added comments to pipestream, including WEXITSTATUS

[libi2ncommon] / src / pipestream.hxx

 /*
The software in this package is distributed under the GNU General
Public License version 2 (with a special exception described below).

A copy of GNU General Public License (GPL) is included in this distribution,
in the file COPYING.GPL.

As a special exception, if other files instantiate templates or use macros
or inline functions from this file, or you compile this file and link it
with other works to produce a work based on this file, this file
does not by itself cause the resulting work to be covered
by the GNU General Public License.

However the source code for this file must still be made available
in accordance with section (3) of the GNU General Public License.

This exception does not invalidate any other reasons why a work based
on this file might be covered by the GNU General Public License.
*/
/***************************************************************************
              inpipestream.hxx  -  C++ streambuffer wrapper 
                             -------------------
    begin                : Thu Dec 27 2001
    copyright            : (C) 2001 by Intra2net AG
 ***************************************************************************/

#ifndef _PIPESTREAM
#define _PIPESTREAM

#include <stdio.h>

#include <string>
#include <streambuf>
#include <istream>
#include <ostream>
#include <cstdio>

#include "exception.hxx"

/** @brief runs command and provides buffered input for it through pipe
 *
 * opens pipe to command using popen; exit status available after destruction
 * (use WEXITSTATUS to get the "regular" return code (lowest byte))
 *
 * ATTENTION: A lot of mysterious STL bugs occured
 *            with a "real" buffer (buffer larger than 1 byte and up to 100 bytes)
 *            -> Keep it slow and working!
 */
class inpipebuf : public std::streambuf
{
protected:
    char buffer;
    FILE *pipe;

    // "callback" variables for destructor to store exit status
    bool *status_set;
    int *exit_status;

public:
    inpipebuf(const std::string& command)
    {
        status_set = NULL;
        exit_status = NULL;

        pipe = popen (command.c_str(), "r");
        if (pipe == NULL)
            throw EXCEPTION (pipestream_error, "can't open program or permission denied");

        // force underflow
        setg (&buffer, &buffer, &buffer);
    }

    ~inpipebuf()
    {
        if (pipe != NULL) {
            int pclose_exit = pclose (pipe);

            if (exit_status && pclose_exit != -1) {
                *status_set = true;
                *exit_status = pclose_exit;
            }

            pipe = NULL;
        }
    }

    /** note: exit status only available after destruction */
    void store_exit_status(bool *_status_set, int *_exit_status)
    { status_set = _status_set; exit_status = _exit_status; }

protected:
    virtual int_type underflow()
    {
        if (gptr() < egptr())
            return traits_type::to_int_type(*gptr());

        buffer = fgetc (pipe);
        if (feof (pipe))
        {
            // ERROR or EOF
            return EOF;
        }

        setg (&buffer, &buffer, &buffer+sizeof(char));

        return traits_type::to_int_type(*gptr());
    }
};

/** @brief stream around inpipebuf -- see comment there */
class inpipestream : public std::istream
{
protected:
    inpipebuf buf;

public:
    inpipestream(const std::string& command)
            : std::istream(&buf), buf(command)
    {}

    void store_exit_status(bool *_status_set, int *_exit_status)
    { buf.store_exit_status(_status_set, _exit_status); }
};


/** @brief runs command and provides buffered ouptput from it through pipe
 *
 * opens pipe to command using popen; exit status available after destruction
 * (use WEXITSTATUS to get the "regular" return code (lowest byte))
 */
class outpipebuf : public std::streambuf
{
protected:
    FILE *pipe;

    // "callback" variables for destructor to store exit status
    bool *status_set;
    int *exit_status;

public:
    outpipebuf(const std::string& command)
    {
        status_set = NULL;
        exit_status = NULL;

        pipe = popen (command.c_str(), "w");
        if (pipe == NULL)
            throw EXCEPTION (pipestream_error, "can't open program or permission denied");
    }

    ~outpipebuf()
    {
        if (pipe != NULL) {
            int pclose_exit = pclose (pipe);

            if (exit_status && pclose_exit != -1) {
                *status_set = true;
                *exit_status = pclose_exit;
            }

            pipe = NULL;
        }
    }

    /** note: exit status only available after destruction */
    void store_exit_status(bool *_status_set, int *_exit_status)
    { status_set = _status_set; exit_status = _exit_status; }

protected:
    virtual int_type overflow(int_type c)
    {
        if (c != EOF)
        {
            if (fputc(c,pipe)==EOF)
                return EOF;
        }
        return c;
    }

    virtual std::streamsize xsputn(const char* s, std::streamsize num)
    {
        return fwrite(s,num,1,pipe);
    }
};


/** @brief stream around outpipebuf -- see comment there */
class outpipestream : public std::ostream
{
protected:
    outpipebuf buf;
public:
    outpipestream(const std::string& command)
            : std::ostream(&buf), buf(command)
    {}

    void store_exit_status(bool *_status_set, int *_exit_status)
    { buf.store_exit_status(_status_set, _exit_status); }
};

#endif