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better parity contexts integration for literal length

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This commit is contained in:
Dennis Ranke
2022-10-15 17:43:18 +02:00
parent dd5b0043dd
commit cac3922b0a
1 changed files with 30 additions and 23 deletions
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53
src/lz.rs
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@@ -17,12 +17,12 @@ impl Op {
encode_length(
coder,
state,
256 * state.parity_contexts + 129,
256 + state.pos % state.parity_contexts * 320,
lit.len() as u32 + 1,
config,
);
for lit in lit {
let literal_base = state.pos % state.parity_contexts * 256;
let literal_base = state.pos % state.parity_contexts * 320;
let mut context_index = 1;
for i in (0..8).rev() {
let bit = (lit >> i) & 1 != 0;
@@ -35,7 +35,13 @@ impl Op {
}
&Op::Match { offset, len } => {
if state.prev_was_match {
encode_length(coder, state, 256 * state.parity_contexts + 129, 1, config);
encode_length(
coder,
state,
256 + state.pos % state.parity_contexts * 320,
1,
config,
);
}
let mut new_offset = true;
if !state.prev_was_match && !config.no_repeated_offsets {
@@ -43,7 +49,7 @@ impl Op {
encode_bit(
coder,
state,
256 * state.parity_contexts,
320 * state.parity_contexts,
new_offset == config.new_offset_bit,
);
}
@@ -52,14 +58,14 @@ impl Op {
encode_length(
coder,
state,
256 * state.parity_contexts + 1,
320 * state.parity_contexts + 1,
offset + if config.eof_in_length { 0 } else { 1 },
config,
);
state.last_offset = offset;
}
assert!(len as usize >= config.min_length() && len as usize <= config.max_length);
encode_length(coder, state, 256 * state.parity_contexts + 65, len, config);
encode_length(coder, state, 320 * state.parity_contexts + 65, len, config);
state.prev_was_match = true;
state.pos += len as usize;
}
@@ -69,21 +75,27 @@ impl Op {
pub fn encode_eof(coder: &mut dyn EntropyCoder, state: &mut CoderState, config: &Config) {
if state.prev_was_match {
encode_length(coder, state, 256 * state.parity_contexts + 129, 1, config);
encode_length(
coder,
state,
256 + state.pos % state.parity_contexts * 320,
1,
config,
);
}
if !state.prev_was_match && !config.no_repeated_offsets {
encode_bit(
coder,
state,
256 * state.parity_contexts,
320 * state.parity_contexts,
config.new_offset_bit ^ config.eof_in_length,
);
}
if !config.eof_in_length || state.prev_was_match || config.no_repeated_offsets {
encode_length(coder, state, 256 * state.parity_contexts + 1, 1, config);
encode_length(coder, state, 320 * state.parity_contexts + 1, 1, config);
}
if config.eof_in_length {
encode_length(coder, state, 256 * state.parity_contexts + 65, 1, config);
encode_length(coder, state, 320 * state.parity_contexts + 65, 1, config);
}
}
@@ -127,10 +139,7 @@ pub struct CoderState {
impl CoderState {
pub fn new(config: &Config) -> CoderState {
CoderState {
contexts: ContextState::new(
(1 + 255) * config.parity_contexts + 1 + 64 + 64 + 64,
config,
),
contexts: ContextState::new((64 + 256) * config.parity_contexts + 1 + 64 + 64, config),
last_offset: 0,
prev_was_match: true,
pos: 0,
@@ -179,10 +188,8 @@ pub fn unpack_internal(
max_size: usize,
) -> Result<isize, UnpackError> {
let mut decoder = RansDecoder::new(packed_data, &config);
let mut contexts = ContextState::new(
(1 + 255) * config.parity_contexts + 1 + 64 + 64 + 64,
&config,
);
let mut contexts =
ContextState::new((64 + 256) * config.parity_contexts + 1 + 64 + 64, &config);
let mut offset = usize::MAX;
let mut position = 0usize;
let mut prev_was_match = false;
@@ -216,11 +223,11 @@ pub fn unpack_internal(
let literal_length = decode_length(
&mut decoder,
&mut contexts,
256 * config.parity_contexts + 129,
256 + position % config.parity_contexts * 320,
config,
)? - 1;
for _ in 0..literal_length {
let literal_base = position % config.parity_contexts * 256;
let literal_base = position % config.parity_contexts * 320;
let mut context_index = 1;
let mut byte = 0;
for i in (0..8).rev() {
@@ -241,13 +248,13 @@ pub fn unpack_internal(
if config.no_repeated_offsets
|| prev_was_match
|| decoder
.decode_with_context(&mut contexts.context_mut(256 * config.parity_contexts))?
.decode_with_context(&mut contexts.context_mut(320 * config.parity_contexts))?
== config.new_offset_bit
{
offset = decode_length(
&mut decoder,
&mut contexts,
256 * config.parity_contexts + 1,
320 * config.parity_contexts + 1,
&config,
)? - if config.eof_in_length { 0 } else { 1 };
if offset == 0 {
@@ -257,7 +264,7 @@ pub fn unpack_internal(
let length = decode_length(
&mut decoder,
&mut contexts,
256 * config.parity_contexts + 65,
320 * config.parity_contexts + 65,
&config,
)?;
if config.eof_in_length && length == 1 {