Merge "logd: add a SerializedLogBuffer suitable for compression"

1 files changed, 114 insertions, 0 deletions

diff --git a/logd/SerializedLogChunk.cpp b/logd/SerializedLogChunk.cpp
new file mode 100644
index 000000000..2516003c1
--- /dev/null
+++ b/logd/SerializedLogChunk.cpp
@@ -0,0 +1,114 @@
+/*
+ * 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 "SerializedLogChunk.h"
+
+#include <android-base/logging.h>
+
+#include "CompressionEngine.h"
+
+SerializedLogChunk::~SerializedLogChunk() {
+    CHECK_EQ(reader_ref_count_, 0U);
+}
+
+void SerializedLogChunk::Compress() {
+    if (compressed_log_.empty()) {
+        CompressionEngine::GetInstance().Compress({contents_.data(), write_offset_},
+                                                  compressed_log_);
+        LOG(INFO) << "Compressed Log, buffer max size: " << contents_.size()
+                  << " size used: " << write_offset_
+                  << " compressed size: " << compressed_log_.size();
+    }
+    contents_.resize(0);
+}
+
+// TODO: Develop a better reference counting strategy to guard against the case where the writer is
+// much faster than the reader, and we needlessly compess / decompress the logs.
+void SerializedLogChunk::IncReaderRefCount() {
+    if (++reader_ref_count_ != 1 || writer_active_) {
+        return;
+    }
+    CompressionEngine::GetInstance().Decompress(compressed_log_, contents_, write_offset_);
+}
+
+void SerializedLogChunk::DecReaderRefCount(bool compress) {
+    CHECK_NE(reader_ref_count_, 0U);
+    if (--reader_ref_count_ != 0) {
+        return;
+    }
+    if (compress && !writer_active_) {
+        Compress();
+    }
+}
+
+bool SerializedLogChunk::ClearUidLogs(uid_t uid, log_id_t log_id, LogStatistics* stats) {
+    CHECK_EQ(reader_ref_count_, 0U);
+    if (write_offset_ == 0) {
+        return true;
+    }
+
+    IncReaderRefCount();
+
+    int read_offset = 0;
+    int new_write_offset = 0;
+    while (read_offset < write_offset_) {
+        const auto* entry = log_entry(read_offset);
+        if (entry->uid() == uid) {
+            read_offset += entry->total_len();
+            if (stats != nullptr) {
+                stats->Subtract(entry->ToLogStatisticsElement(log_id));
+            }
+            continue;
+        }
+        size_t entry_total_len = entry->total_len();
+        if (read_offset != new_write_offset) {
+            memmove(contents_.data() + new_write_offset, contents_.data() + read_offset,
+                    entry_total_len);
+        }
+        read_offset += entry_total_len;
+        new_write_offset += entry_total_len;
+    }
+
+    if (new_write_offset == 0) {
+        DecReaderRefCount(false);
+        return true;
+    }
+
+    // Clear the old compressed logs and set write_offset_ appropriately for DecReaderRefCount()
+    // to compress the new partially cleared log.
+    if (new_write_offset != write_offset_) {
+        compressed_log_.clear();
+        write_offset_ = new_write_offset;
+    }
+
+    DecReaderRefCount(true);
+
+    return false;
+}
+
+bool SerializedLogChunk::CanLog(size_t len) {
+    return write_offset_ + len <= contents_.size();
+}
+
+SerializedLogEntry* SerializedLogChunk::Log(uint64_t sequence, log_time realtime, uid_t uid,
+                                            pid_t pid, pid_t tid, const char* msg, uint16_t len) {
+    auto new_log_address = contents_.data() + write_offset_;
+    auto* entry = new (new_log_address) SerializedLogEntry(uid, pid, tid, sequence, realtime, len);
+    memcpy(entry->msg(), msg, len);
+    write_offset_ += entry->total_len();
+    highest_sequence_number_ = sequence;
+    return entry;
+}
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