pipestream.c

定义了一系列C++类,通过它们来使用socket比直接调用底层的低级函数更有效率

// pipestream.C -*- C++ -*- socket library
// Copyright (C) 1992-1996 Gnanasekaran Swaminathan <[e-mail]>
//
// Permission is granted to use at your own risk and distribute this software
// in source and  binary forms provided  the above copyright notice and  this
// paragraph are  preserved on all copies.  This software is provided "as is"
// with no express or implied warranty.
//
// Version: 12Jan97 1.11


#include <config.h>

#include <pipestream.h>
#include <unistd.h>
#include <sys/socket.h>

// environ is not given a declaration in sun's <unistd.h>
extern char** environ;

// child closes s2 and uses s1
// parent closes s1 and uses s2

enum domain { af_unix = 1 };

iopipestream* iopipestream::head = 0;

static sockbuf* createpipestream (const char* cmd, int mode)
{
  int sockets[2];
  if (::socketpair (af_unix, sockbuf::sock_stream, 0, sockets) == -1)
    throw sockerr (errno);
  
  pid_t pid = ::vfork ();
  if (pid == -1) throw sockerr (errno);
  
  if (pid == 0) {
    // child process
    if (::close (sockets[1]) == -1) throw sockerr (errno);

    if ((mode & ios::in) && ::dup2 (sockets[0], 1) == -1)
      throw sockerr (errno);
    if ((mode & ios::out) && ::dup2 (sockets[0], 0) == -1)
      throw sockerr (errno);
    if (::close (sockets[0]) == -1) throw sockerr (errno);

    const char*	argv[4];
    argv[0] = "/bin/sh";
    argv[1] = "-c";
    argv[2] = cmd;
    argv[3] = 0;
    execve ("/bin/sh", (char**) argv, environ);
    throw sockerr (errno);
  }

  // parent process
  if (::close (sockets[0]) == -1) throw sockerr (errno);

  sockbuf* s = new sockbuf (sockbuf::sockdesc(sockets[1]));
  if (!(mode & ios::out)) s->shutdown (sockbuf::shut_write);
  if (!(mode & ios::in)) s->shutdown (sockbuf::shut_read);
  return s;
}

ipipestream::ipipestream (const char* cmd)
  : ios (createpipestream (cmd, ios::in))
{}

opipestream::opipestream (const char* cmd)
  : ios (createpipestream (cmd, ios::out))
{}

iopipestream::iopipestream (const char* cmd)
  : ios (createpipestream (cmd, ios::in|ios::out)),
    cpid (-1), next (0)
{}

iopipestream::iopipestream(sockbuf::type ty, int proto)
  : ios (0), cpid (-1), next (head)
{
  if (::socketpair(af_unix, ty, proto, sp) == -1)
    throw sockerr (errno);
  head = this;	
}

pid_t iopipestream::fork ()
{
  pid_t pid = ::fork (); // donot use vfork here
  if (pid == -1) throw sockerr (errno);

  if (pid > 0) {
    // parent process
    while (head) {
      if (::close (head->sp[1]) == -1) throw sockerr (errno);
      head->cpid = pid;
      head->init (new sockbuf (sockbuf::sockdesc(head->sp[0])));
      head = head->next;
    }
  } else {
    // child process
    while (head) {
      if (::close (head->sp[0]) == -1) throw sockerr (errno);
      head->cpid = 0;
      head->init (new sockbuf (sockbuf::sockdesc(head->sp[1])));
      head = head->next;
    }
  }
  return pid;
}