A library to read/write bits from a byte slice.
go get -u github.com/nokute78/go-bit/v2
CAUTION: github.com/nokute78/go-bit/pkg/bit/v2 will be deprecated.
Please use github.com/nokute78/go-bit/v2.
The package supports binary.Read like API.
It is an example to decode TCP header. (Big Endian)
- Save below code as tcp.go.
go mod init go-bit-examplego mod tidygo run tcp.go
package main
import (
"bytes"
"encoding/binary"
"fmt"
"github.com/nokute78/go-bit/v2"
)
func main() {
type TcpHeader struct {
SrcPort uint16
DstPort uint16
SeqNo uint32
AckNo uint32
HeaderLen [4]bit.Bit
Reserved [3]bit.Bit `bit:"skip"`
NS bit.Bit
CWR bit.Bit
ECE bit.Bit
URG bit.Bit
ACK bit.Bit
PSH bit.Bit
RST bit.Bit
SYN bit.Bit
FIN bit.Bit
WinSize uint16
CheckSum uint16
EmePointer uint16
}
s := TcpHeader{}
br := bytes.NewReader([]byte{0xd8, 0x65, 0x01, 0xbb, 0x4b, 0xe0, 0x76, 0xcd, 0x48, 0xc8, 0x70, 0x8f, 0x50, 0x10, 0x10,
0x18, 0x0e, 0xc1, 0x00, 0x00})
if err := bit.Read(br, binary.BigEndian, &s); err != nil {
fmt.Printf("error:%s", err)
}
fmt.Printf("src=%d dst=%d\n", s.SrcPort, s.DstPort)
fmt.Printf("SeqNo=%d AckNo=%d\n", s.SeqNo, s.AckNo)
fmt.Printf("HeaderLen(raw)=%v\n", s.HeaderLen)
fmt.Printf("Ack=%t\n", s.ACK)
}The package supports struct tags.
| Tag | Description |
|---|---|
`bit:"skip"` |
Ignore the field. Offset is updated by the size of the field. It is useful for reserved field. |
`bit:"-"` |
Ignore the field. Offset is not updated. |
`bit:"BE"` |
Decode the field as big endian. It is useful for mixed endian data. |
`bit:"LE"` |
Decode the field as little endian. It is useful for mixed endian data. |
https://pkg.go.dev/github.com/nokute78/go-bit/v2