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Concretize decimal counting in itoa (#169)

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This commit is contained in:
Max Graey
2018-07-14 00:37:27 +03:00
committed by Daniel Wirtz
parent 6228233e04
commit 9dfe39c532
3 changed files with 97 additions and 153 deletions
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46
std/assembly/internal/itoa.ts
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@ -67,23 +67,27 @@ function DIGITS(): u32[] {
return table; // inlines to a constant memory offset
}
// Count number of decimals in value
export function decimalCount<T>(value: T): i32 {
var v = abs<T>(value); // NOP if value is unsigned anyway
var l: usize = 8 * sizeof<T>() - <usize>clz<T>(v | 10); // log2
var t = l * 1233 >>> 12; // log10
// Count number of decimals for u32 values
// In our case input value always non-zero so we can simplify some parts
function decimalCountU32(value: u32): i32 {
var l: usize = 32 - <usize>clz<u32>(value); // log2
var t = l * 1233 >>> 12; // log10
var lutbuf = <ArrayBuffer>POWERS10().buffer_;
if (sizeof<T>() <= 4) {
let power = loadUnsafe<u32,T>(lutbuf, t);
t -= <usize>(v < power);
} else { // sizeof<T>() == 8
let le10 = t <= 10;
let offset = select<usize>(0, 10, le10); // offset = t <= 10 ? 0 : 10
let factor = select< T >(1, 10000000000, le10); // factor = t <= 10 ? 1 : 10 ^ 10
let power = loadUnsafe<u32,T>(lutbuf, t - offset);
t -= <usize>(v < factor * power);
}
var power = loadUnsafe<u32,u32>(lutbuf, t);
t -= <usize>(value < power);
return t + 1;
}
// Count number of decimals for u64 values
// In our case input value always greater than 2^32-1 so we can skip some parts
function decimalCountU64(value: u64): i32 {
var l: usize = 64 - <usize>clz<u64>(value); // log2
var t = l * 1233 >>> 12; // log10
var lutbuf = <ArrayBuffer>POWERS10().buffer_;
var power = loadUnsafe<u32,u64>(lutbuf, t - 10);
t -= <usize>(value < 10000000000 * power);
return t + 1;
}
@ -189,7 +193,7 @@ export function utoa64_core(buffer: usize, num: u64, offset: u32): void {
export function utoa32(value: u32): string {
if (!value) return "0";
var decimals = decimalCount<u32>(value);
var decimals = decimalCountU32(value);
var buffer = allocateString(decimals);
utoa32_core(changetype<usize>(buffer), value, decimals);
@ -202,7 +206,7 @@ export function itoa32(value: i32): string {
var isneg = value < 0;
if (isneg) value = -value;
var decimals = decimalCount<u32>(value) + <i32>isneg;
var decimals = decimalCountU32(value) + <i32>isneg;
var buffer = allocateString(decimals);
utoa32_core(changetype<usize>(buffer), value, decimals);
@ -217,11 +221,11 @@ export function utoa64(value: u64): string {
var buffer: String;
if (value <= u32.MAX_VALUE) {
let value32 = <u32>value;
let decimals = decimalCount<u32>(value32);
let decimals = decimalCountU32(value32);
buffer = allocateString(decimals);
utoa32_core(changetype<usize>(buffer), value32, decimals);
} else {
let decimals = decimalCount<u64>(value);
let decimals = decimalCountU64(value);
buffer = allocateString(decimals);
utoa64_core(changetype<usize>(buffer), value, decimals);
}
@ -238,11 +242,11 @@ export function itoa64(value: i64): string {
var buffer: String;
if (<u64>value <= <u64>u32.MAX_VALUE) {
let value32 = <u32>value;
let decimals = decimalCount<u32>(value32) + <i32>isneg;
let decimals = decimalCountU32(value32) + <i32>isneg;
buffer = allocateString(decimals);
utoa32_core(changetype<usize>(buffer), value32, decimals);
} else {
let decimals = decimalCount<u64>(value) + <i32>isneg;
let decimals = decimalCountU64(value) + <i32>isneg;
buffer = allocateString(decimals);
utoa64_core(changetype<usize>(buffer), value, decimals);
}