pstream.h

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// PStreams - POSIX Process I/O for C++

//        Copyright (C) 2001 - 2020 Jonathan Wakely
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          http://www.boost.org/LICENSE_1_0.txt)
//
// SPDX-License-Identifier: BSL-1.0

#ifndef REDI_PSTREAM_H_SEEN
#define REDI_PSTREAM_H_SEEN

#include <ios>
#include <streambuf>
#include <istream>
#include <ostream>
#include <string>
#include <vector>
#include <algorithm>    // for min()
#include <cerrno>       // for errno
#include <cstddef>      // for size_t, NULL
#include <cstdlib>      // for exit()
#include <sys/types.h>  // for pid_t
#include <sys/wait.h>   // for waitpid()
#include <sys/ioctl.h>  // for ioctl() and FIONREAD
// #if defined(__sun)
// # include <sys/filio.h> // for FIONREAD on Solaris 2.5
// #endif
#include <unistd.h>     // for pipe() fork() exec() and filedes functions
#include <signal.h>     // for kill()
#include <fcntl.h>      // for fcntl()
#if REDI_EVISCERATE_PSTREAMS
# include <stdio.h>     // for FILE, fdopen()
#endif


#define PSTREAMS_VERSION 0x0103   // 1.0.3

namespace redi
{
  struct pstreams
  {
    typedef std::ios_base::openmode           pmode;

    typedef std::vector<std::string>          argv_type;

    typedef int                               fd_type;

    static const pmode pstdin  = std::ios_base::out; 
    static const pmode pstdout = std::ios_base::in;  
    static const pmode pstderr = std::ios_base::app; 

    static const pmode newpg   = std::ios_base::trunc;

  protected:
    enum { bufsz = 32 };  
    enum { pbsz  = 2 };   

#if __cplusplus >= 201103L
    template<typename T>
      using stringable = decltype((void)std::string(std::declval<const T&>()));
#endif
  };

  template <typename CharT, typename Traits = std::char_traits<CharT> >
    class basic_pstreambuf
    : public std::basic_streambuf<CharT, Traits>
    , public pstreams
    {
    public:
      // Type definitions for dependent types
      typedef CharT                             char_type;
      typedef Traits                            traits_type;
      typedef typename traits_type::int_type    int_type;
      typedef typename traits_type::off_type    off_type;
      typedef typename traits_type::pos_type    pos_type;
      typedef fd_type                           fd_t;

      basic_pstreambuf();

      basic_pstreambuf(const std::string& cmd, pmode mode);

      basic_pstreambuf( const std::string& file,
                        const argv_type& argv,
                        pmode mode );

#if __cplusplus >= 201103L
      basic_pstreambuf(basic_pstreambuf&&) noexcept;
      basic_pstreambuf& operator=(basic_pstreambuf&&) noexcept;
      void swap(basic_pstreambuf&) noexcept;
#endif

      ~basic_pstreambuf();

      basic_pstreambuf*
      open(const std::string& cmd, pmode mode);

      basic_pstreambuf*
      open(const std::string& file, const argv_type& argv, pmode mode);

      basic_pstreambuf*
      close();

      basic_pstreambuf*
      kill(int signal = SIGTERM);

      basic_pstreambuf*
      killpg(int signal = SIGTERM);

      void
      peof();

      bool
      read_err(bool readerr = true);

      bool
      is_open() const;

      bool
      exited();

#if REDI_EVISCERATE_PSTREAMS
      std::size_t
      fopen(FILE*& in, FILE*& out, FILE*& err);
#endif

      int
      status() const;

      int
      error() const;

    protected:
      int_type
      overflow(int_type c);

      int_type
      underflow();

      int_type
      pbackfail(int_type c = traits_type::eof());

      int
      sync();

      std::streamsize
      xsputn(const char_type* s, std::streamsize n);

      std::streamsize
      write(const char_type* s, std::streamsize n);

      std::streamsize
      read(char_type* s, std::streamsize n);

      std::streamsize
      showmanyc();

    protected:
      enum buf_read_src { rsrc_out = 0, rsrc_err = 1 };

      pid_t
      fork(pmode mode);

      int
      wait(bool nohang = false);

      fd_type&
      wpipe();

      fd_type&
      rpipe();

      fd_type&
      rpipe(buf_read_src which);

      void
      create_buffers(pmode mode);

      void
      destroy_buffers(pmode mode);

      bool
      empty_buffer();

      bool
      fill_buffer(bool non_blocking = false);

      char_type*
      rbuffer();

      buf_read_src
      switch_read_buffer(buf_read_src);

    private:
#if __cplusplus >= 201103L
      using basic_streambuf = std::basic_streambuf<char_type, traits_type>;
#else
      basic_pstreambuf(const basic_pstreambuf&);
      basic_pstreambuf& operator=(const basic_pstreambuf&);
#endif

      void
      init_rbuffers();

      pid_t         ppid_;        // pid of process
      fd_type       wpipe_;       // pipe used to write to process' stdin
      fd_type       rpipe_[2];    // two pipes to read from, stdout and stderr
      char_type*    wbuffer_;
      char_type*    rbuffer_[2];
      char_type*    rbufstate_[3];
      buf_read_src  rsrc_;
      int           status_;      // hold exit status of child process
      int           error_;       // hold errno if fork() or exec() fails
    };

  template <typename CharT, typename Traits = std::char_traits<CharT> >
    class pstream_common
    : virtual public std::basic_ios<CharT, Traits>
    , virtual public pstreams
    {
    protected:
      typedef basic_pstreambuf<CharT, Traits>       streambuf_type;
      typedef std::basic_ios<CharT, Traits>         ios_type;

      typedef pstreams::pmode                       pmode;
      typedef pstreams::argv_type                   argv_type;

      pstream_common();

      pstream_common(const std::string& cmd, pmode mode);

      pstream_common(const std::string& file, const argv_type& argv, pmode mode);

      virtual
      ~pstream_common() = 0;

#if __cplusplus >= 201103L
      pstream_common(pstream_common&& rhs) noexcept
      : command_(std::move(rhs.command_))
      , buf_(std::move(rhs.buf_))
      {
        /* derived class is responsible for ios_type::move(rhs) happening */
      }

      pstream_common&
      operator=(pstream_common&& rhs) noexcept
      {
        command_ = std::move(rhs.command_);
        buf_ = std::move(rhs.buf_);
        return *this;
      }

      void
      swap(pstream_common& rhs) noexcept
      {
        /* derived class is responsible for ios_type::swap(rhs) happening */
        command_.swap(rhs.command_);
        buf_.swap(rhs.buf_);
      }
#endif // C++11

      void
      do_open(const std::string& cmd, pmode mode);

      void
      do_open(const std::string& file, const argv_type& argv, pmode mode);

    public:
      int
      close();

      bool
      is_open() const;

      const std::string&
      command() const;

      streambuf_type*
      rdbuf() const;

#if REDI_EVISCERATE_PSTREAMS
      std::size_t
      fopen(FILE*& in, FILE*& out, FILE*& err);
#endif

    protected:
      std::string       command_; 
      streambuf_type    buf_;     
    };


  template <typename CharT, typename Traits = std::char_traits<CharT> >
    class basic_ipstream
    : public std::basic_istream<CharT, Traits>
    , public pstream_common<CharT, Traits>
    , virtual public pstreams
    {
      typedef std::basic_istream<CharT, Traits>     istream_type;
      typedef pstream_common<CharT, Traits>         pbase_type;

      using pbase_type::buf_;  // declare name in this scope

      // Ensure a basic_ipstream will read from at least one pipe
      pmode readable(pmode mode)
      {
        if (!(mode & (pstdout|pstderr)))
          mode |= pstdout;
        return mode;
      }

    public:
      typedef typename pbase_type::pmode            pmode;

      typedef typename pbase_type::argv_type        argv_type;

      basic_ipstream()
      : istream_type(NULL), pbase_type()
      { }

      explicit
      basic_ipstream(const std::string& cmd, pmode mode = pstdout)
      : istream_type(NULL), pbase_type(cmd, readable(mode))
      { }

      basic_ipstream( const std::string& file,
                      const argv_type& argv,
                      pmode mode = pstdout )
      : istream_type(NULL), pbase_type(file, argv, readable(mode))
      { }

      explicit
      basic_ipstream(const argv_type& argv, pmode mode = pstdout)
      : istream_type(NULL), pbase_type(argv.at(0), argv, readable(mode))
      { }

#if __cplusplus >= 201103L
      template<typename T, typename = stringable<T>>
        explicit
        basic_ipstream(std::initializer_list<T> args, pmode mode = pstdout)
        : basic_ipstream(argv_type(args.begin(), args.end()), mode)
        { }

      basic_ipstream(basic_ipstream&& rhs)
      : istream_type(std::move(rhs))
      , pbase_type(std::move(rhs))
      { istream_type::set_rdbuf(std::addressof(pbase_type::buf_)); }

      basic_ipstream&
      operator=(basic_ipstream&& rhs)
      {
        istream_type::operator=(std::move(rhs));
        pbase_type::operator=(std::move(rhs));
        return *this;
      }

      void
      swap(basic_ipstream& rhs)
      {
        istream_type::swap(rhs);
        pbase_type::swap(rhs);
      }
#endif // C++11

      ~basic_ipstream()
      { }

      void
      open(const std::string& cmd, pmode mode = pstdout)
      {
        this->do_open(cmd, readable(mode));
      }

      void
      open( const std::string& file,
            const argv_type& argv,
            pmode mode = pstdout )
      {
        this->do_open(file, argv, readable(mode));
      }

      basic_ipstream&
      out()
      {
        this->buf_.read_err(false);
        return *this;
      }

      basic_ipstream&
      err()
      {
        this->buf_.read_err(true);
        return *this;
      }
    };


  template <typename CharT, typename Traits = std::char_traits<CharT> >
    class basic_opstream
    : public std::basic_ostream<CharT, Traits>
    , public pstream_common<CharT, Traits>
    , virtual public pstreams
    {
      typedef std::basic_ostream<CharT, Traits>     ostream_type;
      typedef pstream_common<CharT, Traits>         pbase_type;

      using pbase_type::buf_;  // declare name in this scope

    public:
      typedef typename pbase_type::pmode            pmode;

      typedef typename pbase_type::argv_type        argv_type;

      basic_opstream()
      : ostream_type(NULL), pbase_type()
      { }

      explicit
      basic_opstream(const std::string& cmd, pmode mode = pstdin)
      : ostream_type(NULL), pbase_type(cmd, mode|pstdin)
      { }

      basic_opstream( const std::string& file,
                      const argv_type& argv,
                      pmode mode = pstdin )
      : ostream_type(NULL), pbase_type(file, argv, mode|pstdin)
      { }

      explicit
      basic_opstream(const argv_type& argv, pmode mode = pstdin)
      : ostream_type(NULL), pbase_type(argv.at(0), argv, mode|pstdin)
      { }

#if __cplusplus >= 201103L

      template<typename T, typename = stringable<T>>
        explicit
        basic_opstream(std::initializer_list<T> args, pmode mode = pstdin)
        : basic_opstream(argv_type(args.begin(), args.end()), mode)
        { }

      basic_opstream(basic_opstream&& rhs)
      : ostream_type(std::move(rhs))
      , pbase_type(std::move(rhs))
      { ostream_type::set_rdbuf(std::addressof(pbase_type::buf_)); }

      basic_opstream&
      operator=(basic_opstream&& rhs)
      {
        ostream_type::operator=(std::move(rhs));
        pbase_type::operator=(std::move(rhs));
        return *this;
      }

      void
      swap(basic_opstream& rhs)
      {
        ostream_type::swap(rhs);
        pbase_type::swap(rhs);
      }
#endif // C++11

      ~basic_opstream() { }

      void
      open(const std::string& cmd, pmode mode = pstdin)
      {
        this->do_open(cmd, mode|pstdin);
      }

      void
      open( const std::string& file,
            const argv_type& argv,
            pmode mode = pstdin)
      {
        this->do_open(file, argv, mode|pstdin);
      }
    };


  template <typename CharT, typename Traits = std::char_traits<CharT> >
    class basic_pstream
    : public std::basic_iostream<CharT, Traits>
    , public pstream_common<CharT, Traits>
    , virtual public pstreams
    {
      typedef std::basic_iostream<CharT, Traits>    iostream_type;
      typedef pstream_common<CharT, Traits>         pbase_type;

      using pbase_type::buf_;  // declare name in this scope

    public:
      typedef typename pbase_type::pmode            pmode;

      typedef typename pbase_type::argv_type        argv_type;

      basic_pstream()
      : iostream_type(NULL), pbase_type()
      { }

      explicit
      basic_pstream(const std::string& cmd, pmode mode = pstdout|pstdin)
      : iostream_type(NULL), pbase_type(cmd, mode)
      { }

      basic_pstream( const std::string& file,
                     const argv_type& argv,
                     pmode mode = pstdout|pstdin )
      : iostream_type(NULL), pbase_type(file, argv, mode)
      { }

      explicit
      basic_pstream(const argv_type& argv, pmode mode = pstdout|pstdin)
      : iostream_type(NULL), pbase_type(argv.at(0), argv, mode)
      { }

#if __cplusplus >= 201103L

      template<typename T, typename = stringable<T>>
        explicit
        basic_pstream(std::initializer_list<T> l, pmode mode = pstdout|pstdin)
        : basic_pstream(argv_type(l.begin(), l.end()), mode)
        { }

      basic_pstream(basic_pstream&& rhs)
      : iostream_type(std::move(rhs))
      , pbase_type(std::move(rhs))
      { iostream_type::set_rdbuf(std::addressof(pbase_type::buf_)); }

      basic_pstream&
      operator=(basic_pstream&& rhs)
      {
        iostream_type::operator=(std::move(rhs));
        pbase_type::operator=(std::move(rhs));
        return *this;
      }

      void
      swap(basic_pstream& rhs)
      {
        iostream_type::swap(rhs);
        pbase_type::swap(rhs);
      }
#endif // C++11

      ~basic_pstream() { }

      void
      open(const std::string& cmd, pmode mode = pstdout|pstdin)
      {
        this->do_open(cmd, mode);
      }

      void
      open( const std::string& file,
            const argv_type& argv,
            pmode mode = pstdout|pstdin )
      {
        this->do_open(file, argv, mode);
      }

      basic_pstream&
      out()
      {
        this->buf_.read_err(false);
        return *this;
      }

      basic_pstream&
      err()
      {
        this->buf_.read_err(true);
        return *this;
      }
    };


  template <typename CharT, typename Traits = std::char_traits<CharT> >
    class basic_rpstream
    : public std::basic_ostream<CharT, Traits>
    , private std::basic_istream<CharT, Traits>
    , private pstream_common<CharT, Traits>
    , virtual public pstreams
    {
      typedef std::basic_ostream<CharT, Traits>     ostream_type;
      typedef std::basic_istream<CharT, Traits>     istream_type;
      typedef pstream_common<CharT, Traits>         pbase_type;

      using pbase_type::buf_;  // declare name in this scope

    public:
      typedef typename pbase_type::pmode            pmode;

      typedef typename pbase_type::argv_type        argv_type;

      basic_rpstream()
      : ostream_type(NULL), istream_type(NULL), pbase_type()
      { }

      explicit
      basic_rpstream(const std::string& cmd, pmode mode = pstdout|pstdin)
      : ostream_type(NULL) , istream_type(NULL) , pbase_type(cmd, mode)
      { }

      basic_rpstream( const std::string& file,
                      const argv_type& argv,
                      pmode mode = pstdout|pstdin )
      : ostream_type(NULL), istream_type(NULL), pbase_type(file, argv, mode)
      { }

      explicit
      basic_rpstream(const argv_type& argv, pmode mode = pstdout|pstdin)
      : ostream_type(NULL), istream_type(NULL)
      , pbase_type(argv.at(0), argv, mode)
      { }

#if __cplusplus >= 201103L

      template<typename T, typename = stringable<T>>
        explicit
        basic_rpstream(std::initializer_list<T> l, pmode mode = pstdout|pstdin)
        : basic_rpstream(argv_type(l.begin(), l.end()), mode)
        { }

      // TODO: figure out how to move istream and ostream bases separately,
      // but so the virtual basic_ios base is only modified once.
#if 0
      basic_rpstream(basic_rpstream&& rhs)
      : iostream_type(std::move(rhs))
      , pbase_type(std::move(rhs))
      { iostream_type::set_rdbuf(std::addressof(pbase_type::buf_)); }

      basic_rpstream&
      operator=(basic_rpstream&& rhs)
      {
        iostream_type::operator=(std::move(rhs));
        pbase_type::operator=(std::move(rhs));
        return *this;
      }

      void
      swap(basic_rpstream& rhs)
      {
        iostream_type::swap(rhs);
        pbase_type::swap(rhs);
      }
#endif
#endif // C++11

      ~basic_rpstream() { }

      void
      open(const std::string& cmd, pmode mode = pstdout|pstdin)
      {
        this->do_open(cmd, mode);
      }

      void
      open( const std::string& file,
            const argv_type& argv,
            pmode mode = pstdout|pstdin )
      {
        this->do_open(file, argv, mode);
      }

      istream_type&
      out()
      {
        this->buf_.read_err(false);
        return *this;
      }

      istream_type&
      err()
      {
        this->buf_.read_err(true);
        return *this;
      }
    };


  typedef basic_pstreambuf<char> pstreambuf;
  typedef basic_ipstream<char> ipstream;
  typedef basic_opstream<char> opstream;
  typedef basic_pstream<char> pstream;
  typedef basic_rpstream<char> rpstream;


  template <typename C, typename T>
    inline std::basic_ostream<C,T>&
    peof(std::basic_ostream<C,T>& s)
    {
      typedef basic_pstreambuf<C,T> pstreambuf_type;
      if (pstreambuf_type* p = dynamic_cast<pstreambuf_type*>(s.rdbuf()))
        p->peof();
      return s;
    }


  /*
   * member definitions for pstreambuf
   */


  template <typename C, typename T>
    inline
    basic_pstreambuf<C,T>::basic_pstreambuf()
    : ppid_(-1)   // initialise to -1 to indicate no process run yet.
    , wpipe_(-1)
    , wbuffer_()
    , rbuffer_()
    , rbufstate_()
    , rsrc_(rsrc_out)
    , status_(-1)
    , error_(0)
    {
      rpipe_[rsrc_out] = rpipe_[rsrc_err] = -1;
    }

  template <typename C, typename T>
    inline
    basic_pstreambuf<C,T>::basic_pstreambuf(const std::string& cmd, pmode mode)
    : ppid_(-1)   // initialise to -1 to indicate no process run yet.
    , wpipe_(-1)
    , wbuffer_()
    , rbuffer_()
    , rbufstate_()
    , rsrc_(rsrc_out)
    , status_(-1)
    , error_(0)
    {
      rpipe_[rsrc_out] = rpipe_[rsrc_err] = -1;
      open(cmd, mode);
    }

  template <typename C, typename T>
    inline
    basic_pstreambuf<C,T>::basic_pstreambuf( const std::string& file,
                                             const argv_type& argv,
                                             pmode mode )
    : ppid_(-1)   // initialise to -1 to indicate no process run yet.
    , wpipe_(-1)
    , wbuffer_()
    , rbuffer_()
    , rbufstate_()
    , rsrc_(rsrc_out)
    , status_(-1)
    , error_(0)
    {
      rpipe_[rsrc_out] = rpipe_[rsrc_err] = -1;
      open(file, argv, mode);
    }

  template <typename C, typename T>
    inline
    basic_pstreambuf<C,T>::~basic_pstreambuf()
    {
      close();
    }

#if __cplusplus >= 201103L

  template <typename C, typename T>
    inline
    basic_pstreambuf<C,T>::basic_pstreambuf( basic_pstreambuf&& rhs ) noexcept
    : basic_streambuf(static_cast<const basic_streambuf&>(rhs))
    , ppid_(rhs.ppid_)
    , wpipe_(rhs.wpipe_)
    , rpipe_{rhs.rpipe_[0], rhs.rpipe_[1]}
    , wbuffer_(rhs.wbuffer_)
    , rbuffer_{rhs.rbuffer_[0], rhs.rbuffer_[1]}
    , rbufstate_{rhs.rbufstate_[0], rhs.rbufstate_[1], rhs.rbufstate_[2]}
    , rsrc_(rhs.rsrc_)
    , status_(rhs.status_)
    , error_(rhs.error_)
    {
      rhs.ppid_ = -1;
      rhs.wpipe_ = -1;
      rhs.rpipe_[0] = rhs.rpipe_[1] = -1;
      rhs.wbuffer_ = nullptr;
      rhs.rbuffer_[0] = rhs.rbuffer_[1] = nullptr;
      rhs.rbufstate_[0] = rhs.rbufstate_[1] = rhs.rbufstate_[2] = nullptr;
      rhs.rsrc_ = rsrc_out;
      rhs.status_ = -1;
      rhs.error_ = 0;
      rhs.setg(nullptr, nullptr, nullptr);
      rhs.setp(nullptr, nullptr);
    }

  template <typename C, typename T>
    inline basic_pstreambuf<C,T>&
    basic_pstreambuf<C,T>::operator=( basic_pstreambuf&& rhs ) noexcept
    {
      close();
      basic_streambuf::operator=(static_cast<const basic_streambuf&>(rhs));
      swap(rhs);
      return *this;
    }

  template <typename C, typename T>
    inline void
    basic_pstreambuf<C,T>::swap( basic_pstreambuf& rhs ) noexcept
    {
      basic_streambuf::swap(static_cast<basic_streambuf&>(rhs));
      std::swap(ppid_, rhs.ppid_);
      std::swap(wpipe_, rhs.wpipe_);
      std::swap(rpipe_, rhs.rpipe_);
      std::swap(wbuffer_, rhs.wbuffer_);
      std::swap(rbuffer_, rhs.rbuffer_);
      std::swap(rbufstate_, rhs.rbufstate_);
      std::swap(rsrc_, rhs.rsrc_);
      std::swap(status_, rhs.status_);
      std::swap(error_, rhs.error_);
    }
#endif // C++11

  template <typename C, typename T>
    basic_pstreambuf<C,T>*
    basic_pstreambuf<C,T>::open(const std::string& command, pmode mode)
    {
      const char * shell_path = "/bin/sh";
#if 0
      const std::string argv[] = { "sh", "-c", command };
      return this->open(shell_path, argv_type(argv, argv+3), mode);
#else
      basic_pstreambuf<C,T>* ret = NULL;

      if (!is_open())
      {
        switch(fork(mode))
        {
        case 0 :
          // this is the new process, exec command
          ::execl(shell_path, "sh", "-c", command.c_str(), (char*)NULL);

          // can only reach this point if exec() failed

          // parent can get exit code from waitpid()
          ::_exit(errno);
          // using std::exit() would make static dtors run twice

        case -1 :
          // couldn't fork, error already handled in pstreambuf::fork()
          break;

        default :
          // this is the parent process
          // activate buffers
          create_buffers(mode);
          ret = this;
        }
      }
      return ret;
#endif
    }

  inline void
  close_fd(pstreams::fd_type& fd)
  {
    if (fd >= 0 && ::close(fd) == 0)
      fd = -1;
  }

  template <int N>
    inline void
    close_fd_array(pstreams::fd_type (&fds)[N])
    {
      for (std::size_t i = 0; i < N; ++i)
        close_fd(fds[i]);
    }

  template <typename C, typename T>
    basic_pstreambuf<C,T>*
    basic_pstreambuf<C,T>::open( const std::string& file,
                                 const argv_type& argv,
                                 pmode mode )
    {
      basic_pstreambuf<C,T>* ret = NULL;

      if (!is_open())
      {
        // constants for read/write ends of pipe
        enum { RD, WR };

        // open another pipe and set close-on-exec
        fd_type ck_exec[] = { -1, -1 };
        if (-1 == ::pipe(ck_exec)
            || -1 == ::fcntl(ck_exec[RD], F_SETFD, FD_CLOEXEC)
            || -1 == ::fcntl(ck_exec[WR], F_SETFD, FD_CLOEXEC))
        {
          error_ = errno;
          close_fd_array(ck_exec);
        }
        else
        {
          switch(fork(mode))
          {
          case 0 :
            // this is the new process, exec command
            {
              char** arg_v = new char*[argv.size()+1];
              for (std::size_t i = 0; i < argv.size(); ++i)
              {
                const std::string& src = argv[i];
                char*& dest = arg_v[i];
                dest = new char[src.size()+1];
                dest[ src.copy(dest, src.size()) ] = '\0';
              }
              arg_v[argv.size()] = NULL;

              ::execvp(file.c_str(), arg_v);

              // can only reach this point if exec() failed

              // parent can get error code from ck_exec pipe
              error_ = errno;

              while (::write(ck_exec[WR], &error_, sizeof(error_)) == -1
                  && errno == EINTR)
              { }

              ::close(ck_exec[WR]);
              ::close(ck_exec[RD]);

              ::_exit(error_);
              // using std::exit() would make static dtors run twice
            }

          case -1 :
            // couldn't fork, error already handled in pstreambuf::fork()
            close_fd_array(ck_exec);
            break;

          default :
            // this is the parent process

            // check child called exec() successfully
            ::close(ck_exec[WR]);
            switch (::read(ck_exec[RD], &error_, sizeof(error_)))
            {
            case 0:
              // activate buffers
              create_buffers(mode);
              ret = this;
              break;
            case -1:
              error_ = errno;
              break;
            default:
              // error_ contains error code from child
              // call wait() to clean up and set ppid_ to 0
              this->wait();
              break;
            }
            ::close(ck_exec[RD]);
          }
        }
      }
      return ret;
    }

  template <typename C, typename T>
    pid_t
    basic_pstreambuf<C,T>::fork(pmode mode)
    {
      pid_t pid = -1;

      // Three pairs of file descriptors, for pipes connected to the
      // process' stdin, stdout and stderr
      // (stored in a single array so close_fd_array() can close all at once)
      fd_type fd[] = { -1, -1, -1, -1, -1, -1 };
      fd_type* const pin = fd;
      fd_type* const pout = fd+2;
      fd_type* const perr = fd+4;

      // constants for read/write ends of pipe
      enum { RD, WR };

      // N.B.
      // For the pstreambuf pin is an output stream and
      // pout and perr are input streams.

      if (!error_ && mode&pstdin && ::pipe(pin))
        error_ = errno;

      if (!error_ && mode&pstdout && ::pipe(pout))
        error_ = errno;

      if (!error_ && mode&pstderr && ::pipe(perr))
        error_ = errno;

      if (!error_)
      {
        pid = ::fork();
        switch (pid)
        {
          case 0 :
          {
            // this is the new process

            // for each open pipe close one end and redirect the
            // respective standard stream to the other end

            if (*pin >= 0)
            {
              ::close(pin[WR]);
              ::dup2(pin[RD], STDIN_FILENO);
              ::close(pin[RD]);
            }
            if (*pout >= 0)
            {
              ::close(pout[RD]);
              ::dup2(pout[WR], STDOUT_FILENO);
              ::close(pout[WR]);
            }
            if (*perr >= 0)
            {
              ::close(perr[RD]);
              ::dup2(perr[WR], STDERR_FILENO);
              ::close(perr[WR]);
            }

#ifdef _POSIX_JOB_CONTROL
            if (mode&newpg)
              ::setpgid(0, 0); // Change to a new process group
#endif

            break;
          }
          case -1 :
          {
            // couldn't fork for some reason
            error_ = errno;
            // close any open pipes
            close_fd_array(fd);
            break;
          }
          default :
          {
            // this is the parent process, store process' pid
            ppid_ = pid;

            // store one end of open pipes and close other end
            if (*pin >= 0)
            {
              wpipe_ = pin[WR];
              ::close(pin[RD]);
            }
            if (*pout >= 0)
            {
              rpipe_[rsrc_out] = pout[RD];
              ::close(pout[WR]);
            }
            if (*perr >= 0)
            {
              rpipe_[rsrc_err] = perr[RD];
              ::close(perr[WR]);
            }
          }
        }
      }
      else
      {
        // close any pipes we opened before failure
        close_fd_array(fd);
      }
      return pid;
    }

  template <typename C, typename T>
    basic_pstreambuf<C,T>*
    basic_pstreambuf<C,T>::close()
    {
      const bool running = is_open();

      sync(); // this might call wait() and reap the child process

      // rather than trying to work out whether or not we need to clean up
      // just do it anyway, all cleanup functions are safe to call twice.

      destroy_buffers(pstdin|pstdout|pstderr);

      // close pipes before wait() so child gets EOF/SIGPIPE
      close_fd(wpipe_);
      close_fd_array(rpipe_);

      do
      {
        error_ = 0;
      } while (wait() == -1 && error() == EINTR);

      return running ? this : NULL;
    }

  template <typename C, typename T>
#if __cplusplus >= 201402L && __has_cpp_attribute(deprecated)
    [[deprecated]]
#elif __GNUC__
    __attribute__((deprecated))
#endif
    inline void
    basic_pstreambuf<C,T>::init_rbuffers()
    {
      rpipe_[rsrc_out] = rpipe_[rsrc_err] = -1;
      rbuffer_[rsrc_out] = rbuffer_[rsrc_err] = NULL;
      rbufstate_[0] = rbufstate_[1] = rbufstate_[2] = NULL;
    }

  template <typename C, typename T>
    void
    basic_pstreambuf<C,T>::create_buffers(pmode mode)
    {
      if (mode & pstdin)
      {
        delete[] wbuffer_;
        wbuffer_ = new char_type[bufsz];
        this->setp(wbuffer_, wbuffer_ + bufsz);
      }
      if (mode & pstdout)
      {
        delete[] rbuffer_[rsrc_out];
        rbuffer_[rsrc_out] = new char_type[bufsz];
        rsrc_ = rsrc_out;
        this->setg(rbuffer_[rsrc_out] + pbsz, rbuffer_[rsrc_out] + pbsz,
            rbuffer_[rsrc_out] + pbsz);
      }
      if (mode & pstderr)
      {
        delete[] rbuffer_[rsrc_err];
        rbuffer_[rsrc_err] = new char_type[bufsz];
        if (!(mode & pstdout))
        {
          rsrc_ = rsrc_err;
          this->setg(rbuffer_[rsrc_err] + pbsz, rbuffer_[rsrc_err] + pbsz,
              rbuffer_[rsrc_err] + pbsz);
        }
      }
    }

  template <typename C, typename T>
    void
    basic_pstreambuf<C,T>::destroy_buffers(pmode mode)
    {
      if (mode & pstdin)
      {
        this->setp(NULL, NULL);
        delete[] wbuffer_;
        wbuffer_ = NULL;
      }
      if (mode & pstdout)
      {
        if (rsrc_ == rsrc_out)
          this->setg(NULL, NULL, NULL);
        delete[] rbuffer_[rsrc_out];
        rbuffer_[rsrc_out] = NULL;
      }
      if (mode & pstderr)
      {
        if (rsrc_ == rsrc_err)
          this->setg(NULL, NULL, NULL);
        delete[] rbuffer_[rsrc_err];
        rbuffer_[rsrc_err] = NULL;
      }
    }

  template <typename C, typename T>
    typename basic_pstreambuf<C,T>::buf_read_src
    basic_pstreambuf<C,T>::switch_read_buffer(buf_read_src src)
    {
      if (rsrc_ != src)
      {
        char_type* tmpbufstate[] = {this->eback(), this->gptr(), this->egptr()};
        this->setg(rbufstate_[0], rbufstate_[1], rbufstate_[2]);
        for (std::size_t i = 0; i < 3; ++i)
          rbufstate_[i] = tmpbufstate[i];
        rsrc_ = src;
      }
      return rsrc_;
    }

  template <typename C, typename T>
    int
    basic_pstreambuf<C,T>::wait(bool nohang)
    {
      int child_exited = -1;
      if (is_open())
      {
        int exit_status;
        switch(::waitpid(ppid_, &exit_status, nohang ? WNOHANG : 0))
        {
          case 0 :
            // nohang was true and process has not exited
            child_exited = 0;
            break;
          case -1 :
            error_ = errno;
            break;
          default :
            // process has exited
            ppid_ = 0;
            status_ = exit_status;
            child_exited = 1;
            // Close wpipe, would get SIGPIPE if we used it.
            destroy_buffers(pstdin);
            close_fd(wpipe_);
            // Must free read buffers and pipes on destruction
            // or next call to open()/close()
            break;
        }
      }
      return child_exited;
    }

  template <typename C, typename T>
    inline basic_pstreambuf<C,T>*
    basic_pstreambuf<C,T>::kill(int signal)
    {
      basic_pstreambuf<C,T>* ret = NULL;
      if (is_open())
      {
        if (::kill(ppid_, signal))
          error_ = errno;
        else
        {
#if 0
          // TODO call exited() to check for exit and clean up? leave to user?
          if (signal==SIGTERM || signal==SIGKILL)
            this->exited();
#endif
          ret = this;
        }
      }
      return ret;
    }

  template <typename C, typename T>
    inline basic_pstreambuf<C,T>*
    basic_pstreambuf<C,T>::killpg(int signal)
    {
      basic_pstreambuf<C,T>* ret = NULL;
#ifdef _POSIX_JOB_CONTROL
      if (is_open())
      {
        pid_t pgid = ::getpgid(ppid_);
        if (pgid == -1)
          error_ = errno;
        else if (pgid == ::getpgrp())
          error_ = EPERM;  // Don't commit suicide
        else if (::killpg(pgid, signal))
          error_ = errno;
        else
          ret = this;
      }
#else
      error_ = ENOTSUP;
#endif
      return ret;
    }

  template <typename C, typename T>
    inline bool
    basic_pstreambuf<C,T>::exited()
    {
      return ppid_ == 0 || wait(true)==1;
    }


  template <typename C, typename T>
    inline int
    basic_pstreambuf<C,T>::status() const
    {
      return status_;
    }

  template <typename C, typename T>
    inline int
    basic_pstreambuf<C,T>::error() const
    {
      return error_;
    }

  template <typename C, typename T>
    inline void
    basic_pstreambuf<C,T>::peof()
    {
      sync();
      destroy_buffers(pstdin);
      close_fd(wpipe_);
    }

  template <typename C, typename T>
    inline bool
    basic_pstreambuf<C,T>::is_open() const
    {
      return ppid_ > 0;
    }

  template <typename C, typename T>
    inline bool
    basic_pstreambuf<C,T>::read_err(bool readerr)
    {
      buf_read_src src = readerr ? rsrc_err : rsrc_out;
      if (rpipe_[src]>=0)
      {
        switch_read_buffer(src);
        return true;
      }
      return false;
    }

  template <typename C, typename T>
    typename basic_pstreambuf<C,T>::int_type
    basic_pstreambuf<C,T>::overflow(int_type c)
    {
      if (!empty_buffer())
        return traits_type::eof();
      else if (!traits_type::eq_int_type(c, traits_type::eof()))
        return this->sputc(c);
      else
        return traits_type::not_eof(c);
    }


  template <typename C, typename T>
    int
    basic_pstreambuf<C,T>::sync()
    {
      return !exited() && empty_buffer() ? 0 : -1;
    }

  template <typename C, typename T>
    std::streamsize
    basic_pstreambuf<C,T>::xsputn(const char_type* s, std::streamsize n)
    {
      std::streamsize done = 0;
      while (done < n)
      {
        if (std::streamsize nbuf = this->epptr() - this->pptr())
        {
          nbuf = std::min(nbuf, n - done);
          traits_type::copy(this->pptr(), s + done, nbuf);
          this->pbump(nbuf);
          done += nbuf;
        }
        else if (!empty_buffer())
          break;
      }
      return done;
    }

  template <typename C, typename T>
    bool
    basic_pstreambuf<C,T>::empty_buffer()
    {
      const std::streamsize count = this->pptr() - this->pbase();
      if (count > 0)
      {
        const std::streamsize written = this->write(this->wbuffer_, count);
        if (written > 0)
        {
          if (const std::streamsize unwritten = count - written)
            traits_type::move(this->pbase(), this->pbase()+written, unwritten);
          this->pbump(-written);
          return true;
        }
      }
      return false;
    }

  template <typename C, typename T>
    typename basic_pstreambuf<C,T>::int_type
    basic_pstreambuf<C,T>::underflow()
    {
      if (this->gptr() < this->egptr() || fill_buffer())
        return traits_type::to_int_type(*this->gptr());
      else
        return traits_type::eof();
    }

  template <typename C, typename T>
    typename basic_pstreambuf<C,T>::int_type
    basic_pstreambuf<C,T>::pbackfail(int_type c)
    {
      if (this->gptr() != this->eback())
      {
        this->gbump(-1);
        if (!traits_type::eq_int_type(c, traits_type::eof()))
          *this->gptr() = traits_type::to_char_type(c);
        return traits_type::not_eof(c);
      }
      else
         return traits_type::eof();
    }

  template <typename C, typename T>
    std::streamsize
    basic_pstreambuf<C,T>::showmanyc()
    {
      int avail = 0;
      if (sizeof(char_type) == 1)
        avail = fill_buffer(true) ? this->egptr() - this->gptr() : -1;
#ifdef FIONREAD
      else
      {
        if (::ioctl(rpipe(), FIONREAD, &avail) == -1)
          avail = -1;
        else if (avail)
          avail /= sizeof(char_type);
      }
#endif
      return std::streamsize(avail);
    }

  template <typename C, typename T>
    bool
    basic_pstreambuf<C,T>::fill_buffer(bool non_blocking)
    {
      const std::streamsize pb1 = this->gptr() - this->eback();
      const std::streamsize pb2 = pbsz;
      const std::streamsize npb = std::min(pb1, pb2);

      char_type* const rbuf = rbuffer();

      if (npb)
        traits_type::move(rbuf + pbsz - npb, this->gptr() - npb, npb);

      std::streamsize rc = -1;

      if (non_blocking)
      {
        const int flags = ::fcntl(rpipe(), F_GETFL);
        if (flags != -1)
        {
          const bool blocking = !(flags & O_NONBLOCK);
          if (blocking)
            ::fcntl(rpipe(), F_SETFL, flags | O_NONBLOCK);  // set non-blocking

          error_ = 0;
          rc = read(rbuf + pbsz, bufsz - pbsz);

          if (rc == -1 && error_ == EAGAIN)  // nothing available
            rc = 0;
          else if (rc == 0)  // EOF
            rc = -1;

          if (blocking)
            ::fcntl(rpipe(), F_SETFL, flags); // restore
        }
      }
      else
        rc = read(rbuf + pbsz, bufsz - pbsz);

      if (rc > 0 || (rc == 0 && non_blocking))
      {
        this->setg( rbuf + pbsz - npb,
                    rbuf + pbsz,
                    rbuf + pbsz + rc );
        return true;
      }
      else
      {
        this->setg(NULL, NULL, NULL);
        return false;
      }
    }

  template <typename C, typename T>
    inline std::streamsize
    basic_pstreambuf<C,T>::write(const char_type* s, std::streamsize n)
    {
      std::streamsize nwritten = 0;
      if (wpipe() >= 0)
      {
        nwritten = ::write(wpipe(), s, n * sizeof(char_type));
        if (nwritten == -1)
          error_ = errno;
        else
          nwritten /= sizeof(char_type);
      }
      return nwritten;
    }

  template <typename C, typename T>
    inline std::streamsize
    basic_pstreambuf<C,T>::read(char_type* s, std::streamsize n)
    {
      std::streamsize nread = 0;
      if (rpipe() >= 0)
      {
        nread = ::read(rpipe(), s, n * sizeof(char_type));
        if (nread == -1)
          error_ = errno;
        else
          nread /= sizeof(char_type);
      }
      return nread;
    }

  template <typename C, typename T>
    inline pstreams::fd_type&
    basic_pstreambuf<C,T>::wpipe()
    {
      return wpipe_;
    }

  template <typename C, typename T>
    inline pstreams::fd_type&
    basic_pstreambuf<C,T>::rpipe()
    {
      return rpipe_[rsrc_];
    }

  template <typename C, typename T>
    inline pstreams::fd_type&
    basic_pstreambuf<C,T>::rpipe(buf_read_src which)
    {
      return rpipe_[which];
    }

  template <typename C, typename T>
    inline typename basic_pstreambuf<C,T>::char_type*
    basic_pstreambuf<C,T>::rbuffer()
    {
      return rbuffer_[rsrc_];
    }


  /*
   * member definitions for pstream_common
   */

  template <typename C, typename T>
    inline
    pstream_common<C,T>::pstream_common()
    : std::basic_ios<C,T>(NULL)
    , command_()
    , buf_()
    {
      this->std::basic_ios<C,T>::rdbuf(&buf_);
    }

  template <typename C, typename T>
    inline
    pstream_common<C,T>::pstream_common(const std::string& cmd, pmode mode)
    : std::basic_ios<C,T>(NULL)
    , command_(cmd)
    , buf_()
    {
      this->std::basic_ios<C,T>::rdbuf(&buf_);
      do_open(cmd, mode);
    }

  template <typename C, typename T>
    inline
    pstream_common<C,T>::pstream_common( const std::string& file,
                                         const argv_type& argv,
                                         pmode mode )
    : std::basic_ios<C,T>(NULL)
    , command_(file)
    , buf_()
    {
      this->std::basic_ios<C,T>::rdbuf(&buf_);
      do_open(file, argv, mode);
    }

  template <typename C, typename T>
    inline
    pstream_common<C,T>::~pstream_common()
    {
    }

  template <typename C, typename T>
    inline void
    pstream_common<C,T>::do_open(const std::string& cmd, pmode mode)
    {
      if (!buf_.open((command_=cmd), mode))
        this->setstate(std::ios_base::failbit);
    }

  template <typename C, typename T>
    inline void
    pstream_common<C,T>::do_open( const std::string& file,
                                  const argv_type& argv,
                                  pmode mode )
    {
      if (!buf_.open((command_=file), argv, mode))
        this->setstate(std::ios_base::failbit);
    }

  template <typename C, typename T>
    inline int
    pstream_common<C,T>::close()
    {
      if (!buf_.close())
        this->setstate(std::ios_base::failbit);
      return buf_.status();
    }

  template <typename C, typename T>
    inline bool
    pstream_common<C,T>::is_open() const
    {
      return buf_.is_open();
    }

  template <typename C, typename T>
    inline const std::string&
    pstream_common<C,T>::command() const
    {
      return command_;
    }

  // TODO  document behaviour if buffer replaced.
  template <typename C, typename T>
    inline typename pstream_common<C,T>::streambuf_type*
    pstream_common<C,T>::rdbuf() const
    {
      return const_cast<streambuf_type*>(&buf_);
    }


#if REDI_EVISCERATE_PSTREAMS

  template <typename C, typename T>
    std::size_t
    basic_pstreambuf<C,T>::fopen(FILE*& in, FILE*& out, FILE*& err)
    {
      in = out = err = NULL;
      std::size_t open_files = 0;
      if (wpipe() > -1)
      {
        if ((in = ::fdopen(wpipe(), "w")))
        {
            open_files |= pstdin;
        }
      }
      if (rpipe(rsrc_out) > -1)
      {
        if ((out = ::fdopen(rpipe(rsrc_out), "r")))
        {
            open_files |= pstdout;
        }
      }
      if (rpipe(rsrc_err) > -1)
      {
        if ((err = ::fdopen(rpipe(rsrc_err), "r")))
        {
            open_files |= pstderr;
        }
      }
      return open_files;
    }

  template <typename C, typename T>
    inline std::size_t
    pstream_common<C,T>::fopen(FILE*& fin, FILE*& fout, FILE*& ferr)
    {
      return buf_.fopen(fin, fout, ferr);
    }

#endif // REDI_EVISCERATE_PSTREAMS


} // namespace redi

#endif  // REDI_PSTREAM_H_SEEN

// vim: ts=2 sw=2 expandtab