/
ifsc_packet.go
62 lines (49 loc) · 1.33 KB
/
ifsc_packet.go
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package par2
import (
"bytes"
"crypto/md5"
"encoding/binary"
"errors"
"reflect"
)
var ifscPacketType = packetType{'P', 'A', 'R', ' ', '2', '.', '0', '\x00', 'I', 'F', 'S', 'C'}
type checksumPair struct {
MD5 [md5.Size]byte
CRC32 [4]byte
}
type ifscPacket struct {
checksumPairs []checksumPair
}
func readIFSCPacket(body []byte) (fileID, ifscPacket, error) {
buf := bytes.NewBuffer(body)
var id fileID
err := binary.Read(buf, binary.LittleEndian, &id)
if err != nil {
return fileID{}, ifscPacket{}, err
}
checksumPairSize := int(reflect.TypeOf(checksumPair{}).Size())
if buf.Len() == 0 || buf.Len()%checksumPairSize != 0 {
return fileID{}, ifscPacket{}, errors.New("invalid size")
}
checksumPairs := make([]checksumPair, buf.Len()/checksumPairSize)
err = binary.Read(buf, binary.LittleEndian, checksumPairs)
if err != nil {
return fileID{}, ifscPacket{}, err
}
return id, ifscPacket{checksumPairs}, nil
}
func writeIFSCPacket(id fileID, packet ifscPacket) ([]byte, error) {
if len(packet.checksumPairs) == 0 {
return nil, errors.New("no checksum pairs to write")
}
buf := bytes.NewBuffer(nil)
err := binary.Write(buf, binary.LittleEndian, id)
if err != nil {
return nil, err
}
err = binary.Write(buf, binary.LittleEndian, packet.checksumPairs)
if err != nil {
return nil, err
}
return buf.Bytes(), nil
}