2013/06/27

先日twitterで「C++でデバッグする時、よくやるよね」って言ったら結構知らない人がいたのでここでも紹介してみる。
既存のコードでcout/cerrを使ったデバッグ文がわんさかあって、これログファイルとして出力したいな...って場合ありますよね。
そんな場合
#include <iostream>
#include <fstream>

using namespace std;

int main() {
    // こんなの
    ofstream ofs("debug.log");
    cout.rdbuf(ofs.rdbuf());
    // いれとく

    cout << "debug string" << endl;
}

こうしておくと、その後のcoutへの出力が全てdebug.logというファイルへ出力される。
なおrdbufを元に戻すには
#include <iostream>
#include <fstream>

using namespace std;

int main() {
    ofstream ofs("debug.log");
    streambuf* oldrdbuf = cout.rdbuf(ofs.rdbuf());

    cout << "output to file" << endl;

    cout.rdbuf(oldrdbuf);

    cout << "output to console" << endl;
}
こうやる。
ちなみに、昔のC言語使いのオッサン達はこうやる。
freopen("file.txt""w"stdout);
これをもう少し発展させて、coutへの出力をログファイルぽくする物を先日書いたので紹介してみる。
/* Copyright 2011 by Yasuhiro Matsumoto
 * modification, are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#include <streambuf>
#include <sstream>
#include <ctime>

template <class CharT, class Traits = std::char_traits<CharT> >
class basic_clogger : public std::basic_streambuf<CharT, Traits> {
public:
  typedef std::basic_streambuf<CharT, Traits> streambuf_type;
  typedef Traits traits_t;
  typedef CharT char_t;
  typedef typename traits_t::int_type int_t;
  typedef std::streamsize streamsize_t;
  typedef std::basic_stringstream<char_t, traits_t> sstream_t;

private:
  streambuf_type* sbuf_;
  char_t* cbuf_;
  static int const BUFFER_SIZE = 256;

public:

  basic_clogger(streambuf_type* buf) :sbuf_(buf),
      cbuf_(new char_t[BUFFER_SIZE]) {
    this->setp(cbuf_, cbuf_ + BUFFER_SIZE);
  }

  ~basic_clogger() {
    this->pubsync();
    delete[] cbuf_;
  }

protected:

  int_t
  overflow(int_t c = traits_t::eof()) {
    streamsize_t n = static_cast<streamsize_t>(this->pptr() - this->pbase());
    time_t ct;
    int year, month, day, hour, minute, second;
    time(&ct);
    struct tm* d = localtime(&ct);
    std::basic_stringstream<char_t, traits_t> ss;

    for (streamsize_t i = 0; i < n; i++)
      if (cbuf_[i] == '\n') { n = i; break; }
    if (n) {
#define CLOGGER_PAD4(o,d) if(d<10)o<<'0'<<'0'<<d; else if (d<100)o<<'0'<<d; else o<<d;
#define CLOGGER_PAD2(o,d) if(d<10)o<<'0'<<d; else o<<d;
      CLOGGER_PAD4(ss, d->tm_year + 1900);
      ss << '/';
      CLOGGER_PAD2(ss, d->tm_mon + 1)
      ss << '/';
      CLOGGER_PAD2(ss, d->tm_mday + 1)
      ss << ' ';
      CLOGGER_PAD2(ss, d->tm_hour)
      ss << ':';
      CLOGGER_PAD2(ss, d->tm_min)
      ss << ':';
      CLOGGER_PAD2(ss, d->tm_sec)
#undef CLOGGER_PAD4
#undef CLOGGER_PAD2
      ss << '\t';
      ss << std::basic_string<char_t>(cbuf_, n) << std::endl;
      std::basic_string<char_t> s = ss.str();
      if (sbuf_->sputn(s.c_str(), s.size()) != s.size())
        return traits_t::eof();
      this->setp(cbuf_, cbuf_ + BUFFER_SIZE);
    } 

    if (!traits_t::eq_int_type(c, traits_t::eof())) {
      traits_t::assign(*this->pptr(), traits_t::to_char_type(c));
      this->pbump(1);
    } 
    return traits_t::not_eof(c);
  }

  int
  sync() {
    if (traits_t::eq_int_type(overflow(traits_t::eof()), traits_t::eof())) {
      return -1;
    }
    return sbuf_->pubsync() == -1 ? -1 : 0;
  }
};

typedef basic_clogger<char> clogger;
ちょっと長ったらしいけど...。これを以下の様にして使う。
#include <iostream>
#include <fstream>
#ifdef _WIN32
#include <windows.h>
#define sleep(x) Sleep(x*1000)
#else
#include <unistd.h>
#endif

int
main() {
  std::ofstream file("debug.log", std::ios::out | std::ios::app);
  clogger logger(file.rdbuf());
  std::streambuf* oldrdbuf = std::cout.rdbuf(&logger);

  std::cout << "Yes" << std::endl;
  sleep(1);
  std::cout << "高洲" << std::endl;
  sleep(1);
  std::cout << "クリニック" << std::endl;

  std::cout.rdbuf(oldrdbuf);
}
するとdebug.logというファイルに
2011/04/03 01:26:09 Yes
2011/04/03 01:26:10 高洲
2011/04/03 01:26:11 クリニック
こう出力される。

Yes 高須クリニック!


良いC++デバッグライフをお送り下さい。
Posted at 14:32 | WriteBacks () | Edit
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