resume download use kotlin

download.kt

import java.io.*
import java.net.URL
import java.net.HttpURLConnection as http

data class Response(val status: Int=200, var header: Map<String, List<String>>, var stream: InputStream)


object Request {

    private fun method(method:String, url: String, header: Map<String, String>, followRedirect:Boolean=true): Pair<Response, http> {
        val client = URL(url).openConnection() as http
        client.requestMethod = method
        client.instanceFollowRedirects = followRedirect
        client.addHeaders(header)
        val respHeader = client.headerFields.filter { m->m.key != null }
        return Pair(Response(client.responseCode, respHeader, client.inputStream), client)
    }

    fun get(url: String, header:Map<String, String>): Pair<Response,http> {
        return method("GET", url, header)
    }

    fun range(url: String, header:Map<String, String>, start:Int=0, end:Int=0): Pair<Response,http> {
        val endIndex = if (end == 0) "" else end
        val rangeStr = "bytes=%d-%s".format(start, endIndex)
        val mutableMap = header as MutableMap
        mutableMap.put("Range", rangeStr)
        return method("GET", url, header)
    }


    fun head(url: String, header:Map<String, String>): Pair<Response,http> {
        return method("HEAD", url, header)
    }
}

val headers = mutableMapOf(
        "User-Agent" to "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.113 Safari/537.36",
        "Accept" to "*",
        "Range" to "bytes=0-1024",
        "Connection" to "keep-alive",
        "Referer" to "",
        "Accept-Encoding" to "en;q=0.4,en-US;q=0.2",
        "Accept-Encoding" to "gzip, deflate"
)

val name = "test"

fun getLength(url:String): Int? {
     val (headResp, client)  = Request.head(url, headers)
     val status = headResp.status
     if (status != 200) {
         println("failed!")
     }
    client.close()
    return headResp.header.get("Content-Length")?.get(0)?.toInt()
}


fun downloadFile(url:String) {
    //获取文件信息，恢复断点
    val fileInfo = findFile(name)
    if (fileInfo == null) {
        println("info file not found")
        return
    }
    val (resp, client) = Request.range(url, headers, fileInfo!!.offset!!)
    when(resp.status) {
        200,206 -> {
            writeFile(client.inputStream, name, fileInfo!!.offset!!, fun (bytes: Int){
                println(bytes)
                val sourceSize = fileInfo.offset!!.plus(bytes)
                fileInfo.offset = sourceSize
                writeFileInfo(name, fileInfo.size, sourceSize)
            })
        }
        else-> println("download failed!")
    }
}

fun main(args:Array<String>) {
    val url = ""
    var fileInfo = findFile(name)
    if(fileInfo == null) {
        val vSize = getLength(url)
        writeFileInfo(name, vSize, 0)
    }
    downloadFile(url)
}

fun http.addHeaders(headers:Map<String,String>) {
    headers.forEach { k, v -> this.addRequestProperty(k, v) }
}

fun http.close() {
    this.disconnect()
}

fun writeFile(stream: InputStream, name:String, offset:Int=0, callback:(bytes:Int)->Unit={}) {
    val buff = ByteArray(65535)
    val accessFile = RandomAccessFile(File(name), "rw")
    val contentLength = 0
    accessFile.seek(offset.toLong())
    accessFile.use {
        var contentLength = 0
        while (true) {
            val len = stream.read(buff)
            if (len == -1) {
                println("exited!")
                break
            }
            contentLength = contentLength + len
            it.write(buff, 0, len)
            callback(len)
        }
    }
    println("%s length is %d".format(name, contentLength))
}

fun findFile(name:String):FileInfo? {
    val infoFileName = "%s.info".format(name)
    val infoFile = File(infoFileName)
    if (infoFile.exists()) {
        val fileInfo = FileInfo()
        val textInfo = infoFile.readText().split("\n")
        textInfo.forEach { it ->
            val pair = it.split("=")
            when(pair[0]) {
                "name" -> fileInfo.name = pair[1]
                "size" -> fileInfo.size = pair[1].toInt()
                "offset" -> fileInfo.offset = pair[1].toInt()
                "ok" -> fileInfo.ok = pair[1].toBoolean()
            }
        }
        return fileInfo
    }
    return null
}

fun writeFileInfo(name:String, size:Int?, offset: Int):FileInfo {

    val infPath = "%s.info".format(name)
    val ok = offset >0 && offset == size
    val infContent= "name=%s\nsize=%d\noffset=%d\nok=%b".format(name, size, offset, ok)
    File(infPath).writeText(infContent)
    return FileInfo(name, size)
}

data class FileInfo(var name:String?=null, var size:Int?=0, var offset: Int?=0, var ok:Boolean?=false)