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/*
3dsspec - Nintendo 3DS Sinclair Spectrum 48K emulator.
Copyright (C) 2021 Ian Cowburn
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.
This program 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 this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
$Id: snap.c 4 2006-09-15 00:30:18Z ianc $
*/
#include <stdlib.h>
#include <stdio.h>
#include "snap.h"
#include "debug.h"
/* ---------------------------------------- MACROS
*/
#ifndef TRUE
#define TRUE 1
#endif
#ifndef FALSE
#define FALSE 0
#endif
#define ROMLEN 0x4000
/* ---------------------------------------- PRIVATE DATA
*/
static FILE *tapfile;
/* ---------------------------------------- PRIVATE FUNCTIONS
*/
static Z80Byte GetTAPByte(void)
{
int ret=0;
if (tapfile)
{
ret = fgetc(tapfile);
if (ret == EOF)
{
ret = 0;
fclose(tapfile);
tapfile = NULL;
}
}
return (Z80Byte)ret;
}
static Z80Word GetTAPLSBWord(void)
{
int c1,c2;
c1=GetTAPByte();
c2=GetTAPByte();
return (Z80Word)(c1+(c2<<8));
}
/* ---------------------------------------- INTERFACES
*/
void TAPOpenTape(const char *path)
{
tapfile = fopen(path, "rb");
}
void TAPCloseTape(void)
{
if (tapfile)
{
fclose(tapfile);
tapfile = NULL;
}
}
int TAPLoad(Z80Byte id, Z80Word *addr, Z80Word *len, SNAP_Poke poke)
{
Z80Word blen;
Z80Byte type,b,csum,tape_csum;
b = 0;
blen = GetTAPLSBWord();
type = GetTAPByte();
csum = type;
if (!tapfile)
{
SPEC_DEBUG("Tape not open, returning FALSE\n");
return FALSE;
}
SPEC_DEBUG("Read block. len=%u type=%u\n", (unsigned)blen, (unsigned)type);
SPEC_DEBUG("Requested block len=%u type=%u addr=%u\n",
(unsigned)*len, (unsigned)id, (unsigned)*addr);
/* Have we found the requested block?
*/
if (id == type)
{
/* Knock of block type
*/
blen--;
while(blen && *len)
{
b = GetTAPByte();
if (blen > 1)
{
csum ^= b;
poke(*addr,b);
}
(*addr)++;
(*len)--;
blen--;
}
SPEC_DEBUG("Finished block. Remaining blen=%u len=%u\n",
(unsigned)blen, (unsigned)*len);
/* Get the checksum. If the length was correct there should be just
byte left in blen, but decrement it in a loop to skip to the end.
*/
if (blen)
{
while(blen--)
{
tape_csum=GetTAPByte();
if (blen)
{
csum ^= tape_csum;
}
}
}
else
{
tape_csum=b;
}
/* Check the checksum
*/
if (csum == tape_csum)
{
SPEC_DEBUG("Checksum %u (calc) and %u (tape) match\n",
(unsigned)csum, (unsigned)tape_csum);
return TRUE;
}
else
{
SPEC_DEBUG("Checksum %u (calc) and %u (tape) DON'T match\n",
(unsigned)csum, (unsigned)tape_csum);
return FALSE;
}
}
else
{
/* If it's the wrong type, skip it
*/
while(blen--)
{
GetTAPByte();
}
return FALSE;
}
}
/* END OF FILE */
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