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/*
* 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)
{
return kmap_atomic(scatterwalk_page(walk)) +
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);
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);
}
}
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);
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