update_engine: Add ExtentReader

Currently Each operation in DeltaPerformer has the responsibility of
reading from the source device by itself. Adding an
ExtentReader (similar to ExtentWriter) aggregates all these
responsibilities on DeltaPerformer.source_fd_. This simplifies the
design as each operation does not need to invent is own open/read/close
etc. This specially will be used in conjunction with bspatch and puffin.

BUG=chromium:761138
TEST=FEATURES="test" emerge-amd64-generic update_engine;

Change-Id: I2c7a21a02bd1df06bbaa7ebf374a13f654768721
Reviewed-on: https://chromium-review.googlesource.com/651336
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Andrew de los Reyes <adlr@chromium.org>
Reviewed-by: Sen Jiang <senj@chromium.org>
diff --git a/payload_consumer/extent_reader_unittest.cc b/payload_consumer/extent_reader_unittest.cc
new file mode 100644
index 0000000..9821775
--- /dev/null
+++ b/payload_consumer/extent_reader_unittest.cc
@@ -0,0 +1,170 @@
+//
+// Copyright (C) 2017 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/payload_consumer/extent_reader.h"
+
+#include <fcntl.h>
+
+#include <algorithm>
+#include <string>
+#include <vector>
+
+#include <brillo/secure_blob.h>
+#include <gtest/gtest.h>
+
+#include "update_engine/common/test_utils.h"
+#include "update_engine/common/utils.h"
+#include "update_engine/payload_consumer/file_descriptor.h"
+#include "update_engine/payload_consumer/payload_constants.h"
+#include "update_engine/payload_generator/extent_ranges.h"
+#include "update_engine/payload_generator/extent_utils.h"
+
+using chromeos_update_engine::test_utils::ExpectVectorsEq;
+using std::min;
+using std::string;
+using std::vector;
+
+namespace chromeos_update_engine {
+
+namespace {
+const size_t kBlockSize = 8;
+const size_t kRandomIterations = 1000;
+}  // namespace
+
+class ExtentReaderTest : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    sample_.resize(4096 * 10);
+    srand(time(nullptr));
+    unsigned int rand_seed;
+    for (size_t i = 0; i < sample_.size(); i++) {
+      sample_[i] = rand_r(&rand_seed) % 256;
+    }
+    ASSERT_TRUE(utils::WriteFile(
+        temp_file_.path().c_str(), sample_.data(), sample_.size()));
+
+    fd_.reset(new EintrSafeFileDescriptor());
+    ASSERT_TRUE(fd_->Open(temp_file_.path().c_str(), O_RDONLY, 0600));
+  }
+  void TearDown() override { fd_->Close(); }
+
+  void ReadExtents(vector<Extent> extents, brillo::Blob* blob) {
+    blob->clear();
+    for (const auto& extent : extents) {
+      blob->insert(
+          blob->end(),
+          &sample_[extent.start_block() * kBlockSize],
+          &sample_[(extent.start_block() + extent.num_blocks()) * kBlockSize]);
+    }
+  }
+
+  FileDescriptorPtr fd_;
+  test_utils::ScopedTempFile temp_file_{"ExtentReaderTest-file.XXXXXX"};
+  brillo::Blob sample_;
+};
+
+TEST_F(ExtentReaderTest, SimpleTest) {
+  vector<Extent> extents = {ExtentForRange(1, 1)};
+  DirectExtentReader reader;
+  EXPECT_TRUE(reader.Init(fd_, {extents.begin(), extents.end()}, kBlockSize));
+  EXPECT_TRUE(reader.Seek(0));
+  brillo::Blob blob1(BlocksInExtents(extents) * kBlockSize);
+  EXPECT_TRUE(reader.Read(blob1.data(), blob1.size()));
+  brillo::Blob blob2;
+  ReadExtents(extents, &blob2);
+  ExpectVectorsEq(blob1, blob2);
+}
+
+TEST_F(ExtentReaderTest, ZeroExtentLengthTest) {
+  vector<Extent> extents = {ExtentForRange(1, 0)};
+  DirectExtentReader reader;
+  EXPECT_TRUE(reader.Init(fd_, {extents.begin(), extents.end()}, kBlockSize));
+  EXPECT_TRUE(reader.Seek(0));
+  brillo::Blob blob(1);
+  EXPECT_TRUE(reader.Read(blob.data(), 0));
+  EXPECT_FALSE(reader.Read(blob.data(), 1));
+}
+
+TEST_F(ExtentReaderTest, NoExtentTest) {
+  DirectExtentReader reader;
+  EXPECT_TRUE(reader.Init(fd_, {}, kBlockSize));
+  EXPECT_TRUE(reader.Seek(0));
+  brillo::Blob blob(1);
+  EXPECT_TRUE(reader.Read(blob.data(), 0));
+  EXPECT_FALSE(reader.Read(blob.data(), 1));
+}
+
+TEST_F(ExtentReaderTest, OverflowExtentTest) {
+  vector<Extent> extents = {ExtentForRange(1, 1)};
+  DirectExtentReader reader;
+  EXPECT_TRUE(reader.Init(fd_, {extents.begin(), extents.end()}, kBlockSize));
+  EXPECT_TRUE(reader.Seek(0));
+  brillo::Blob blob(BlocksInExtents(extents) * kBlockSize + 1);
+  EXPECT_FALSE(reader.Read(blob.data(), blob.size()));
+}
+
+TEST_F(ExtentReaderTest, SeekOverflow1Test) {
+  vector<Extent> extents = {ExtentForRange(1, 0)};
+  DirectExtentReader reader;
+  EXPECT_TRUE(reader.Init(fd_, {extents.begin(), extents.end()}, kBlockSize));
+  EXPECT_TRUE(reader.Seek(0));
+  EXPECT_FALSE(reader.Seek(1));
+}
+
+TEST_F(ExtentReaderTest, SeekOverflow2Test) {
+  DirectExtentReader reader;
+  reader.Init(fd_, {}, kBlockSize);
+  EXPECT_TRUE(reader.Seek(0));
+  EXPECT_FALSE(reader.Seek(1));
+}
+
+TEST_F(ExtentReaderTest, SeekOverflow3Test) {
+  vector<Extent> extents = {ExtentForRange(1, 1)};
+  DirectExtentReader reader;
+  EXPECT_TRUE(reader.Init(fd_, {extents.begin(), extents.end()}, kBlockSize));
+  // Seek to the end of the extents should be fine as long as nothing is read.
+  EXPECT_TRUE(reader.Seek(kBlockSize));
+  EXPECT_FALSE(reader.Seek(kBlockSize + 1));
+}
+
+TEST_F(ExtentReaderTest, RandomReadTest) {
+  vector<Extent> extents = {ExtentForRange(0, 0),
+                            ExtentForRange(1, 1),
+                            ExtentForRange(3, 0),
+                            ExtentForRange(4, 2),
+                            ExtentForRange(7, 1)};
+  DirectExtentReader reader;
+  EXPECT_TRUE(reader.Init(fd_, {extents.begin(), extents.end()}, kBlockSize));
+
+  brillo::Blob result;
+  ReadExtents(extents, &result);
+
+  brillo::Blob blob(BlocksInExtents(extents) * kBlockSize);
+  srand(time(nullptr));
+  uint32_t rand_seed;
+  for (size_t idx = 0; idx < kRandomIterations; idx++) {
+    // zero to full size available.
+    size_t start = rand_r(&rand_seed) % blob.size();
+    size_t size = rand_r(&rand_seed) % (blob.size() - start);
+    EXPECT_TRUE(reader.Seek(start));
+    EXPECT_TRUE(reader.Read(blob.data(), size));
+    for (size_t i = 0; i < size; i++) {
+      ASSERT_EQ(blob[i], result[start + i]);
+    }
+  }
+}
+
+}  // namespace chromeos_update_engine