Make stream() sample size configurable

Improve document stream() detection limitation.

Related: #426, #452

core.d.ts

@@ -356,42 +356,46 @@ declare namespace core {
 	const mimeTypes: Set<core.MimeType>;
 
 	/**
-	 * Stream options.
+	 * Option object, used by `stream()`.
 	 */
-	interface IStreamOptions {
+	interface StreamOptions {
 		/**
 		 *  Sample size in bytes.
 		 */
 		readonly sampleSize?: number
 	}
 
 	/**
-	Detect the file type of a readable stream.
+	Returns a `Promise` which resolves to the original readable stream argument, but with an added `fileType` property, which is an object like the one returned from `FileType.fromFile()`.
+
+	This method can be handy to put in between a stream, but it comes with a price.
+	Internally `stream()` builds up a buffer of `sampleSize` bytes, used as a sample, to determine the file type.
+	The sample size impacts the file detection resolution.
+	A smaller sample size will result in lower probability of the best file type detection.
+
+	 *Note:* This method is only available using Node.js.
 
 	@param readableStream - A [readable stream](https://nodejs.org/api/stream.html#stream_class_stream_readable) containing a file to examine.
-	@param options - Options
+	@param options - Option object
 	@returns A `Promise` which resolves to the original readable stream argument, but with an added `fileType` property, which is an object like the one returned from `FileType.fromFile()`.
 
 	@example
-	```
-	import * as fs from 'fs';
-	import * as crypto from 'crypto';
-	import fileType = require('file-type');
+	```js
+	const got = require('got');
+	const FileType = require('file-type');
 
-	(async () => {
-		const read = fs.createReadStream('encrypted.enc');
-		const decipher = crypto.createDecipheriv(alg, key, iv);
-		const stream = await fileType.stream(read.pipe(decipher), {sampleSize: 1024});
-
-		console.log(stream.fileType);
-		//=> {ext: 'mov', mime: 'video/quicktime'}
+	const url = 'https://upload.wikimedia.org/wikipedia/en/a/a9/Example.jpg';
 
-		const write = fs.createWriteStream(`decrypted.${stream.fileType.ext}`);
-		stream.pipe(write);
+	(async () => {
+		const stream1 = got.stream(url);
+		const stream2 = await FileType.stream(stream1, {sampleSize: 1024});
+		if (stream2.fileType && stream2.fileType.mime === 'image/jpeg') {
+			// stream2 can be used to stream the JPEG image (from the very beginning of the stream)
+  	}
 	})();
 	```
 	*/
-	function stream(readableStream: ReadableStream, options?: IStreamOptions): Promise<core.ReadableStreamWithFileType>
+	function stream(readableStream: ReadableStream, options?: StreamOptions): Promise<core.ReadableStreamWithFileType>
 }
 
 export = core;

readme.md

@@ -278,20 +278,47 @@ Type: [`ITokenizer`](https://github.com/Borewit/strtok3#tokenizer)
 
 A file source implementing the [tokenizer interface](https://github.com/Borewit/strtok3#tokenizer).
 
-### FileType.stream(readableStream, sampleSize)
-
-Detect the file type of a readable stream.
-
-If `sampleSize` is not provided, a backward compatible sample size of 4100 bytes is used.
+### FileType.stream(readableStream, options?)
 
 Returns a `Promise` which resolves to the original readable stream argument, but with an added `fileType` property, which is an object like the one returned from `FileType.fromFile()`.
 
 This method can be handy to put in between a stream, but it comes with a price.
 Internally `stream()` builds up a buffer of `sampleSize` bytes, used as a sample, to determine the file type.
-The sample size impacts the file detection resolution. A smaller sample size will result in lower probability of the best file type detection.
+The sample size impacts the file detection resolution.
+A smaller sample size will result in lower probability of the best file type detection.
 
 *Note:* This method is only available using Node.js.
 
+#### readableStream
+Type: [`Readable`](https://nodejs.org/api/stream.html#stream_class_stream_readable)
+
+#### options
+Type: `Object`, for example:
+```js
+{ sampleSize: 400 }
+```
+
+##### sampleSize
+Type: `number`, change default sample size of 4100 bytes.
+
+#### Example
+
+```js
+const got = require('got');
+const FileType = require('file-type');
+
+const url = 'https://upload.wikimedia.org/wikipedia/en/a/a9/Example.jpg';
+
+(async () => {
+  const stream1 = got.stream(url);
+  const stream2 = await FileType.stream(stream1, {sampleSize: 1024});
+  if (stream2.fileType && stream2.fileType.mime === 'image/jpeg') {
+    // stream2 can be used to stream the JPEG image (from the very beginning of the stream)
+  }
+})();
+```
+
+
 #### readableStream
 
 Type: [`stream.Readable`](https://nodejs.org/api/stream.html#stream_class_stream_readable)

test.js

@@ -337,7 +337,7 @@ test('.stream() method - short stream', async t => {
 	t.deepEqual(bufferA, bufferB);
 });
 
-test('.stream() method - no End-Of-Stream errors', async t => {
+test('.stream() method - no end-of-stream errors', async t => {
 	const file = path.join(__dirname, 'fixture', 'fixture.ogm');
 	const stream = await FileType.stream(fs.createReadStream(file), {sampleSize: 30});
 	t.is(stream.fileType, undefined);