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/* Copyright 2021 Alain Knaff.
* This file is part of mtools.
*
* Mtools 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 3 of the License, or
* (at your option) any later version.
*
* Mtools is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Mtools. If not, see <http://www.gnu.org/licenses/>.
*
* filter to support byte-swapped filesystems
*/
#include "sysincludes.h"
#include "msdos.h"
#include "mtools.h"
#include "swap.h"
typedef struct Swap_t {
struct Stream_t head;
} Swap_t;
static void swap_buffer(char *buf, size_t len)
{
unsigned int i;
for (i=0; i<len; i+=2) {
char temp = buf[i];
buf[i] = buf[i+1];
buf[i+1] = temp;
}
}
static ssize_t swap_pread(Stream_t *Stream, char *buf,
mt_off_t where, size_t len)
{
DeclareThis(Swap_t);
ssize_t result = PREADS(This->head.Next, buf, where, len);
if(result < 0)
return result;
swap_buffer( buf, (size_t) result);
return result;
}
static ssize_t swap_pwrite(Stream_t *Stream, char *buf,
mt_off_t where, size_t len)
{
DeclareThis(Swap_t);
ssize_t result;
char *swapping = malloc( len );
memcpy( swapping, buf, len );
swap_buffer( swapping, len );
result = PWRITES(This->head.Next, swapping, where, len);
free(swapping);
return result;
}
static Class_t SwapClass = {
0,
0,
swap_pread,
swap_pwrite,
0, /* flush */
0, /* free */
set_geom_pass_through, /* set_geom */
0, /* get_data */
0, /* pre-allocate */
get_dosConvert_pass_through, /* dos convert */
0, /* discard */
};
Stream_t *OpenSwap(Stream_t *Next) {
Swap_t *This;
This = New(Swap_t);
if (!This){
printOom();
return 0;
}
memset((void*)This, 0, sizeof(Swap_t));
init_head(&This->head, &SwapClass, Next);
return &This->head;
}
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