/*
   * Copyright (c) 2013, 2014
   * Phillip Lougher <phillip@squashfs.org.uk>
   *
   * This work is licensed under the terms of the GNU GPL, version 2. See
   * the COPYING file in the top-level directory.
   */
  
  #include <linux/buffer_head.h>
  #include <linux/mutex.h>
  #include <linux/slab.h>
  #include <linux/vmalloc.h>
  #include <linux/lz4.h>
  
  #include "squashfs_fs.h"
  #include "squashfs_fs_sb.h"
  #include "squashfs.h"
  #include "decompressor.h"
  #include "page_actor.h"
  
  #define LZ4_LEGACY	1
  
  struct lz4_comp_opts {
  	__le32 version;
  	__le32 flags;
  };
  
  struct squashfs_lz4 {
  	void *input;
  	void *output;
  };
  
  
  static void *lz4_comp_opts(struct squashfs_sb_info *msblk,
  	void *buff, int len)
  {
  	struct lz4_comp_opts *comp_opts = buff;
  
  	/* LZ4 compressed filesystems always have compression options */
  	if (comp_opts == NULL || len < sizeof(*comp_opts))
  		return ERR_PTR(-EIO);
  
  	if (le32_to_cpu(comp_opts->version) != LZ4_LEGACY) {
  		/* LZ4 format currently used by the kernel is the 'legacy'
  		 * format */
  		ERROR("Unknown LZ4 version
  ");
  		return ERR_PTR(-EINVAL);
  	}
  
  	return NULL;
  }
  
  
  static void *lz4_init(struct squashfs_sb_info *msblk, void *buff)
  {
  	int block_size = max_t(int, msblk->block_size, SQUASHFS_METADATA_SIZE);
  	struct squashfs_lz4 *stream;
  
  	stream = kzalloc(sizeof(*stream), GFP_KERNEL);
  	if (stream == NULL)
  		goto failed;
  	stream->input = vmalloc(block_size);
  	if (stream->input == NULL)
  		goto failed2;
  	stream->output = vmalloc(block_size);
  	if (stream->output == NULL)
  		goto failed3;
  
  	return stream;
  
  failed3:
  	vfree(stream->input);
  failed2:
  	kfree(stream);
  failed:
  	ERROR("Failed to initialise LZ4 decompressor
  ");
  	return ERR_PTR(-ENOMEM);
  }
  
  
  static void lz4_free(void *strm)
  {
  	struct squashfs_lz4 *stream = strm;
  
  	if (stream) {
  		vfree(stream->input);
  		vfree(stream->output);
  	}
  	kfree(stream);
  }
  
  
  static int lz4_uncompress(struct squashfs_sb_info *msblk, void *strm,
  	struct buffer_head **bh, int b, int offset, int length,
  	struct squashfs_page_actor *output)
  {
  	struct squashfs_lz4 *stream = strm;
  	void *buff = stream->input, *data;
  	int avail, i, bytes = length, res;

  
  	for (i = 0; i < b; i++) {
  		avail = min(bytes, msblk->devblksize - offset);
  		memcpy(buff, bh[i]->b_data + offset, avail);
  		buff += avail;
  		bytes -= avail;
  		offset = 0;
  		put_bh(bh[i]);
  	}

  	res = LZ4_decompress_safe(stream->input, stream->output,
  		length, output->length);
  
  	if (res < 0)

  		return -EIO;

  	bytes = res;

  	data = squashfs_first_page(output);
  	buff = stream->output;
  	while (data) {

  		if (bytes <= PAGE_SIZE) {

  			memcpy(data, buff, bytes);
  			break;
  		}

  		memcpy(data, buff, PAGE_SIZE);
  		buff += PAGE_SIZE;
  		bytes -= PAGE_SIZE;

  		data = squashfs_next_page(output);
  	}
  	squashfs_finish_page(output);

  	return res;

  }
  
  const struct squashfs_decompressor squashfs_lz4_comp_ops = {
  	.init = lz4_init,
  	.comp_opts = lz4_comp_opts,
  	.free = lz4_free,
  	.decompress = lz4_uncompress,
  	.id = LZ4_COMPRESSION,
  	.name = "lz4",
  	.supported = 1
  };