake_extent_writer_ = new FakeExtentWriter();
+    xz_writer_.reset(
+        new XzExtentWriter(chromeos::make_unique_ptr(fake_extent_writer_)));
+  }
+
+  void WriteAll(const chromeos::Blob& compressed) {
+    EXPECT_TRUE(xz_writer_->Init(fd_, {}, 1024));
+    EXPECT_TRUE(xz_writer_->Write(compressed.data(), compressed.size()));
+    EXPECT_TRUE(xz_writer_->End());
+
+    EXPECT_TRUE(fake_extent_writer_->InitCalled());
+    EXPECT_TRUE(fake_extent_writer_->EndCalled());
+  }
+
+  // Owned by |xz_writer_|. This object is invalidated after |xz_writer_| is
+  // deleted.
+  FakeExtentWriter* fake_extent_writer_{nullptr};
+  std::unique_ptr<XzExtentWriter> xz_writer_;
+
+  const chromeos::Blob sample_data_{
+      std::begin(kSampleData),
+      std::begin(kSampleData) + strlen(kSampleData)};
+  FileDescriptorPtr fd_;
+};
+
+TEST_F(XzExtentWriterTest, CreateAndDestroy) {
+  // Test that no Init() or End() called doesn't crash the program.
+  EXPECT_FALSE(fake_extent_writer_->InitCalled());
+  EXPECT_FALSE(fake_extent_writer_->EndCalled());
+}
+
+TEST_F(XzExtentWriterTest, CompressedSampleData) {
+  WriteAll(chromeos::Blob(std::begin(kCompressedDataNoCheck),
+                          std::end(kCompressedDataNoCheck)));
+  EXPECT_EQ(sample_data_, fake_extent_writer_->WrittenData());
+}
+
+TEST_F(XzExtentWriterTest, CompressedSampleDataWithCrc) {
+  WriteAll(chromeos::Blob(std::begin(kCompressedDataCRC32),
+                          std::end(kCompressedDataCRC32)));
+  EXPECT_EQ(sample_data_, fake_extent_writer_->WrittenData());
+}
+
+TEST_F(XzExtentWriterTest, CompressedDataBiggerThanTheBuffer) {
+  // Test that even if the output data is bigger than the internal buffer, all
+  // the data is written.
+  WriteAll(chromeos::Blob(std::begin(kCompressed30KiBofA),
+                          std::end(kCompressed30KiBofA)));
+  chromeos::Blob expected_data(30 * 1024, 'a');
+  EXPECT_EQ(expected_data, fake_extent_writer_->WrittenData());
+}
+
+TEST_F(XzExtentWriterTest, GarbageDataRejected) {
+  EXPECT_TRUE(xz_writer_->Init(fd_, {}, 1024));
+  // The sample_data_ is an uncompressed string.
+  EXPECT_FALSE(xz_writer_->Write(sample_data_.data(), sample_data_.size()));
+  EXPECT_TRUE(xz_writer_->End());
+
+  EXPECT_TRUE(fake_extent_writer_->EndCalled());
+}
+
+TEST_F(XzExtentWriterTest, PartialDataIsKept) {
+  chromeos::Blob compressed(std::begin(kCompressed30KiBofA),
+                            std::end(kCompressed30KiBofA));
+  EXPECT_TRUE(xz_writer_->Init(fd_, {}, 1024));
+  for (uint8_t byte : compressed) {
+    EXPECT_TRUE(xz_writer_->Write(&byte, 1));
+  }
+  EXPECT_TRUE(xz_writer_->End());
+
+  // The sample_data_ is an uncompressed string.
+  chromeos::Blob expected_data(30 * 1024, 'a');
+  EXPECT_EQ(expected_data, fake_extent_writer_->WrittenData());
+}
+
+}  // namespace chromeos_update_engine