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/SerializedFlushToState.cpp b/logd/SerializedFlushToState.cpp
new file mode 100644
index 0000000..17ecb6d
--- /dev/null
+++ b/logd/SerializedFlushToState.cpp
@@ -0,0 +1,158 @@
+/*
+ * 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.
+ */
+
+#include "SerializedFlushToState.h"
+
+#include <android-base/logging.h>
+
+SerializedFlushToState::SerializedFlushToState(uint64_t start, LogMask log_mask)
+ : FlushToState(start, log_mask) {
+ log_id_for_each(i) {
+ if (((1 << i) & log_mask) == 0) {
+ continue;
+ }
+ logs_needed_from_next_position_[i] = true;
+ }
+}
+
+SerializedFlushToState::~SerializedFlushToState() {
+ log_id_for_each(i) {
+ if (log_positions_[i]) {
+ log_positions_[i]->buffer_it->DecReaderRefCount(true);
+ }
+ }
+}
+
+void SerializedFlushToState::CreateLogPosition(log_id_t log_id) {
+ CHECK(!logs_[log_id].empty());
+ LogPosition log_position;
+ auto it = logs_[log_id].begin();
+ while (it != logs_[log_id].end() && start() > it->highest_sequence_number()) {
+ ++it;
+ }
+ if (it == logs_[log_id].end()) {
+ --it;
+ }
+ it->IncReaderRefCount();
+ log_position.buffer_it = it;
+
+ // Find the offset of the first log with sequence number >= start().
+ int read_offset = 0;
+ while (read_offset < it->write_offset()) {
+ const auto* entry = it->log_entry(read_offset);
+ if (entry->sequence() >= start()) {
+ break;
+ }
+ read_offset += entry->total_len();
+ }
+ log_position.read_offset = read_offset;
+
+ log_positions_[log_id].emplace(std::move(log_position));
+}
+
+void SerializedFlushToState::AddMinHeapEntry(log_id_t log_id) {
+ auto& buffer_it = log_positions_[log_id]->buffer_it;
+ auto read_offset = log_positions_[log_id]->read_offset;
+
+ // If there is another log to read in this buffer, add it to the min heap.
+ if (read_offset < buffer_it->write_offset()) {
+ auto* entry = buffer_it->log_entry(read_offset);
+ min_heap_.emplace(log_id, entry);
+ } else if (read_offset == buffer_it->write_offset()) {
+ // If there are no more logs to read in this buffer and it's the last buffer, then
+ // set logs_needed_from_next_position_ to wait until more logs get logged.
+ if (buffer_it == std::prev(logs_[log_id].end())) {
+ logs_needed_from_next_position_[log_id] = true;
+ } else {
+ // Otherwise, if there is another buffer piece, move to that and do the same check.
+ buffer_it->DecReaderRefCount(true);
+ ++buffer_it;
+ buffer_it->IncReaderRefCount();
+ log_positions_[log_id]->read_offset = 0;
+ if (buffer_it->write_offset() == 0) {
+ logs_needed_from_next_position_[log_id] = true;
+ } else {
+ auto* entry = buffer_it->log_entry(0);
+ min_heap_.emplace(log_id, entry);
+ }
+ }
+ } else {
+ // read_offset > buffer_it->write_offset() should never happen.
+ CHECK(false);
+ }
+}
+
+void SerializedFlushToState::CheckForNewLogs() {
+ log_id_for_each(i) {
+ if (!logs_needed_from_next_position_[i]) {
+ continue;
+ }
+ if (!log_positions_[i]) {
+ if (logs_[i].empty()) {
+ continue;
+ }
+ CreateLogPosition(i);
+ }
+ logs_needed_from_next_position_[i] = false;
+ // If it wasn't possible to insert, logs_needed_from_next_position will be set back to true.
+ AddMinHeapEntry(i);
+ }
+}
+
+MinHeapElement SerializedFlushToState::PopNextUnreadLog() {
+ auto top = min_heap_.top();
+ min_heap_.pop();
+
+ auto* entry = top.entry;
+ auto log_id = top.log_id;
+
+ log_positions_[log_id]->read_offset += entry->total_len();
+
+ AddMinHeapEntry(log_id);
+
+ return top;
+}
+
+void SerializedFlushToState::Prune(log_id_t log_id,
+ const std::list<SerializedLogChunk>::iterator& buffer_it) {
+ // If we don't have a position for this log or if we're not referencing buffer_it, ignore.
+ if (!log_positions_[log_id].has_value() || log_positions_[log_id]->buffer_it != buffer_it) {
+ return;
+ }
+
+ // // Decrease the ref count since we're deleting our reference.
+ buffer_it->DecReaderRefCount(false);
+
+ // Delete in the reference.
+ log_positions_[log_id].reset();
+
+ // Remove the MinHeapElement referencing log_id, if it exists, but retain the others.
+ std::vector<MinHeapElement> old_elements;
+ while (!min_heap_.empty()) {
+ auto& element = min_heap_.top();
+ if (element.log_id != log_id) {
+ old_elements.emplace_back(element);
+ }
+ min_heap_.pop();
+ }
+ for (auto&& element : old_elements) {
+ min_heap_.emplace(std::move(element));
+ }
+
+ // Finally set logs_needed_from_next_position_, so CheckForNewLogs() will re-create the
+ // log_position_ object during the next read.
+ logs_needed_from_next_position_[log_id] = true;
+}