/* fmemopen implementation.

   Copyright (C) 2015-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C 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

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

/* fmemopen() from 2.22 and forward works as defined by POSIX.  It also

   provides an older symbol, version 2.2.5, that behaves different regarding

   SEEK_END (libio/oldfmemopen.c).  */

#include <errno.h>

#include <stdio.h>

#include <stdlib.h>

#include <stdint.h>

#include <string.h>

#include <sys/types.h>

#include "libioP.h"

typedef struct fmemopen_cookie_struct fmemopen_cookie_t;

struct fmemopen_cookie_struct

{

  char        *buffer;   /* memory buffer.  */

  int         mybuffer;  /* allocated my buffer?  */

  int         append;    /* buffer open for append?  */

  size_t      size;      /* buffer length in bytes.  */

  off64_t     pos;       /* current position at the buffer.  */

  size_t      maxpos;    /* max position in buffer.  */

};

static ssize_t

fmemopen_read (void *cookie, char *b, size_t s)

{

  fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;

  if (c->pos + s > c->maxpos)

    {

      s = c->maxpos - c->pos;

      if ((size_t) c->pos > c->maxpos)

	s = 0;

    }

  memcpy (b, &(c->buffer[c->pos]), s);

  c->pos += s;

  return s;

}

static ssize_t

fmemopen_write (void *cookie, const char *b, size_t s)

{

  fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;;

  off64_t pos = c->append ? c->maxpos : c->pos;

  int addnullc = (s == 0 || b[s - 1] != '\0');

  if (pos + s > c->size)

    {

      if ((size_t) (c->pos + addnullc) >= c->size)

	{

	  __set_errno (ENOSPC);

	  return 0;

	}

      s = c->size - pos;

    }

  memcpy (&(c->buffer[pos]), b, s);

  c->pos = pos + s;

  if ((size_t) c->pos > c->maxpos)

    {

      c->maxpos = c->pos;

      if (c->maxpos < c->size && addnullc)

	c->buffer[c->maxpos] = '\0';

      /* A null byte is written in a stream open for update iff it fits.  */

      else if (c->append == 0 && addnullc != 0)

	c->buffer[c->size-1] = '\0';

    }

  return s;

}

static int

fmemopen_seek (void *cookie, off64_t *p, int w)

{

  off64_t np;

  fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;

  switch (w)

    {

    case SEEK_SET:

      np = *p;

      break;

    case SEEK_CUR:

      np = c->pos + *p;

      break;

    case SEEK_END:

      np = c->maxpos + *p;

      break;

    default:

      return -1;

    }

  if (np < 0 || (size_t) np > c->size)

    {

      __set_errno (EINVAL);

      return -1;

    }

  *p = c->pos = np;

  return 0;

}

static int

fmemopen_close (void *cookie)

{

  fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;

  if (c->mybuffer)

    free (c->buffer);

  free (c);

  return 0;

}

FILE *

__fmemopen (void *buf, size_t len, const char *mode)

{

  cookie_io_functions_t iof;

  fmemopen_cookie_t *c;

  FILE *result;

  c = (fmemopen_cookie_t *) calloc (sizeof (fmemopen_cookie_t), 1);

  if (c == NULL)

    return NULL;

  c->mybuffer = (buf == NULL);

  if (c->mybuffer)

    {

      c->buffer = (char *) malloc (len);

      if (c->buffer == NULL)

	{

	  free (c);

	  return NULL;

	}

      c->buffer[0] = '\0';

    }

  else

    {

      if (__glibc_unlikely ((uintptr_t) len > -(uintptr_t) buf))

	{

	  free (c);

	  __set_errno (EINVAL);

	  return NULL;

	}

      c->buffer = buf;

      /* POSIX states that w+ mode should truncate the buffer.  */

      if (mode[0] == 'w' && mode[1] == '+')

	c->buffer[0] = '\0';

      if (mode[0] == 'a')

        c->maxpos = strnlen (c->buffer, len);

    }

  /* Mode   |  starting position (cookie::pos) |          size (cookie::size)

     ------ |----------------------------------|-----------------------------

     read   |          beginning of the buffer |                size argument

     write  |          beginning of the buffer |                         zero

     append |    first null or size buffer + 1 |  first null or size argument

   */

  c->size = len;

  if (mode[0] == 'r')

    c->maxpos = len;

  c->append = mode[0] == 'a';

  if (c->append)

    c->pos = c->maxpos;

  else

    c->pos = 0;

  iof.read = fmemopen_read;

  iof.write = fmemopen_write;

  iof.seek = fmemopen_seek;

  iof.close = fmemopen_close;

  result = _IO_fopencookie (c, mode, iof);

  if (__glibc_unlikely (result == NULL))

    {

      if (c->mybuffer)

	free (c->buffer);

      free (c);

    }

  return result;

}

libc_hidden_def (__fmemopen)

versioned_symbol (libc, __fmemopen, fmemopen, GLIBC_2_22);