mosesdecoder/moses/TranslationModel/DynSAInclude/fdstream.h

/* Class modified by ADL for randlm namespace on Feb 15th, 2008.
 *
 * The following code declares classes to read from and write to
 * file descriptore or file handles.
 *
 * See
 *      http://www.josuttis.com/cppcode
 * for details and the latest version.
 *
 * - open:
 *      - integrating BUFSIZ on some systems?
 *      - optimized reading of multiple characters
 *      - stream for reading AND writing
 *      - i18n
 *
 * (C) Copyright Nicolai M. Josuttis 2001.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 *
 * Version: Jul 28, 2002
 * History:
 *  Jul 28, 2002: bugfix memcpy() => memmove()
 *                fdinbuf::underflow(): cast for return statements
 *  Aug 05, 2001: first public version
 */
#ifndef moses_DynSAInclude_fdstream_h
#define moses_DynSAInclude_fdstream_h

#include <streambuf>
// for EOF:
#include <cstdio>
// for memmove():
#include <cstring>


// low-level read and write functions
#ifdef _MSC_VER
# include <io.h>
#else
# include <unistd.h>
//extern "C" {
//    int write (int fd, const char* buf, int num);
//    int read (int fd, char* buf, int num);
//}
#endif


// BEGIN namespace
//namespace randlm {

/************************************************************
 * fdstreambuf
 * - a stream that reads on a file descriptor
 ************************************************************/

class fdstreambuf : public std::streambuf
{
protected:
  int fd;		// file descriptor
protected:
  /* data buffer:
   * - at most, pbSize characters in putback area plus
   * - at most, bufSize characters in ordinary read buffer
   */
  static const int pbSize = 4;				// size of putback area
  static const int bufSize = 1024;		// size of the data buffer
  char buffer[bufSize+pbSize];				// data buffer

public:
  /* constructor
   * - initialize file descriptor
   * - initialize empty data buffer
   * - no putback area
   * => force underflow()
   */
  fdstreambuf (int _fd) : fd(_fd) {
    setg (buffer+pbSize,		 // beginning of putback area
          buffer+pbSize,		 // read position
          buffer+pbSize);		// end position
  }
protected:
  // insert new characters into the buffer
  virtual int_type underflow () {
#ifndef _MSC_VER
    using std::memmove;
#endif

    // is read position before end of buffer?
    if (gptr() < egptr()) {
      return traits_type::to_int_type(*gptr());
    }
    /* process size of putback area
     * - use number of characters read
     * - but at most size of putback area
     */
    int numPutback;
    numPutback = gptr() - eback();
    if (numPutback > pbSize) {
      numPutback = pbSize;
    }

    /* copy up to pbSize characters previously read into
     * the putback area
     */
    memmove (buffer+(pbSize-numPutback), gptr()-numPutback,
             numPutback);

    // read at most bufSize new characters
    int num;
    num = read (fd, buffer+pbSize, bufSize);
    if (num <= 0) {
      // ERROR or EOF
      return EOF;
    }

    // reset buffer pointers
    setg (buffer+(pbSize-numPutback),	// beginning of putback area
          buffer+pbSize,			// read position
          buffer+pbSize+num);		// end of buffer

    // return next character
    return traits_type::to_int_type(*gptr());
  }

  // write one character
  virtual int_type overflow (int_type c) {
    if (c != EOF) {
      char z = c;
      if (write (fd, &z, 1) != 1) {
        return EOF;
      }
    }
    return c;
  }
  // write multiple characters
  virtual
  std::streamsize xsputn (const char* s,
                          std::streamsize num) {
    return write(fd,s,num);
  }
};
//} // END namespace

#endif