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read_file: introduce read_file_2 

read_file has some limitations:

- It is not possible to check the error code since read_file returns
  NULL for failure
- It is not possible to limit the buffer size to sensible limits.

This patch introduces read_file_2 which doesn't have these limitations.
read_file becomes a wrapper around read_file_2.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
This commit is contained in:
Sascha Hauer 2014-07-30 10:54:16 +02:00
parent 3cfa4bc00c
commit 28ce918d96
2 changed files with 89 additions and 43 deletions
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3
include/libfile.h
View File

@ -8,6 +8,9 @@ char *read_file_line(const char *fmt, ...);
void *read_file(const char *filename, size_t *size);
int read_file_2(const char *filename, size_t *size, void **outbuf,
loff_t max_size);
int write_file(const char *filename, void *buf, size_t size);
int copy_file(const char *src, const char *dst, int verbose);

129
lib/libfile.c
View File

@ -115,6 +115,88 @@ out:
}
EXPORT_SYMBOL_GPL(read_file_line);
/**
* read_file_2 - read a file to an allocated buffer
* @filename: The filename to read
* @size: After successful return contains the size of the file
* @outbuf: contains a pointer to the file data after successful return
* @max_size: The maximum size to read. Use FILESIZE_MAX for reading files
* of any size.
*
* This function reads a file to an allocated buffer. At maximum @max_size
* bytes are read. The actual read size is returned in @size. -EFBIG is
* returned if the file is bigger than @max_size, but the buffer is read
* anyway up to @max_size in this case. Free the buffer with free() after
* usage.
*
* Return: 0 for success, or negative error code. -EFBIG is returned
* when the file has been bigger than max_size.
*/
int read_file_2(const char *filename, size_t *size, void **outbuf,
loff_t max_size)
{
int fd;
struct stat s;
void *buf = NULL;
const char *tmpfile = "/.read_file_tmp";
int ret;
loff_t read_size;
again:
ret = stat(filename, &s);
if (ret)
return ret;
if (max_size == FILESIZE_MAX)
read_size = s.st_size;
else
read_size = max_size;
if (read_size == FILESIZE_MAX) {
ret = copy_file(filename, tmpfile, 0);
if (ret)
return ret;
filename = tmpfile;
goto again;
}
buf = xzalloc(read_size + 1);
fd = open(filename, O_RDONLY);
if (fd < 0)
goto err_out;
ret = read_full(fd, buf, read_size);
if (ret < 0)
goto err_out1;
close(fd);
if (size)
*size = ret;
if (filename == tmpfile)
unlink(tmpfile);
*outbuf = buf;
if (read_size < s.st_size)
return -EFBIG;
else
return 0;
err_out1:
close(fd);
err_out:
free(buf);
if (filename == tmpfile)
unlink(tmpfile);
return ret;
}
EXPORT_SYMBOL(read_file_2);
/**
* read_file - read a file to an allocated buffer
* @filename: The filename to read
@ -128,51 +210,12 @@ EXPORT_SYMBOL_GPL(read_file_line);
*/
void *read_file(const char *filename, size_t *size)
{
int fd;
struct stat s;
void *buf = NULL;
const char *tmpfile = "/.read_file_tmp";
int ret;
void *buf;
again:
if (stat(filename, &s))
return NULL;
if (s.st_size == FILESIZE_MAX) {
ret = copy_file(filename, tmpfile, 0);
if (ret)
return NULL;
filename = tmpfile;
goto again;
}
buf = xzalloc(s.st_size + 1);
fd = open(filename, O_RDONLY);
if (fd < 0)
goto err_out;
ret = read_full(fd, buf, s.st_size);
if (ret < 0)
goto err_out1;
close(fd);
if (size)
*size = s.st_size;
if (filename == tmpfile)
unlink(tmpfile);
return buf;
err_out1:
close(fd);
err_out:
free(buf);
if (filename == tmpfile)
unlink(tmpfile);
ret = read_file_2(filename, size, &buf, FILESIZE_MAX);
if (!ret)
return buf;
return NULL;
}