move utf32ToString to TextDecoder.ts

src/core/input/TextDecoder.test.ts

@@ -4,64 +4,64 @@
  */
 
 import { assert } from 'chai';
-import { StringToUtf32, stringFromCodePoint } from './TextDecoder';
+import { StringToUtf32, stringFromCodePoint, utf32ToString } from './TextDecoder';
 
-
-// convert UTF32 codepoints to string
-function toString(data: Uint32Array, length: number): string {
-  if ((String as any).fromCodePoint) {
-    return (String as any).fromCodePoint.apply(null, data.subarray(0, length));
-  }
-  let result = '';
-  for (let i = 0; i < length; ++i) {
-    result += stringFromCodePoint(data[i]);
-  }
-  return result;
-}
-
-describe('StringToUtf32 Decoder', () => {
-  describe('full codepoint test', () => {
-    it('0..65535', () => {
-      const decoder = new StringToUtf32();
-      const target = new Uint32Array(5);
-      for (let i = 0; i < 65536; ++i) {
-        // skip surrogate pairs
-        if (i >= 0xD800 && i <= 0xDFFF) {
-          continue;
-        }
-        const length = decoder.decode(String.fromCharCode(i), target);
-        assert.equal(length, 1);
-        assert.equal(target[0], i);
-        assert.equal(toString(target, length), String.fromCharCode(i));
-        decoder.clear();
-      }
-    });
-    it('65536..0x10FFFF (surrogates)', function(): void {
-      this.timeout(20000);
-      const decoder = new StringToUtf32();
-      const target = new Uint32Array(5);
-      for (let i = 65536; i < 0x10FFFF; ++i) {
-        const codePoint = i - 0x10000;
-        const s = String.fromCharCode((codePoint >> 10) + 0xD800) + String.fromCharCode((codePoint % 0x400) + 0xDC00);
-        const length = decoder.decode(s, target);
-        assert.equal(length, 1);
-        assert.equal(target[0], i);
-        assert.equal(toString(target, length), s);
-        decoder.clear();
-      }
-    });
+describe('text encodings', () => {
+  it('stringFromCodePoint/utf32ToString', () => {
+    const s = 'abcdefg';
+    const data = new Uint32Array(s.length);
+    for (let i = 0; i < s.length; ++i) {
+      data[i] = s.charCodeAt(i);
+      assert.equal(stringFromCodePoint(data[i]), s[i]);
+    }
+    assert.equal(utf32ToString(data), s);
   });
-  describe('stream handling', () => {
-    it('surrogates mixed advance by 1', () => {
-      const decoder = new StringToUtf32();
-      const target = new Uint32Array(5);
-      const input = 'Ä€𝄞Ö𝄞€Ü𝄞€';
-      let decoded = '';
-      for (let i = 0; i < input.length; ++i) {
-        const written = decoder.decode(input[i], target);
-        decoded += toString(target, written);
-      }
-      assert(decoded, 'Ä€𝄞Ö𝄞€Ü𝄞€');
+
+  describe('StringToUtf32 Decoder', () => {
+    describe('full codepoint test', () => {
+      it('0..65535', () => {
+        const decoder = new StringToUtf32();
+        const target = new Uint32Array(5);
+        for (let i = 0; i < 65536; ++i) {
+          // skip surrogate pairs
+          if (i >= 0xD800 && i <= 0xDFFF) {
+            continue;
+          }
+          const length = decoder.decode(String.fromCharCode(i), target);
+          assert.equal(length, 1);
+          assert.equal(target[0], i);
+          assert.equal(utf32ToString(target, 0, length), String.fromCharCode(i));
+          decoder.clear();
+        }
+      });
+      it('65536..0x10FFFF (surrogates)', function(): void {
+        this.timeout(20000);
+        const decoder = new StringToUtf32();
+        const target = new Uint32Array(5);
+        for (let i = 65536; i < 0x10FFFF; ++i) {
+          const codePoint = i - 0x10000;
+          const s = String.fromCharCode((codePoint >> 10) + 0xD800) + String.fromCharCode((codePoint % 0x400) + 0xDC00);
+          const length = decoder.decode(s, target);
+          assert.equal(length, 1);
+          assert.equal(target[0], i);
+          assert.equal(utf32ToString(target, 0, length), s);
+          decoder.clear();
+        }
+      });
+    });
+
+    describe('stream handling', () => {
+      it('surrogates mixed advance by 1', () => {
+        const decoder = new StringToUtf32();
+        const target = new Uint32Array(5);
+        const input = 'Ä€𝄞Ö𝄞€Ü𝄞€';
+        let decoded = '';
+        for (let i = 0; i < input.length; ++i) {
+          const written = decoder.decode(input[i], target);
+          decoded += utf32ToString(target, written);
+        }
+        assert(decoded, 'Ä€𝄞Ö𝄞€Ü𝄞€');
+      });
     });
   });
 });

src/core/input/TextDecoder.ts

@@ -2,6 +2,7 @@
  * Copyright (c) 2019 The xterm.js authors. All rights reserved.
  * @license MIT
  */
+import { TypedArray } from '../../common/Types';
 
 /**
  * StringToUtf32 - decodes UTF16 sequences into UTF32 codepoints.
@@ -73,15 +74,31 @@ export class StringToUtf32 {
 }
 
 /**
- * Polyfill - Convert UTF32 codepoint into JS string.
+ * Convert UTF32 codepoint into JS string.
  */
 export function stringFromCodePoint(codePoint: number): string {
-  if ((String as any).fromCodePoint) {
-    return (String as any).fromCodePoint(codePoint);
-  }
   if (codePoint > 0xFFFF) {
     codePoint -= 0x10000;
     return String.fromCharCode((codePoint >> 10) + 0xD800) + String.fromCharCode((codePoint % 0x400) + 0xDC00);
   }
   return String.fromCharCode(codePoint);
 }
+
+/**
+ * Convert UTF32 char codes into JS string.
+ * Basically the same as `stringFromCodePoint` but for multiple codepoints
+ * in a loop (which is a lot faster).
+ */
+export function utf32ToString<T extends TypedArray>(data: T, start: number = 0, end: number = data.length): string {
+  let result = '';
+  let cp;
+  for (let i = start; i < end; ++i) {
+    if ((cp = data[i]) > 0xFFFF) {
+      cp -= 0x10000;
+      result += String.fromCharCode((cp >> 10) + 0xD800) + String.fromCharCode((cp % 0x400) + 0xDC00);
+    } else {
+      result += String.fromCharCode(cp);
+    }
+  }
+  return result;
+}