neoneo-go/pkg/io/binaryWriter.go
Evgeniy Stratonikov dacf025dd9 io: add Grow to BinWriter
Signed-off-by: Evgeniy Stratonikov <evgeniy@nspcc.ru>
2021-08-09 12:05:31 +03:00

155 lines
3.7 KiB
Go

package io
import (
"bytes"
"encoding/binary"
"io"
"reflect"
)
// BinWriter is a convenient wrapper around a io.Writer and err object.
// Used to simplify error handling when writing into a io.Writer
// from a struct with many fields.
type BinWriter struct {
w io.Writer
Err error
uv [9]byte
}
// NewBinWriterFromIO makes a BinWriter from io.Writer.
func NewBinWriterFromIO(iow io.Writer) *BinWriter {
return &BinWriter{w: iow}
}
// WriteU64LE writes an uint64 value into the underlying io.Writer in
// little-endian format.
func (w *BinWriter) WriteU64LE(u64 uint64) {
binary.LittleEndian.PutUint64(w.uv[:8], u64)
w.WriteBytes(w.uv[:8])
}
// WriteU32LE writes an uint32 value into the underlying io.Writer in
// little-endian format.
func (w *BinWriter) WriteU32LE(u32 uint32) {
binary.LittleEndian.PutUint32(w.uv[:4], u32)
w.WriteBytes(w.uv[:4])
}
// WriteU16LE writes an uint16 value into the underlying io.Writer in
// little-endian format.
func (w *BinWriter) WriteU16LE(u16 uint16) {
binary.LittleEndian.PutUint16(w.uv[:2], u16)
w.WriteBytes(w.uv[:2])
}
// WriteU16BE writes an uint16 value into the underlying io.Writer in
// big-endian format.
func (w *BinWriter) WriteU16BE(u16 uint16) {
binary.BigEndian.PutUint16(w.uv[:2], u16)
w.WriteBytes(w.uv[:2])
}
// WriteB writes a byte into the underlying io.Writer.
func (w *BinWriter) WriteB(u8 byte) {
w.uv[0] = u8
w.WriteBytes(w.uv[:1])
}
// 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")
}
}
// WriteVarUint writes a uint64 into the underlying writer using variable-length encoding.
func (w *BinWriter) WriteVarUint(val uint64) {
if w.Err != nil {
return
}
n := PutVarUint(w.uv[:], val)
w.WriteBytes(w.uv[:n])
}
// PutVarUint puts val in varint form to the pre-allocated buffer.
func PutVarUint(data []byte, val uint64) int {
_ = data[8]
if val < 0xfd {
data[0] = byte(val)
return 1
}
if val < 0xFFFF {
data[0] = byte(0xfd)
binary.LittleEndian.PutUint16(data[1:], uint16(val))
return 3
}
if val < 0xFFFFFFFF {
data[0] = byte(0xfe)
binary.LittleEndian.PutUint32(data[1:], uint32(val))
return 5
}
data[0] = byte(0xff)
binary.LittleEndian.PutUint64(data[1:], val)
return 9
}
// 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)
}
// WriteString writes a variable length string into the underlying io.Writer.
func (w *BinWriter) WriteString(s string) {
w.WriteVarBytes([]byte(s))
}
// Grow tries to increase underlying buffer capacity so that at least n bytes
// can be written without reallocation. If the writer is not a buffer, this is a no-op.
func (w *BinWriter) Grow(n int) {
if b, ok := w.w.(*bytes.Buffer); ok {
b.Grow(n)
}
}