/* read-file.c -- read file contents into a string
- Copyright (C) 2006, 2009 Free Software Foundation, Inc.
+ Copyright (C) 2006, 2009-2011 Free Software Foundation, Inc.
Written by Simon Josefsson and Bruno Haible.
This program is free software; you can redistribute it and/or modify
#include "read-file.h"
-/* Get realloc, free. */
+/* 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. */
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. */
+ values set by system functions (if any), and NULL is returned. */
char *
-fread_file (FILE * stream, size_t * length)
+fread_file (FILE *stream, size_t *length)
{
char *buf = NULL;
- size_t alloc = 0;
- size_t size = 0;
- int save_errno;
+ 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;
- for (;;)
- {
- size_t count;
- size_t requested;
+ /* 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;
+ }
- if (size + BUFSIZ + 1 > alloc)
{
char *new_buf;
- alloc += alloc / 2;
- if (alloc < size + BUFSIZ + 1)
- alloc = size + BUFSIZ + 1;
+ if (alloc == SIZE_MAX)
+ {
+ save_errno = ENOMEM;
+ break;
+ }
+
+ if (alloc < SIZE_MAX - alloc / 2)
+ alloc = alloc + alloc / 2;
+ else
+ alloc = SIZE_MAX;
- new_buf = realloc (buf, alloc);
- if (!new_buf)
+ if (!(new_buf = realloc (buf, alloc)))
{
save_errno = errno;
break;
buf = new_buf;
}
+ }
- requested = alloc - size - 1;
- count = fread (buf + size, 1, requested, stream);
- size += count;
-
- if (count != requested)
- {
- save_errno = errno;
- if (ferror (stream))
- break;
- buf[size] = '\0';
- *length = size;
- return buf;
- }
- }
-
- free (buf);
- errno = save_errno;
- return NULL;
+ free (buf);
+ errno = save_errno;
+ return NULL;
+ }
}
static char *
-internal_read_file (const char *filename, size_t * length, const char *mode)
+internal_read_file (const char *filename, size_t *length, const char *mode)
{
FILE *stream = fopen (filename, mode);
char *out;
undefined, errno preserves the values set by system functions (if
any), and NULL is returned. */
char *
-read_file (const char *filename, size_t * length)
+read_file (const char *filename, size_t *length)
{
return internal_read_file (filename, length, "r");
}
preserves the values set by system functions (if any), and NULL is
returned. */
char *
-read_binary_file (const char *filename, size_t * length)
+read_binary_file (const char *filename, size_t *length)
{
return internal_read_file (filename, length, "rb");
}