Rename squashfs/squashfs to squashfs/low

squashfs/low library name is now squashfslow

low/data/reader.go

@@ -0,0 +1,97 @@
+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      int
+	curIndex       uint64
+	finalBlockSize uint64
+	blockSize      uint32
+}
+
+func NewReader(r io.Reader, d decompress.Decompressor, sizes []uint32, finalBlockSize uint64, blockSize uint32) *Reader {
+	return &Reader{
+		r:              r,
+		d:              d,
+		sizes:          sizes,
+		finalBlockSize: finalBlockSize,
+		blockSize:      blockSize,
+	}
+}
+
+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)) && r.frag != nil {
+		r.dat, err = io.ReadAll(r.frag)
+		return err
+	} else if r.curIndex >= uint64(len(r.sizes)) {
+		return io.EOF
+	}
+	realSize := r.sizes[r.curIndex] &^ (1 << 24)
+	if realSize == 0 {
+		if r.curIndex == uint64(len(r.sizes))-1 && r.frag == nil {
+			r.dat = make([]byte, r.finalBlockSize)
+		} else {
+			r.dat = make([]byte, r.blockSize)
+		}
+		return nil
+	}
+	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 >= len(r.dat) {
+			if err := r.advance(); err != nil {
+				return curRead, err
+			}
+		}
+		toRead = len(b) - curRead
+		if toRead > len(r.dat)-r.curOffset {
+			toRead = len(r.dat) - r.curOffset
+		}
+		toRead = copy(b[curRead:], r.dat[r.curOffset:r.curOffset+toRead])
+		r.curOffset += toRead
+		curRead += toRead
+	}
+	return curRead, nil
+}
+
+func (r *Reader) Close() error {
+	if r.frag != nil {
+		if l, ok := r.frag.(*io.LimitedReader); ok {
+			if cl, ok := l.R.(io.Closer); ok {
+				cl.Close()
+			}
+		}
+	}
+	r.dat = nil
+	return nil
+}