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/* read-file.c -- read file contents into a string
Copyright (C) 2006, 2009-2020 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 General Public License as published by
the Free Software Foundation; either version 3, 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
#include "read-file.h"
/* Get fstat. */
#include <sys/stat.h>
/* Get ftello. */
#include <stdio.h>
/* Get PTRDIFF_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 (PTRDIFF_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 == PTRDIFF_MAX)
{
save_errno = ENOMEM;
break;
}
if (alloc < PTRDIFF_MAX - alloc / 2)
alloc = alloc + alloc / 2;
else
alloc = PTRDIFF_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");
}
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