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use super::*;
use crate::ByteReader;
#[derive(Debug)]
pub(crate) struct Bcj2Decoder {
pub(crate) bufs: [usize; BCJ2_NUM_STREAMS],
pub(crate) lims: [usize; BCJ2_NUM_STREAMS],
dest: usize,
// BCJ2_STREAM_MAIN has more priority than BCJ2_STATE_ORIG.
pub(crate) state: usize,
ip: u32,
temp: [u8; 4],
range: u32,
pub(crate) code: u32,
probs: [u16; 2 + 256],
}
impl Bcj2Decoder {
pub(crate) fn new() -> Self {
Self {
bufs: Default::default(),
lims: Default::default(),
dest: Default::default(),
state: BCJ2_DEC_STATE_OK,
ip: Default::default(),
temp: Default::default(),
range: Default::default(),
code: Default::default(),
probs: [BIT_MODEL_TOTAL >> 1; 2 + 256],
}
}
#[inline(always)]
pub(crate) fn dest(&self) -> usize {
self.dest
}
#[inline(always)]
pub(crate) fn set_dest(&mut self, dest: usize) {
self.dest = dest;
}
pub(crate) fn decode(&mut self, src_bufs: &mut [u8], dest_buf: &mut [u8]) -> bool {
let dest_lim = dest_buf.len();
if self.range <= 5 {
self.state = BCJ2_DEC_STATE_OK;
while self.range != 5 {
if self.range == 1 && self.code != 0 {
return false;
}
if self.bufs[BCJ2_STREAM_RC] == self.lims[BCJ2_STREAM_RC] {
self.state = BCJ2_STREAM_RC;
return true;
}
self.code = (self.code << 8) | src_bufs[self.bufs[BCJ2_STREAM_RC]] as u32;
self.bufs[BCJ2_STREAM_RC] = self.bufs[BCJ2_STREAM_RC].wrapping_add(1);
self.range += 1;
}
if self.code == 0xFFFFFFFF {
return false;
}
self.range = 0xFFFFFFFF;
} else if self.state >= BCJ2_DEC_STATE_ORIG_0 {
while self.state <= BCJ2_DEC_STATE_ORIG_3 {
let dest = self.dest;
if dest == dest_lim {
return true;
}
dest_buf[dest] = self.temp[self.state - BCJ2_DEC_STATE_ORIG_0];
self.state += 1;
self.dest = dest + 1;
}
}
loop {
if bcj2_is_32bit_stream(self.state) {
self.state = BCJ2_DEC_STATE_OK;
} else {
if self.range < K_TOP_VALUE {
if self.bufs[BCJ2_STREAM_RC] == self.lims[BCJ2_STREAM_RC] {
self.state = BCJ2_STREAM_RC;
return true;
}
self.range <<= 8;
self.code = (self.code << 8) | src_bufs[self.bufs[BCJ2_STREAM_RC]] as u32;
self.bufs[BCJ2_STREAM_RC] = self.bufs[BCJ2_STREAM_RC].wrapping_add(1);
}
{
let mut src = self.bufs[BCJ2_STREAM_MAIN];
let mut num = self.lims[BCJ2_STREAM_MAIN] - src;
if num == 0 {
self.state = BCJ2_STREAM_MAIN;
return true;
}
let mut dest = self.dest;
if num > (dest_lim - dest) {
num = dest_lim - dest;
if num == 0 {
self.state = BCJ2_DEC_STATE_ORIG;
return true;
}
}
let src_lim = src + num;
if self.temp[3] == 0x0F && (src_bufs[src] & 0xF0) == 0x80 {
dest_buf[dest] = src_bufs[src];
} else {
loop {
let b = src_bufs[src];
dest_buf[dest] = b;
if b != 0x0F {
if (b & 0xFE) == 0xE8 {
break;
}
dest += 1;
src += 1;
if src != src_lim {
continue;
}
break;
}
dest += 1;
src += 1;
if src == src_lim {
break;
}
if (src_bufs[src] & 0xF0) != 0x80 {
continue;
}
dest_buf[dest] = src_bufs[src];
break;
}
}
num = src - self.bufs[BCJ2_STREAM_MAIN];
if src == src_lim {
self.temp[3] = src_bufs[src - 1];
self.bufs[BCJ2_STREAM_MAIN] = src;
self.ip += num as u32;
self.dest += num;
self.state = if self.bufs[BCJ2_STREAM_MAIN] == self.lims[BCJ2_STREAM_MAIN] {
BCJ2_STREAM_MAIN
} else {
BCJ2_DEC_STATE_ORIG
};
return true;
}
{
let b = src_bufs[src];
let prev = if num == 0 {
self.temp[3]
} else {
src_bufs[src - 1]
};
self.temp[3] = b;
self.bufs[BCJ2_STREAM_MAIN] = src + 1;
num += 1;
self.ip += num as u32;
self.dest += num;
let prob = &mut self.probs[if b == 0xE8 {
2 + prev as usize
} else if b == 0xE9 {
1
} else {
0
}];
// _IF_BIT_0
let ttt = *prob;
let bound = (self.range >> NUM_MODEL_BITS) * ttt as u32;
if self.code < bound {
// _UPDATE_0
self.range = bound;
*prob = (ttt + ((BIT_MODEL_TOTAL - ttt) >> NUM_MOVE_BITS)) as _;
continue;
}
// _UPDATE_1
self.range -= bound;
self.code -= bound;
*prob = ttt - (ttt >> NUM_MOVE_BITS);
}
}
}
{
let cj = if self.temp[3] == 0xE8 {
BCJ2_STREAM_CALL
} else {
BCJ2_STREAM_JUMP
};
let cur = self.bufs[cj];
if cur == self.lims[cj] {
self.state = cj;
break;
}
let mut val = if let Ok(v) = (&mut &src_bufs[cur..]).read_u32_be() {
v
} else {
return false;
};
self.bufs[cj] = cur + 4;
self.ip += 4;
val = val.wrapping_sub(self.ip);
let dest = self.dest;
let rem = dest_lim - dest;
if rem < 4 {
self.temp[0] = val as u8;
if rem > 0 {
dest_buf[dest] = val as u8;
}
val >>= 8;
self.temp[1] = val as u8;
if rem > 1 {
dest_buf[dest + 1] = val as u8;
}
val >>= 8;
self.temp[2] = val as u8;
if rem > 2 {
dest_buf[dest + 2] = val as u8;
}
val >>= 8;
self.temp[3] = val as u8;
self.dest = dest + rem;
self.state = BCJ2_DEC_STATE_ORIG_0 + rem;
break;
}
dest_buf[dest..dest + 4].copy_from_slice(&val.to_le_bytes());
// SetUi32(dest, val);
self.temp[3] = (val >> 24) as u8;
self.dest = dest + 4;
}
}
if self.range < K_TOP_VALUE && self.bufs[BCJ2_STREAM_RC] != self.lims[BCJ2_STREAM_RC] {
self.range <<= 8;
self.code = (self.code << 8) | src_bufs[self.bufs[BCJ2_STREAM_RC]] as u32;
self.bufs[BCJ2_STREAM_RC] = self.bufs[BCJ2_STREAM_RC].wrapping_add(1);
}
true
}
}