1 files changed, 52 insertions, 0 deletions
diff --git a/plugin/src/main/kotlin/moe/nea/archenemy/util/DownloadUtils.kt b/plugin/src/main/kotlin/moe/nea/archenemy/util/DownloadUtils.kt
new file mode 100644
index 0000000..cec2c55
--- /dev/null
+++ b/plugin/src/main/kotlin/moe/nea/archenemy/util/DownloadUtils.kt
@@ -0,0 +1,52 @@
+package moe.nea.archenemy.util
+
+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")
+    }
+}
+\ No newline at end of file