/* read-file.c -- read file contents into a string

   Copyright (C) 2006, 2009-2016 Free Software Foundation, Inc.

   Written by Simon Josefsson and Bruno Haible.

   This program 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, or (at your option)

   any later version.

   This program 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 this program; if not, see <http://www.gnu.org/licenses/>.  */

#include <config.h>

#include "read-file.h"

/* Get fstat.  */

#include <sys/stat.h>

/* Get ftello.  */

#include <stdio.h>

/* Get SIZE_MAX.  */

#include <stdint.h>

/* Get malloc, realloc, free. */

#include <stdlib.h>

/* Get errno. */

#include <errno.h>

/* Read a STREAM and return a newly allocated string with the content,

   and set *LENGTH to the length of the string.  The string is

   zero-terminated, but the terminating zero byte is not counted in

   *LENGTH.  On errors, *LENGTH is undefined, errno preserves the

   values set by system functions (if any), and NULL is returned.  */

char *

fread_file (FILE *stream, size_t *length)

{

  char *buf = NULL;

  size_t alloc = BUFSIZ;

  /* For a regular file, allocate a buffer that has exactly the right

     size.  This avoids the need to do dynamic reallocations later.  */

  {

    struct stat st;

    if (fstat (fileno (stream), &st) >= 0 && S_ISREG (st.st_mode))

      {

        off_t pos = ftello (stream);

        if (pos >= 0 && pos < st.st_size)

          {

            off_t alloc_off = st.st_size - pos;

            /* '1' below, accounts for the trailing NUL.  */

            if (SIZE_MAX - 1 < alloc_off)

              {

                errno = ENOMEM;

                return NULL;

              }

            alloc = alloc_off + 1;

          }

      }

  }

  if (!(buf = malloc (alloc)))

    return NULL; /* errno is ENOMEM.  */

  {

    size_t size = 0; /* number of bytes read so far */

    int save_errno;

    for (;;)

      {

        /* This reads 1 more than the size of a regular file

           so that we get eof immediately.  */

        size_t requested = alloc - size;

        size_t count = fread (buf + size, 1, requested, stream);

        size += count;

        if (count != requested)

          {

            save_errno = errno;

            if (ferror (stream))

              break;

            /* Shrink the allocated memory if possible.  */

            if (size < alloc - 1)

              {

                char *smaller_buf = realloc (buf, size + 1);

                if (smaller_buf != NULL)

                  buf = smaller_buf;

              }

            buf[size] = '\0';

            *length = size;

            return buf;

          }

        {

          char *new_buf;

          if (alloc == SIZE_MAX)

            {

              save_errno = ENOMEM;

              break;

            }

          if (alloc < SIZE_MAX - alloc / 2)

            alloc = alloc + alloc / 2;

          else

            alloc = SIZE_MAX;

          if (!(new_buf = realloc (buf, alloc)))

            {

              save_errno = errno;

              break;

            }

          buf = new_buf;

        }

      }

    free (buf);

    errno = save_errno;

    return NULL;

  }

}

static char *

internal_read_file (const char *filename, size_t *length, const char *mode)

{

  FILE *stream = fopen (filename, mode);

  char *out;

  int save_errno;

  if (!stream)

    return NULL;

  out = fread_file (stream, length);

  save_errno = errno;

  if (fclose (stream) != 0)

    {

      if (out)

        {

          save_errno = errno;

          free (out);

        }

      errno = save_errno;

      return NULL;

    }

  return out;

}

/* Open and read the contents of FILENAME, and return a newly

   allocated string with the content, and set *LENGTH to the length of

   the string.  The string is zero-terminated, but the terminating

   zero byte is not counted in *LENGTH.  On errors, *LENGTH is

   undefined, errno preserves the values set by system functions (if

   any), and NULL is returned.  */

char *

read_file (const char *filename, size_t *length)

{

  return internal_read_file (filename, length, "r");

}

/* Open (on non-POSIX systems, in binary mode) and read the contents

   of FILENAME, and return a newly allocated string with the content,

   and set LENGTH to the length of the string.  The string is

   zero-terminated, but the terminating zero byte is not counted in

   the LENGTH variable.  On errors, *LENGTH is undefined, errno

   preserves the values set by system functions (if any), and NULL is

   returned.  */

char *

read_binary_file (const char *filename, size_t *length)

{

  return internal_read_file (filename, length, "rb");

}