golang实现断点续传

这里只展示了核心代码部分，使用了封装request和response的gin框架，若小伙伴没使用可用改成go自带的http。

func SendFile(r *gin.Context) {
	//断点续传标志
	var range_ext = r.GetHeader("Range")

	filePath := "." + r.Request.URL.Path

	if filePath == "./" {
		filePath = "./index.html"
	}

	parts := strings.Split(filePath, ".")

	print(parts[len(parts)-1] + "\n")
	print(filePath + "\n")

	file1, _ := os.Open(filePath)
	data, _ := ioutil.ReadAll(file1)

	//获取content type
	contentType := extensionToContentType[parts[len(parts)-1]]
	print(contentType + "\n")

	if file1 == nil {
		r.HTML(404, "404.html", gin.H{})
		return
	}

	var FileStreamSize int64 = r.Request.ContentLength

	if FileStreamSize == 0 {
		fi, _ := file1.Stat()
		FileStreamSize = fi.Size()
	}
	var FileStreamLen string = strconv.FormatInt(FileStreamSize, 10)

	//Range字段为空, 直接发送数据
	if range_ext == "" {
		r.Writer.Header().Set("Content-Type", contentType)
		r.Writer.Header().Set("Content-Length", FileStreamLen)
		r.Writer.WriteHeader(200)
		r.Writer.Write(data)
		return
	}

	//Range字段非空，断点续传模式
	fmt.Printf("part  download...\n")
	fmt.Printf("head range is:%s\n", range_ext)

	length := strings.Index(range_ext, "=")
	allRange := range_ext[length+1:]

	remove := strings.Index(allRange, "-")
	prelen := allRange[:remove]
	behind := allRange[remove+1:]
	var start int64
	var end int64

	if prelen == "" {
		behindint, _ := strconv.ParseInt(behind, 10, 64)
		start = FileStreamSize - behindint
		end = FileStreamSize
		FileStreamLen = behind
	}

	if behind == "" {
		prelenint, _ := strconv.ParseInt(prelen, 10, 64)
		start = prelenint
		end = FileStreamSize
		FileStreamLen = strconv.FormatInt(end-start, 10)
	}

	if prelen != "" && behind != "" {
		prelenint, _ := strconv.ParseInt(prelen, 10, 64)
		behindint, _ := strconv.ParseInt(behind, 10, 64)
		start = prelenint
		end = behindint
		FileStreamLen = strconv.FormatInt(end-start+1, 10)
	}

	allRange = allRange + strconv.FormatInt(FileStreamSize, 10)
	fmt.Printf("start:%v, end:%v, allRange:%v, FileSize:%v, FileLen:%v\n", start, end, allRange, FileStreamSize, FileStreamLen)

	r.Writer.Header().Set("Content-Type", contentType)
	r.Writer.Header().Set("Accept-Ranges", "bytes")
	r.Writer.Header().Set("Content-Length", FileStreamLen)
	r.Writer.Header().Set("Content-Range", "bytes "+allRange+"/"+strconv.FormatInt(FileStreamSize, 10))

	r.Writer.WriteHeader(206)

	r.Writer.Write(data[start:end])

	fmt.Println("file Wirte finished")
}