Fix frag, id, inode table values on block boundries

Fixes bug mention in #30

internal/toreader/offsetreader.go

@@ -0,0 +1,19 @@
+package toreader
+
+import "io"
+
+type OffsetReader struct {
+	r   io.ReaderAt
+	off int64
+}
+
+func NewOffsetReader(r io.ReaderAt, off int64) *OffsetReader {
+	return &OffsetReader{
+		r:   r,
+		off: off,
+	}
+}
+
+func (r OffsetReader) ReadAt(p []byte, off int64) (n int, e error) {
+	return r.r.ReadAt(p, off+r.off)
+}

low/reader.go

@@ -3,6 +3,7 @@ package squashfslow
 import (
 	"encoding/binary"
 	"errors"
+	"fmt"
 	"io"
 	"math"
 
@@ -88,7 +89,7 @@ func (r *Reader) Id(i uint16) (uint32, error) {
 	// Populate the id table as needed
 	var blockNum uint32
 	if i != 0 { // If i == 0, we go negatives causing issues with uint32s
-		blockNum = uint32(math.Ceil(float64(i)/2048)) - 1
+		blockNum = uint32(math.Ceil(float64(i+1)/2048)) - 1
 	} else {
 		blockNum = 0
 	}
@@ -131,10 +132,11 @@ func (r *Reader) fragEntry(i uint32) (fragEntry, error) {
 	// Populate the fragment table as needed
 	var blockNum uint32
 	if i != 0 { // If i == 0, we go negatives causing issues with uint32s
-		blockNum = uint32(math.Ceil(float64(i)/512)) - 1
+		blockNum = uint32(math.Ceil(float64(i+1)/512)) - 1
 	} else {
 		blockNum = 0
 	}
+	fmt.Println(blockNum)
 	blocksRead := len(r.fragTable) / 512
 	blocksToRead := int(blockNum) - blocksRead + 1
 
@@ -177,7 +179,7 @@ func (r *Reader) inodeRef(i uint32) (uint64, error) {
 	// Populate the export table as needed
 	var blockNum uint32
 	if i != 0 { // If i == 0, we go negatives causing issues with uint32s
-		blockNum = uint32(math.Ceil(float64(i)/1024)) - 1
+		blockNum = uint32(math.Ceil(float64(i+1)/1024)) - 1
 	} else {
 		blockNum = 0
 	}

low/reader_test.go

@@ -1,4 +1,4 @@
-package squashfslow_test
+package squashfslow
 
 import (
 	"fmt"
@@ -8,13 +8,11 @@ import (
 	"os/exec"
 	"path/filepath"
 	"testing"
-
-	squashfslow "github.com/CalebQ42/squashfs/low"
 )
 
 const (
 	squashfsURL  = "https://darkstorm.tech/files/LinuxPATest.sfs"
-	squashfsName = "LinuxPATest.sfs"
+	squashfsName = "airootfs.sfs"
 )
 
 func preTest(dir string) (fil *os.File, err error) {
@@ -50,6 +48,21 @@ func preTest(dir string) (fil *os.File, err error) {
 	return
 }
 
+func TestMisc(t *testing.T) {
+	tmpDir := "../testing"
+	fil, err := preTest(tmpDir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer fil.Close()
+	rdr, err := NewReader(fil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Log(rdr.Superblock.FragCount)
+	t.Fatal(rdr.fragEntry(1233))
+}
+
 func TestReader(t *testing.T) {
 	tmpDir := "../testing"
 	fil, err := preTest(tmpDir)
@@ -57,7 +70,7 @@ func TestReader(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer fil.Close()
-	rdr, err := squashfslow.NewReader(fil)
+	rdr, err := NewReader(fil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -77,7 +90,7 @@ func TestSingleFile(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer fil.Close()
-	rdr, err := squashfslow.NewReader(fil)
+	rdr, err := NewReader(fil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -92,7 +105,7 @@ func TestSingleFile(t *testing.T) {
 	t.Fatal(err)
 }
 
-func extractToDir(rdr *squashfslow.Reader, b *squashfslow.FileBase, folder string) error {
+func extractToDir(rdr *Reader, b *FileBase, folder string) error {
 	path := filepath.Join(folder, b.Name)
 	if b.IsDir() {
 		d, err := b.ToDir(rdr)
@@ -103,7 +116,7 @@ func extractToDir(rdr *squashfslow.Reader, b *squashfslow.FileBase, folder strin
 		if err != nil {
 			return err
 		}
-		var nestBast squashfslow.FileBase
+		var nestBast FileBase
 		for _, e := range d.Entries {
 			nestBast, err = rdr.BaseFromEntry(e)
 			if err != nil {

reader.go

@@ -4,6 +4,7 @@ import (
 	"io"
 	"time"
 
+	"github.com/CalebQ42/squashfs/internal/toreader"
 	squashfslow "github.com/CalebQ42/squashfs/low"
 )
 
@@ -27,6 +28,10 @@ func NewReader(r io.ReaderAt) (*Reader, error) {
 	return out, nil
 }
 
+func NewReaderAtOffset(r io.ReaderAt, offset int64) (*Reader, error) {
+	return NewReader(toreader.NewOffsetReader(r, offset))
+}
+
 func (r *Reader) ModTime() time.Time {
 	return time.Unix(int64(r.Low.Superblock.ModTime), 0)
 }