Add support for CHM

core.d.ts

@@ -135,7 +135,8 @@ declare namespace core {
 		| 'lzh'
 		| 'pgp'
 		| 'asar'
-		| 'stl';
+		| 'stl'
+		| 'chm';
 
 	type MimeType =
 		| 'image/jpeg'
@@ -264,7 +265,8 @@ declare namespace core {
 		| 'application/x-lzh-compressed'
 		| 'application/pgp-encrypted'
 		| 'application/x-asar'
-		| 'model/stl';
+		| 'model/stl'
+		| 'application/vnd.ms-htmlhelp';
 
 	interface FileTypeResult {
 		/**

core.js

@@ -880,6 +880,13 @@ async function _fromTokenizer(tokenizer) {
 		}
 	}
 
+	if (checkString('ITSF')) {
+		return {
+			ext: 'chm',
+			mime: 'application/vnd.ms-htmlhelp'
+		};
+	}
+
 	// -- 6-byte signatures --
 
 	if (check([0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00])) {

package.json

@@ -179,7 +179,8 @@
 		"lzh",
 		"pgp",
 		"asar",
-		"stl"
+		"stl",
+		"chm"
 	],
 	"devDependencies": {
 		"@types/node": "^13.1.4",

readme.md

@@ -404,6 +404,7 @@ Returns a set of supported MIME types.
 - [`pgp`](https://en.wikipedia.org/wiki/Pretty_Good_Privacy) - Pretty Good Privacy
 - [`asar`](https://github.com/electron/asar#format) - Archive format primarily used to enclose Electron applications
 - [`stl`](https://en.wikipedia.org/wiki/STL_(file_format)) - Standard Tesselated Geometry File Format (ASCII only)
+- [`chm`](https://en.wikipedia.org/wiki/Microsoft_Compiled_HTML_Help) - Microsoft Compiled HTML Help
 
 *Pull requests are welcome for additional commonly used file types.*
 

supported.js

@@ -133,7 +133,8 @@ module.exports = {
 		'lzh',
 		'pgp',
 		'asar',
-		'stl'
+		'stl',
+		'chm'
 	],
 	mimeTypes: [
 		'image/jpeg',
@@ -262,6 +263,7 @@ module.exports = {
 		'application/x-lzh-compressed',
 		'application/pgp-encrypted',
 		'application/x-asar',
-		'model/stl'
+		'model/stl',
+		'application/vnd.ms-htmlhelp'
 	]
 };