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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef THIRD_PARTY_LEVELDATABASE_CHROMIUM_LOGGER_H_
#define THIRD_PARTY_LEVELDATABASE_CHROMIUM_LOGGER_H_
#include <cstdarg>
#include <utility>
#include "base/files/file.h"
#include "base/format_macros.h"
#include "base/strings/string_util.h"
#include "base/threading/platform_thread.h"
#include "base/time/time.h"
namespace leveldb {
class ChromiumLogger : public Logger {
public:
explicit ChromiumLogger(base::File file) : file_(std::move(file)) {}
~ChromiumLogger() override = default;
void Logv(const char* format, va_list arguments) override {
// Record the time as close to the Logv() call as possible.
base::Time::Exploded now_exploded;
base::Time::Now().LocalExplode(&now_exploded);
const base::PlatformThreadId thread_id = base::PlatformThread::CurrentId();
// We first attempt to print into a stack-allocated buffer. If this attempt
// fails, we make a second attempt with a dynamically allocated buffer.
constexpr const int kStackBufferSize = 512;
char stack_buffer[kStackBufferSize];
static_assert(sizeof(stack_buffer) == static_cast<size_t>(kStackBufferSize),
"sizeof(char) is expected to be 1 in C++");
int dynamic_buffer_size = 0; // Computed in the first iteration.
for (int iteration = 0; iteration < 2; ++iteration) {
const int buffer_size =
(iteration == 0) ? kStackBufferSize : dynamic_buffer_size;
char* const buffer =
(iteration == 0) ? stack_buffer : new char[dynamic_buffer_size];
// Print the header into the buffer.
int buffer_offset = base::snprintf(
buffer, buffer_size,
"%04d/%02d/%02d-%02d:%02d:%02d.%03d %" PRIx64 " ",
now_exploded.year,
now_exploded.month,
now_exploded.day_of_month,
now_exploded.hour,
now_exploded.minute,
now_exploded.second,
now_exploded.millisecond,
static_cast<uint64_t>(thread_id));
// The header can be at most 45 characters (10 date + 12 time + 3 spacing
// + 20 thread ID), which should fit comfortably into the static buffer.
DCHECK_LE(buffer_offset, 45);
static_assert(45 < kStackBufferSize,
"stack-allocated buffer may not fit the message header");
DCHECK_LT(buffer_offset, buffer_size);
// Print the message into the buffer.
std::va_list arguments_copy;
va_copy(arguments_copy, arguments);
buffer_offset += std::vsnprintf(buffer + buffer_offset,
buffer_size - buffer_offset, format,
arguments_copy);
va_end(arguments_copy);
// The code below may append a newline at the end of the buffer, which
// requires an extra character.
if (buffer_offset >= buffer_size - 1) {
// The message did not fit into the buffer.
if (iteration == 0) {
// Re-run the loop and use a dynamically-allocated buffer. The buffer
// will be large enough for the log message, an extra newline and a
// null terminator.
dynamic_buffer_size = buffer_offset + 2;
continue;
}
// The dynamically-allocated buffer was incorrectly sized. This should
// not happen, assuming a correct implementation of (v)snprintf. Fail
// in tests, recover by truncating the log message in production.
NOTREACHED();
buffer_offset = buffer_size - 1;
}
// Add a newline if necessary.
if (buffer[buffer_offset - 1] != '\n') {
buffer[buffer_offset] = '\n';
++buffer_offset;
}
DCHECK_LE(buffer_offset, buffer_size);
file_.WriteAtCurrentPos(buffer, buffer_offset);
if (iteration != 0) {
delete[] buffer;
}
break;
}
}
private:
base::File file_;
};
} // namespace leveldb
#endif // THIRD_PARTY_LEVELDATABASE_CHROMIUM_LOGGER_H_
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