[browser][non-icu] HybridGlobalization faster encoding for change case. (#85516)

* This speeds it up ~twice.

* JS's decoder always changes the codepoint.

* @kg's optimization idea.

Author: ilonatommy

src/libraries/System.Globalization/tests/System/Globalization/TextInfoTests.cs

@@ -325,12 +325,14 @@ public void ToLower_Netcore(string name, string str, string expected)
         [Fact]
         public void ToLower_InvalidSurrogates()
         {
+            bool usesTextDecoder = PlatformDetection.IsHybridGlobalizationOnBrowser && PlatformDetection.IsBrowserDomSupportedOrNodeJS;
+
             // Invalid UTF-16 in a string (mismatched surrogate pairs) should be unchanged.
             foreach (string cultureName in new string[] { "", "en-US", "fr" })
             {
-                ToLower(cultureName, "BE CAREFUL, \uD83C\uD83C, THIS ONE IS TRICKY", "be careful, \uD83C\uD83C, this one is tricky");
-                ToLower(cultureName, "BE CAREFUL, \uDF08\uD83C, THIS ONE IS TRICKY", "be careful, \uDF08\uD83C, this one is tricky");
-                ToLower(cultureName, "BE CAREFUL, \uDF08\uDF08, THIS ONE IS TRICKY", "be careful, \uDF08\uDF08, this one is tricky");
+                ToLower(cultureName, "\uD83C\uD83C", usesTextDecoder ? "\uFFFD\uFFFD" : "\uD83C\uD83C");
+                ToLower(cultureName, "BE CAREFUL, \uDF08\uD83C, THIS ONE IS TRICKY", usesTextDecoder ? "be careful, \uFFFD\uFFFD, this one is tricky" : "be careful, \uDF08\uD83C, this one is tricky");
+                ToLower(cultureName, "BE CAREFUL, \uDF08\uDF08, THIS ONE IS TRICKY", usesTextDecoder ? "be careful, \uFFFD\uFFFD, this one is tricky" : "be careful, \uDF08\uDF08, this one is tricky");
             }
         }
 
@@ -452,12 +454,14 @@ public void ToUpper_netcore(string name, string str, string expected)
         [Fact]
         public void ToUpper_InvalidSurrogates()
         {
+            bool usesTextDecoder = PlatformDetection.IsHybridGlobalizationOnBrowser && PlatformDetection.IsBrowserDomSupportedOrNodeJS;
+
             // Invalid UTF-16 in a string (mismatched surrogate pairs) should be unchanged.
             foreach (string cultureName in new string[] { "", "en-US", "fr"})
             {
-                ToUpper(cultureName, "be careful, \uD83C\uD83C, this one is tricky", "BE CAREFUL, \uD83C\uD83C, THIS ONE IS TRICKY");
-                ToUpper(cultureName, "be careful, \uDF08\uD83C, this one is tricky", "BE CAREFUL, \uDF08\uD83C, THIS ONE IS TRICKY");
-                ToUpper(cultureName, "be careful, \uDF08\uDF08, this one is tricky", "BE CAREFUL, \uDF08\uDF08, THIS ONE IS TRICKY");
+                ToUpper(cultureName, "be careful, \uD83C\uD83C, this one is tricky", usesTextDecoder ? "BE CAREFUL, \uFFFD\uFFFD, THIS ONE IS TRICKY" : "BE CAREFUL, \uD83C\uD83C, THIS ONE IS TRICKY");
+                ToUpper(cultureName, "be careful, \uDF08\uD83C, this one is tricky", usesTextDecoder ? "BE CAREFUL, \uFFFD\uFFFD, THIS ONE IS TRICKY" : "BE CAREFUL, \uDF08\uD83C, THIS ONE IS TRICKY");
+                ToUpper(cultureName, "be careful, \uDF08\uDF08, this one is tricky", usesTextDecoder ? "BE CAREFUL, \uFFFD\uFFFD, THIS ONE IS TRICKY" : "BE CAREFUL, \uDF08\uDF08, THIS ONE IS TRICKY");
             }
         }
 

src/mono/wasm/runtime/hybrid-globalization.ts

@@ -1,24 +1,23 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-import { Module } from "./globals";
 import { mono_wasm_new_external_root } from "./roots";
 import { MonoString, MonoStringRef } from "./types";
 import { Int32Ptr } from "./types/emscripten";
 import { conv_string_root, js_string_to_mono_string_root, string_decoder } from "./strings";
-import { setU16 } from "./memory";
+import { setU16_unchecked } from "./memory";
 
-export function mono_wasm_change_case_invariant(exceptionMessage: Int32Ptr, src: number, srcLength: number, dst: number, dstLength: number, toUpper: number): void {
-    try {
-        const input = get_utf16_string(src, srcLength);
+export function mono_wasm_change_case_invariant(exceptionMessage: Int32Ptr, src: number, srcLength: number, dst: number, dstLength: number, toUpper: number) : void{
+    try{
+        const input = string_decoder.decode(<any>src, <any>(src + 2*srcLength));
         let result = toUpper ? input.toUpperCase() : input.toLowerCase();
         // Unicode defines some codepoints which expand into multiple codepoints,
         // originally we do not support this expansion
         if (result.length > dstLength)
             result = input;
 
-        for (let i = 0; i < result.length; i++)
-            setU16(dst + i * 2, result.charCodeAt(i));
+        for (let i = 0, j = dst; i < result.length; i++, j += 2)
+            setU16_unchecked(j, result.charCodeAt(i));
     }
     catch (ex: any) {
         pass_exception_details(ex, exceptionMessage);
@@ -31,13 +30,13 @@ export function mono_wasm_change_case(exceptionMessage: Int32Ptr, culture: MonoS
         const cultureName = conv_string_root(cultureRoot);
         if (!cultureName)
             throw new Error("Cannot change case, the culture name is null.");
-        const input = get_utf16_string(src, srcLength);
+        const input = string_decoder.decode(<any>src, <any>(src + 2*srcLength));
         let result = toUpper ? input.toLocaleUpperCase(cultureName) : input.toLocaleLowerCase(cultureName);
         if (result.length > destLength)
             result = input;
 
-        for (let i = 0; i < destLength; i++)
-            setU16(dst + i * 2, result.charCodeAt(i));
+        for (let i = 0, j = dst; i < result.length; i++, j += 2)
+            setU16_unchecked(j, result.charCodeAt(i));
     }
     catch (ex: any) {
         pass_exception_details(ex, exceptionMessage);
@@ -47,14 +46,6 @@ export function mono_wasm_change_case(exceptionMessage: Int32Ptr, culture: MonoS
     }
 }
 
-function get_utf16_string(ptr: number, length: number): string {
-    const view = new Uint16Array(Module.HEAPU16.buffer, ptr, length);
-    let string = "";
-    for (let i = 0; i < length; i++)
-        string += String.fromCharCode(view[i]);
-    return string;
-}
-
 export function mono_wasm_compare_string(exceptionMessage: Int32Ptr, culture: MonoStringRef, str1: number, str1Length: number, str2: number, str2Length: number, options: number): number {
     const cultureRoot = mono_wasm_new_external_root<MonoString>(culture);
     try {

src/mono/wasm/runtime/memory.ts

@@ -2,10 +2,10 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 import monoWasmThreads from "consts:monoWasmThreads";
-import { Module, runtimeHelpers } from "./globals";
 import { mono_assert, MemOffset, NumberOrPointer } from "./types";
 import { VoidPtr, CharPtr } from "./types/emscripten";
 import cwraps, { I52Error } from "./cwraps";
+import { Module, runtimeHelpers } from "./globals";
 
 const alloca_stack: Array<VoidPtr> = [];
 const alloca_buffer_size = 32 * 1024;
@@ -73,6 +73,10 @@ export function setU16(offset: MemOffset, value: number): void {
     Module.HEAPU16[<any>offset >>> 1] = value;
 }
 
+export function setU16_unchecked(offset: MemOffset, value: number): void {
+    Module.HEAPU16[<any>offset >>> 1] = value;
+}
+
 export function setU32_unchecked(offset: MemOffset, value: NumberOrPointer): void {
     Module.HEAPU32[<any>offset >>> 2] = <number><any>value;
 }