nes-proj/backyard/platform/c64/loader/c64-fs-raw.c

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/**
* \addtogroup c64fs
* @{
*/
/**
* \file
* "Raw" C64 file system access.
* \author Adam Dunkels <adam@dunkels.com>
*
* This file provides functions that allow reading data from files
* without updating the file descriptor pointer. The functions are not
* automatically included in the core Contiki code and therefore
* application programs that use tham must manually link with this
* file.
*
*/
/*
* Copyright (c) 2003, Adam Dunkels.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* This file is part of the Contiki desktop environment
*
* $Id: c64-fs-raw.c,v 1.1 2007/05/23 23:11:28 oliverschmidt Exp $
*
*/
#include "c64-fs-raw.h"
#include <string.h>
struct directory_entry {
unsigned char type;
unsigned char track, sect;
unsigned char name[16];
unsigned char reltrack, relsect, relreclen;
unsigned char unused1, unused2, unused3, unused4;
unsigned char tmptrack, tmpsect;
unsigned char blockslo, blockshi;
};
extern unsigned char _c64_fs_dirbuf[256];
extern unsigned char _c64_fs_dirbuftrack, _c64_fs_dirbufsect;
extern unsigned char _c64_fs_filebuf[256];
extern unsigned char _c64_fs_filebuftrack, _c64_fs_filebufsect;
void _c64_fs_readdirbuf(unsigned char track, unsigned char sect);
/*-----------------------------------------------------------------------------------*/
/**
* Read data from a file without updating the file descriptor pointer.
*
* This function reads data from an open file into a buffer than must
* be allocated by the caller, but does not update the file
* description pointer like the c64_fs_read() function does.
*
* \param f A pointer to a file descriptor structure that must have
* been opened with c64_fs_open().
*
* \param buf A pointer to the buffer in which the data should be placed.
*
* \param len The maxiumum amount of bytes to read.
*
* \return The number of bytes that actually was read, or 0 if an end
* of file was encountered.
*
*/
/*-----------------------------------------------------------------------------------*/
int __fastcall__
c64_fs_read_raw(register struct c64_fs_file *f, char *buf, int len)
{
int i;
unsigned char fptr, ftrack, fsect;
/* Check if current block is already in buffer, and if not read it
from disk. */
if(_c64_fs_filebuftrack != f->track ||
_c64_fs_filebufsect != f->sect) {
_c64_fs_filebuftrack = f->track;
_c64_fs_filebufsect = f->sect;
c64_dio_read_block(_c64_fs_filebuftrack,
_c64_fs_filebufsect, _c64_fs_filebuf);
}
if(_c64_fs_filebuf[0] == 0 &&
f->ptr == _c64_fs_filebuf[1]) {
return 0; /* EOF */
}
fptr = f->ptr;
ftrack = f->track;
fsect = f->sect;
for(i = 0; i < len; ++i) {
*buf = _c64_fs_filebuf[fptr];
++fptr;
if(_c64_fs_filebuf[0] == 0) {
if(fptr == _c64_fs_filebuf[1]) {
/* End of file reached, we return the amount of bytes read so
far. */
return i + 1;
}
} else if(fptr == 0) {
/* Read new block into buffer and set buffer state
accordingly. */
_c64_fs_filebuftrack = ftrack = _c64_fs_filebuf[0];
_c64_fs_filebufsect = fsect = _c64_fs_filebuf[1];
fptr = 2;
c64_dio_read_block(_c64_fs_filebuftrack,
_c64_fs_filebufsect, _c64_fs_filebuf);
}
++buf;
}
return i;
}
/*-----------------------------------------------------------------------------------*/
/**
* Move the file descriptior pointer forward in the file.
*
*
* \param f A pointer to a file descriptor structure that must have
* been opened with c64_fs_open().
*
* \param len The number of bytes the pointer should be moved forward.
*
* \return The number of bytes that the pointer actually was moved, or
* 0 if an end of file was encountered.
*/
/*-----------------------------------------------------------------------------------*/
int
c64_fs_read_next(register struct c64_fs_file *f, int len)
{
int i;
/* Check if current block is already in buffer, and if not read it
from disk. */
if(_c64_fs_filebuftrack != f->track ||
_c64_fs_filebufsect != f->sect) {
_c64_fs_filebuftrack = f->track;
_c64_fs_filebufsect = f->sect;
c64_dio_read_block(_c64_fs_filebuftrack,
_c64_fs_filebufsect, _c64_fs_filebuf);
}
if(_c64_fs_filebuf[0] == 0 &&
f->ptr == _c64_fs_filebuf[1]) {
return 0; /* EOF */
}
for(i = 0; i < len; ++i) {
++f->ptr;
if(_c64_fs_filebuf[0] == 0) {
if(f->ptr == _c64_fs_filebuf[1]) {
/* End of file reached, we return the amount of bytes read so
far. */
return i + 1;
}
} else if(f->ptr == 0) {
/* Read new block into buffer and set buffer state
accordingly. */
_c64_fs_filebuftrack = f->track = _c64_fs_filebuf[0];
_c64_fs_filebufsect = f->sect = _c64_fs_filebuf[1];
f->ptr = 2;
c64_dio_read_block(_c64_fs_filebuftrack,
_c64_fs_filebufsect, _c64_fs_filebuf);
}
}
return i;
}
/*-----------------------------------------------------------------------------------*/
/** @} */