Add BufferReleaseChannel

BufferReleaseChannel will be used to communicate buffer releases from SurfaceFlinger to BLASTBufferQueue.

Bug: 294133380
Flag: com.android.graphics.libgui.flags.buffer_release_channel
Test: BufferReleaseChannelTest
Change-Id: Ic38e8eefc96abc0b2bbe780115b7628413e8b829
diff --git a/libs/gui/tests/BufferReleaseChannel_test.cpp b/libs/gui/tests/BufferReleaseChannel_test.cpp
new file mode 100644
index 0000000..11d122b
--- /dev/null
+++ b/libs/gui/tests/BufferReleaseChannel_test.cpp
@@ -0,0 +1,138 @@
+/*
+ * Copyright (C) 2024 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 <string>
+#include <vector>
+
+#include <gtest/gtest.h>
+#include <gui/BufferReleaseChannel.h>
+
+using namespace std::string_literals;
+using android::gui::BufferReleaseChannel;
+
+namespace android {
+
+namespace {
+
+// Helper function to check if two file descriptors point to the same file.
+bool is_same_file(int fd1, int fd2) {
+    struct stat stat1;
+    if (fstat(fd1, &stat1) != 0) {
+        return false;
+    }
+    struct stat stat2;
+    if (fstat(fd2, &stat2) != 0) {
+        return false;
+    }
+    return (stat1.st_dev == stat2.st_dev) && (stat1.st_ino == stat2.st_ino);
+}
+
+} // namespace
+
+TEST(BufferReleaseChannelTest, MessageFlattenable) {
+    ReleaseCallbackId releaseCallbackId{1, 2};
+    sp<Fence> releaseFence = sp<Fence>::make(memfd_create("fake-fence-fd", 0));
+    uint32_t maxAcquiredBufferCount = 5;
+
+    std::vector<uint8_t> dataBuffer;
+    std::vector<int> fdBuffer;
+
+    // Verify that we can flatten a message
+    {
+        BufferReleaseChannel::Message message{releaseCallbackId, releaseFence,
+                                              maxAcquiredBufferCount};
+
+        dataBuffer.resize(message.getFlattenedSize());
+        void* dataPtr = dataBuffer.data();
+        size_t dataSize = dataBuffer.size();
+
+        fdBuffer.resize(message.getFdCount());
+        int* fdPtr = fdBuffer.data();
+        size_t fdSize = fdBuffer.size();
+
+        ASSERT_EQ(OK, message.flatten(dataPtr, dataSize, fdPtr, fdSize));
+
+        // Fence's unique_fd uses fdsan to check ownership of the file descriptor. Normally the file
+        // descriptor is passed through the Unix socket and duplicated (and sent to another process)
+        // so there's no problem with duplicate file descriptor ownership. For this unit test, we
+        // need to set up a duplicate file descriptor to avoid crashing due to duplicate ownership.
+        ASSERT_EQ(releaseFence->get(), fdBuffer[0]);
+        fdBuffer[0] = message.releaseFence->dup();
+    }
+
+    // Verify that we can unflatten a message
+    {
+        BufferReleaseChannel::Message message;
+
+        const void* dataPtr = dataBuffer.data();
+        size_t dataSize = dataBuffer.size();
+
+        const int* fdPtr = fdBuffer.data();
+        size_t fdSize = fdBuffer.size();
+
+        ASSERT_EQ(OK, message.unflatten(dataPtr, dataSize, fdPtr, fdSize));
+        ASSERT_EQ(releaseCallbackId, message.releaseCallbackId);
+        ASSERT_TRUE(is_same_file(releaseFence->get(), message.releaseFence->get()));
+        ASSERT_EQ(maxAcquiredBufferCount, message.maxAcquiredBufferCount);
+    }
+}
+
+// Verify that the BufferReleaseChannel consume returns WOULD_BLOCK when there's no message
+// available.
+TEST(BufferReleaseChannelTest, ConsumerEndpointIsNonBlocking) {
+    std::unique_ptr<BufferReleaseChannel::ConsumerEndpoint> consumer;
+    std::shared_ptr<BufferReleaseChannel::ProducerEndpoint> producer;
+    ASSERT_EQ(OK, BufferReleaseChannel::open("test-channel"s, consumer, producer));
+
+    ReleaseCallbackId releaseCallbackId;
+    sp<Fence> releaseFence;
+    uint32_t maxAcquiredBufferCount;
+    ASSERT_EQ(WOULD_BLOCK,
+              consumer->readReleaseFence(releaseCallbackId, releaseFence, maxAcquiredBufferCount));
+}
+
+// Verify that we can write a message to the BufferReleaseChannel producer and read that message
+// using the BufferReleaseChannel consumer.
+TEST(BufferReleaseChannelTest, ProduceAndConsume) {
+    std::unique_ptr<BufferReleaseChannel::ConsumerEndpoint> consumer;
+    std::shared_ptr<BufferReleaseChannel::ProducerEndpoint> producer;
+    ASSERT_EQ(OK, BufferReleaseChannel::open("test-channel"s, consumer, producer));
+
+    sp<Fence> fence = sp<Fence>::make(memfd_create("fake-fence-fd", 0));
+
+    for (uint64_t i = 0; i < 64; i++) {
+        ReleaseCallbackId producerId{i, i + 1};
+        uint32_t maxAcquiredBufferCount = i + 2;
+        ASSERT_EQ(OK, producer->writeReleaseFence(producerId, fence, maxAcquiredBufferCount));
+    }
+
+    for (uint64_t i = 0; i < 64; i++) {
+        ReleaseCallbackId expectedId{i, i + 1};
+        uint32_t expectedMaxAcquiredBufferCount = i + 2;
+
+        ReleaseCallbackId consumerId;
+        sp<Fence> consumerFence;
+        uint32_t maxAcquiredBufferCount;
+        ASSERT_EQ(OK,
+                  consumer->readReleaseFence(consumerId, consumerFence, maxAcquiredBufferCount));
+
+        ASSERT_EQ(expectedId, consumerId);
+        ASSERT_TRUE(is_same_file(fence->get(), consumerFence->get()));
+        ASSERT_EQ(expectedMaxAcquiredBufferCount, maxAcquiredBufferCount);
+    }
+}
+
+} // namespace android
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