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package moe.nea.archenemy
import java.io.File
import java.io.IOException
import java.net.URL
import java.security.MessageDigest
object DownloadUtils {
fun bytesToHex(hash: ByteArray): String {
val hexString = StringBuilder(2 * hash.size)
for (i in hash.indices) {
val hex = Integer.toHexString(0xff and hash[i].toInt())
if (hex.length == 1) {
hexString.append('0')
}
hexString.append(hex)
}
return hexString.toString()
}
fun sha1Hash(file: File): String {
if (!file.exists()) return ""
val messageDigest = MessageDigest.getInstance("SHA-1")
file.inputStream().use {
val r = ByteArray(4096)
while (true) {
val d = it.read(r)
if (d < 0) break
messageDigest.update(r, 0, d)
}
}
return bytesToHex(messageDigest.digest())
}
fun areHashesEqual(a: String, b: String): Boolean {
return b.equals(a, ignoreCase = true)
}
fun downloadFile(source: URL, sha1: String, targetFile: File) {
targetFile.parentFile.mkdirs()
if (areHashesEqual(sha1Hash(targetFile), sha1)) return
source.openStream().use { inp ->
targetFile.outputStream().use { out ->
inp.copyTo(out)
}
}
if (!areHashesEqual(sha1Hash(targetFile), sha1))
throw IOException("$targetFile should hash to $sha1, but does not")
}
}
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