Fix handling of Uint8Array and ArrayBuffer (#214)

index.js

@@ -1,5 +1,5 @@
 'use strict';
-const {stringToBytes, readUInt64LE, tarHeaderChecksumMatches} = require('./util');
+const {stringToBytes, readUInt64LE, tarHeaderChecksumMatches, uint8ArrayUtf8ByteString} = require('./util');
 
 const xpiZipFilename = stringToBytes('META-INF/mozilla.rsa');
 const oxmlContentTypes = stringToBytes('[Content_Types].xml');
@@ -289,7 +289,7 @@ const fileType = input => {
 	) {
 		// They all can have MIME `video/mp4` except `application/mp4` special-case which is hard to detect.
 		// For some cases, we're specific, everything else falls to `video/mp4` with `mp4` extension.
-		const brandMajor = buffer.toString('utf8', 8, 12);
+		const brandMajor = uint8ArrayUtf8ByteString(buffer, 8, 12);
 		switch (brandMajor) {
 			case 'mif1':
 				return {ext: 'heic', mime: 'image/heif'};

test.js

@@ -6,11 +6,6 @@ import readChunk from 'read-chunk';
 import pify from 'pify';
 import fileType from '.';
 
-const check = (ext, name) => {
-	const file = path.join(__dirname, 'fixture', `${(name || 'fixture')}.${ext}`);
-	return fileType(readChunk.sync(file, 0, 4 + 4096)) || {};
-};
-
 const types = [
 	'jpg',
 	'png',
@@ -209,12 +204,20 @@ const names = {
 	]
 };
 
-const testFile = (t, type, name) => {
-	const {ext, mime} = check(type, name);
+const checkBufferLike = (t, type, bufferLike) => {
+	const {ext, mime} = fileType(bufferLike) || {};
 	t.is(ext, type);
 	t.is(typeof mime, 'string');
 };
 
+const testFile = (t, ext, name) => {
+	const file = path.join(__dirname, 'fixture', `${(name || 'fixture')}.${ext}`);
+	const chunk = readChunk.sync(file, 0, 4 + 4096);
+	checkBufferLike(t, ext, chunk);
+	checkBufferLike(t, ext, new Uint8Array(chunk));
+	checkBufferLike(t, ext, chunk.buffer);
+};
+
 const testFileFromStream = async (t, ext, name) => {
 	const file = path.join(__dirname, 'fixture', `${(name || 'fixture')}.${ext}`);
 	const readableStream = await fileType.stream(fs.createReadStream(file));

util.js

@@ -2,6 +2,10 @@
 
 exports.stringToBytes = string => [...string].map(character => character.charCodeAt(0));
 
+const uint8ArrayUtf8ByteString = (array, start, end) => {
+	return String.fromCharCode(...array.slice(start, end));
+};
+
 exports.readUInt64LE = (buffer, offset = 0) => {
 	let n = buffer[offset];
 	let mul = 1;
@@ -39,7 +43,7 @@ exports.tarHeaderChecksumMatches = buffer => { // Does not check if checksum fie
 		signedBitSum += byte & MASK_8TH_BIT; // Add signed bit to signed bit sum
 	}
 
-	const readSum = parseInt(buffer.toString('utf8', 148, 154), 8); // Read sum in header
+	const readSum = parseInt(uint8ArrayUtf8ByteString(buffer, 148, 154), 8); // Read sum in header
 
 	// Some implementations compute checksum incorrectly using signed bytes
 	return (
@@ -50,3 +54,5 @@ exports.tarHeaderChecksumMatches = buffer => { // Does not check if checksum fie
 		readSum === (sum - (signedBitSum << 1))
 	);
 };
+
+exports.uint8ArrayUtf8ByteString = uint8ArrayUtf8ByteString;