xesite/vendor/layeh.com/asar/decoder.go

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2017-01-09 21:41:39 +00:00
package asar // import "layeh.com/asar"
import (
"encoding/binary"
"errors"
"io"
)
var (
errMalformed = errors.New("asar: malformed archive")
)
// Decode decodes the ASAR archive in ra.
//
// Returns the root element and nil on success. nil and an error is returned on
// failure.
func Decode(ra io.ReaderAt) (*Entry, error) {
headerSize := uint32(0)
headerStringSize := uint32(0)
// [pickle object header (4 bytes) == 4]
// [pickle uint32 = $header_object_size]
{
var buff [8]byte
if n, _ := ra.ReadAt(buff[:], 0); n != 8 {
return nil, errMalformed
}
dataSize := binary.LittleEndian.Uint32(buff[:4])
if dataSize != 4 {
return nil, errMalformed
}
headerSize = binary.LittleEndian.Uint32(buff[4:8])
}
// [pickle object header (4 bytes)]
// [pickle data header (4 bytes) == $string_size]
// [pickle string ($string_size bytes)]
{
var buff [8]byte
if n, _ := ra.ReadAt(buff[:], 8); n != 8 {
return nil, errMalformed
}
headerObjectSize := binary.LittleEndian.Uint32(buff[:4])
if headerObjectSize != headerSize-4 {
return nil, errMalformed
}
headerStringSize = binary.LittleEndian.Uint32(buff[4:8])
}
// read header string
headerSection := io.NewSectionReader(ra, 8+8, int64(headerStringSize))
baseOffset := 8 + 8 + int64(headerStringSize)
baseOffset += baseOffset % 4 // pickle objects are uint32 aligned
root, err := decodeHeader(ra, headerSection, baseOffset)
if err != nil {
return nil, err
}
return root, nil
}