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optimize c_unpacker state update a bit, add -b flag to --help

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This commit is contained in:
Dennis Ranke
2022-09-09 19:10:31 +02:00
parent a205473ad6
commit 629c5fce7d
2 changed files with 17 additions and 10 deletions
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16
c_unpacker/unpack.c
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@@ -32,13 +32,17 @@ int upkr_decode_bit(int context_index) {
int prob = upkr_probs[context_index];
int bit = (upkr_state & 255) < prob ? 1 : 0;
if(bit) {
upkr_state = prob * (upkr_state >> 8) + (upkr_state & 255);
upkr_probs[context_index] = prob + ((256 - prob + 8) >> 4);
} else {
upkr_state = (256 - prob) * (upkr_state >> 8) + (upkr_state & 255) - prob;
upkr_probs[context_index] = prob - ((prob + 8) >> 4);
int tmp = prob;
if(!bit) {
tmp = 256 - tmp;
}
upkr_state = tmp * (upkr_state >> 8) + (upkr_state & 255);
tmp += (256 - tmp + 8) >> 4;
if(!bit) {
upkr_state -= prob;
tmp = 256 - tmp;
}
upkr_probs[context_index] = tmp;
return bit;
}

7
src/main.rs
View File

@@ -58,7 +58,10 @@ fn main() -> Result<()> {
fn print_help() {
eprintln!("Usage:");
eprintln!(" upkr pack [-l level(0-9)] <infile> <outfile>");
eprintln!(" upkr unpack <infile> <outfile>");
eprintln!(" upkr pack [-b] [-l level(0-9)] <infile> <outfile>");
eprintln!(" upkr unpack [-b] <infile> <outfile>");
eprintln!();
eprintln!(" -b, --bitstream bitstream mode");
eprintln!(" -l, --level N compression level 0-9");
std::process::exit(1);
}