fdstream.hpp

`/* 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 BOOST_FDSTREAM_HPP
#define BOOST_FDSTREAM_HPP
#include <istream>
#include <ostream>
#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 BOOST
namespace boost {
/************************************************************
* fdostream
* - a stream that writes on a file descriptor
************************************************************/
class fdoutbuf : public std::streambuf {
protected:
int fd; // file descriptor
public:
// constructor
fdoutbuf (int _fd) : fd(_fd) {
}
protected:
// 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);
}
};
class fdostream : public std::ostream {
protected:
fdoutbuf buf;
public:
fdostream (int fd) : std::ostream(0), buf(fd) {
rdbuf(&buf);
}
};
/************************************************************
* fdistream
* - a stream that reads on a file descriptor
************************************************************/
class fdinbuf : 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()
*/
fdinbuf (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());
}
};
class fdistream : public std::istream {
protected:
fdinbuf buf;
public:
fdistream (int fd) : std::istream(0), buf(fd) {
rdbuf(&buf);
}
};
} // END namespace boost
#endif /*BOOST_FDSTREAM_HPP*/
`