basic_file_stdio.cc

// Wrapper of C-language FILE struct -*- C++ -*-

// Copyright (C) 2000-2023 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

//
// ISO C++ 14882: 27.8  File-based streams
//

#include <bits/largefile-config.h>
#include <bits/basic_file.h>
#include <fcntl.h>
#include <errno.h>

#ifdef _GLIBCXX_HAVE_POLL
#include <poll.h>
#endif

// Pick up ioctl on Solaris 2.8
#ifdef _GLIBCXX_HAVE_UNISTD_H
#include <unistd.h>
#endif

// Pick up FIONREAD on Solaris 2
#ifdef _GLIBCXX_HAVE_SYS_IOCTL_H
#define BSD_COMP
#include <sys/ioctl.h>
#endif

// Pick up FIONREAD on Solaris 2.5.
#ifdef _GLIBCXX_HAVE_SYS_FILIO_H
#include <sys/filio.h>
#endif

#ifdef _GLIBCXX_HAVE_SYS_UIO_H
#include <sys/uio.h>
#endif

#if defined(_GLIBCXX_HAVE_S_ISREG) || defined(_GLIBCXX_HAVE_S_IFREG)
# include <sys/stat.h>
# ifdef _GLIBCXX_HAVE_S_ISREG
#  define _GLIBCXX_ISREG(x) S_ISREG(x)
# else
#  define _GLIBCXX_ISREG(x) (((x) & S_IFMT) == S_IFREG)
# endif
#endif

#include <limits> // For <off_t>::max() and min() and <streamsize>::max()

#if _GLIBCXX_USE__GET_OSFHANDLE
# include <stdint.h> // For intptr_t
# include <io.h>     // For _get_osfhandle
#endif

namespace
{
  // Map ios_base::openmode flags to a string for use in fopen().
  // Table of valid combinations as given in [lib.filebuf.members]/2.
  static const char*
  fopen_mode(std::ios_base::openmode mode)
  {
    enum
      {
	in     = std::ios_base::in,
	out    = std::ios_base::out,
	trunc  = std::ios_base::trunc,
	app    = std::ios_base::app,
	binary = std::ios_base::binary,
	noreplace = std::_S_noreplace
      };

    // _GLIBCXX_RESOLVE_LIB_DEFECTS
    // 596. 27.8.1.3 Table 112 omits "a+" and "a+b" modes.
    switch (mode & (in|out|trunc|app|binary|noreplace))
      {
      case (   out                           ): return "w";
      case (   out                 |noreplace): return "wx";
      case (   out|trunc                     ): return "w";
      case (   out|trunc           |noreplace): return "wx";
      case (   out      |app                 ): return "a";
      case (             app                 ): return "a";
      case (in                               ): return "r";
      case (in|out                           ): return "r+";
      case (in|out|trunc                     ): return "w+";
      case (in|out|trunc           |noreplace): return "w+x";
      case (in|out      |app                 ): return "a+";
      case (in          |app                 ): return "a+";

      case (   out          |binary          ): return "wb";
      case (   out          |binary|noreplace): return "wbx";
      case (   out      |app|binary          ): return "ab";
      case (             app|binary          ): return "ab";
      case (   out|trunc    |binary          ): return "wb";
      case (in              |binary          ): return "rb";
      case (in|out          |binary          ): return "r+b";
      case (in|out|trunc    |binary          ): return "w+b";
      case (in|out|trunc    |binary|noreplace): return "w+bx";
      case (in|out      |app|binary          ): return "a+b";
      case (in          |app|binary          ): return "a+b";

      default: return 0; // invalid
      }
  }

  // Wrapper handling partial write.
  static std::streamsize
#ifdef _GLIBCXX_USE_STDIO_PURE
  xwrite(FILE *__file, const char* __s, std::streamsize __n)
#else
  xwrite(int __fd, const char* __s, std::streamsize __n)
#endif
  {
    std::streamsize __nleft = __n;

    for (;;)
      {
#ifdef _GLIBCXX_USE_STDIO_PURE
	const std::streamsize __ret = fwrite(__s, 1, __nleft, __file);
	if (__ret == 0 && ferror(__file))
	  break;
#else
	const std::streamsize __ret = write(__fd, __s, __nleft);
	if (__ret == -1L && errno == EINTR)
	  continue;
	if (__ret == -1L)
	  break;
#endif
	__nleft -= __ret;
	if (__nleft == 0)
	  break;

	__s += __ret;
      }

    return __n - __nleft;
  }

#if defined(_GLIBCXX_HAVE_WRITEV) && !defined(_GLIBCXX_USE_STDIO_PURE)
  // Wrapper handling partial writev.
  static std::streamsize
  xwritev(int __fd, const char* __s1, std::streamsize __n1,
	  const char* __s2, std::streamsize __n2)
  {
    std::streamsize __nleft = __n1 + __n2;
    std::streamsize __n1_left = __n1;

    struct iovec __iov[2];
    __iov[1].iov_base = const_cast<char*>(__s2);
    __iov[1].iov_len = __n2;

    for (;;)
      {
	__iov[0].iov_base = const_cast<char*>(__s1);
	__iov[0].iov_len = __n1_left;

	const std::streamsize __ret = writev(__fd, __iov, 2);
	if (__ret == -1L && errno == EINTR)
	  continue;
	if (__ret == -1L)
	  break;

	__nleft -= __ret;
	if (__nleft == 0)
	  break;

	const std::streamsize __off = __ret - __n1_left;
	if (__off >= 0)
	  {
	    __nleft -= xwrite(__fd, __s2 + __off, __n2 - __off);
	    break;
	  }

	__s1 += __ret;
	__n1_left -= __ret;
      }

    return __n1 + __n2 - __nleft;
  }
#endif
} // anonymous namespace


namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  // Definitions for __basic_file<char>.
  __basic_file<char>::__basic_file(__c_lock* /*__lock*/) throw()
  : _M_cfile(NULL), _M_cfile_created(false) { }

  __basic_file<char>::~__basic_file()
  { this->close(); }

  __basic_file<char>*
  __basic_file<char>::sys_open(__c_file* __file, ios_base::openmode)
  {
    __basic_file* __ret = NULL;
    if (!this->is_open() && __file)
      {
	int __err, __save_errno = errno;
	// POSIX guarantees that fflush sets errno on error, but C doesn't.
	errno = 0;
	do
	  __err = fflush(__file);
	while (__err && errno == EINTR);
	errno = __save_errno;
	if (!__err)
	  {
	    _M_cfile = __file;
	    _M_cfile_created = false;
	    __ret = this;
	  }
      }
    return __ret;
  }

  __basic_file<char>*
  __basic_file<char>::sys_open(int __fd, ios_base::openmode __mode) throw ()
  {
    __basic_file* __ret = NULL;
    const char* __c_mode = fopen_mode(__mode);
    if (__c_mode && !this->is_open() && (_M_cfile = fdopen(__fd, __c_mode)))
      {
	char* __buf = NULL;
	_M_cfile_created = true;
	if (__fd == 0)
	  setvbuf(_M_cfile, __buf, _IONBF, 0);
	__ret = this;
      }
    return __ret;
  }

  __basic_file<char>*
  __basic_file<char>::open(const char* __name, ios_base::openmode __mode,
			   int /*__prot*/)
  {
    __basic_file* __ret = NULL;
    const char* __c_mode = fopen_mode(__mode);
    if (__c_mode && !this->is_open())
      {
	if ((_M_cfile = fopen(__name, __c_mode)))
	  {
	    _M_cfile_created = true;
	    __ret = this;
	  }
      }
    return __ret;
  }

#if _GLIBCXX_HAVE__WFOPEN && _GLIBCXX_USE_WCHAR_T
  __basic_file<char>*
  __basic_file<char>::open(const wchar_t* __name, ios_base::openmode __mode)
  {
    __basic_file* __ret = NULL;
    const char* __c_mode = fopen_mode(__mode);
    if (__c_mode && !this->is_open())
      {
	wchar_t __wc_mode[4] = { };
	int __i = 0;
	do
	  {
	    switch(__c_mode[__i]) {
	    case 'a': __wc_mode[__i] = L'a'; break;
	    case 'b': __wc_mode[__i] = L'b'; break;
	    case 'r': __wc_mode[__i] = L'r'; break;
	    case 'w': __wc_mode[__i] = L'w'; break;
	    case '+': __wc_mode[__i] = L'+'; break;
	    default: return __ret;
	    }
	  }
	while (__c_mode[++__i]);

	if ((_M_cfile = _wfopen(__name, __wc_mode)))
	  {
	    _M_cfile_created = true;
	    __ret = this;
	  }
      }
    return __ret;
  }
#endif

  bool
  __basic_file<char>::is_open() const throw ()
  { return _M_cfile != 0; }

#ifndef _GLIBCCXX_USE_STDIO_PURE
  int
  __basic_file<char>::fd() throw ()
  { return fileno(_M_cfile); }
#endif

  __c_file*
  __basic_file<char>::file() throw ()
  { return _M_cfile; }

  __basic_file<char>*
  __basic_file<char>::close()
  {
    __basic_file* __ret = static_cast<__basic_file*>(NULL);
    if (this->is_open())
      {
	int __err = 0;
	if (_M_cfile_created)
	  __err = fclose(_M_cfile);
	_M_cfile = 0;
	if (!__err)
	  __ret = this;
      }
    return __ret;
  }

  streamsize
  __basic_file<char>::xsgetn(char* __s, streamsize __n)
  {
    streamsize __ret;
#ifdef _GLIBCXX_USE_STDIO_PURE
    __ret = fread(__s, 1, __n, this->file());
    if (__ret == 0 && ferror(this->file()))
      __ret = -1;
#else
    do
      __ret = read(this->fd(), __s, __n);
    while (__ret == -1L && errno == EINTR);
#endif
    return __ret;
  }

  streamsize
  __basic_file<char>::xsputn(const char* __s, streamsize __n)
  {
#ifdef _GLIBCXX_USE_STDIO_PURE
    return xwrite(this->file(), __s, __n);
#else
    return xwrite(this->fd(), __s, __n);
#endif
  }

  streamsize
  __basic_file<char>::xsputn_2(const char* __s1, streamsize __n1,
			       const char* __s2, streamsize __n2)
  {
    streamsize __ret = 0;
#if defined(_GLIBCXX_HAVE_WRITEV) && !defined(_GLIBCXX_USE_STDIO_PURE)
    __ret = xwritev(this->fd(), __s1, __n1, __s2, __n2);
#else
    if (__n1)
#ifdef _GLIBCXX_USE_STDIO_PURE
      __ret = xwrite(this->file(), __s1, __n1);
#else
      __ret = xwrite(this->fd(), __s1, __n1);
#endif

    if (__ret == __n1)
#ifdef _GLIBCXX_USE_STDIO_PURE
      __ret += xwrite(this->file(), __s2, __n2);
#else
      __ret += xwrite(this->fd(), __s2, __n2);
#endif
#endif
    return __ret;
  }

  namespace
  {
    inline streamoff
    get_file_offset(__basic_file<char>* __f)
    {
#ifdef _GLIBCXX_USE_STDIO_PURE
# ifdef _GLIBCXX_USE_FSEEKO_FTELLO
      return ftello(__f->file());
# else
      return ftell(__f->file());
# endif
#else
      return lseek(__f->fd(), 0, (int)ios_base::cur);
#endif
    }
  }

  streamoff
  __basic_file<char>::seekoff(streamoff __off, ios_base::seekdir __way) throw ()
  {
#ifdef _GLIBCXX_USE_STDIO_PURE
#ifdef _GLIBCXX_USE_FSEEKO_FTELLO
    if _GLIBCXX17_CONSTEXPR (sizeof(off_t) > sizeof(long))
      {
	if (fseeko(this->file(), __off, __way))
	  return -1;
      }
    else
#endif
      {
	if (__off > numeric_limits<long>::max()
	      || __off < numeric_limits<long>::min())
	  return -1;
	if (fseek(this->file(), __off, __way))
	  return -1;
      }
    return __way == ios_base::beg ? __off : std::get_file_offset(this);
#else
    if _GLIBCXX17_CONSTEXPR (sizeof(streamoff) > sizeof(off_t))
      if (__off > numeric_limits<off_t>::max()
	    || __off < numeric_limits<off_t>::min())
      return -1L;
    return lseek(this->fd(), __off, __way);
#endif
  }

  int
  __basic_file<char>::sync()
  { return fflush(_M_cfile); }

  streamsize
  __basic_file<char>::showmanyc()
  {
#if !defined(_GLIBCXX_NO_IOCTL) && !defined(_GLIBCXX_USE_STDIO_PURE)
#ifdef FIONREAD
    // Pipes and sockets.
    int __num = 0;
    int __r = ioctl(this->fd(), FIONREAD, &__num);
    if (!__r && __num >= 0)
      return __num;
#endif
#endif

#if defined(_GLIBCXX_HAVE_POLL) && !defined(_GLIBCXX_USE_STDIO_PURE)
    // Cheap test.
    struct pollfd __pfd[1];
    __pfd[0].fd = this->fd();
    __pfd[0].events = POLLIN;
    if (poll(__pfd, 1, 0) <= 0)
      return 0;
#endif

#if defined(_GLIBCXX_HAVE_S_ISREG) || defined(_GLIBCXX_HAVE_S_IFREG)
    // Regular files.
    struct stat __buffer;
    const int __err = fstat(this->fd(), &__buffer);
    if (!__err && _GLIBCXX_ISREG(__buffer.st_mode))
      {
	const streamoff __off = __buffer.st_size - std::get_file_offset(this);
	return std::min(__off, streamoff(numeric_limits<streamsize>::max()));
      }
#endif
    return 0;
  }

  __basic_file<char>::native_handle_type
  __basic_file<char>::native_handle() const noexcept
  {
#ifdef _GLIBCXX_USE_STDIO_PURE
    return _M_cfile;
#elif _GLIBCXX_USE__GET_OSFHANDLE
    const intptr_t handle = _M_cfile ? _get_osfhandle(fileno(_M_cfile)) : -1;
    return reinterpret_cast<native_handle>(handle);
#else
    return fileno(_M_cfile);
#endif
  }

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace