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/*
* MinIO Go Library for Amazon S3 Compatible Cloud Storage
* Copyright 2015-2025 MinIO, Inc.
*
* 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 peeker
import (
"bytes"
"errors"
"io"
)
// PeekReadCloser offers a way to peek a ReadCloser stream and then
// return the exact stream of the underlying ReadCloser
type PeekReadCloser struct {
io.ReadCloser
recordMode bool
recordMaxBuf int
recordBuf *bytes.Buffer
}
// ReplayFromStart ensures next Read() will restart to stream the
// underlying ReadCloser stream from the beginning
func (prc *PeekReadCloser) ReplayFromStart() {
prc.recordMode = false
}
func (prc *PeekReadCloser) Read(p []byte) (int, error) {
if prc.recordMode {
if prc.recordBuf.Len() > prc.recordMaxBuf {
return 0, errors.New("maximum peek buffer exceeded")
}
n, err := prc.ReadCloser.Read(p)
prc.recordBuf.Write(p[:n])
return n, err
}
// Replay mode
if prc.recordBuf.Len() > 0 {
pn, _ := prc.recordBuf.Read(p)
return pn, nil
}
return prc.ReadCloser.Read(p)
}
// Close releases the record buffer memory and close the underlying ReadCloser
func (prc *PeekReadCloser) Close() error {
prc.recordBuf.Reset()
return prc.ReadCloser.Close()
}
// NewPeekReadCloser returns a new peek reader
func NewPeekReadCloser(rc io.ReadCloser, maxBufSize int) *PeekReadCloser {
return &PeekReadCloser{
ReadCloser: rc,
recordMode: true, // recording mode by default
recordBuf: bytes.NewBuffer(make([]byte, 0, 1024)),
recordMaxBuf: maxBufSize,
}
}
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