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size optimized uncompress function in loader

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This commit is contained in:
Dennis Ranke
2021-12-28 17:32:11 +01:00
parent 6f22e00487
commit 4521fb73ef
2 changed files with 9 additions and 16 deletions
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platform/bin/loader.wasm
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25
platform/src/loader.cwa
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@@ -96,7 +96,8 @@ export fn uncompress(src_ptr: i32, dest_ptr: i32) -> i32 {
block finished {
loop unpack_loop {
if upkr_bit(0) {
let lazy is_match = upkr_bit(0);
if is_match {
let inline new_offset = if prev_was_match { 1 } else { upkr_bit(256) };
if new_offset {
offset = upkr_length(257) - 1;
@@ -108,19 +109,16 @@ export fn uncompress(src_ptr: i32, dest_ptr: i32) -> i32 {
dest_ptr = dest_ptr + 1;
branch_if (length := length - 1): copy;
}
prev_was_match = 1;
} else {
// literal
i = 0;
byte = 1;
loop literal {
byte = (byte << 1) | upkr_bit(byte);
branch_if (i := i + 1) < 8: literal;
branch_if (byte := (byte << 1) | upkr_bit(byte)) < 256: literal;
}
dest_ptr?0 = byte;
dest_ptr = dest_ptr + 1;
prev_was_match = 0;
}
prev_was_match = is_match;
branch unpack_loop;
}
}
@@ -143,7 +141,7 @@ fn upkr_length(context_index: i32) -> i32 {
}
fn upkr_bit(context_index: i32) -> i32 {
let prob = context_index?0x3c000;
let lazy prob = context_index?0x3c000;
loop refill {
if upkr_state < 1<<12 {
@@ -154,17 +152,12 @@ fn upkr_bit(context_index: i32) -> i32 {
}
let lazy state_low = upkr_state & 0xff;
let bit = state_low < prob;
let lazy state_hi = upkr_state >> 8;
let lazy bit = state_low < prob;
if bit {
upkr_state = prob * (upkr_state >> 8) + state_low;
prob = prob + ((0x108 - prob) >> 4);
} else {
upkr_state = (0x100 - prob) * (upkr_state >> 8) + state_low - prob;
prob = prob - ((prob + 8) >> 4);
}
upkr_state = state_low + select(bit, prob * state_hi, (0x100 - prob) * state_hi - prob);
context_index?0x3c000 = prob;
context_index?0x3c000 = prob + ((7 + bit * 257 - prob) >> 4);
bit
}