diff --git a/util/posix_logger.h b/util/posix_logger.h
index 1909e61..a01a4fe 100644
--- a/util/posix_logger.h
+++ b/util/posix_logger.h
@@ -8,89 +8,119 @@
#ifndef STORAGE_LEVELDB_UTIL_POSIX_LOGGER_H_
#define STORAGE_LEVELDB_UTIL_POSIX_LOGGER_H_
-#include <algorithm>
-#include <stdio.h>
#include <sys/time.h>
-#include <time.h>
+
+#include <cassert>
+#include <cinttypes>
+#include <cstdarg>
+#include <cstdio>
+#include <ctime>
+
#include "leveldb/env.h"
namespace leveldb {
-class PosixLogger : public Logger {
- private:
- FILE* file_;
- uint64_t (*gettid_)(); // Return the thread id for the current thread
+class PosixLogger final : public Logger {
public:
- PosixLogger(FILE* f, uint64_t (*gettid)()) : file_(f), gettid_(gettid) { }
- virtual ~PosixLogger() {
- fclose(file_);
+ PosixLogger(FILE* fp, uint64_t (*gettid)()) : fp_(fp), gettid_(gettid) {
+ assert(fp != nullptr);
+ }
+
+ ~PosixLogger() override {
+ std::fclose(fp_);
}
- virtual void Logv(const char* format, va_list ap) {
+
+ void Logv(const char* format, va_list arguments) override {
+ // Record the time as close to the Logv() call as possible.
+ struct ::timeval now_timeval;
+ ::gettimeofday(&now_timeval, nullptr);
+ const std::time_t now_seconds = now_timeval.tv_sec;
+ struct std::tm now_components;
+ ::localtime_r(&now_seconds, &now_components);
+
const uint64_t thread_id = (*gettid_)();
- // We try twice: the first time with a fixed-size stack allocated buffer,
- // and the second time with a much larger dynamically allocated buffer.
- char buffer[500];
- for (int iter = 0; iter < 2; iter++) {
- char* base;
- int bufsize;
- if (iter == 0) {
- bufsize = sizeof(buffer);
- base = buffer;
- } else {
- bufsize = 30000;
- base = new char[bufsize];
- }
- char* p = base;
- char* limit = base + bufsize;
-
- struct timeval now_tv;
- gettimeofday(&now_tv, nullptr);
- const time_t seconds = now_tv.tv_sec;
- struct tm t;
- localtime_r(&seconds, &t);
- p += snprintf(p, limit - p,
- "%04d/%02d/%02d-%02d:%02d:%02d.%06d %llx ",
- t.tm_year + 1900,
- t.tm_mon + 1,
- t.tm_mday,
- t.tm_hour,
- t.tm_min,
- t.tm_sec,
- static_cast<int>(now_tv.tv_usec),
- static_cast<long long unsigned int>(thread_id));
-
- // Print the message
- if (p < limit) {
- va_list backup_ap;
- va_copy(backup_ap, ap);
- p += vsnprintf(p, limit - p, format, backup_ap);
- va_end(backup_ap);
- }
+ // 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++");
- // Truncate to available space if necessary
- if (p >= limit) {
- if (iter == 0) {
- continue; // Try again with larger buffer
- } else {
- p = limit - 1;
+ 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 = snprintf(
+ buffer, buffer_size,
+ "%04d/%02d/%02d-%02d:%02d:%02d.%06d %" PRIx64 " ",
+ now_components.tm_year + 1900,
+ now_components.tm_mon + 1,
+ now_components.tm_mday,
+ now_components.tm_hour,
+ now_components.tm_min,
+ now_components.tm_sec,
+ static_cast<int>(now_timeval.tv_usec),
+ thread_id);
+
+ // The header can be at most 48 characters (10 date + 15 time + 3 spacing
+ // + 20 thread ID), which should fit comfortably into the static buffer.
+ assert(buffer_offset <= 48);
+ static_assert(48 < kStackBufferSize,
+ "stack-allocated buffer may not fit the message header");
+ assert(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.
+ assert(false);
+ buffer_offset = buffer_size - 1;
}
- // Add newline if necessary
- if (p == base || p[-1] != '\n') {
- *p++ = '\n';
+ // Add a newline if necessary.
+ if (buffer[buffer_offset - 1] != '\n') {
+ buffer[buffer_offset] = '\n';
+ ++buffer_offset;
}
- assert(p <= limit);
- fwrite(base, 1, p - base, file_);
- fflush(file_);
- if (base != buffer) {
- delete[] base;
+ assert(buffer_offset <= buffer_size);
+ std::fwrite(buffer, 1, buffer_offset, fp_);
+ std::fflush(fp_);
+
+ if (iteration != 0) {
+ delete[] buffer;
}
break;
}
}
+
+ private:
+ std::FILE* const fp_;
+ uint64_t (* const gettid_)(); // Return the thread id for the current thread.
};
} // namespace leveldb