feat(download): 后端支持 Range 分块; 前端引入多线程分块下载加速音频加载

public/src/js/abstractfile.js

@@ -51,6 +51,55 @@ class RemoteFile{
 			request.responseType = "arraybuffer"
 		})
 	}
+	arrayBufferFast(threads){
+		var t = threads || 4
+		var head = new XMLHttpRequest()
+		head.open("HEAD", this.url)
+		var headPromise = pageEvents.load(head).then(() => {
+			if(head.status !== 200){
+				return Promise.reject()
+			}
+			var len = parseInt(head.getResponseHeader("Content-Length"))
+			if(!len || len < 262144){
+				return this.arrayBuffer()
+			}
+			var chunk = Math.ceil(len / t)
+			var ranges = []
+			for(var i = 0; i < t; i++){
+				var start = i * chunk
+				var end = Math.min(len - 1, (i + 1) * chunk - 1)
+				if(start > end){ break }
+				ranges.push([start, end])
+			}
+			var promises = ranges.map(r => {
+				var req = new XMLHttpRequest()
+				req.open("GET", this.url)
+				req.responseType = "arraybuffer"
+				req.setRequestHeader("Range", "bytes=" + r[0] + "-" + r[1])
+				return pageEvents.load(req).then(() => {
+					if(req.status !== 206 && req.status !== 200){
+						return Promise.reject()
+					}
+					return req.response
+				})
+			})
+			return Promise.all(promises).then(parts => {
+				var total = 0
+				for(var i = 0; i < parts.length; i++){
+					total += parts[i].byteLength
+				}
+				var out = new Uint8Array(total)
+				var offset = 0
+				for(var i = 0; i < parts.length; i++){
+					out.set(new Uint8Array(parts[i]), offset)
+					offset += parts[i].byteLength
+				}
+				return out.buffer
+			})
+		})
+		head.send()
+		return headPromise.catch(() => this.arrayBuffer())
+	}
 	read(encoding){
 		if(encoding){
 			return this.blob().then(blob => readFile(blob, false, encoding))

public/src/js/soundbuffer.js

@@ -1,4 +1,4 @@
-class SoundBuffer{
+class SoundBuffer{
 	constructor(...args){
 		this.init(...args)
 	}
@@ -12,7 +12,8 @@
 	}
 	load(file, gain){
 		var decoder = file.name.endsWith(".ogg") ? this.oggDecoder : this.audioDecoder
-		return file.arrayBuffer().then(response => {
+		var promise = typeof file.arrayBufferFast === "function" ? file.arrayBufferFast(4) : file.arrayBuffer()
+		return promise.then(response => {
 			return new Promise((resolve, reject) => {
 				return decoder(response, resolve, reject)
 			}).catch(error => Promise.reject([error, file.url]))