logd: add a SerializedLogBuffer suitable for compression
Initial commit for a SerializedLogBuffer. The intention here is for
the serialized data to be compressed (currently using zlib) to allow
for substantially longer logs in the same memory footprint.
Test: unit tests
Change-Id: I2528e4e1ff1cf3bc91130173a107f371f04d911a
diff --git a/logd/SerializedLogChunk.h b/logd/SerializedLogChunk.h
new file mode 100644
index 0000000..75cb936
--- /dev/null
+++ b/logd/SerializedLogChunk.h
@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2020 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 <sys/types.h>
+
+#include <vector>
+
+#include "LogWriter.h"
+#include "SerializedLogEntry.h"
+
+class SerializedLogChunk {
+ public:
+ SerializedLogChunk(size_t size) : contents_(size) {}
+ ~SerializedLogChunk();
+
+ void Compress();
+ void IncReaderRefCount();
+ // Decrease the reader ref count and compress the log if appropriate. `compress` should only be
+ // set to false in the case that the log buffer will be deleted afterwards.
+ void DecReaderRefCount(bool compress);
+
+ // Must have no readers referencing this. Return true if there are no logs left in this chunk.
+ bool ClearUidLogs(uid_t uid, log_id_t log_id, LogStatistics* stats);
+
+ bool CanLog(size_t len);
+ SerializedLogEntry* Log(uint64_t sequence, log_time realtime, uid_t uid, pid_t pid, pid_t tid,
+ const char* msg, uint16_t len);
+
+ // If this buffer has been compressed, we only consider its compressed size when accounting for
+ // memory consumption for pruning. This is since the uncompressed log is only by used by
+ // readers, and thus not a representation of how much these logs cost to keep in memory.
+ size_t PruneSize() const { return compressed_log_.size() ?: contents_.size(); }
+
+ void FinishWriting() {
+ writer_active_ = false;
+ if (reader_ref_count_ == 0) {
+ Compress();
+ }
+ }
+
+ const SerializedLogEntry* log_entry(int offset) const {
+ return reinterpret_cast<const SerializedLogEntry*>(data() + offset);
+ }
+ const uint8_t* data() const { return contents_.data(); }
+ int write_offset() const { return write_offset_; }
+ uint64_t highest_sequence_number() const { return highest_sequence_number_; }
+
+ private:
+ // The decompressed contents of this log buffer. Deallocated when the ref_count reaches 0 and
+ // writer_active_ is false.
+ std::vector<uint8_t> contents_;
+ int write_offset_ = 0;
+ uint32_t reader_ref_count_ = 0;
+ bool writer_active_ = true;
+ uint64_t highest_sequence_number_ = 1;
+ std::vector<uint8_t> compressed_log_;
+};