ebml-go/reader.go
2021-02-17 13:01:07 +09:00

79 lines
1.6 KiB
Go

// Copyright 2021 The ebml-go authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package ebml
import (
"bytes"
"io"
)
type rollbackReader interface {
Set(io.Reader)
Get() io.Reader
Read([]byte) (int, error)
Reset()
RollbackTo(int)
}
type rollbackReaderImpl struct {
io.Reader
buf []byte
}
func (r *rollbackReaderImpl) Set(v io.Reader) {
r.Reader = v
}
func (r *rollbackReaderImpl) Get() io.Reader {
return r.Reader
}
func (r *rollbackReaderImpl) Read(b []byte) (int, error) {
n, err := r.Reader.Read(b)
r.buf = append(r.buf, b[:n]...)
return n, err
}
func (r *rollbackReaderImpl) Reset() {
r.buf = r.buf[0:0]
}
func (r *rollbackReaderImpl) RollbackTo(i int) {
buf := r.buf
r.Reader = io.MultiReader(
bytes.NewReader(buf[i:]),
r.Reader,
)
r.buf = nil
}
type rollbackReaderNop struct {
io.Reader
}
func (r *rollbackReaderNop) Set(v io.Reader) {
r.Reader = v
}
func (r *rollbackReaderNop) Get() io.Reader {
return r.Reader
}
func (*rollbackReaderNop) Reset() {
}
func (*rollbackReaderNop) RollbackTo(i int) {
panic("can't rollback nop rollback reader")
}