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/*
* FFv1 codec
*
* Copyright (c) 2024 Lynne <dev@lynne.ee>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
struct RangeCoder {
uint64_t bytestream_start;
uint64_t bytestream;
uint64_t bytestream_end;
int low;
int range;
uint16_t outstanding_count;
uint8_t outstanding_byte;
};
#ifdef FULL_RENORM
/* Full renorm version that can handle outstanding_byte == 0xFF */
void renorm_encoder(inout RangeCoder c)
{
int bs_cnt = 0;
u8buf bytestream = u8buf(c.bytestream);
if (c.outstanding_byte == 0xFF) {
c.outstanding_byte = uint8_t(c.low >> 8);
} else if (c.low <= 0xFF00) {
bytestream[bs_cnt++].v = c.outstanding_byte;
uint16_t cnt = c.outstanding_count;
for (; cnt > 0; cnt--)
bytestream[bs_cnt++].v = uint8_t(0xFF);
c.outstanding_count = uint16_t(0);
c.outstanding_byte = uint8_t(c.low >> 8);
} else if (c.low >= 0x10000) {
bytestream[bs_cnt++].v = c.outstanding_byte + uint8_t(1);
uint16_t cnt = c.outstanding_count;
for (; cnt > 0; cnt--)
bytestream[bs_cnt++].v = uint8_t(0x00);
c.outstanding_count = uint16_t(0);
c.outstanding_byte = uint8_t(bitfieldExtract(c.low, 8, 8));
} else {
c.outstanding_count++;
}
c.bytestream += bs_cnt;
c.range <<= 8;
c.low = bitfieldInsert(0, c.low, 8, 8);
}
#else
/* Cannot deal with outstanding_byte == -1 in the name of speed */
void renorm_encoder(inout RangeCoder c)
{
uint16_t oc = c.outstanding_count + uint16_t(1);
int low = c.low;
c.range <<= 8;
c.low = bitfieldInsert(0, low, 8, 8);
if (low > 0xFF00 && low < 0x10000) {
c.outstanding_count = oc;
return;
}
u8buf bs = u8buf(c.bytestream);
uint8_t outstanding_byte = c.outstanding_byte;
c.bytestream = uint64_t(bs) + oc;
c.outstanding_count = uint16_t(0);
c.outstanding_byte = uint8_t(low >> 8);
uint8_t obs = uint8_t(low > 0xFF00);
uint8_t fill = obs - uint8_t(1); /* unsigned underflow */
bs[0].v = outstanding_byte + obs;
for (int i = 1; i < oc; i++)
bs[i].v = fill;
}
#endif
void put_rac_internal(inout RangeCoder c, const int range1, bool bit)
{
#ifdef DEBUG
if (range1 >= c.range)
debugPrintfEXT("Error: range1 >= c.range");
if (range1 <= 0)
debugPrintfEXT("Error: range1 <= 0");
#endif
int ranged = c.range - range1;
c.low += bit ? ranged : 0;
c.range = bit ? range1 : ranged;
if (expectEXT(c.range < 0x100, false))
renorm_encoder(c);
}
void put_rac_direct(inout RangeCoder c, inout uint8_t state, bool bit)
{
put_rac_internal(c, (c.range * state) >> 8, bit);
state = zero_one_state[(uint(bit) << 8) + state];
}
void put_rac(inout RangeCoder c, uint64_t state, bool bit)
{
put_rac_direct(c, u8buf(state).v, bit);
}
/* Equiprobable bit */
void put_rac_equi(inout RangeCoder c, bool bit)
{
put_rac_internal(c, c.range >> 1, bit);
}
void put_rac_terminate(inout RangeCoder c)
{
int range1 = (c.range * 129) >> 8;
#ifdef DEBUG
if (range1 >= c.range)
debugPrintfEXT("Error: range1 >= c.range");
if (range1 <= 0)
debugPrintfEXT("Error: range1 <= 0");
#endif
c.range -= range1;
if (expectEXT(c.range < 0x100, false))
renorm_encoder(c);
}
/* Return the number of bytes written. */
uint32_t rac_terminate(inout RangeCoder c)
{
put_rac_terminate(c);
c.range = uint16_t(0xFF);
c.low += 0xFF;
renorm_encoder(c);
c.range = uint16_t(0xFF);
renorm_encoder(c);
#ifdef DEBUG
if (c.low != 0)
debugPrintfEXT("Error: c.low != 0");
if (c.range < 0x100)
debugPrintfEXT("Error: range < 0x100");
#endif
return uint32_t(uint64_t(c.bytestream) - uint64_t(c.bytestream_start));
}
void rac_init(out RangeCoder r, u8buf data, uint buf_size)
{
r.bytestream_start = uint64_t(data);
r.bytestream = uint64_t(data);
r.bytestream_end = uint64_t(data) + buf_size;
r.low = 0;
r.range = 0xFF00;
r.outstanding_count = uint16_t(0);
r.outstanding_byte = uint8_t(0xFF);
}
/* Decoder */
uint overread = 0;
bool corrupt = false;
void rac_init_dec(out RangeCoder r, u8buf data, uint buf_size)
{
overread = 0;
corrupt = false;
/* Skip priming bytes */
rac_init(r, OFFBUF(u8buf, data, 2), buf_size - 2);
u8vec2 prime = u8vec2buf(data).v;
/* Switch endianness of the priming bytes */
r.low = pack16(prime.yx);
if (r.low >= 0xFF00) {
r.low = 0xFF00;
r.bytestream_end = uint64_t(data) + 2;
}
}
void refill(inout RangeCoder c)
{
c.range <<= 8;
c.low <<= 8;
if (expectEXT(c.bytestream < c.bytestream_end, false)) {
c.low |= u8buf(c.bytestream).v;
c.bytestream++;
} else {
overread++;
}
}
bool get_rac_internal(inout RangeCoder c, const int range1)
{
int ranged = c.range - range1;
bool bit = c.low >= ranged;
c.low -= bit ? ranged : 0;
c.range = (bit ? 0 : ranged) + (bit ? range1 : 0);
if (expectEXT(c.range < 0x100, false))
refill(c);
return bit;
}
bool get_rac_direct(inout RangeCoder c, inout uint8_t state)
{
bool bit = get_rac_internal(c, c.range * state >> 8);
state = zero_one_state[state + (bit ? 256 : 0)];
return bit;
}
bool get_rac(inout RangeCoder c, uint64_t state)
{
return get_rac_direct(c, u8buf(state).v);
}
bool get_rac_equi(inout RangeCoder c)
{
return get_rac_internal(c, c.range >> 1);
}
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