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Improve bswap implementation (#323)

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This commit is contained in:
Max Graey
2018-11-09 18:51:32 +02:00
committed by Daniel Wirtz
parent 63b64ba69e
commit 54311fd0ab
5 changed files with 494 additions and 780 deletions
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51
std/assembly/polyfills.ts
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@ -1,33 +1,40 @@
export function bswap<T>(value: T): T {
assert(sizeof<T>() == 1 || sizeof<T>() == 2 || sizeof<T>() == 4 || sizeof<T>() == 8);
if (isInteger<T>()) {
if (sizeof<T>() == 2) {
return <T>((value << 8) | ((value >> 8) & <T>0x00FF));
}
if (sizeof<T>() == 4) {
return <T>(
rotl<u32>(<u32>value & 0xFF00FF00, 8) |
rotr<u32>(<u32>value & 0x00FF00FF, 8)
);
}
if (sizeof<T>() == 8) {
let a = (<u64>value >> 8) & 0x00FF00FF00FF00FF;
let b = (<u64>value & 0x00FF00FF00FF00FF) << 8;
let v = a | b;
if (sizeof<T>() == 2) {
return bswap16<T>(value);
}
if (sizeof<T>() == 4) {
return <T>(
rotl<u32>(<u32>value & 0xFF00FF00, 8) |
rotr<u32>(<u32>value & 0x00FF00FF, 8)
);
}
if (sizeof<T>() == 8) {
let a: u64 = (<u64>value >> 8) & 0x00FF00FF00FF00FF;
let b: u64 = (<u64>value & 0x00FF00FF00FF00FF) << 8;
let v: u64 = a | b;
a = (v >> 16) & 0x0000FFFF0000FFFF;
b = (v & 0x0000FFFF0000FFFF) << 16;
a = (v >> 16) & 0x0000FFFF0000FFFF;
b = (v & 0x0000FFFF0000FFFF) << 16;
return <T>rotr<u64>(a | b, 32);
return <T>rotr<u64>(a | b, 32);
}
return value;
}
assert(false);
return value;
}
@inline
export function bswap16<T>(value: T): T {
assert(sizeof<T>() == 1 || sizeof<T>() == 2 || sizeof<T>() == 4);
if (sizeof<T>() == 2 || sizeof<T>() == 4) {
return <T>(((value << 8) & <T>0xFF00) | ((value >> 8) & <T>0x00FF) | (value & <T>0xFFFF0000));
if (isInteger<T>() && sizeof<T>() <= 4) {
if (sizeof<T>() == 2) {
return <T>((value << 8) | ((value >> 8) & <T>0x00FF));
} else if (sizeof<T>() == 4) {
return <T>(((value << 8) & <T>0xFF00) | ((value >> 8) & <T>0x00FF) | (value & <T>0xFFFF0000));
}
return value;
}
assert(false);
return value;
}