Add dump of hdr event history

Track & dump the HDRLayerInfo callback history to
aid debugging when HDR brightness changes aren't
happening

Bug: 234181960
Test: adb shell dumpsys surfaceflinger --hdrinfo
Change-Id: Ia8376517877d4c7844af6be4d488299554c164f5
diff --git a/services/surfaceflinger/Tracing/TransactionRingBuffer.h b/services/surfaceflinger/Tracing/TransactionRingBuffer.h
new file mode 100644
index 0000000..e6f85ca
--- /dev/null
+++ b/services/surfaceflinger/Tracing/TransactionRingBuffer.h
@@ -0,0 +1,133 @@
+/*
+ * Copyright 2021 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.
+ */
+
+#pragma once
+
+#include <android-base/file.h>
+#include <android-base/stringprintf.h>
+
+#include <log/log.h>
+#include <utils/Errors.h>
+#include <utils/Timers.h>
+#include <utils/Trace.h>
+#include <chrono>
+#include <fstream>
+#include <queue>
+
+namespace android {
+
+class SurfaceFlinger;
+
+template <typename FileProto, typename EntryProto>
+class TransactionRingBuffer {
+public:
+    size_t size() const { return mSizeInBytes; }
+    size_t used() const { return mUsedInBytes; }
+    size_t frameCount() const { return mStorage.size(); }
+    void setSize(size_t newSize) { mSizeInBytes = newSize; }
+    const std::string& front() const { return mStorage.front(); }
+    const std::string& back() const { return mStorage.back(); }
+
+    void reset() {
+        // use the swap trick to make sure memory is released
+        std::deque<std::string>().swap(mStorage);
+        mUsedInBytes = 0U;
+    }
+
+    void writeToProto(FileProto& fileProto) {
+        fileProto.mutable_entry()->Reserve(static_cast<int>(mStorage.size()) +
+                                           fileProto.entry().size());
+        for (const std::string& entry : mStorage) {
+            EntryProto* entryProto = fileProto.add_entry();
+            entryProto->ParseFromString(entry);
+        }
+    }
+
+    status_t writeToFile(FileProto& fileProto, std::string filename) {
+        ATRACE_CALL();
+        writeToProto(fileProto);
+        std::string output;
+        if (!fileProto.SerializeToString(&output)) {
+            ALOGE("Could not serialize proto.");
+            return UNKNOWN_ERROR;
+        }
+
+        // -rw-r--r--
+        const mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
+        if (!android::base::WriteStringToFile(output, filename, mode, getuid(), getgid(), true)) {
+            ALOGE("Could not save the proto file %s", filename.c_str());
+            return PERMISSION_DENIED;
+        }
+        return NO_ERROR;
+    }
+
+    status_t appendToStream(FileProto& fileProto, std::ofstream& out) {
+        ATRACE_CALL();
+        writeToProto(fileProto);
+        std::string output;
+        if (!fileProto.SerializeToString(&output)) {
+            ALOGE("Could not serialize proto.");
+            return UNKNOWN_ERROR;
+        }
+
+        out << output;
+        return NO_ERROR;
+    }
+
+    std::vector<std::string> emplace(std::string&& serializedProto) {
+        std::vector<std::string> replacedEntries;
+        size_t protoSize = static_cast<size_t>(serializedProto.size());
+        while (mUsedInBytes + protoSize > mSizeInBytes) {
+            if (mStorage.empty()) {
+                return {};
+            }
+            mUsedInBytes -= static_cast<size_t>(mStorage.front().size());
+            replacedEntries.emplace_back(mStorage.front());
+            mStorage.pop_front();
+        }
+        mUsedInBytes += protoSize;
+        mStorage.emplace_back(serializedProto);
+        return replacedEntries;
+    }
+
+    std::vector<std::string> emplace(EntryProto&& proto) {
+        std::string serializedProto;
+        proto.SerializeToString(&serializedProto);
+        return emplace(std::move(serializedProto));
+    }
+
+    void dump(std::string& result) const {
+        std::chrono::milliseconds duration(0);
+        if (frameCount() > 0) {
+            EntryProto entry;
+            entry.ParseFromString(mStorage.front());
+            duration = std::chrono::duration_cast<std::chrono::milliseconds>(
+                    std::chrono::nanoseconds(systemTime() - entry.elapsed_realtime_nanos()));
+        }
+        const int64_t durationCount = duration.count();
+        base::StringAppendF(&result,
+                            "  number of entries: %zu (%.2fMB / %.2fMB) duration: %" PRIi64 "ms\n",
+                            frameCount(), float(used()) / (1024.f * 1024.f),
+                            float(size()) / (1024.f * 1024.f), durationCount);
+    }
+
+private:
+    size_t mUsedInBytes = 0U;
+    size_t mSizeInBytes = 0U;
+    std::deque<std::string> mStorage;
+};
+
+} // namespace android