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#include "../copyright"
/* 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 <string.h>
#include "port.h"
#include "sdd1emu.h"
static int valid_bits;
static uint16_t in_stream;
static uint8_t* in_buf;
static uint8_t bit_ctr[8];
static uint8_t 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_t code_size;
uint8_t MPS_next;
uint8_t 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_t 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_t GetCodeword(int bits)
{
uint8_t 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_t 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_t ProbGetBit(uint8_t context)
{
uint8_t state = context_states[context];
uint8_t 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_t GetBit(uint8_t cur_bitplane)
{
uint8_t 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_t* out, uint8_t* in, int len)
{
uint8_t bit, i, plane;
uint8_t 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;
}
}
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