package binary
Import Path
encoding/binary (on go.dev)
Dependency Relation
imports 6 packages, and imported by 38 packages
Involved Source Files
Package binary implements simple translation between numbers and byte
sequences and encoding and decoding of varints.
Numbers are translated by reading and writing fixed-size values.
A fixed-size value is either a fixed-size arithmetic
type (bool, int8, uint8, int16, float32, complex64, ...)
or an array or struct containing only fixed-size values.
The varint functions encode and decode single integer values using
a variable-length encoding; smaller values require fewer bytes.
For a specification, see
https://developers.google.com/protocol-buffers/docs/encoding.
This package favors simplicity over efficiency. Clients that require
high-performance serialization, especially for large data structures,
should look at more advanced solutions such as the [encoding/gob]
package or [google.golang.org/protobuf] for protocol buffers.
native_endian_little.go
varint.go
Code Examples
package main
import (
"encoding/binary"
"fmt"
)
func main() {
b := []byte{0xe8, 0x03, 0xd0, 0x07}
x1 := binary.LittleEndian.Uint16(b[0:])
x2 := binary.LittleEndian.Uint16(b[2:])
fmt.Printf("%#04x %#04x\n", x1, x2)
}
package main
import (
"encoding/binary"
"fmt"
)
func main() {
b := make([]byte, 4)
binary.LittleEndian.PutUint16(b[0:], 0x03e8)
binary.LittleEndian.PutUint16(b[2:], 0x07d0)
fmt.Printf("% x\n", b)
}
package main
import (
"encoding/binary"
"fmt"
)
func main() {
buf := make([]byte, binary.MaxVarintLen64)
for _, x := range []uint64{1, 2, 127, 128, 255, 256} {
n := binary.PutUvarint(buf, x)
fmt.Printf("%x\n", buf[:n])
}
}
package main
import (
"encoding/binary"
"fmt"
)
func main() {
buf := make([]byte, binary.MaxVarintLen64)
for _, x := range []int64{-65, -64, -2, -1, 0, 1, 2, 63, 64} {
n := binary.PutVarint(buf, x)
fmt.Printf("%x\n", buf[:n])
}
}
package main
import (
"bytes"
"encoding/binary"
"fmt"
)
func main() {
var pi float64
b := []byte{0x18, 0x2d, 0x44, 0x54, 0xfb, 0x21, 0x09, 0x40}
buf := bytes.NewReader(b)
err := binary.Read(buf, binary.LittleEndian, &pi)
if err != nil {
fmt.Println("binary.Read failed:", err)
}
fmt.Print(pi)
}
package main
import (
"bytes"
"encoding/binary"
"fmt"
)
func main() {
b := []byte{0x18, 0x2d, 0x44, 0x54, 0xfb, 0x21, 0x09, 0x40, 0xff, 0x01, 0x02, 0x03, 0xbe, 0xef}
r := bytes.NewReader(b)
var data struct {
PI float64
Uate uint8
Mine [3]byte
Too uint16
}
if err := binary.Read(r, binary.LittleEndian, &data); err != nil {
fmt.Println("binary.Read failed:", err)
}
fmt.Println(data.PI)
fmt.Println(data.Uate)
fmt.Printf("% x\n", data.Mine)
fmt.Println(data.Too)
}
package main
import (
"encoding/binary"
"fmt"
)
func main() {
inputs := [][]byte{
{0x01},
{0x02},
{0x7f},
{0x80, 0x01},
{0xff, 0x01},
{0x80, 0x02},
}
for _, b := range inputs {
x, n := binary.Uvarint(b)
if n != len(b) {
fmt.Println("Uvarint did not consume all of in")
}
fmt.Println(x)
}
}
package main
import (
"encoding/binary"
"fmt"
)
func main() {
inputs := [][]byte{
{0x81, 0x01},
{0x7f},
{0x03},
{0x01},
{0x00},
{0x02},
{0x04},
{0x7e},
{0x80, 0x01},
}
for _, b := range inputs {
x, n := binary.Varint(b)
if n != len(b) {
fmt.Println("Varint did not consume all of in")
}
fmt.Println(x)
}
}
package main
import (
"bytes"
"encoding/binary"
"fmt"
"math"
)
func main() {
buf := new(bytes.Buffer)
var pi float64 = math.Pi
err := binary.Write(buf, binary.LittleEndian, pi)
if err != nil {
fmt.Println("binary.Write failed:", err)
}
fmt.Printf("% x", buf.Bytes())
}
package main
import (
"bytes"
"encoding/binary"
"fmt"
)
func main() {
buf := new(bytes.Buffer)
var data = []any{
uint16(61374),
int8(-54),
uint8(254),
}
for _, v := range data {
err := binary.Write(buf, binary.LittleEndian, v)
if err != nil {
fmt.Println("binary.Write failed:", err)
}
}
fmt.Printf("%x", buf.Bytes())
}
Package-Level Type Names (total 2)
AppendByteOrder specifies how to append 16-, 32-, or 64-bit unsigned integers
into a byte slice.
It is implemented by [LittleEndian], [BigEndian], and [NativeEndian].
( AppendByteOrder) AppendUint16([]byte, uint16) []byte
( AppendByteOrder) AppendUint32([]byte, uint32) []byte
( AppendByteOrder) AppendUint64([]byte, uint64) []byte
( AppendByteOrder) String() string
AppendByteOrder : expvar.Var
AppendByteOrder : fmt.Stringer
A ByteOrder specifies how to convert byte slices into
16-, 32-, or 64-bit unsigned integers.
It is implemented by [LittleEndian], [BigEndian], and [NativeEndian].
( ByteOrder) PutUint16([]byte, uint16)
( ByteOrder) PutUint32([]byte, uint32)
( ByteOrder) PutUint64([]byte, uint64)
( ByteOrder) String() string
( ByteOrder) Uint16([]byte) uint16
( ByteOrder) Uint32([]byte) uint32
( ByteOrder) Uint64([]byte) uint64
ByteOrder : expvar.Var
ByteOrder : fmt.Stringer
func debug/dwarf.(*Reader).ByteOrder() ByteOrder
func Append(buf []byte, order ByteOrder, data any) ([]byte, error)
func Decode(buf []byte, order ByteOrder, data any) (int, error)
func Encode(buf []byte, order ByteOrder, data any) (int, error)
func Read(r io.Reader, order ByteOrder, data any) error
func Write(w io.Writer, order ByteOrder, data any) error
Package-Level Functions (total 14)
Append appends the binary representation of data to buf.
buf may be nil, in which case a new buffer will be allocated.
See [Write] on which data are acceptable.
It returns the (possibily extended) buffer containing data or an error.
AppendUvarint appends the varint-encoded form of x,
as generated by [PutUvarint], to buf and returns the extended buffer.
AppendVarint appends the varint-encoded form of x,
as generated by [PutVarint], to buf and returns the extended buffer.
Decode decodes binary data from buf into data according to
the given byte order.
It returns an error if buf is too small, otherwise the number of
bytes consumed from buf.
Encode encodes the binary representation of data into buf according to
the given byte order.
It returns an error if buf is too small, otherwise the number of
bytes written into buf.
PutUvarint encodes a uint64 into buf and returns the number of bytes written.
If the buffer is too small, PutUvarint will panic.
PutVarint encodes an int64 into buf and returns the number of bytes written.
If the buffer is too small, PutVarint will panic.
Read reads structured binary data from r into data.
Data must be a pointer to a fixed-size value or a slice
of fixed-size values.
Bytes read from r are decoded using the specified byte order
and written to successive fields of the data.
When decoding boolean values, a zero byte is decoded as false, and
any other non-zero byte is decoded as true.
When reading into structs, the field data for fields with
blank (_) field names is skipped; i.e., blank field names
may be used for padding.
When reading into a struct, all non-blank fields must be exported
or Read may panic.
The error is [io.EOF] only if no bytes were read.
If an [io.EOF] happens after reading some but not all the bytes,
Read returns [io.ErrUnexpectedEOF].
ReadUvarint reads an encoded unsigned integer from r and returns it as a uint64.
The error is [io.EOF] only if no bytes were read.
If an [io.EOF] happens after reading some but not all the bytes,
ReadUvarint returns [io.ErrUnexpectedEOF].
ReadVarint reads an encoded signed integer from r and returns it as an int64.
The error is [io.EOF] only if no bytes were read.
If an [io.EOF] happens after reading some but not all the bytes,
ReadVarint returns [io.ErrUnexpectedEOF].
Size returns how many bytes [Write] would generate to encode the value v, which
must be a fixed-size value or a slice of fixed-size values, or a pointer to such data.
If v is neither of these, Size returns -1.
Uvarint decodes a uint64 from buf and returns that value and the
number of bytes read (> 0). If an error occurred, the value is 0
and the number of bytes n is <= 0 meaning:
n == 0: buf too small
n < 0: value larger than 64 bits (overflow)
and -n is the number of bytes read
Varint decodes an int64 from buf and returns that value and the
number of bytes read (> 0). If an error occurred, the value is 0
and the number of bytes n is <= 0 with the following meaning:
n == 0: buf too small
n < 0: value larger than 64 bits (overflow)
and -n is the number of bytes read
Write writes the binary representation of data into w.
Data must be a fixed-size value or a slice of fixed-size
values, or a pointer to such data.
Boolean values encode as one byte: 1 for true, and 0 for false.
Bytes written to w are encoded using the specified byte order
and read from successive fields of the data.
When writing structs, zero values are written for fields
with blank (_) field names.
Package-Level Variables (total 3)
BigEndian is the big-endian implementation of [ByteOrder] and [AppendByteOrder].
LittleEndian is the little-endian implementation of [ByteOrder] and [AppendByteOrder].
NativeEndian is the native-endian implementation of [ByteOrder] and [AppendByteOrder].
Package-Level Constants (total 3)
MaxVarintLenN is the maximum length of a varint-encoded N-bit integer.
MaxVarintLenN is the maximum length of a varint-encoded N-bit integer.
MaxVarintLenN is the maximum length of a varint-encoded N-bit integer.
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