ring_log_sink.h

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#pragma once
 
#include <spdlog/sinks/base_sink.h>
 
#include <cstddef>
#include <deque>
#include <mutex>
#include <string>
#include <utility>
#include <vector>
 
namespace mm {
 
template <typename Mutex>
class RingLogSink : public spdlog::sinks::base_sink<Mutex> {
 public:
  explicit RingLogSink(std::size_t capacity = 100000) : capacity_(capacity) {}
 
  std::vector<std::string> entries() {
    std::lock_guard<Mutex> lock(this->mutex_);
    return {buffer_.begin(), buffer_.end()};
  }
 
 protected:
  void sink_it_(const spdlog::details::log_msg& msg) override {
    spdlog::memory_buf_t formatted;
    this->formatter_->format(msg, formatted);
    std::string entry{formatted.data(), formatted.size()};
    // Strip the trailing end-of-line. spdlog uses "\n" on POSIX and "\r\n" on
    // Windows, so drop the newline and any preceding carriage return.
    if (!entry.empty() && entry.back() == '\n') {
      entry.pop_back();
    }
    if (!entry.empty() && entry.back() == '\r') {
      entry.pop_back();
    }
    if (buffer_.size() >= capacity_) {
      buffer_.pop_front();
    }
    buffer_.push_back(std::move(entry));
  }
 
  void flush_() override {}
 
 private:
  std::size_t capacity_;
  std::deque<std::string> buffer_;
};
 
using RingLogSinkMt = RingLogSink<std::mutex>;
 
}  // namespace mm