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experimental string cache in encoder but it's slow #62

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12 changes: 6 additions & 6 deletions benchmark/string.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -4,8 +4,8 @@ import { WASM_AVAILABLE } from "../src/wasmFunctions";

console.log(`WASM_AVAILABLE=${WASM_AVAILABLE}`);

const ascii = "A".repeat(40000);
const emoji = "🌏".repeat(20000);
const ascii = "A".repeat(30);
const emoji = "🌏".repeat(8);

{
// warm up ascii
Expand All @@ -17,13 +17,13 @@ const emoji = "🌏".repeat(20000);
// run

console.time("encode ascii");
for (let i = 0; i < 1000; i++) {
for (let i = 0; i < 1000000; i++) {
encode(data);
}
console.timeEnd("encode ascii");

console.time("decode ascii");
for (let i = 0; i < 1000; i++) {
for (let i = 0; i < 1000000; i++) {
decode(encoded);
}
console.timeEnd("decode ascii");
Expand All @@ -40,13 +40,13 @@ const emoji = "🌏".repeat(20000);
// run

console.time("encode emoji");
for (let i = 0; i < 1000; i++) {
for (let i = 0; i < 1000000; i++) {
encode(data);
}
console.timeEnd("encode emoji");

console.time("decode emoji");
for (let i = 0; i < 1000; i++) {
for (let i = 0; i < 1000000; i++) {
decode(encoded);
}
console.timeEnd("decode emoji");
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18 changes: 17 additions & 1 deletion src/Encoder.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -8,11 +8,15 @@ import { WASM_AVAILABLE, utf8EncodeWasm, WASM_STR_THRESHOLD } from "./wasmFuncti
export const DEFAULT_MAX_DEPTH = 100;
export const DEFAULT_INITIAL_BUFFER_SIZE = 2048;

const STR_CACHE_THRESHOLD = 32;

export class Encoder {
private pos = 0;
private view = new DataView(new ArrayBuffer(this.initialBufferSize));
private bytes = new Uint8Array(this.view.buffer);

private readonly strCache: Record<string, Uint8Array> = Object.create(null);

constructor(
readonly extensionCodec = ExtensionCodec.defaultCodec,
readonly maxDepth = DEFAULT_MAX_DEPTH,
Expand Down Expand Up @@ -146,6 +150,16 @@ export class Encoder {
const maxHeaderSize = 1 + 4;
const strLength = object.length;

if (strLength < STR_CACHE_THRESHOLD) {
const buffer = this.strCache[object];
if (buffer != null) {
this.writeStringHeader(buffer.byteLength);
this.bytes.set(buffer, this.pos);
this.pos += buffer.byteLength;
return;
}
}

if (WASM_AVAILABLE && strLength > WASM_STR_THRESHOLD) {
// ensure max possible size
const maxSize = maxHeaderSize + strLength * 4;
Expand All @@ -154,12 +168,14 @@ export class Encoder {
// utf8EncodeWasm() handles headByte+size as well as string itself
const ouputLength = utf8EncodeWasm(object, this.bytes, this.pos);
this.pos += ouputLength;
return;
} else {
const byteLength = utf8Count(object);
this.ensureBufferSizeToWrite(maxHeaderSize + byteLength);
this.writeStringHeader(byteLength);
utf8Encode(object, this.bytes, this.pos);
if (byteLength < STR_CACHE_THRESHOLD) {
this.strCache[object] = this.bytes.subarray(this.pos, this.pos + byteLength);
}
this.pos += byteLength;
}
}
Expand Down