neoneo-go/pkg/io/binaryBufWriter.go
2021-08-20 11:38:42 +03:00

48 lines
1.3 KiB
Go

package io
import (
"bytes"
"errors"
)
// ErrDrained is returned on an attempt to use already drained write buffer.
var ErrDrained = errors.New("buffer already drained")
// BufBinWriter is an additional layer on top of BinWriter that
// automatically creates buffer to write into that you can get after all
// writes via Bytes().
type BufBinWriter struct {
*BinWriter
buf bytes.Buffer
}
// NewBufBinWriter makes a BufBinWriter with an empty byte buffer.
func NewBufBinWriter() *BufBinWriter {
b := new(BufBinWriter)
b.BinWriter = NewBinWriterFromIO(&b.buf)
return b
}
// Len returns the number of bytes of the unread portion of the buffer.
func (bw *BufBinWriter) Len() int {
return bw.buf.Len()
}
// Bytes returns resulting buffer and makes future writes return an error.
func (bw *BufBinWriter) Bytes() []byte {
if bw.Err != nil {
return nil
}
bw.Err = ErrDrained
return bw.buf.Bytes()
}
// Reset resets the state of the buffer, making it usable again. It can
// make buffer usage somewhat more efficient, because you don't need to
// create it again, but beware that the buffer is gonna be the same as the one
// returned by Bytes(), so if you need that data after Reset() you have to copy
// it yourself.
func (bw *BufBinWriter) Reset() {
bw.Err = nil
bw.buf.Reset()
}