Caleb Gardner
81 lines
1.9 KiB
Go
81 lines
1.9 KiB
Go
package squashfs
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import (
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"encoding/binary"
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"errors"
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"io"
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"github.com/CalebQ42/squashfs/internal/inode"
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)
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//FragmentEntry is an entry in the fragment table
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type fragmentEntry struct {
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Start uint64
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Size uint32
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_ uint32 //unused
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}
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//GetFragmentDataFromInode returns the fragment data for a given inode.
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//If the inode does not have a fragment, harmlessly returns an empty slice without an error.
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func (r *Reader) getFragmentDataFromInode(in *inode.Inode) ([]byte, error) {
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var size uint64
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var fragIndex uint32
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var fragOffset uint32
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if in.Type == inode.FileType {
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bf := in.Info.(inode.File)
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if !bf.Fragmented {
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return make([]byte, 0), nil
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}
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if bf.BlockStart == 0 {
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size = uint64(bf.Size)
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} else {
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size = uint64(bf.BlockSizes[len(bf.BlockSizes)-1])
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}
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fragIndex = bf.FragmentIndex
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fragOffset = bf.FragmentOffset
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} else if in.Type == inode.ExtFileType {
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bf := in.Info.(inode.ExtFile)
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if !bf.Fragmented {
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return make([]byte, 0), nil
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}
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if bf.BlockStart == 0 {
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size = bf.Size
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} else {
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size = uint64(bf.BlockSizes[len(bf.BlockSizes)-1])
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}
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fragIndex = bf.FragmentIndex
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fragOffset = bf.FragmentOffset
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} else {
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return nil, errors.New("inode type not supported")
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}
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//reading the fragment entry first
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fragEntryRdr, err := r.newMetadataReader(int64(r.fragOffsets[int(fragIndex/512)]))
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if err != nil {
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return nil, err
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}
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_, err = fragEntryRdr.Seek(int64(16*fragIndex), io.SeekStart)
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if err != nil {
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return nil, err
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}
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var entry fragmentEntry
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err = binary.Read(fragEntryRdr, binary.LittleEndian, &entry)
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if err != nil {
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return nil, err
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}
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//now reading the actual fragment
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dr, err := r.newDataReader(int64(entry.Start), []uint32{entry.Size})
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if err != nil {
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return nil, err
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}
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_, err = dr.Read(make([]byte, fragOffset))
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if err != nil {
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return nil, err
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}
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tmp := make([]byte, size)
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err = binary.Read(dr, binary.LittleEndian, &tmp)
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if err != nil {
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return nil, err
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}
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return tmp, nil
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}
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