internal/pkg: decompress xz streams

This uses a port of the public domain xz implementation.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/xz/dec_util.go

@@ -0,0 +1,52 @@
+/*
+ * XZ decompressor utility functions
+ *
+ * Author: Michael Cross <https://github.com/xi2>
+ *
+ * This file has been put into the public domain.
+ * You can do whatever you want with this file.
+ */
+
+package xz
+
+func getLE32(buf []byte) uint32 {
+	return uint32(buf[0]) |
+		uint32(buf[1])<<8 |
+		uint32(buf[2])<<16 |
+		uint32(buf[3])<<24
+}
+
+func getBE32(buf []byte) uint32 {
+	return uint32(buf[0])<<24 |
+		uint32(buf[1])<<16 |
+		uint32(buf[2])<<8 |
+		uint32(buf[3])
+}
+
+func putLE32(val uint32, buf []byte) {
+	buf[0] = byte(val)
+	buf[1] = byte(val >> 8)
+	buf[2] = byte(val >> 16)
+	buf[3] = byte(val >> 24)
+	return
+}
+
+func putBE32(val uint32, buf []byte) {
+	buf[0] = byte(val >> 24)
+	buf[1] = byte(val >> 16)
+	buf[2] = byte(val >> 8)
+	buf[3] = byte(val)
+	return
+}
+
+func putLE64(val uint64, buf []byte) {
+	buf[0] = byte(val)
+	buf[1] = byte(val >> 8)
+	buf[2] = byte(val >> 16)
+	buf[3] = byte(val >> 24)
+	buf[4] = byte(val >> 32)
+	buf[5] = byte(val >> 40)
+	buf[6] = byte(val >> 48)
+	buf[7] = byte(val >> 56)
+	return
+}