snapuserd: Add XorSink
We can compute the xor while decompessing by computing it within a
buffer. This would allow us to use a smaller buffer than the full block
size if we wish to cut down on the extra memory required.
Bug: 177104308
Test: cow_snapuserd_test (Snapuserd_Test.xor_buffer)
Change-Id: Id18505841c77340760cea2d20e83454f1142b9b5
diff --git a/fs_mgr/libsnapshot/snapuserd/cow_snapuserd_test.cpp b/fs_mgr/libsnapshot/snapuserd/cow_snapuserd_test.cpp
index a718328..c663d86 100644
--- a/fs_mgr/libsnapshot/snapuserd/cow_snapuserd_test.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/cow_snapuserd_test.cpp
@@ -1039,6 +1039,35 @@
}
}
+TEST(Snapuserd_Test, xor_buffer) {
+ std::string data = "Test String";
+ std::string jumbled = {0x0C, 0x2A, 0x21, 0x54, 0x73, 0x27, 0x06, 0x1B, 0x07, 0x09, 0x46};
+ std::string result = "XOR String!";
+
+ BufferSink sink;
+ XorSink xor_sink;
+ sink.Initialize(sizeof(struct dm_user_header) + 10);
+ int buffsize = 5;
+ xor_sink.Initialize(&sink, buffsize);
+
+ void* buff = sink.GetPayloadBuffer(data.length());
+ memcpy(buff, data.data(), data.length());
+
+ size_t actual;
+ size_t count = 0;
+ while (count < data.length()) {
+ void* xor_buff = xor_sink.GetBuffer(10, &actual);
+ ASSERT_EQ(actual, buffsize);
+ ASSERT_NE(xor_buff, nullptr);
+ memcpy(xor_buff, jumbled.data() + count, buffsize);
+ xor_sink.ReturnData(xor_buff, actual);
+ count += actual;
+ }
+
+ std::string answer = reinterpret_cast<char*>(sink.GetPayloadBufPtr());
+ ASSERT_EQ(answer, result);
+}
+
TEST(Snapuserd_Test, Snapshot_Metadata) {
CowSnapuserdMetadataTest harness;
harness.Setup();
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd.h b/fs_mgr/libsnapshot/snapuserd/snapuserd.h
index 3cb5ee2..6814a98 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd.h
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd.h
@@ -107,6 +107,20 @@
size_t buffer_size_;
};
+class XorSink : public IByteSink {
+ public:
+ void Initialize(BufferSink* sink, size_t size);
+ void Reset();
+ void* GetBuffer(size_t requested, size_t* actual) override;
+ bool ReturnData(void* buffer, size_t len) override;
+
+ private:
+ BufferSink* bufsink_;
+ std::unique_ptr<uint8_t[]> buffer_;
+ size_t buffer_size_;
+ size_t returned_;
+};
+
class Snapuserd;
class ReadAheadThread {
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd_worker.cpp b/fs_mgr/libsnapshot/snapuserd/snapuserd_worker.cpp
index d515f64..ffb19b1 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd_worker.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd_worker.cpp
@@ -71,6 +71,39 @@
return msg->payload.buf;
}
+void XorSink::Initialize(BufferSink* sink, size_t size) {
+ bufsink_ = sink;
+ buffer_size_ = size;
+ returned_ = 0;
+ buffer_ = std::make_unique<uint8_t[]>(size);
+}
+
+void XorSink::Reset() {
+ returned_ = 0;
+}
+
+void* XorSink::GetBuffer(size_t requested, size_t* actual) {
+ if (requested > buffer_size_) {
+ *actual = buffer_size_;
+ } else {
+ *actual = requested;
+ }
+ return buffer_.get();
+}
+
+bool XorSink::ReturnData(void* buffer, size_t len) {
+ uint8_t* xor_data = reinterpret_cast<uint8_t*>(buffer);
+ uint8_t* buff = reinterpret_cast<uint8_t*>(bufsink_->GetPayloadBuffer(len + returned_));
+ if (buff == nullptr) {
+ return false;
+ }
+ for (size_t i = 0; i < len; i++) {
+ buff[returned_ + i] ^= xor_data[i];
+ }
+ returned_ += len;
+ return true;
+}
+
WorkerThread::WorkerThread(const std::string& cow_device, const std::string& backing_device,
const std::string& control_device, const std::string& misc_name,
std::shared_ptr<Snapuserd> snapuserd) {