optimize utf8count wasm

Author: gfx

benchmark/count-utf8.ts

@@ -0,0 +1,57 @@
+/* eslint-disable no-console */
+import { utf8CountJs, WASM_AVAILABLE } from "../src/utils/utf8.ts";
+import { getWasmError, utf8CountWasm } from "../src/utils/utf8-wasm.ts";
+
+// @ts-ignore
+import Benchmark from "benchmark";
+
+// description
+console.log("utf8CountJs - pure JS implementation");
+console.log("utf8CountWasm - WebAssembly implementation");
+
+// Show wasm status
+console.log("=".repeat(60));
+console.log("WebAssembly Status:");
+console.log(`  WASM_AVAILABLE: ${WASM_AVAILABLE}`);
+if (WASM_AVAILABLE) {
+  console.log("  js-string-builtins: enabled");
+} else {
+  const error = getWasmError();
+  console.log(`  Error: ${error?.message || "unknown"}`);
+  if (error?.message?.includes("js-string") || error?.message?.includes("builtin")) {
+    console.log("\n  js-string-builtins is enabled by default in Node.js 24+ (V8 13.6+).");
+    console.log("  For older versions, run with:");
+    console.log("    node --experimental-wasm-imported-strings node_modules/.bin/ts-node benchmark/count-utf8.ts");
+  }
+}
+console.log("=".repeat(60));
+
+for (const baseStr of ["A", "あ", "🌏"]) {
+  const dataSet = [10, 30, 50, 100, 200, 500, 1000].map((n) => {
+    return baseStr.repeat(n);
+  });
+
+  for (const str of dataSet) {
+    const byteLength = utf8CountJs(str);
+
+    console.log(`\n## string "${baseStr}" (strLength=${str.length}, byteLength=${byteLength})\n`);
+
+    const suite = new Benchmark.Suite();
+
+    suite.add("utf8CountJs", () => {
+      utf8CountJs(str);
+    });
+
+    if (WASM_AVAILABLE) {
+      suite.add("utf8CountWasm", () => {
+        utf8CountWasm(str);
+      });
+    }
+
+    suite.on("cycle", (event: any) => {
+      console.log(String(event.target));
+    });
+
+    suite.run();
+  }
+}

src/utils/utf8-wasm-binary.ts

@@ -2,22 +2,22 @@
 // Source: wasm/utf8.wat
 
 export const wasmBinary = `
-AGFzbQEAAAABNQhedwFgAW8Bf2ADb2QAfwF/YANkAH9/AWRvYAJvfwF/YAJ/ZAABf2ABfwFkAGADZA
-B/fwFvAl8DDndhc206anMtc3RyaW5nBmxlbmd0aAABDndhc206anMtc3RyaW5nEWludG9DaGFyQ29k
-ZUFycmF5AAIOd2FzbTpqcy1zdHJpbmcRZnJvbUNoYXJDb2RlQXJyYXkAAwMGBQEEBQYHBQMBAAEHVA
-YGbWVtb3J5AgAJdXRmOENvdW50AAMKdXRmOEVuY29kZQAEEXV0ZjhEZWNvZGVUb0FycmF5AAUKYWxs
-b2NBcnJheQAGDWFycmF5VG9TdHJpbmcABwqQBgWEAQIEfwFkACAAEAAiBEUEQEEADwsgACAE+wcAIg
-VBABABGgNAIAEgBE9FBEAgBSAB+w0AIgNBgAFJBH8gAkEBagUgA0GAEEkEfyACQQJqBSADQf+3A00g
-A0GAsANPcQR/IAFBAWohASACQQRqBSACQQNqCwsLIQIgAUEBaiEBDAELCyACC7MCAgR/AWQAIAEhAi
-AAIAAQACIF+wcAIgZBABABGgNAIAQgBU9FBEAgBiAE+w0AIgNBgAFJBH8gAiADOgAAIAJBAWoFIANB
-gBBJBH8gAiADQQZ2QcABcjoAACACQQFqIANBP3FBgAFyOgAAIAJBAmoFIANB/7cDTSADQYCwA09xBH
-8gAiADQQp0IAYgBEEBaiIE+w0AakGAuP8aayIDQRJ2QfABcjoAACACQQFqIANBDHZBP3FBgAFyOgAA
-IAJBAmogA0EGdkE/cUGAAXI6AAAgAkEDaiADQT9xQYABcjoAACACQQRqBSACIANBDHZB4AFyOgAAIA
-JBAWogA0EGdkE/cUGAAXI6AAAgAkECaiADQT9xQYABcjoAACACQQNqCwsLIQIgBEEBaiEEDAELCyAC
-IAFrC78CAQN/A0AgACACSwRAIAItAAAiBEGAAXFFBEAgASADIAT7DgAgA0EBaiEDIAJBAWohAgwCCy
-AEQeABcUHAAUYEQCABIAMgAkEBai0AAEE/cSAEQR9xQQZ0cvsOACADQQFqIQMgAkECaiECDAILIARB
-8AFxQeABRgRAIAEgAyACQQJqLQAAQT9xIARBD3FBDHQgAkEBai0AAEE/cUEGdHJy+w4AIANBAWohAy
-ACQQNqIQIMAgsgBEH4AXFB8AFGBEAgASADIAJBA2otAABBP3EgBEEHcUESdCACQQFqLQAAQT9xQQx0
-ciACQQJqLQAAQT9xQQZ0cnJBgIAEayIEQQp2QYCwA3L7DgAgASADQQFqIgMgBEH/B3FBgLgDcvsOAC
-ADQQFqIQMgAkEEaiECDAIFIAJBAWohAgwCCwALCyADCwcAIAD7BwALCgAgACABIAIQAgs=
+AGFzbQEAAAABNQhedwFgAW8Bf2ACb38Bf2ADb2QAfwF/YANkAH9/AWRvYAJ/ZAABf2ABfwFkAGADZA
+B/fwFvAnsEDndhc206anMtc3RyaW5nBmxlbmd0aAABDndhc206anMtc3RyaW5nCmNoYXJDb2RlQXQA
+Ag53YXNtOmpzLXN0cmluZxFpbnRvQ2hhckNvZGVBcnJheQADDndhc206anMtc3RyaW5nEWZyb21DaG
+FyQ29kZUFycmF5AAQDBgUBAgUGBwUDAQABB1QGBm1lbW9yeQIACXV0ZjhDb3VudAAECnV0ZjhFbmNv
+ZGUABRF1dGY4RGVjb2RlVG9BcnJheQAGCmFsbG9jQXJyYXkABw1hcnJheVRvU3RyaW5nAAgK9gUFaw
+EEfyAAEAAhBANAIAEgBE9FBEAgACABEAEiA0GAAUkEfyACQQFqBSADQYAQSQR/IAJBAmoFIANB/7cD
+TSADQYCwA09xBH8gAUEBaiEBIAJBBGoFIAJBA2oLCwshAiABQQFqIQEMAQsLIAILswICBH8BZAAgAS
+ECIAAgABAAIgX7BwAiBkEAEAIaA0AgBCAFT0UEQCAGIAT7DQAiA0GAAUkEfyACIAM6AAAgAkEBagUg
+A0GAEEkEfyACIANBBnZBwAFyOgAAIAJBAWogA0E/cUGAAXI6AAAgAkECagUgA0H/twNNIANBgLADT3
+EEfyACIANBCnQgBiAEQQFqIgT7DQBqQYC4/xprIgNBEnZB8AFyOgAAIAJBAWogA0EMdkE/cUGAAXI6
+AAAgAkECaiADQQZ2QT9xQYABcjoAACACQQNqIANBP3FBgAFyOgAAIAJBBGoFIAIgA0EMdkHgAXI6AA
+AgAkEBaiADQQZ2QT9xQYABcjoAACACQQJqIANBP3FBgAFyOgAAIAJBA2oLCwshAiAEQQFqIQQMAQsL
+IAIgAWsLvwIBA38DQCAAIAJLBEAgAi0AACIEQYABcUUEQCABIAMgBPsOACADQQFqIQMgAkEBaiECDA
+ILIARB4AFxQcABRgRAIAEgAyACQQFqLQAAQT9xIARBH3FBBnRy+w4AIANBAWohAyACQQJqIQIMAgsg
+BEHwAXFB4AFGBEAgASADIAJBAmotAABBP3EgBEEPcUEMdCACQQFqLQAAQT9xQQZ0cnL7DgAgA0EBai
+EDIAJBA2ohAgwCCyAEQfgBcUHwAUYEQCABIAMgAkEDai0AAEE/cSAEQQdxQRJ0IAJBAWotAABBP3FB
+DHRyIAJBAmotAABBP3FBBnRyckGAgARrIgRBCnZBgLADcvsOACABIANBAWoiAyAEQf8HcUGAuANy+w
+4AIANBAWohAyACQQRqIQIMAgUgAkEBaiECDAILAAsLIAMLBwAgAPsHAAsKACAAIAEgAhADCw==
 `;

wasm/utf8.wat

@@ -11,6 +11,8 @@
   ;; Import js-string builtins
   (import "wasm:js-string" "length"
     (func $str_length (param externref) (result i32)))
+  (import "wasm:js-string" "charCodeAt"
+    (func $str_charCodeAt (param externref i32) (result i32)))
   (import "wasm:js-string" "intoCharCodeArray"
     (func $str_into_array (param externref (ref $i16_array) i32) (result i32)))
   (import "wasm:js-string" "fromCharCodeArray"
@@ -20,30 +22,21 @@
   (memory (export "memory") 1)
 
   ;; Count UTF-8 byte length of a JS string
-  ;; Uses GC array to get all char codes at once
+  ;; Uses charCodeAt directly to avoid array allocation overhead
   (func (export "utf8Count") (param $str externref) (result i32)
     (local $len i32)
-    (local $arr (ref $i16_array))
     (local $i i32)
     (local $byteLen i32)
     (local $code i32)
 
     (local.set $len (call $str_length (local.get $str)))
 
-    ;; Handle empty string
-    (if (i32.eqz (local.get $len))
-      (then (return (i32.const 0))))
-
-    ;; Allocate array and copy string chars
-    (local.set $arr (array.new $i16_array (i32.const 0) (local.get $len)))
-    (drop (call $str_into_array (local.get $str) (local.get $arr) (i32.const 0)))
-
     ;; Count UTF-8 bytes
     (block $break
       (loop $continue
         (br_if $break (i32.ge_u (local.get $i) (local.get $len)))
 
-        (local.set $code (array.get_u $i16_array (local.get $arr) (local.get $i)))
+        (local.set $code (call $str_charCodeAt (local.get $str) (local.get $i)))
 
         ;; 1-byte: 0x00-0x7F
         (if (i32.lt_u (local.get $code) (i32.const 0x80))