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65 lines
1.4 KiB
Go
65 lines
1.4 KiB
Go
package asar // import "b612.me/asar"
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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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)
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var (
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errMalformed = errors.New("asar: malformed archive")
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)
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// Decode decodes the ASAR archive in ra.
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//
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// Returns the root element and nil on success. nil and an error is returned on
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// failure.
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func Decode(ra io.ReaderAt) (*Entry, error) {
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headerSize := uint32(0)
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headerStringSize := uint32(0)
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// [pickle object header (4 bytes) == 4]
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// [pickle uint32 = $header_object_size]
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{
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var buff [8]byte
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if n, _ := ra.ReadAt(buff[:], 0); n != 8 {
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return nil, errMalformed
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}
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dataSize := binary.LittleEndian.Uint32(buff[:4])
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if dataSize != 4 {
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return nil, errMalformed
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}
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headerSize = binary.LittleEndian.Uint32(buff[4:8])
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}
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// [pickle object header (4 bytes)]
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// [pickle data header (4 bytes) == $string_size]
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// [pickle string ($string_size bytes)]
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{
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var buff [8]byte
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if n, _ := ra.ReadAt(buff[:], 8); n != 8 {
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return nil, errMalformed
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}
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headerObjectSize := binary.LittleEndian.Uint32(buff[:4])
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if headerObjectSize != headerSize-4 {
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return nil, errMalformed
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}
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headerStringSize = binary.LittleEndian.Uint32(buff[4:8])
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}
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// read header string
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headerSection := io.NewSectionReader(ra, 8+8, int64(headerStringSize))
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baseOffset := 8 + int64(headerSize)
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baseOffset += baseOffset % 4 // pickle objects are uint32 aligned
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root, err := decodeHeader(ra, headerSection, baseOffset)
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if err != nil {
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return nil, err
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}
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return root, nil
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}
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