// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   * 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>

   */

  
  #include <crypto/scatterwalk.h>

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

  #include <linux/module.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_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;

  		if (out != 2) {
  			vaddr = scatterwalk_map(walk);
  			memcpy_dir(buf, vaddr, len_this_page, out);
  			scatterwalk_unmap(vaddr);
  		}

  		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, 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;

  	struct scatterlist tmp[2];

  	if (!nbytes)
  		return;

  	sg = scatterwalk_ffwd(tmp, sg, start);

  	scatterwalk_start(&walk, sg);

  	scatterwalk_copychunks(buf, &walk, nbytes, out);
  	scatterwalk_done(&walk, out, 0);
  }
  EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);

  struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
  				     struct scatterlist *src,
  				     unsigned int len)
  {
  	for (;;) {
  		if (!len)
  			return src;
  
  		if (src->length > len)
  			break;
  
  		len -= src->length;
  		src = sg_next(src);
  	}

  	sg_init_table(dst, 2);

  	sg_set_page(dst, sg_page(src), src->length - len, src->offset + len);

  	scatterwalk_crypto_chain(dst, sg_next(src), 2);

  
  	return dst;
  }
  EXPORT_SYMBOL_GPL(scatterwalk_ffwd);