cpp-logger/src/loggers/file_appender.cxx

//
//  file_logger.cxx
//  logging
//
//  Created by Sam Jaffe on 4/1/19.
//

#include <fstream>

#include "expect/expect.hpp"
#include "resource_factory/prototype_factory.hpp"

#include "logger/detail/appender.h"
#include "logger/detail/layout.h"
#include "logger/log_manager.h"
#include "logger/properties.h"

using namespace logging;

struct buffer : std::filebuf {
  buffer(properties const & props);
  buffer * setbuf(char* data, std::streamsize n);
};

class file_appender : public simple_appender {
public:
  static std::shared_ptr<appender> create(properties const & props);
  
  explicit file_appender(properties const & props);
  
  std::ostream & stream() override { return out_; }
  void write(logpacket const & packet, layout & withLayout) override;
private:
  bool flush_immediately_;
  buffer rdbuf_;
  std::ostream out_;
  std::unique_ptr<char[]> buffer_;
};

using namespace logging::property;
properties const DEFAULT_FILE_APPENDER{_obj({
  {"immediateFlush", _v(true)},
  {"threshold", _v("ERROR")},
  {"filename", {}}, // Will throw if accessed
  {"fileAppend", _v(true)},
  {"bufferedIO", _v(false)},
  {"bufferSize", _v(8192)}
})};

std::shared_ptr<appender> file_appender::create(properties const & props) {
  properties const actual = DEFAULT_FILE_APPENDER.mergedWith(props);
  return std::make_shared<file_appender>(actual);
}

static std::ios_base::openmode mode(bool append) {
  return append ? std::ios_base::app : std::ios_base::out;
}

buffer::buffer(properties const & props) : std::filebuf() {
  if (open(props["filename"], mode(props["fileAppend"])) == nullptr) {
    throw std::runtime_error("Cannot open file");
  }
}

buffer * buffer::setbuf(char* data, std::streamsize n) {
  std::filebuf::setbuf(data, n);
  return this;
}

file_appender::file_appender(properties const & props)
: simple_appender(props),
  flush_immediately_(props["immediateFlush"]),
  rdbuf_(props), out_(&rdbuf_) {
  if (props["bufferedIO"]) {
    int const size = props["bufferSize"];
    buffer_.reset(new char[size]);
    rdbuf_.setbuf(buffer_.get(), size);
  }
}

void file_appender::write(logpacket const & packet, layout & withLayout) {
  withLayout.format(out_, packet);
  if (flush_immediately_) { flush(); }
}

namespace {
  bool _ = appenders::instance().bind("File", file_appender::create);
}