From 6c508922fcfe285213a524b2331f4f18d8a18fc2 Mon Sep 17 00:00:00 2001 From: Graham Date: Sat, 29 Jan 2022 21:38:11 +0000 Subject: [PATCH] Add JagexGzipOutputStream Equivalent to the built-in GZIPOutputStream, except it produces output that is bit-for-bit identical to Jagex's implementation. Signed-off-by: Graham --- .../compress/gzip/JagexGzipOutputStream.kt | 75 +++++++++++++++++++ 1 file changed, 75 insertions(+) create mode 100644 compress/src/main/kotlin/org/openrs2/compress/gzip/JagexGzipOutputStream.kt diff --git a/compress/src/main/kotlin/org/openrs2/compress/gzip/JagexGzipOutputStream.kt b/compress/src/main/kotlin/org/openrs2/compress/gzip/JagexGzipOutputStream.kt new file mode 100644 index 00000000..5265a3ec --- /dev/null +++ b/compress/src/main/kotlin/org/openrs2/compress/gzip/JagexGzipOutputStream.kt @@ -0,0 +1,75 @@ +package org.openrs2.compress.gzip + +import com.google.common.io.LittleEndianDataOutputStream +import java.io.DataOutputStream +import java.io.OutputStream +import java.util.zip.CRC32 +import java.util.zip.Deflater + +public class JagexGzipOutputStream( + private val output: OutputStream +) : OutputStream() { + private val deflater = Deflater(Deflater.DEFAULT_COMPRESSION, true) + private val buffer = ByteArray(4096) + private val checksum = CRC32() + private var size = 0 + private var closed = false + + init { + val dataOutput = DataOutputStream(output) + dataOutput.writeShort(HEADER_MAGIC) + dataOutput.writeByte(METHOD_DEFLATE) + dataOutput.writeByte(0) // FLG + dataOutput.writeInt(0) // MTIME + dataOutput.writeByte(0) // XFL + dataOutput.writeByte(0) // OS + } + + override fun write(b: Int) { + buffer[0] = b.toByte() + write(buffer, 0, 1) + } + + override fun write(b: ByteArray, off: Int, len: Int) { + checksum.update(b, off, len) + size += len + + deflater.setInput(b, off, len) + + while (!deflater.needsInput()) { + drain() + } + } + + private fun drain() { + val n = deflater.deflate(buffer) + if (n != 0) { + output.write(buffer, 0, n) + } + } + + override fun close() { + if (!closed) { + deflater.finish() + + while (!deflater.finished()) { + drain() + } + + val dataOutput = LittleEndianDataOutputStream(output) + dataOutput.writeInt(checksum.value.toInt()) + dataOutput.writeInt(size) + + deflater.end() + output.close() + + closed = true + } + } + + private companion object { + private const val HEADER_MAGIC = 0x1F8B + + private const val METHOD_DEFLATE = 8 + } +}