linux/lib/xz/xz_dec_test.c

/*
 * XZ decoder tester
 *
 * Author: Lasse Collin <[email protected]>
 *
 * This file has been put into the public domain.
 * You can do whatever you want with this file.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/crc32.h>
#include <linux/xz.h>

/* Maximum supported dictionary size */
#define DICT_MAX …

/* Device name to pass to register_chrdev(). */
#define DEVICE_NAME …

/* Dynamically allocated device major number */
static int device_major;

/*
 * We reuse the same decoder state, and thus can decode only one
 * file at a time.
 */
static bool device_is_open;

/* XZ decoder state */
static struct xz_dec *state;

/*
 * Return value of xz_dec_run(). We need to avoid calling xz_dec_run() after
 * it has returned XZ_STREAM_END, so we make this static.
 */
static enum xz_ret ret;

/*
 * Input and output buffers. The input buffer is used as a temporary safe
 * place for the data coming from the userspace.
 */
static uint8_t buffer_in[1024];
static uint8_t buffer_out[1024];

/*
 * Structure to pass the input and output buffers to the XZ decoder.
 * A few of the fields are never modified so we initialize them here.
 */
static struct xz_buf buffers = …;

/*
 * CRC32 of uncompressed data. This is used to give the user a simple way
 * to check that the decoder produces correct output.
 */
static uint32_t crc;

static int xz_dec_test_open(struct inode *i, struct file *f)
{ … }

static int xz_dec_test_release(struct inode *i, struct file *f)
{ … }

/*
 * Decode the data given to us from the userspace. CRC32 of the uncompressed
 * data is calculated and is printed at the end of successful decoding. The
 * uncompressed data isn't stored anywhere for further use.
 *
 * The .xz file must have exactly one Stream and no Stream Padding. The data
 * after the first Stream is considered to be garbage.
 */
static ssize_t xz_dec_test_write(struct file *file, const char __user *buf,
				 size_t size, loff_t *pos)
{ … }

/* Allocate the XZ decoder state and register the character device. */
static int __init xz_dec_test_init(void)
{ … }

static void __exit xz_dec_test_exit(void)
{ … }

module_init(…) …;
module_exit(xz_dec_test_exit);

MODULE_DESCRIPTION(…) …;
MODULE_VERSION(…) …;
MODULE_AUTHOR(…) …;

/*
 * This code is in the public domain, but in Linux it's simplest to just
 * say it's GPL and consider the authors as the copyright holders.
 */
MODULE_LICENSE(…) …;