libretro/snes9x
1
0
Fork 0
mirror of https://github.com/libretro/snes9x.git synced 2024-11-27 10:30:31 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity
8eca5590e1
snes9x/sdd1emu.cpp
Brandon Wright 5f56cadafb Use a license stub everywhere. 
This points to the full license in the root directory.
2018-11-15 17:31:39 -06:00

334 lines
9.1 KiB
C++
Raw Blame History

/*****************************************************************************\
Snes9x - Portable Super Nintendo Entertainment System (TM) emulator.
This file is licensed under the Snes9x License.
For further information, consult the LICENSE file in the root directory.
\*****************************************************************************/
/* S-DD1 decompressor
*
* Based on code and documentation by Andreas Naive, who deserves a great deal
* of thanks and credit for figuring this out.
*
* Andreas says:
* The author is greatly indebted with The Dumper, without whose help and
* patience providing him with real S-DD1 data the research had never been
* possible. He also wish to note that in the very beggining of his research,
* Neviksti had done some steps in the right direction. By last, the author is
* indirectly indebted to all the people that worked and contributed in the
* S-DD1 issue in the past.
*/
#include "port.h"
#include "sdd1emu.h"
static int valid_bits;
static uint16 in_stream;
static uint8 *in_buf;
static uint8 bit_ctr[8];
static uint8 context_states[32];
static int context_MPS[32];
static int bitplane_type;
static int high_context_bits;
static int low_context_bits;
static int prev_bits[8];
static struct {
uint8 code_size;
uint8 MPS_next;
uint8 LPS_next;
} evolution_table[] = {
/* 0 */ { 0,25,25},
/* 1 */ { 0, 2, 1},
/* 2 */ { 0, 3, 1},
/* 3 */ { 0, 4, 2},
/* 4 */ { 0, 5, 3},
/* 5 */ { 1, 6, 4},
/* 6 */ { 1, 7, 5},
/* 7 */ { 1, 8, 6},
/* 8 */ { 1, 9, 7},
/* 9 */ { 2,10, 8},
/* 10 */ { 2,11, 9},
/* 11 */ { 2,12,10},
/* 12 */ { 2,13,11},
/* 13 */ { 3,14,12},
/* 14 */ { 3,15,13},
/* 15 */ { 3,16,14},
/* 16 */ { 3,17,15},
/* 17 */ { 4,18,16},
/* 18 */ { 4,19,17},
/* 19 */ { 5,20,18},
/* 20 */ { 5,21,19},
/* 21 */ { 6,22,20},
/* 22 */ { 6,23,21},
/* 23 */ { 7,24,22},
/* 24 */ { 7,24,23},
/* 25 */ { 0,26, 1},
/* 26 */ { 1,27, 2},
/* 27 */ { 2,28, 4},
/* 28 */ { 3,29, 8},
/* 29 */ { 4,30,12},
/* 30 */ { 5,31,16},
/* 31 */ { 6,32,18},
/* 32 */ { 7,24,22}
};
static uint8 run_table[128] = {
128, 64, 96, 32, 112, 48, 80, 16, 120, 56, 88, 24, 104, 40, 72,
8, 124, 60, 92, 28, 108, 44, 76, 12, 116, 52, 84, 20, 100, 36,
68, 4, 126, 62, 94, 30, 110, 46, 78, 14, 118, 54, 86, 22, 102,
38, 70, 6, 122, 58, 90, 26, 106, 42, 74, 10, 114, 50, 82, 18,
98, 34, 66, 2, 127, 63, 95, 31, 111, 47, 79, 15, 119, 55, 87,
23, 103, 39, 71, 7, 123, 59, 91, 27, 107, 43, 75, 11, 115, 51,
83, 19, 99, 35, 67, 3, 125, 61, 93, 29, 109, 45, 77, 13, 117,
53, 85, 21, 101, 37, 69, 5, 121, 57, 89, 25, 105, 41, 73, 9,
113, 49, 81, 17, 97, 33, 65, 1
};
static inline uint8 GetCodeword(int bits){
uint8 tmp;
if(!valid_bits){
in_stream|=*(in_buf++);
valid_bits=8;
}
in_stream<<=1;
valid_bits--;
in_stream^=0x8000;
if(in_stream&0x8000) return 0x80+(1<<bits);
tmp=(in_stream>>8) | (0x7f>>bits);
in_stream<<=bits;
valid_bits-=bits;
if(valid_bits<0){
in_stream |= (*(in_buf++))<<(-valid_bits);
valid_bits+=8;
}
return run_table[tmp];
}
static inline uint8 GolombGetBit(int code_size){
if(!bit_ctr[code_size]) bit_ctr[code_size]=GetCodeword(code_size);
bit_ctr[code_size]--;
if(bit_ctr[code_size]==0x80){
bit_ctr[code_size]=0;
return 2; /* secret code for 'last zero'. ones are always last. */
}
return (bit_ctr[code_size]==0)?1:0;
}
static inline uint8 ProbGetBit(uint8 context){
uint8 state=context_states[context];
uint8 bit=GolombGetBit(evolution_table[state].code_size);
if(bit&1){
context_states[context]=evolution_table[state].LPS_next;
if(state<2){
context_MPS[context]^=1;
return context_MPS[context]; /* just inverted, so just return it */
} else{
return context_MPS[context]^1; /* we know bit is 1, so use a constant */
}
} else if(bit){
context_states[context]=evolution_table[state].MPS_next;
/* zero here, zero there, no difference so drop through. */
}
return context_MPS[context]; /* we know bit is 0, so don't bother xoring */
}
static inline uint8 GetBit(uint8 cur_bitplane){
uint8 bit;
bit=ProbGetBit(((cur_bitplane&1)<<4)
| ((prev_bits[cur_bitplane]&high_context_bits)>>5)
| (prev_bits[cur_bitplane]&low_context_bits));
prev_bits[cur_bitplane] <<= 1;
prev_bits[cur_bitplane] |= bit;
return bit;
}
void SDD1_decompress(uint8 *out, uint8 *in, int len){
uint8 bit, i, plane;
uint8 byte1, byte2;
if(len==0) len=0x10000;
bitplane_type=in[0]>>6;
switch(in[0]&0x30){
case 0x00:
high_context_bits=0x01c0;
low_context_bits =0x0001;
break;
case 0x10:
high_context_bits=0x0180;
low_context_bits =0x0001;
break;
case 0x20:
high_context_bits=0x00c0;
low_context_bits =0x0001;
break;
case 0x30:
high_context_bits=0x0180;
low_context_bits =0x0003;
break;
}
in_stream=(in[0]<<11) | (in[1]<<3);
valid_bits=5;
in_buf=in+2;
memset(bit_ctr, 0, sizeof(bit_ctr));
memset(context_states, 0, sizeof(context_states));
memset(context_MPS, 0, sizeof(context_MPS));
memset(prev_bits, 0, sizeof(prev_bits));
switch(bitplane_type){
case 0:
while(1) {
for(byte1=byte2=0, bit=0x80; bit; bit>>=1){
if(GetBit(0)) byte1 |= bit;
if(GetBit(1)) byte2 |= bit;
}
*(out++)=byte1;
if(!--len) return;
*(out++)=byte2;
if(!--len) return;
}
break;
case 1:
i=plane=0;
while(1) {
for(byte1=byte2=0, bit=0x80; bit; bit>>=1){
if(GetBit(plane)) byte1 |= bit;
if(GetBit(plane+1)) byte2 |= bit;
}
*(out++)=byte1;
if(!--len) return;
*(out++)=byte2;
if(!--len) return;
if(!(i+=32)) plane = (plane+2)&7;
}
break;
case 2:
i=plane=0;
while(1) {
for(byte1=byte2=0, bit=0x80; bit; bit>>=1){
if(GetBit(plane)) byte1 |= bit;
if(GetBit(plane+1)) byte2 |= bit;
}
*(out++)=byte1;
if(!--len) return;
*(out++)=byte2;
if(!--len) return;
if(!(i+=32)) plane ^= 2;
}
break;
case 3:
do {
for(byte1=plane=0, bit=1; bit; bit<<=1, plane++){
if(GetBit(plane)) byte1 |= bit;
}
*(out++)=byte1;
} while(--len);
break;
}
}
#if 0
static uint8 cur_plane;
static uint8 num_bits;
static uint8 next_byte;
void SDD1_init(uint8 *in){
bitplane_type=in[0]>>6;
switch(in[0]&0x30){
case 0x00:
high_context_bits=0x01c0;
low_context_bits =0x0001;
break;
case 0x10:
high_context_bits=0x0180;
low_context_bits =0x0001;
break;
case 0x20:
high_context_bits=0x00c0;
low_context_bits =0x0001;
break;
case 0x30:
high_context_bits=0x0180;
low_context_bits =0x0003;
break;
}
in_stream=(in[0]<<11) | (in[1]<<3);
valid_bits=5;
in_buf=in+2;
memset(bit_ctr, 0, sizeof(bit_ctr));
memset(context_states, 0, sizeof(context_states));
memset(context_MPS, 0, sizeof(context_MPS));
memset(prev_bits, 0, sizeof(prev_bits));
cur_plane=0;
num_bits=0;
}
uint8 SDD1_get_byte(void){
uint8 bit;
uint8 byte=0;
switch(bitplane_type){
case 0:
num_bits+=16;
if(num_bits&16){
next_byte=0;
for(bit=0x80; bit; bit>>=1){
if(GetBit(0)) byte |= bit;
if(GetBit(1)) next_byte |= bit;
}
return byte;
} else {
return next_byte;
}
case 1:
num_bits+=16;
if(num_bits&16){
next_byte=0;
for(bit=0x80; bit; bit>>=1){
if(GetBit(cur_plane)) byte |= bit;
if(GetBit(cur_plane+1)) next_byte |= bit;
}
return byte;
} else {
if(!num_bits) cur_plane = (cur_plane+2)&7;
return next_byte;
}
case 2:
num_bits+=16;
if(num_bits&16){
next_byte=0;
for(bit=0x80; bit; bit>>=1){
if(GetBit(cur_plane)) byte |= bit;
if(GetBit(cur_plane+1)) next_byte |= bit;
}
return byte;
} else {
if(!num_bits) cur_plane ^= 2;
return next_byte;
}
case 3:
for(cur_plane=0, bit=1; bit; bit<<=1, cur_plane++){
if(GetBit(cur_plane)) byte |= bit;
}
return byte;
default:
/* should never happen */
return 0;
}
}
#endif
Reference in New Issue View Git Blame Copy Permalink