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/* Copyright (C) 2007 Eric Blake

 * Permission to use, copy, modify, and distribute this software

 * is freely granted, provided that this notice is preserved.

 */

/*

FUNCTION

<<funopen>>, <<fropen>>, <<fwopen>>---open a stream with custom callbacks

INDEX

        funopen

INDEX

        fropen

INDEX

        fwopen

ANSI_SYNOPSIS

        #include <stdio.h>

        FILE *funopen(const void *<[cookie]>,

                      int (*<[readfn]>) (void *cookie, char *buf, int n),

                      int (*<[writefn]>) (void *cookie, const char *buf, int n),

                      fpos_t (*<[seekfn]>) (void *cookie, fpos_t off, int whence),

                      int (*<[closefn]>) (void *cookie));

        FILE *fropen(const void *<[cookie]>,

                     int (*<[readfn]>) (void *cookie, char *buf, int n));

        FILE *fwopen(const void *<[cookie]>,

                     int (*<[writefn]>) (void *cookie, const char *buf, int n));

DESCRIPTION

<<funopen>> creates a <<FILE>> stream where I/O is performed using

custom callbacks.  At least one of <[readfn]> and <[writefn]> must be

provided, which determines whether the stream behaves with mode <"r">,

<"w">, or <"r+">.

<[readfn]> should return -1 on failure, or else the number of bytes

read (0 on EOF).  It is similar to <<read>>, except that <int> rather

than <size_t> bounds a transaction size, and <[cookie]> will be passed

as the first argument.  A NULL <[readfn]> makes attempts to read the

stream fail.

<[writefn]> should return -1 on failure, or else the number of bytes

written.  It is similar to <<write>>, except that <int> rather than

<size_t> bounds a transaction size, and <[cookie]> will be passed as

the first argument.  A NULL <[writefn]> makes attempts to write the

stream fail.

<[seekfn]> should return (fpos_t)-1 on failure, or else the current

file position.  It is similar to <<lseek>>, except that <[cookie]>

will be passed as the first argument.  A NULL <[seekfn]> makes the

stream behave similarly to a pipe in relation to stdio functions that

require positioning.  This implementation assumes fpos_t and off_t are

the same type.

<[closefn]> should return -1 on failure, or 0 on success.  It is

similar to <<close>>, except that <[cookie]> will be passed as the

first argument.  A NULL <[closefn]> merely flushes all data then lets

<<fclose>> succeed.  A failed close will still invalidate the stream.

Read and write I/O functions are allowed to change the underlying

buffer on fully buffered or line buffered streams by calling

<<setvbuf>>.  They are also not required to completely fill or empty

the buffer.  They are not, however, allowed to change streams from

unbuffered to buffered or to change the state of the line buffering

flag.  They must also be prepared to have read or write calls occur on

buffers other than the one most recently specified.

The functions <<fropen>> and <<fwopen>> are convenience macros around

<<funopen>> that only use the specified callback.

RETURNS

The return value is an open FILE pointer on success.  On error,

<<NULL>> is returned, and <<errno>> will be set to EINVAL if a

function pointer is missing, ENOMEM if the stream cannot be created,

or EMFILE if too many streams are already open.

PORTABILITY

This function is a newlib extension, copying the prototype from BSD.

It is not portable.  See also the <<fopencookie>> interface from Linux.

Supporting OS subroutines required: <<sbrk>>.

*/

#include <stdio.h>

#include <errno.h>

#include <sys/lock.h>

#include "local.h"

typedef int (*funread)(void *_cookie, char *_buf, int _n);

typedef int (*funwrite)(void *_cookie, const char *_buf, int _n);

#ifdef __LARGE64_FILES

typedef _fpos64_t (*funseek)(void *_cookie, _fpos64_t _off, int _whence);

#else

typedef fpos_t (*funseek)(void *_cookie, fpos_t _off, int _whence);

#endif

typedef int (*funclose)(void *_cookie);

typedef struct funcookie {

  void *cookie;

  funread readfn;

  funwrite writefn;

  funseek seekfn;

  funclose closefn;

} funcookie;

static _READ_WRITE_RETURN_TYPE

_DEFUN(funreader, (ptr, cookie, buf, n),

       struct _reent *ptr _AND

       void *cookie _AND

       char *buf _AND

       int n)

{

  int result;

  funcookie *c = (funcookie *) cookie;

  errno = 0;

  if ((result = c->readfn (c->cookie, buf, n)) < 0 && errno)

    ptr->_errno = errno;

  return result;

}

static _READ_WRITE_RETURN_TYPE

_DEFUN(funwriter, (ptr, cookie, buf, n),

       struct _reent *ptr _AND

       void *cookie _AND

       const char *buf _AND

       int n)

{

  int result;

  funcookie *c = (funcookie *) cookie;

  errno = 0;

  if ((result = c->writefn (c->cookie, buf, n)) < 0 && errno)

    ptr->_errno = errno;

  return result;

}

static _fpos_t

_DEFUN(funseeker, (ptr, cookie, off, whence),

       struct _reent *ptr _AND

       void *cookie _AND

       _fpos_t off _AND

       int whence)

{

  funcookie *c = (funcookie *) cookie;

#ifndef __LARGE64_FILES

  fpos_t result;

  errno = 0;

  if ((result = c->seekfn (c->cookie, (fpos_t) off, whence)) < 0 && errno)

    ptr->_errno = errno;

#else /* __LARGE64_FILES */

  _fpos64_t result;

  errno = 0;

  if ((result = c->seekfn (c->cookie, (_fpos64_t) off, whence)) < 0 && errno)

    ptr->_errno = errno;

  else if ((_fpos_t)result != result)

    {

      ptr->_errno = EOVERFLOW;

      result = -1;

    }

#endif /* __LARGE64_FILES */

  return result;

}

#ifdef __LARGE64_FILES

static _fpos64_t

_DEFUN(funseeker64, (ptr, cookie, off, whence),

       struct _reent *ptr _AND

       void *cookie _AND

       _fpos64_t off _AND

       int whence)

{

  _fpos64_t result;

  funcookie *c = (funcookie *) cookie;

  errno = 0;

  if ((result = c->seekfn (c->cookie, off, whence)) < 0 && errno)

    ptr->_errno = errno;

  return result;

}

#endif /* __LARGE64_FILES */

static int

_DEFUN(funcloser, (ptr, cookie),

       struct _reent *ptr _AND

       void *cookie)

{

  int result = 0;

  funcookie *c = (funcookie *) cookie;

  if (c->closefn)

    {

      errno = 0;

      if ((result = c->closefn (c->cookie)) < 0 && errno)

        ptr->_errno = errno;

    }

  _free_r (ptr, c);

  return result;

}

FILE *

_DEFUN(_funopen_r, (ptr, cookie, readfn, writefn, seekfn, closefn),

       struct _reent *ptr _AND

       const void *cookie _AND

       funread readfn _AND

       funwrite writefn _AND

       funseek seekfn _AND

       funclose closefn)

{

  FILE *fp;

  funcookie *c;

  if (!readfn && !writefn)

    {

      ptr->_errno = EINVAL;

      return NULL;

    }

  if ((fp = __sfp (ptr)) == NULL)

    return NULL;

  if ((c = (funcookie *) _malloc_r (ptr, sizeof *c)) == NULL)

    {

      __sfp_lock_acquire ();

      fp->_flags = 0;            /* release */

#ifndef __SINGLE_THREAD__

      __lock_close_recursive (fp->_lock);

#endif

      __sfp_lock_release ();

      return NULL;

    }

  _flockfile (fp);

  fp->_file = -1;

  c->cookie = (void *) cookie; /* cast away const */

  fp->_cookie = c;

  if (readfn)

    {

      c->readfn = readfn;

      fp->_read = funreader;

      if (writefn)

        {

          fp->_flags = __SRW;

          c->writefn = writefn;

          fp->_write = funwriter;

        }

      else

        {

          fp->_flags = __SRD;

          c->writefn = NULL;

          fp->_write = NULL;

        }

    }

  else

    {

      fp->_flags = __SWR;

      c->writefn = writefn;

      fp->_write = funwriter;

      c->readfn = NULL;

      fp->_read = NULL;

    }

  c->seekfn = seekfn;

  fp->_seek = seekfn ? funseeker : NULL;

#ifdef __LARGE64_FILES

  fp->_seek64 = seekfn ? funseeker64 : NULL;

  fp->_flags |= __SL64;

#endif

  c->closefn = closefn;

  fp->_close = funcloser;

  _funlockfile (fp);

  return fp;

}

#ifndef _REENT_ONLY

FILE *

_DEFUN(funopen, (cookie, readfn, writefn, seekfn, closefn),

       const void *cookie _AND

       funread readfn _AND

       funwrite writefn _AND

       funseek seekfn _AND

       funclose closefn)

{

  return _funopen_r (_REENT, cookie, readfn, writefn, seekfn, closefn);

}

#endif /* !_REENT_ONLY */