/*
   * Cryptographic API.
   *
   * Cipher operations.
   *
   * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
   *               2002 Adam J. Richter <adam@yggdrasil.com>
   *               2004 Jean-Luc Cooke <jlcooke@certainkey.com>
   *
   * 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 2 of the License, or (at your option)
   * any later version.
   *
   */

  
  #include <crypto/scatterwalk.h>

  #include <linux/kernel.h>
  #include <linux/mm.h>

  #include <linux/module.h>

  #include <linux/pagemap.h>
  #include <linux/highmem.h>

  #include <linux/scatterlist.h>

  static inline void memcpy_dir(void *buf, void *sgdata, size_t nbytes, int out)

  {

  	void *src = out ? buf : sgdata;
  	void *dst = out ? sgdata : buf;
  
  	memcpy(dst, src, nbytes);

  }
  
  void scatterwalk_start(struct scatter_walk *walk, struct scatterlist *sg)
  {

  	walk->sg = sg;

  	BUG_ON(!sg->length);

  	walk->offset = sg->offset;
  }

  EXPORT_SYMBOL_GPL(scatterwalk_start);

  void *scatterwalk_map(struct scatter_walk *walk, int out)

  {

  	return crypto_kmap(scatterwalk_page(walk), out) +
  	       offset_in_page(walk->offset);

  }

  EXPORT_SYMBOL_GPL(scatterwalk_map);

  
  static void scatterwalk_pagedone(struct scatter_walk *walk, int out,
  				 unsigned int more)
  {

  	if (out) {
  		struct page *page;

  		page = sg_page(walk->sg) + ((walk->offset - 1) >> PAGE_SHIFT);

  		if (!PageSlab(page))
  			flush_dcache_page(page);

  	}

  
  	if (more) {

  		walk->offset += PAGE_SIZE - 1;
  		walk->offset &= PAGE_MASK;
  		if (walk->offset >= walk->sg->offset + walk->sg->length)

  			scatterwalk_start(walk, scatterwalk_sg_next(walk->sg));

  	}
  }
  
  void scatterwalk_done(struct scatter_walk *walk, int out, int more)
  {

  	if (!(scatterwalk_pagelen(walk) & (PAGE_SIZE - 1)) || !more)

  		scatterwalk_pagedone(walk, out, more);
  }

  EXPORT_SYMBOL_GPL(scatterwalk_done);

  void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
  			    size_t nbytes, int out)

  {

  	for (;;) {
  		unsigned int len_this_page = scatterwalk_pagelen(walk);
  		u8 *vaddr;
  
  		if (len_this_page > nbytes)
  			len_this_page = nbytes;
  
  		vaddr = scatterwalk_map(walk, out);
  		memcpy_dir(buf, vaddr, len_this_page, out);
  		scatterwalk_unmap(vaddr, out);

  		scatterwalk_advance(walk, len_this_page);

  		if (nbytes == len_this_page)
  			break;
  
  		buf += len_this_page;
  		nbytes -= len_this_page;

  		scatterwalk_pagedone(walk, out, 1);

  	}

  }

  EXPORT_SYMBOL_GPL(scatterwalk_copychunks);

  
  void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
  			      unsigned int start, unsigned int nbytes, int out)
  {
  	struct scatter_walk walk;
  	unsigned int offset = 0;

  	if (!nbytes)
  		return;

  	for (;;) {
  		scatterwalk_start(&walk, sg);
  
  		if (start < offset + sg->length)
  			break;
  
  		offset += sg->length;

  		sg = scatterwalk_sg_next(sg);

  	}
  
  	scatterwalk_advance(&walk, start - offset);
  	scatterwalk_copychunks(buf, &walk, nbytes, out);
  	scatterwalk_done(&walk, out, 0);
  }
  EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);