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130 行
4.6 KiB
130 行
4.6 KiB
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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//
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// Logger implementation that can be shared by all environments
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// where enough posix functionality is available.
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#ifndef STORAGE_LEVELDB_UTIL_POSIX_LOGGER_H_
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#define STORAGE_LEVELDB_UTIL_POSIX_LOGGER_H_
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#include <sys/time.h>
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#include <cassert>
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#include <cstdarg>
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#include <cstdio>
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#include <ctime>
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#include <sstream>
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#include <thread>
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#include "leveldb/env.h"
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namespace leveldb {
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class PosixLogger final : public Logger {
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public:
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// Creates a logger that writes to the given file.
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//
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// The PosixLogger instance takes ownership of the file handle.
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explicit PosixLogger(std::FILE* fp) : fp_(fp) { assert(fp != nullptr); }
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~PosixLogger() override { std::fclose(fp_); }
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void Logv(const char* format, std::va_list arguments) override {
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// Record the time as close to the Logv() call as possible.
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struct ::timeval now_timeval;
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::gettimeofday(&now_timeval, nullptr);
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const std::time_t now_seconds = now_timeval.tv_sec;
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struct std::tm now_components;
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::localtime_r(&now_seconds, &now_components);
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// Record the thread ID.
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constexpr const int kMaxThreadIdSize = 32;
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std::ostringstream thread_stream;
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thread_stream << std::this_thread::get_id();
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std::string thread_id = thread_stream.str();
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if (thread_id.size() > kMaxThreadIdSize) {
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thread_id.resize(kMaxThreadIdSize);
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}
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// We first attempt to print into a stack-allocated buffer. If this attempt
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// fails, we make a second attempt with a dynamically allocated buffer.
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constexpr const int kStackBufferSize = 512;
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char stack_buffer[kStackBufferSize];
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static_assert(sizeof(stack_buffer) == static_cast<size_t>(kStackBufferSize),
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"sizeof(char) is expected to be 1 in C++");
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int dynamic_buffer_size = 0; // Computed in the first iteration.
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for (int iteration = 0; iteration < 2; ++iteration) {
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const int buffer_size =
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(iteration == 0) ? kStackBufferSize : dynamic_buffer_size;
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char* const buffer =
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(iteration == 0) ? stack_buffer : new char[dynamic_buffer_size];
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// Print the header into the buffer.
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int buffer_offset = std::snprintf(
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buffer, buffer_size, "%04d/%02d/%02d-%02d:%02d:%02d.%06d %s ",
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now_components.tm_year + 1900, now_components.tm_mon + 1,
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now_components.tm_mday, now_components.tm_hour, now_components.tm_min,
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now_components.tm_sec, static_cast<int>(now_timeval.tv_usec),
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thread_id.c_str());
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// The header can be at most 28 characters (10 date + 15 time +
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// 3 delimiters) plus the thread ID, which should fit comfortably into the
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// static buffer.
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assert(buffer_offset <= 28 + kMaxThreadIdSize);
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static_assert(28 + kMaxThreadIdSize < kStackBufferSize,
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"stack-allocated buffer may not fit the message header");
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assert(buffer_offset < buffer_size);
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// Print the message into the buffer.
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std::va_list arguments_copy;
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va_copy(arguments_copy, arguments);
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buffer_offset +=
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std::vsnprintf(buffer + buffer_offset, buffer_size - buffer_offset,
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format, arguments_copy);
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va_end(arguments_copy);
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// The code below may append a newline at the end of the buffer, which
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// requires an extra character.
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if (buffer_offset >= buffer_size - 1) {
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// The message did not fit into the buffer.
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if (iteration == 0) {
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// Re-run the loop and use a dynamically-allocated buffer. The buffer
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// will be large enough for the log message, an extra newline and a
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// null terminator.
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dynamic_buffer_size = buffer_offset + 2;
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continue;
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}
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// The dynamically-allocated buffer was incorrectly sized. This should
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// not happen, assuming a correct implementation of std::(v)snprintf.
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// Fail in tests, recover by truncating the log message in production.
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assert(false);
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buffer_offset = buffer_size - 1;
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}
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// Add a newline if necessary.
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if (buffer[buffer_offset - 1] != '\n') {
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buffer[buffer_offset] = '\n';
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++buffer_offset;
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}
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assert(buffer_offset <= buffer_size);
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std::fwrite(buffer, 1, buffer_offset, fp_);
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std::fflush(fp_);
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if (iteration != 0) {
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delete[] buffer;
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}
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break;
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}
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}
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private:
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std::FILE* const fp_;
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};
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} // namespace leveldb
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#endif // STORAGE_LEVELDB_UTIL_POSIX_LOGGER_H_
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