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encoder.go
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encoder.go
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package binstruct
import (
"bytes"
"io"
"reflect"
"strconv"
)
type encoder struct {
buf *bytes.Buffer
}
//Encode struct to byte array
func Encode(request interface{}) []byte {
value := reflect.ValueOf(request)
buf := bytes.NewBuffer(make([]byte, 0, 200))
encoder := &encoder{buf}
encoder.encode(value)
return buf.Bytes()
}
func (e *encoder) encode(value reflect.Value) {
switch value.Kind() {
case reflect.Ptr:
e.pointer(value)
case reflect.Struct:
e.strukt(value)
}
}
func (e *encoder) strukt(value reflect.Value) {
var bitmaskBytes uint64
for i := 0; i < value.NumField(); i++ {
field := value.Field(i)
fieldType := value.Type().Field(i)
tags := tags(fieldType.Tag)
if !(tags.transient() == "true") && checkConditions(tags.cond(), value) {
switch field.Kind() {
case reflect.Ptr:
e.pointer(field)
case reflect.String:
e.string(field, tags)
case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
e.uint(field, tags, &bitmaskBytes)
case reflect.Array:
e.array(field, tags)
case reflect.Slice:
e.slice(field, tags)
case reflect.Interface:
e.pointer(field)
}
}
}
}
func (e *encoder) slice(value reflect.Value, tags tags) {
length := value.Len()
e.dynamicLength(length, tags)
for i := 0; i < length; i++ {
sliceElement := value.Index(i)
switch sliceElement.Kind() {
case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
e.uint(sliceElement, tags, nil)
case reflect.String:
e.string(sliceElement, tags)
case reflect.Ptr:
e.pointer(sliceElement)
case reflect.Struct:
e.strukt(sliceElement)
}
}
}
func (e *encoder) array(value reflect.Value, tags tags) {
for i := 0; i < value.Len(); i++ {
e.write(tags.endianness(), value.Index(i))
}
}
func (e *encoder) string(value reflect.Value, tags tags) {
s := value.String()
if tags.hex().nonEmpty() {
size, _ := strconv.Atoi(string(tags.hex()))
v, _ := strconv.ParseUint(s[2:], 16, size*8)
e.writeUint(tags.endianness(), v, size)
} else {
e.dynamicLength(len(s), tags)
e.writeUintSlice(tags.endianness(), []uint8(s))
}
}
func (e *encoder) uint(value reflect.Value, tags tags, bitmaskBytes *uint64) {
if tags.bits().nonEmpty() {
bytes := *bitmaskBytes
if tags.bitmask() == "start" {
bytes = 0
}
bitmaskBits := bitmaskBits(tags.bits())
pos := FirstBitPosition(bitmaskBits)
bytes = bytes | ((value.Uint() << pos) & bitmaskBits)
if tags.bitmask() == "end" {
e.writeUint(tags.endianness(), bytes, int(value.Type().Size()))
}
*bitmaskBytes = bytes
} else if tags.bound().nonEmpty() {
size, _ := strconv.Atoi(string(tags.bound()))
e.writeUint(tags.endianness(), value.Uint(), size)
} else {
e.write(tags.endianness(), value)
}
}
func serialize(value reflect.Value, w io.Writer) {
value.MethodByName("Serialize").Call([]reflect.Value{reflect.ValueOf(w)})
}
func (e *encoder) pointer(value reflect.Value) {
if value.Type().Implements(serializable) {
serialize(value, e.buf)
} else {
e.encode(value.Elem())
}
}
func (e *encoder) dynamicLength(length int, tags tags) {
if tags.size().nonEmpty() {
size, _ := strconv.Atoi(string(tags.size()))
e.writeUint(tags.endianness(), uint64(length), size)
}
}
func (e *encoder) write(endianness tag, v reflect.Value) {
switch v.Kind() {
case reflect.Uint8:
e.buf.WriteByte(uint8(v.Uint()))
case reflect.Uint16:
e.writeUint(endianness, v.Uint(), 2)
case reflect.Uint32:
e.writeUint(endianness, v.Uint(), 4)
case reflect.Uint64:
e.writeUint(endianness, v.Uint(), 8)
}
}
func (e *encoder) writeUintSlice(endianness tag, v interface{}) {
switch s := v.(type) {
case []uint8:
for i := 0; i < len(s); i++ {
e.writeUint(endianness, uint64(s[i]), 1)
}
case []uint16:
for i := 0; i < len(s); i++ {
e.writeUint(endianness, uint64(s[i]), 2)
}
case []uint32:
for i := 0; i < len(s); i++ {
e.writeUint(endianness, uint64(s[i]), 4)
}
case []uint64:
for i := 0; i < len(s); i++ {
e.writeUint(endianness, uint64(s[i]), 8)
}
}
}
func (e *encoder) writeUint(endianness tag, t uint64, size int) {
if endianness == "be" {
for i := 0; i < size; i++ {
e.buf.WriteByte(byte(t >> byte((size-i-1)*8)))
}
} else {
for i := 0; i < size; i++ {
e.buf.WriteByte(byte(t >> byte(i*8)))
}
}
}