feat: Add ASCII encoding support (#78)

Author: dnicolson

.github/workflows/test-build.js

@@ -8,6 +8,7 @@ assert(typeof chardet.detectFile, 'function');
 assert(typeof chardet.detectFileSync, 'function');
 
 assert.deepStrictEqual(chardet.analyse(Buffer.from('This is a test')), [
+  { confidence: 100, name: 'ASCII', lang: undefined },
   { confidence: 98, name: 'ISO-8859-1', lang: 'en' },
   { confidence: 98, name: 'ISO-8859-2', lang: 'hu' },
   { confidence: 10, name: 'UTF-8', lang: undefined },

.github/workflows/test-build.ts

@@ -9,6 +9,7 @@ const main = async () => {
   assert(typeof chardet.detectFileSync, 'function');
 
   assert.deepStrictEqual(chardet.analyse(Buffer.from('This is a test')), [
+    { confidence: 100, name: 'ASCII', lang: undefined },
     { confidence: 98, name: 'ISO-8859-1', lang: 'en' },
     { confidence: 98, name: 'ISO-8859-2', lang: 'hu' },
     { confidence: 10, name: 'UTF-8', lang: undefined },

src/encoding/ascii.test.ts

@@ -0,0 +1,9 @@
+import * as chardet from '..';
+
+describe('ASCII', () => {
+  it('should return ASCII', () => {
+    expect(
+      chardet.detectFileSync(__dirname + '/../test/data/encodings/ascii')
+    ).toBe('ASCII');
+  });
+});

src/encoding/ascii.ts

@@ -0,0 +1,21 @@
+import { Context, Recogniser } from '.';
+import match, { Match } from '../match';
+
+export default class Ascii implements Recogniser {
+  name() {
+    return 'ASCII';
+  }
+
+  match(det: Context): Match | null {
+    const input = det.rawInput;
+
+    for (let i = 0; i < det.rawLen; i++) {
+      const b = input[i];
+      if (b < 32 || b > 126) {
+        return match(det, this, 0);
+      }
+    }
+
+    return match(det, this, 100);
+  }
+}

src/index.test.ts

@@ -15,6 +15,7 @@ describe('chardet', () => {
     { 'confidence': 6, 'name': 'windows-1250', 'lang': 'pl' },
     { 'confidence': 4, 'name': 'windows-1254', 'lang': 'tr' },
     { 'confidence': 2, 'name': 'windows-1251', 'lang': 'ru' },
+    { 'confidence': 0, 'name': 'ASCII', 'lang': undefined },
   ];
 
   it('has both named and default exports', () => {

src/index.ts

@@ -3,6 +3,7 @@ import { Recogniser, Context } from './encoding';
 
 import loadFs from './fs/node';
 
+import Ascii from './encoding/ascii';
 import Utf8 from './encoding/utf8';
 import * as unicode from './encoding/unicode';
 import * as mbcs from './encoding/mbcs';
@@ -40,6 +41,7 @@ const recognisers: Recogniser[] = [
   new sbcs.windows_1251(),
   new sbcs.windows_1256(),
   new sbcs.KOI8_R(),
+  new Ascii(),
 ];
 
 export type AnalyseResult = Match[];

src/test/data/encodings/ascii

@@ -0,0 +1 @@
+ !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~