internal/pkg: decompress xz streams

This uses a port of the public domain xz implementation.

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

1 files changed, 124 insertions, 0 deletions

diff --git a/internal/xz/dec_xz.go b/internal/xz/dec_xz.go
new file mode 100644
index 00000000..1b18a838
--- /dev/null
+++ b/internal/xz/dec_xz.go
@@ -0,0 +1,124 @@
+/*
+ * XZ decompressor
+ *
+ * Authors: Lasse Collin <lasse.collin@tukaani.org>
+ *          Igor Pavlov <http://7-zip.org/>
+ *
+ * Translation to Go: 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
+
+/* from linux/include/linux/xz.h **************************************/
+
+/**
+ * xzRet - Return codes
+ * @xzOK:                   Everything is OK so far. More input or more
+ *                          output space is required to continue.
+ * @xzStreamEnd:            Operation finished successfully.
+ * @xzUnSupportedCheck:     Integrity check type is not supported. Decoding
+ *                          is still possible by simply calling xzDecRun
+ *                          again.
+ * @xzMemlimitError:        A bigger LZMA2 dictionary would be needed than
+ *                          allowed by the dictMax argument given to
+ *                          xzDecInit.
+ * @xzFormatError:          File format was not recognized (wrong magic
+ *                          bytes).
+ * @xzOptionsError:         This implementation doesn't support the requested
+ *                          compression options. In the decoder this means
+ *                          that the header CRC32 matches, but the header
+ *                          itself specifies something that we don't support.
+ * @xzDataError:            Compressed data is corrupt.
+ * @xzBufError:             Cannot make any progress.
+ *
+ * xzBufError is returned when two consecutive calls to XZ code cannot
+ * consume any input and cannot produce any new output.  This happens
+ * when there is no new input available, or the output buffer is full
+ * while at least one output byte is still pending. Assuming your code
+ * is not buggy, you can get this error only when decoding a
+ * compressed stream that is truncated or otherwise corrupt.
+ */
+type xzRet int
+
+const (
+	xzOK xzRet = iota
+	xzStreamEnd
+	xzUnsupportedCheck
+	xzMemlimitError
+	xzFormatError
+	xzOptionsError
+	xzDataError
+	xzBufError
+)
+
+/**
+ * xzBuf - Passing input and output buffers to XZ code
+ * @in:         Input buffer.
+ * @inPos:      Current position in the input buffer. This must not exceed
+ *              input buffer size.
+ * @out:        Output buffer.
+ * @outPos:     Current position in the output buffer. This must not exceed
+ *              output buffer size.
+ *
+ * Only the contents of the output buffer from out[outPos] onward, and
+ * the variables inPos and outPos are modified by the XZ code.
+ */
+type xzBuf struct {
+	in     []byte
+	inPos  int
+	out    []byte
+	outPos int
+}
+
+/* All XZ filter IDs */
+type xzFilterID int64
+
+const (
+	idDelta       xzFilterID = 0x03
+	idBCJX86      xzFilterID = 0x04
+	idBCJPowerPC  xzFilterID = 0x05
+	idBCJIA64     xzFilterID = 0x06
+	idBCJARM      xzFilterID = 0x07
+	idBCJARMThumb xzFilterID = 0x08
+	idBCJSPARC    xzFilterID = 0x09
+	idLZMA2       xzFilterID = 0x21
+)
+
+// CheckID is the type of the data integrity check in an XZ stream
+// calculated from the uncompressed data.
+type CheckID int
+
+func (id CheckID) String() string {
+	switch id {
+	case CheckNone:
+		return "None"
+	case CheckCRC32:
+		return "CRC32"
+	case CheckCRC64:
+		return "CRC64"
+	case CheckSHA256:
+		return "SHA256"
+	default:
+		return "Unknown"
+	}
+}
+
+const (
+	CheckNone   CheckID = 0x00
+	CheckCRC32  CheckID = 0x01
+	CheckCRC64  CheckID = 0x04
+	CheckSHA256 CheckID = 0x0A
+	checkMax    CheckID = 0x0F
+	checkUnset  CheckID = -1
+)
+
+// An XZ stream contains a stream header which holds information about
+// the stream. That information is exposed as fields of the
+// Reader. Currently it contains only the stream's data integrity
+// check type.
+type Header struct {
+	CheckType CheckID // type of the stream's data integrity check
+}