From 1299d2cdad260a472e98c40b51fd3f61da9e75da Mon Sep 17 00:00:00 2001
From: "FUJI Goro (gfx)" <gfuji@cpan.org>
Date: Fri, 7 Jun 2019 22:59:37 +0900
Subject: [PATCH] experimental string cache in encoder but it's slow

---
 benchmark/string.ts | 12 ++++++------
 src/Encoder.ts      | 18 +++++++++++++++++-
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/benchmark/string.ts b/benchmark/string.ts
index e6b18708..6610c8b6 100644
--- a/benchmark/string.ts
+++ b/benchmark/string.ts
@@ -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
@@ -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");
@@ -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");
diff --git a/src/Encoder.ts b/src/Encoder.ts
index b0636a7f..baf6063a 100644
--- a/src/Encoder.ts
+++ b/src/Encoder.ts
@@ -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,
@@ -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;
@@ -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;
     }
   }