neoneo-go/pkg/io/binaryWriter.go

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package io
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import (
"encoding/binary"
"io"
"reflect"
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)
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// BinWriter is a convenient wrapper around a io.Writer and err object.
// Used to simplify error handling when writing into a io.Writer
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// from a struct with many fields.
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type BinWriter struct {
w io.Writer
u64 []byte
u32 []byte
u16 []byte
u8 []byte
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Err error
}
// NewBinWriterFromIO makes a BinWriter from io.Writer.
func NewBinWriterFromIO(iow io.Writer) *BinWriter {
u64 := make([]byte, 8)
u32 := u64[:4]
u16 := u64[:2]
u8 := u64[:1]
return &BinWriter{w: iow, u64: u64, u32: u32, u16: u16, u8: u8}
}
// WriteU64LE writes an uint64 value into the underlying io.Writer in
// little-endian format.
func (w *BinWriter) WriteU64LE(u64 uint64) {
binary.LittleEndian.PutUint64(w.u64, u64)
w.WriteBytes(w.u64)
}
// WriteU32LE writes an uint32 value into the underlying io.Writer in
// little-endian format.
func (w *BinWriter) WriteU32LE(u32 uint32) {
binary.LittleEndian.PutUint32(w.u32, u32)
w.WriteBytes(w.u32)
}
// WriteU16LE writes an uint16 value into the underlying io.Writer in
// little-endian format.
func (w *BinWriter) WriteU16LE(u16 uint16) {
binary.LittleEndian.PutUint16(w.u16, u16)
w.WriteBytes(w.u16)
}
// WriteU16BE writes an uint16 value into the underlying io.Writer in
// big-endian format.
func (w *BinWriter) WriteU16BE(u16 uint16) {
binary.BigEndian.PutUint16(w.u16, u16)
w.WriteBytes(w.u16)
}
// WriteB writes a byte into the underlying io.Writer.
func (w *BinWriter) WriteB(u8 byte) {
w.u8[0] = u8
w.WriteBytes(w.u8)
}
// WriteBool writes a boolean value into the underlying io.Writer encoded as
// a byte with values of 0 or 1.
func (w *BinWriter) WriteBool(b bool) {
var i byte
if b {
i = 1
}
w.WriteB(i)
}
// WriteArray writes a slice or an array arr into w. Note that nil slices and
// empty slices are gonna be treated the same resulting in equal zero-length
// array encoded.
func (w *BinWriter) WriteArray(arr interface{}) {
switch val := reflect.ValueOf(arr); val.Kind() {
case reflect.Slice, reflect.Array:
if w.Err != nil {
return
}
typ := val.Type().Elem()
w.WriteVarUint(uint64(val.Len()))
for i := 0; i < val.Len(); i++ {
el, ok := val.Index(i).Interface().(encodable)
if !ok {
el, ok = val.Index(i).Addr().Interface().(encodable)
if !ok {
panic(typ.String() + " is not encodable")
}
}
el.EncodeBinary(w)
}
default:
panic("not an array")
}
}
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// WriteVarUint writes a uint64 into the underlying writer using variable-length encoding.
func (w *BinWriter) WriteVarUint(val uint64) {
if w.Err != nil {
return
}
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if val < 0xfd {
w.WriteB(byte(val))
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return
}
if val < 0xFFFF {
w.WriteB(byte(0xfd))
w.WriteU16LE(uint16(val))
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return
}
if val < 0xFFFFFFFF {
w.WriteB(byte(0xfe))
w.WriteU32LE(uint32(val))
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return
}
w.WriteB(byte(0xff))
w.WriteU64LE(val)
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}
// WriteBytes writes a variable byte into the underlying io.Writer without prefix.
func (w *BinWriter) WriteBytes(b []byte) {
if w.Err != nil {
return
}
_, w.Err = w.w.Write(b)
}
// WriteVarBytes writes a variable length byte array into the underlying io.Writer.
func (w *BinWriter) WriteVarBytes(b []byte) {
w.WriteVarUint(uint64(len(b)))
w.WriteBytes(b)
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}
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// WriteString writes a variable length string into the underlying io.Writer.
func (w *BinWriter) WriteString(s string) {
w.WriteVarBytes([]byte(s))
}