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