// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// 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 (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 protocol buffers.
package binary
import (
"errors"
"io"
"math"
"reflect"
)
// A ByteOrder specifies how to convert byte sequences into
// 16-, 32-, or 64-bit unsigned integers.
type ByteOrder interface {
Uint16([]byte) uint16
Uint32([]byte) uint32
Uint64([]byte) uint64
PutUint16([]byte, uint16)
PutUint32([]byte, uint32)
PutUint64([]byte, uint64)
String() string
}
// LittleEndian is the little-endian implementation of ByteOrder.
var LittleEndian littleEndian
// BigEndian is the big-endian implementation of ByteOrder.
var BigEndian bigEndian
type littleEndian struct{}
func (littleEndian) Uint16(b []byte) uint16 { return uint16(b[0]) | uint16(b[1])<<8 }
func (littleEndian) PutUint16(b []byte, v uint16) {
b[0] = byte(v)
b[1] = byte(v >> 8)
}
func (littleEndian) Uint32(b []byte) uint32 {
return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
}
func (littleEndian) PutUint32(b []byte, v uint32) {
b[0] = byte(v)
b[1] = byte(v >> 8)
b[2] = byte(v >> 16)
b[3] = byte(v >> 24)
}
func (littleEndian) Uint64(b []byte) uint64 {
return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
}
func (littleEndian) PutUint64(b []byte, v uint64) {
b[0] = byte(v)
b[1] = byte(v >> 8)
b[2] = byte(v >> 16)
b[3] = byte(v >> 24)
b[4] = byte(v >> 32)
b[5] = byte(v >> 40)
b[6] = byte(v >> 48)
b[7] = byte(v >> 56)
}
func (littleEndian) String() string { return "LittleEndian" }
func (littleEndian) GoString() string { return "binary.LittleEndian" }
type bigEndian struct{}
func (bigEndian) Uint16(b []byte) uint16 { return uint16(b[1]) | uint16(b[0])<<8 }
func (bigEndian) PutUint16(b []byte, v uint16) {
b[0] = byte(v >> 8)
b[1] = byte(v)
}
func (bigEndian) Uint32(b []byte) uint32 {
return uint32(b[3]) | uint32(b[2])<<8 | uint32(b[1])<<16 | uint32(b[0])<<24
}
func (bigEndian) PutUint32(b []byte, v uint32) {
b[0] = byte(v >> 24)
b[1] = byte(v >> 16)
b[2] = byte(v >> 8)
b[3] = byte(v)
}
func (bigEndian) Uint64(b []byte) uint64 {
return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
}
func (bigEndian) PutUint64(b []byte, v uint64) {
b[0] = byte(v >> 56)
b[1] = byte(v >> 48)
b[2] = byte(v >> 40)
b[3] = byte(v >> 32)
b[4] = byte(v >> 24)
b[5] = byte(v >> 16)
b[6] = byte(v >> 8)
b[7] = byte(v)
}
func (bigEndian) String() string { return "BigEndian" }
func (bigEndian) GoString() string { return "binary.BigEndian" }
// 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 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.
func Read(r io.Reader, order ByteOrder, data interface{}) error {
// Fast path for basic types and slices.
if n := intDataSize(data); n != 0 {
var b [8]byte
var bs []byte
if n > len(b) {
bs = make([]byte, n)
} else {
bs = b[:n]
}
if _, err := io.ReadFull(r, bs); err != nil {
return err
}
switch data := data.(type) {
case *int8:
*data = int8(b[0])
case *uint8:
*data = b[0]
case *int16:
*data = int16(order.Uint16(bs))
case *uint16:
*data = order.Uint16(bs)
case *int32:
*data = int32(order.Uint32(bs))
case *uint32:
*data = order.Uint32(bs)
case *int64:
*data = int64(order.Uint64(bs))
case *uint64:
*data = order.Uint64(bs)
case []int8:
for i, x := range bs { // Easier to loop over the input for 8-bit values.
data[i] = int8(x)
}
case []uint8:
copy(data, bs)
case []int16:
for i := range data {
data[i] = int16(order.Uint16(bs[2*i:]))
}
case []uint16:
for i := range data {
data[i] = order.Uint16(bs[2*i:])
}
case []int32:
for i := range data {
data[i] = int32(order.Uint32(bs[4*i:]))
}
case []uint32:
for i := range data {
data[i] = order.Uint32(bs[4*i:])
}
case []int64:
for i := range data {
data[i] = int64(order.Uint64(bs[8*i:]))
}
case []uint64:
for i := range data {
data[i] = order.Uint64(bs[8*i:])
}
}
return nil
}
// Fallback to reflect-based decoding.
v := reflect.ValueOf(data)
size := -1
switch v.Kind() {
case reflect.Ptr:
v = v.Elem()
size = dataSize(v)
case reflect.Slice:
size = dataSize(v)
}
if size < 0 {
return errors.New("binary.Read: invalid type " + reflect.TypeOf(data).String())
}
d := &decoder{order: order, buf: make([]byte, size)}
if _, err := io.ReadFull(r, d.buf); err != nil {
return err
}
d.value(v)
return nil
}
// 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.
// 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.
func Write(w io.Writer, order ByteOrder, data interface{}) error {
// Fast path for basic types and slices.
if n := intDataSize(data); n != 0 {
var b [8]byte
var bs []byte
if n > len(b) {
bs = make([]byte, n)
} else {
bs = b[:n]
}
switch v := data.(type) {
case *int8:
b[0] = byte(*v)
case int8:
b[0] = byte(v)
case []int8:
for i, x := range v {
bs[i] = byte(x)
}
case *uint8:
b[0] = *v
case uint8:
b[0] = byte(v)
case []uint8:
bs = v
case *int16:
order.PutUint16(bs, uint16(*v))
case int16:
order.PutUint16(bs, uint16(v))
case []int16:
for i, x := range v {
order.PutUint16(bs[2*i:], uint16(x))
}
case *uint16:
order.PutUint16(bs, *v)
case uint16:
order.PutUint16(bs, v)
case []uint16:
for i, x := range v {
order.PutUint16(bs[2*i:], x)
}
case *int32:
order.PutUint32(bs, uint32(*v))
case int32:
order.PutUint32(bs, uint32(v))
case []int32:
for i, x := range v {
order.PutUint32(bs[4*i:], uint32(x))
}
case *uint32:
order.PutUint32(bs, *v)
case uint32:
order.PutUint32(bs, v)
case []uint32:
for i, x := range v {
order.PutUint32(bs[4*i:], x)
}
case *int64:
order.PutUint64(bs, uint64(*v))
case int64:
order.PutUint64(bs, uint64(v))
case []int64:
for i, x := range v {
order.PutUint64(bs[8*i:], uint64(x))
}
case *uint64:
order.PutUint64(bs, *v)
case uint64:
order.PutUint64(bs, v)
case []uint64:
for i, x := range v {
order.PutUint64(bs[8*i:], x)
}
}
_, err := w.Write(bs)
return err
}
// Fallback to reflect-based encoding.
v := reflect.Indirect(reflect.ValueOf(data))
size := dataSize(v)
if size < 0 {
return errors.New("binary.Write: invalid type " + reflect.TypeOf(data).String())
}
buf := make([]byte, size)
e := &encoder{order: order, buf: buf}
e.value(v)
_, err := w.Write(buf)
return err
}
// 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.
func Size(v interface{}) int {
return dataSize(reflect.Indirect(reflect.ValueOf(v)))
}
// dataSize returns the number of bytes the actual data represented by v occupies in memory.
// For compound structures, it sums the sizes of the elements. Thus, for instance, for a slice
// it returns the length of the slice times the element size and does not count the memory
// occupied by the header. If the type of v is not acceptable, dataSize returns -1.
func dataSize(v reflect.Value) int {
if v.Kind() == reflect.Slice {
if s := sizeof(v.Type().Elem()); s >= 0 {
return s * v.Len()
}
return -1
}
return sizeof(v.Type())
}
// sizeof returns the size >= 0 of variables for the given type or -1 if the type is not acceptable.
func sizeof(t reflect.Type) int {
switch t.Kind() {
case reflect.Array:
if s := sizeof(t.Elem()); s >= 0 {
return s * t.Len()
}
case reflect.Struct:
sum := 0
for i, n := 0, t.NumField(); i < n; i++ {
s := sizeof(t.Field(i).Type)
if s < 0 {
return -1
}
sum += s
}
return sum
case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
return int(t.Size())
}
return -1
}
type coder struct {
order ByteOrder
buf []byte
}
type decoder coder
type encoder coder
func (d *decoder) uint8() uint8 {
x := d.buf[0]
d.buf = d.buf[1:]
return x
}
func (e *encoder) uint8(x uint8) {
e.buf[0] = x
e.buf = e.buf[1:]
}
func (d *decoder) uint16() uint16 {
x := d.order.Uint16(d.buf[0:2])
d.buf = d.buf[2:]
return x
}
func (e *encoder) uint16(x uint16) {
e.order.PutUint16(e.buf[0:2], x)
e.buf = e.buf[2:]
}
func (d *decoder) uint32() uint32 {
x := d.order.Uint32(d.buf[0:4])
d.buf = d.buf[4:]
return x
}
func (e *encoder) uint32(x uint32) {
e.order.PutUint32(e.buf[0:4], x)
e.buf = e.buf[4:]
}
func (d *decoder) uint64() uint64 {
x := d.order.Uint64(d.buf[0:8])
d.buf = d.buf[8:]
return x
}
func (e *encoder) uint64(x uint64) {
e.order.PutUint64(e.buf[0:8], x)
e.buf = e.buf[8:]
}
func (d *decoder) int8() int8 { return int8(d.uint8()) }
func (e *encoder) int8(x int8) { e.uint8(uint8(x)) }
func (d *decoder) int16() int16 { return int16(d.uint16()) }
func (e *encoder) int16(x int16) { e.uint16(uint16(x)) }
func (d *decoder) int32() int32 { return int32(d.uint32()) }
func (e *encoder) int32(x int32) { e.uint32(uint32(x)) }
func (d *decoder) int64() int64 { return int64(d.uint64()) }
func (e *encoder) int64(x int64) { e.uint64(uint64(x)) }
func (d *decoder) value(v reflect.Value) {
switch v.Kind() {
case reflect.Array:
l := v.Len()
for i := 0; i < l; i++ {
d.value(v.Index(i))
}
case reflect.Struct:
t := v.Type()
l := v.NumField()
for i := 0; i < l; i++ {
// Note: Calling v.CanSet() below is an optimization.
// It would be sufficient to check the field name,
// but creating the StructField info for each field is
// costly (run "go test -bench=ReadStruct" and compare
// results when making changes to this code).
if v := v.Field(i); v.CanSet() || t.Field(i).Name != "_" {
d.value(v)
} else {
d.skip(v)
}
}
case reflect.Slice:
l := v.Len()
for i := 0; i < l; i++ {
d.value(v.Index(i))
}
case reflect.Int8:
v.SetInt(int64(d.int8()))
case reflect.Int16:
v.SetInt(int64(d.int16()))
case reflect.Int32:
v.SetInt(int64(d.int32()))
case reflect.Int64:
v.SetInt(d.int64())
case reflect.Uint8:
v.SetUint(uint64(d.uint8()))
case reflect.Uint16:
v.SetUint(uint64(d.uint16()))
case reflect.Uint32:
v.SetUint(uint64(d.uint32()))
case reflect.Uint64:
v.SetUint(d.uint64())
case reflect.Float32:
v.SetFloat(float64(math.Float32frombits(d.uint32())))
case reflect.Float64:
v.SetFloat(math.Float64frombits(d.uint64()))
case reflect.Complex64:
v.SetComplex(complex(
float64(math.Float32frombits(d.uint32())),
float64(math.Float32frombits(d.uint32())),
))
case reflect.Complex128:
v.SetComplex(complex(
math.Float64frombits(d.uint64()),
math.Float64frombits(d.uint64()),
))
}
}
func (e *encoder) value(v reflect.Value) {
switch v.Kind() {
case reflect.Array:
l := v.Len()
for i := 0; i < l; i++ {
e.value(v.Index(i))
}
case reflect.Struct:
t := v.Type()
l := v.NumField()
for i := 0; i < l; i++ {
// see comment for corresponding code in decoder.value()
if v := v.Field(i); v.CanSet() || t.Field(i).Name != "_" {
e.value(v)
} else {
e.skip(v)
}
}
case reflect.Slice:
l := v.Len()
for i := 0; i < l; i++ {
e.value(v.Index(i))
}
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
switch v.Type().Kind() {
case reflect.Int8:
e.int8(int8(v.Int()))
case reflect.Int16:
e.int16(int16(v.Int()))
case reflect.Int32:
e.int32(int32(v.Int()))
case reflect.Int64:
e.int64(v.Int())
}
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
switch v.Type().Kind() {
case reflect.Uint8:
e.uint8(uint8(v.Uint()))
case reflect.Uint16:
e.uint16(uint16(v.Uint()))
case reflect.Uint32:
e.uint32(uint32(v.Uint()))
case reflect.Uint64:
e.uint64(v.Uint())
}
case reflect.Float32, reflect.Float64:
switch v.Type().Kind() {
case reflect.Float32:
e.uint32(math.Float32bits(float32(v.Float())))
case reflect.Float64:
e.uint64(math.Float64bits(v.Float()))
}
case reflect.Complex64, reflect.Complex128:
switch v.Type().Kind() {
case reflect.Complex64:
x := v.Complex()
e.uint32(math.Float32bits(float32(real(x))))
e.uint32(math.Float32bits(float32(imag(x))))
case reflect.Complex128:
x := v.Complex()
e.uint64(math.Float64bits(real(x)))
e.uint64(math.Float64bits(imag(x)))
}
}
}
func (d *decoder) skip(v reflect.Value) {
d.buf = d.buf[dataSize(v):]
}
func (e *encoder) skip(v reflect.Value) {
n := dataSize(v)
for i := range e.buf[0:n] {
e.buf[i] = 0
}
e.buf = e.buf[n:]
}
// intDataSize returns the size of the data required to represent the data when encoded.
// It returns zero if the type cannot be implemented by the fast path in Read or Write.
func intDataSize(data interface{}) int {
switch data := data.(type) {
case int8, uint8, *int8, *uint8:
return 1
case []int8:
return len(data)
case []uint8:
return len(data)
case int16, uint16, *int16, *uint16:
return 2
case []int16:
return 2 * len(data)
case []uint16:
return 2 * len(data)
case int32, uint32, *int32, *uint32:
return 4
case []int32:
return 4 * len(data)
case []uint32:
return 4 * len(data)
case int64, uint64, *int64, *uint64:
return 8
case []int64:
return 8 * len(data)
case []uint64:
return 8 * len(data)
}
return 0
}