From 89b19b06f67dde5d427a09a3d066ce97f32b62df Mon Sep 17 00:00:00 2001
From: Caleb Gardner <calebq23@gmail.com>
Date: Tue, 10 Nov 2020 22:31:21 -0600
Subject: [PATCH] more work on decompression

---
 compressionoptions.go | 84 +++++++++++++++++++++++++++++++++++++++----
 reader.go             |  2 +-
 squashfs.go           | 19 +++++++---
 3 files changed, 93 insertions(+), 12 deletions(-)

diff --git a/compressionoptions.go b/compressionoptions.go
index ca9d2e5..5f2d881 100644
--- a/compressionoptions.go
+++ b/compressionoptions.go
@@ -1,6 +1,9 @@
 package squashfs
 
-import "io"
+import (
+	"compress/zlib"
+	"io"
+)
 
 const (
 	zlibCompression = 1 + iota
@@ -13,10 +16,10 @@ const (
 
 //TODO: implement decompress for each type of Options
 type CompressionOptions interface {
-	Decompress([]byte) []byte
-	DecompressCopy(*io.Reader, *io.Writer)
-	Compress([]byte) []byte
-	CompressCopy(*io.Reader, *io.Writer)
+	Decompress(*io.SectionReader, int) ([]byte, error)
+	DecompressCopy(*io.Reader, *io.Writer) (int, error)
+	Compress(*io.SectionReader, int) ([]byte, error)
+	CompressCopy(*io.Reader, *io.Writer) (int, error)
 }
 
 //TODO: Allow creation of options for compression.
@@ -29,7 +32,7 @@ type gzipOptionsRaw struct {
 
 //GzipOptions is the options used for gzip compression. Backed by the raw format, with strategies parsed.
 type GzipOptions struct {
-	CompressionOptions
+	CompressionOptions       //TODO: remove
 	raw                      *gzipOptionsRaw
 	DefaultStrategy          bool
 	FilteredStrategy         bool
@@ -45,11 +48,80 @@ func NewGzipOptions(raw gzipOptionsRaw) GzipOptions {
 	}
 }
 
+func (gzipOp *GzipOptions) Decompress(rdr *io.SectionReader, blockSize int) ([]byte, error) {
+	zlibRdr, err := zlib.NewReader(rdr)
+	defer zlibRdr.Close()
+	if err != nil {
+		return nil, err
+	}
+	out := make([]byte, 0)
+	var tmp []byte
+	read := blockSize
+	for read == blockSize {
+		tmp = make([]byte, blockSize)
+		read, err = zlibRdr.Read(tmp)
+		if err != io.EOF {
+			return nil, err
+		}
+		if read < blockSize {
+			tmp = tmp[:read]
+		}
+		out = append(out, tmp...)
+	}
+	return out, nil
+}
+
+func (gzipOp *GzipOptions) DecompressCopy(rdr *io.Reader, wrt *io.Writer) (int, error) {
+	zlibRdr, err := zlib.NewReader(*rdr)
+	defer zlibRdr.Close()
+	if err != nil {
+		return 0, err
+	}
+	n, err := io.Copy(*wrt, zlibRdr)
+	return int(n), err
+}
+
+func (gzipOp *GzipOptions) Compress(rdr *io.SectionReader, blockSize int) ([]byte, error) {
+
+}
+
+func (gzipOp *GzipOptions) CompressCopy(rdr *io.Reader, wrt *io.Writer) (int, error) {
+	zlibWrt, err := zlib.NewWriter(*wrt) //TODO: allow setting level
+	defer zlibWrt.Close()
+	if err != nil {
+		return 0, err
+	}
+
+}
+
 type xzOptionsRaw struct {
 	dictionarySize    int32
 	executableFilters int32
 }
 
+type XzOptions struct {
+	CompressionOptions //TODO: Remove
+	raw                *xzOptionsRaw
+	Execx86            bool
+	ExecPower          bool
+	Execa64            bool
+	ExecArm            bool
+	ExecArmThumb       bool
+	ExecSparc          bool
+}
+
+func NewXzOption(raw xzOptionsRaw) XzOptions {
+	return XzOptions{
+		raw:          &raw,
+		Execx86:      raw.executableFilters&0x1 == 0x1,
+		ExecPower:    raw.executableFilters&0x2 == 0x2,
+		Execa64:      raw.executableFilters&0x4 == 0x4,
+		ExecArm:      raw.executableFilters&0x8 == 0x8,
+		ExecArmThumb: raw.executableFilters&0x10 == 0x10,
+		ExecSparc:    raw.executableFilters&0x20 == 0x20,
+	}
+}
+
 type lz4OptionsRaw struct {
 	version int32
 	flags   int32
diff --git a/reader.go b/reader.go
index c5d2161..f688d44 100644
--- a/reader.go
+++ b/reader.go
@@ -16,7 +16,7 @@ type Reader struct {
 	offset int64
 }
 
-//NewReader creates a
+//NewReader creates a squashfs.Reader from a io.ReaderAt
 func NewReader(baseReader io.ReaderAt) Reader {
 	return Reader{
 		rdr:    baseReader,
diff --git a/squashfs.go b/squashfs.go
index 77a8009..9729626 100644
--- a/squashfs.go
+++ b/squashfs.go
@@ -13,7 +13,7 @@ var (
 
 //Squashfs is a squashfs backed by a ReadSeeker.
 type Squashfs struct {
-	rdr                *io.SectionReader //underlying reader
+	rdr                *Reader //underlying reader
 	offset             int
 	super              Superblock
 	flags              SuperblockFlags
@@ -21,9 +21,10 @@ type Squashfs struct {
 }
 
 //NewSquashfs creates a new Squashfs backed by the given reader
-func NewSquashfs(reader *io.SectionReader) (*Squashfs, error) {
+func NewSquashfs(reader io.ReaderAt) (*Squashfs, error) {
+	rdr := NewReader(reader)
 	var superblock Superblock
-	err := binary.Read(reader, binary.LittleEndian, &superblock)
+	err := binary.Read(&rdr, binary.LittleEndian, &superblock)
 	if err != nil {
 		return nil, err
 	}
@@ -36,12 +37,20 @@ func NewSquashfs(reader *io.SectionReader) (*Squashfs, error) {
 		switch superblock.Compression {
 		case zlibCompression:
 			var gzipOpRaw gzipOptionsRaw
-			err = binary.Read(reader, binary.LittleEndian, &gzipOpRaw)
+			err = binary.Read(&rdr, binary.LittleEndian, &gzipOpRaw)
 			if err != nil {
 				return nil, err
 			}
 			compressionOptions = NewGzipOptions(gzipOpRaw)
 			break
+		case xzCompression:
+			var xzOpRaw xzOptionsRaw
+			err = binary.Read(&rdr, binary.LittleEndian, xzOpRaw)
+			if err != nil {
+				return nil, err
+			}
+			compressionOptions = NewXzOption(xzOpRaw)
+			break
 		default:
 			//TODO: all the compression options
 			return nil, errors.New("This type of compression isn't supported yet")
@@ -49,7 +58,7 @@ func NewSquashfs(reader *io.SectionReader) (*Squashfs, error) {
 	}
 	//TODO: parse more info
 	return &Squashfs{
-		rdr:                reader,
+		rdr:                &rdr,
 		super:              superblock,
 		flags:              flags,
 		compressionOptions: compressionOptions,