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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 {
u8buf bytestream_start;
u8buf bytestream;
uint low;
uint16_t range;
uint16_t outstanding_count;
uint8_t outstanding_byte;
};
/* Full renorm version that can handle outstanding_byte == 0xFF */
void renorm_encoder_full(inout RangeCoder c)
{
int bs_cnt = 0;
if (c.outstanding_byte == 0xFF) {
c.outstanding_byte = uint8_t(c.low >> 8);
} else if (c.low <= 0xFF00) {
c.bytestream[bs_cnt++].v = c.outstanding_byte;
uint16_t cnt = c.outstanding_count;
for (; cnt > 0; cnt--)
c.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) {
c.bytestream[bs_cnt++].v = c.outstanding_byte + uint8_t(1);
uint16_t cnt = c.outstanding_count;
for (; cnt > 0; cnt--)
c.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 = OFFBUF(u8buf, c.bytestream, bs_cnt);
c.range <<= 8;
c.low = bitfieldInsert(0, c.low, 8, 8);
}
/* 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);
uint 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 = c.bytestream;
uint8_t outstanding_byte = c.outstanding_byte;
c.bytestream = OFFBUF(u8buf, 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;
}
void put_rac_norenorm(inout RangeCoder c, uint64_t state, bool bit)
{
u8buf sb = u8buf(state);
uint val = uint(sb.v);
uint16_t range1 = uint16_t((uint(c.range) * val) >> 8);
#ifdef DEBUG
if (val == 0)
debugPrintfEXT("Error: state is zero (addr: 0x%lx)", uint64_t(sb));
if (range1 >= c.range)
debugPrintfEXT("Error: range1 >= c.range");
if (range1 <= 0)
debugPrintfEXT("Error: range1 <= 0");
#endif
uint16_t diff = c.range - range1;
if (bit) {
c.low += diff;
c.range = range1;
} else {
c.range = diff;
}
sb.v = zero_one_state[(uint(bit) << 8) + val];
#ifdef DEBUG
if (sb.v == 0)
debugPrintfEXT("Error: inserted zero state from tab %i idx %i", bit, val);
#endif
}
/* Equiprobable bit */
void put_rac_equi(inout RangeCoder c, bool bit)
{
uint16_t range1 = c.range >> 1;
#ifdef DEBUG
if (range1 >= c.range)
debugPrintfEXT("Error: range1 >= c.range");
if (range1 <= 0)
debugPrintfEXT("Error: range1 <= 0");
#endif
if (bit) {
c.low += c.range - range1;
c.range = range1;
} else {
c.range -= range1;
}
if (c.range < 0x100)
renorm_encoder(c);
}
void put_rac_terminate(inout RangeCoder c)
{
uint16_t range1 = uint16_t((uint(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 (c.range < 0x100)
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, uint64_t buf_size)
{
r.bytestream_start = data;
r.bytestream = data;
r.low = 0;
r.range = uint16_t(0xFF00);
r.outstanding_count = uint16_t(0);
r.outstanding_byte = uint8_t(0xFF);
}
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