Initial work

Create Reader
Pulled back in Inode decoding and superblock
New Data and Metadata readers
Added getting of id, fragment, and export table data lazily
Added README to squashfs/squashfs

internal/data/reader.go

@@ -0,0 +1,73 @@
+package data
+
+import (
+	"encoding/binary"
+	"io"
+
+	"github.com/CalebQ42/squashfs/internal/decompress"
+)
+
+type Reader struct {
+	r         io.Reader
+	d         decompress.Decompressor
+	frag      io.Reader
+	sizes     []uint32
+	dat       []byte
+	curOffset uint16
+	curIndex  uint64
+}
+
+func NewReader(r io.Reader, d decompress.Decompressor, sizes []uint32) (*Reader, error) {
+	return &Reader{
+		r:     r,
+		d:     d,
+		sizes: sizes,
+	}, nil
+}
+
+func (r *Reader) AddFrag(fragRdr io.Reader) {
+	r.frag = fragRdr
+}
+
+func (r *Reader) advance() error {
+	r.curOffset = 0
+	defer func() { r.curIndex++ }()
+	var err error
+	if r.curIndex == uint64(len(r.sizes))-1 && r.frag != nil {
+		r.dat, err = io.ReadAll(r.frag)
+		return err
+	} else if r.curIndex >= uint64(len(r.sizes))-1 {
+		return io.EOF
+	}
+	realSize := r.sizes[r.curIndex] &^ 0x8000
+	r.dat = make([]byte, realSize)
+	err = binary.Read(r.r, binary.LittleEndian, &r.dat)
+	if err != nil {
+		return err
+	}
+	if r.sizes[r.curIndex] != realSize {
+		return nil
+	}
+	r.dat, err = r.d.Decompress(r.dat)
+	return err
+}
+
+func (r *Reader) Read(b []byte) (int, error) {
+	curRead := 0
+	var toRead int
+	for curRead < len(b) {
+		if r.curOffset >= uint16(len(r.dat)) {
+			if err := r.advance(); err != nil {
+				return curRead, err
+			}
+		}
+		toRead = len(b) - curRead
+		if toRead > len(r.dat)-int(r.curOffset) {
+			toRead = len(r.dat) - int(r.curOffset)
+		}
+		copy(b[curRead:], r.dat[r.curOffset:int(r.curOffset)+toRead])
+		r.curOffset += uint16(toRead)
+		curRead += toRead
+	}
+	return curRead, nil
+}

internal/decompress/decompress.go

@@ -0,0 +1,5 @@
+package decompress
+
+type Decompressor interface {
+	Decompress([]byte) ([]byte, error)
+}

internal/decompress/lz4.go

@@ -0,0 +1,15 @@
+package decompress
+
+import (
+	"bytes"
+	"io"
+
+	"github.com/pierrec/lz4/v4"
+)
+
+type Lz4 struct{}
+
+func (l Lz4) Decompress(data []byte) ([]byte, error) {
+	rdr := lz4.NewReader(bytes.NewReader(data))
+	return io.ReadAll(rdr)
+}

internal/decompress/lzma.go

@@ -0,0 +1,18 @@
+package decompress
+
+import (
+	"bytes"
+	"io"
+
+	"github.com/ulikunitz/xz/lzma"
+)
+
+type Lzma struct{}
+
+func (l Lzma) Decompress(data []byte) ([]byte, error) {
+	rdr, err := lzma.NewReader(bytes.NewReader(data))
+	if err != nil {
+		return nil, err
+	}
+	return io.ReadAll(rdr)
+}

internal/decompress/lzo.go

@@ -0,0 +1,13 @@
+package decompress
+
+import (
+	"bytes"
+
+	"github.com/rasky/go-lzo"
+)
+
+type Lzo struct{}
+
+func (l Lzo) Decompress(data []byte) ([]byte, error) {
+	return lzo.Decompress1X(bytes.NewReader(data), len(data), 0)
+}

internal/decompress/xz.go

@@ -0,0 +1,18 @@
+package decompress
+
+import (
+	"bytes"
+	"io"
+
+	"github.com/therootcompany/xz"
+)
+
+type Xz struct{}
+
+func (x Xz) Decompress(data []byte) ([]byte, error) {
+	rdr, err := xz.NewReader(bytes.NewReader(data), 0)
+	if err != nil {
+		return nil, err
+	}
+	return io.ReadAll(rdr)
+}

internal/decompress/zlib.go

@@ -0,0 +1,18 @@
+package decompress
+
+import (
+	"bytes"
+	"compress/zlib"
+	"io"
+)
+
+type Zlib struct{}
+
+func (z Zlib) Decompress(data []byte) ([]byte, error) {
+	rdr, err := zlib.NewReader(bytes.NewReader(data))
+	if err != nil {
+		return nil, err
+	}
+	defer rdr.Close()
+	return io.ReadAll(rdr)
+}

internal/decompress/zstd.go

@@ -0,0 +1,19 @@
+package decompress
+
+import (
+	"bytes"
+	"io"
+
+	"github.com/klauspost/compress/zstd"
+)
+
+type Zstd struct{}
+
+func (z Zstd) Decompress(data []byte) ([]byte, error) {
+	rdr, err := zstd.NewReader(bytes.NewReader(data))
+	if err != nil {
+		return nil, err
+	}
+	defer rdr.Close()
+	return io.ReadAll(rdr)
+}

internal/metadata/reader.go

@@ -0,0 +1,62 @@
+package metadata
+
+import (
+	"encoding/binary"
+	"io"
+
+	"github.com/CalebQ42/squashfs/internal/decompress"
+)
+
+type Reader struct {
+	r         io.Reader
+	d         decompress.Decompressor
+	dat       []byte
+	curOffset uint16
+}
+
+func NewReader(r io.Reader, d decompress.Decompressor) *Reader {
+	return &Reader{
+		r: r,
+		d: d,
+	}
+}
+
+func (r *Reader) advance() error {
+	r.curOffset = 0
+	var size uint16
+	err := binary.Read(r.r, binary.LittleEndian, &size)
+	if err != nil {
+		return err
+	}
+	realSize := size &^ 0x8000
+	r.dat = make([]byte, realSize)
+	err = binary.Read(r.r, binary.LittleEndian, &r.dat)
+	if err != nil {
+		return err
+	}
+	if size != realSize {
+		return nil
+	}
+	r.dat, err = r.d.Decompress(r.dat)
+	return err
+}
+
+func (r *Reader) Read(b []byte) (int, error) {
+	curRead := 0
+	var toRead int
+	for curRead < len(b) {
+		if r.curOffset >= uint16(len(r.dat)) {
+			if err := r.advance(); err != nil {
+				return curRead, err
+			}
+		}
+		toRead = len(b) - curRead
+		if toRead > len(r.dat)-int(r.curOffset) {
+			toRead = len(r.dat) - int(r.curOffset)
+		}
+		copy(b[curRead:], r.dat[r.curOffset:int(r.curOffset)+toRead])
+		r.curOffset += uint16(toRead)
+		curRead += toRead
+	}
+	return curRead, nil
+}

internal/toreader/toreader.go

@@ -0,0 +1,21 @@
+package toreader
+
+import "io"
+
+type Reader struct {
+	r      io.ReaderAt
+	offset int64
+}
+
+func NewReader(r io.ReaderAt, start int64) *Reader {
+	return &Reader{
+		r:      r,
+		offset: start,
+	}
+}
+
+func (r *Reader) Read(b []byte) (int, error) {
+	n, err := r.r.ReadAt(b, r.offset)
+	r.offset += int64(n)
+	return n, err
+}