104 lines
2.2 KiB
Go
104 lines
2.2 KiB
Go
package chunk7
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import (
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"fmt"
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"github.com/teeworlds-go/go-teeworlds-protocol/packer"
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)
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const (
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chunkFlagVital = 1
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chunkFlagResend = 2
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)
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type ChunkFlags struct {
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Vital bool
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Resend bool
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}
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func (flags *ChunkFlags) ToInt() int {
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v := 0
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if flags.Resend {
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v |= chunkFlagResend
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}
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if flags.Vital {
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v |= chunkFlagVital
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}
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return v
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}
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type ChunkHeader struct {
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Flags ChunkFlags
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Size int
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// sequence number
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// will be acknowledged in the packet header ack
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Seq int
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}
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type Chunk struct {
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Header ChunkHeader
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Data []byte
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}
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func (header *ChunkHeader) Pack() []byte {
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len := 2
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if header.Flags.Vital {
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len = 3
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}
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data := make([]byte, len)
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data[0] = (byte(header.Flags.ToInt()&0x03) << 6) | ((byte(header.Size) >> 6) & 0x3f)
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data[1] = (byte(header.Size) & 0x3f)
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if header.Flags.Vital {
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data[1] |= (byte(header.Seq) >> 2) & 0xc0
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data[2] = byte(header.Seq) & 0xff
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}
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return data
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}
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func (header *ChunkHeader) Unpack(u *packer.Unpacker) error {
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data, err := u.GetRaw(2)
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if err != nil {
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return err
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}
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flagBits := (data[0] >> 6) & 0x03
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header.Flags.Vital = (flagBits & chunkFlagVital) != 0
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header.Flags.Resend = (flagBits & chunkFlagResend) != 0
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header.Size = (int(data[0]&0x3F) << 6) | (int(data[1]) & 0x3F)
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if header.Flags.Vital {
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thirdByte, err := u.GetByte()
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if err != nil {
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return err
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}
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header.Seq = int((data[1]&0xC0)<<2) | int(thirdByte)
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}
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return nil
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}
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// TODO: give this a better name
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//
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// but it would be nice to have two unpack methods for all structs
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//
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// Unpack(u *packer.Unpacker)
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// UnpackTodoFindAGoodName(data []byte)
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//
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// See https://github.com/teeworlds-go/go-teeworlds-protocol/issues/5
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func (header *ChunkHeader) UnpackRaw(data []byte) error {
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if len(data) < 2 {
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return fmt.Errorf("size=%d not enough data to read chunk header", len(data))
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}
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flagBits := (data[0] >> 6) & 0x03
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header.Flags.Vital = (flagBits & chunkFlagVital) != 0
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header.Flags.Resend = (flagBits & chunkFlagResend) != 0
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header.Size = (int(data[0]&0x3F) << 6) | (int(data[1]) & 0x3F)
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if header.Flags.Vital {
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if len(data) < 3 {
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return fmt.Errorf("size=%d not enough data to read vital chunk header", len(data))
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}
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header.Seq = int((data[1]&0xC0)<<2) | int(data[2])
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}
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return nil
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}
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