forked from knative/serving
/
rewinder.go
80 lines (63 loc) · 1.7 KB
/
rewinder.go
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/*
Copyright 2018 The Knative 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 util
import (
"bytes"
"io"
"sync"
)
type rewinder struct {
sync.Mutex
original io.ReadCloser
current io.Reader
next io.ReadWriter
eof bool
}
// NewRewinder wraps a single-use `ReadCloser` into a `ReadCloser`
// that can be read multiple times
func NewRewinder(rc io.ReadCloser) io.ReadCloser {
r := &rewinder{original: rc}
r.next = new(bytes.Buffer)
r.current = r.original
return r
}
func (r *rewinder) Read(b []byte) (int, error) {
r.Lock()
defer r.Unlock()
// Buffer everything we read
n, err := io.TeeReader(r.current, r.next).Read(b)
// Keep track of when we reach the end
if err == io.EOF {
r.eof = true
}
return n, err
}
func (r *rewinder) Close() error {
r.Lock()
defer r.Unlock()
// Start = what we've read already + what we haven't read yet
start := io.MultiReader(r.next, r.current)
// Close the original ReadCloser if we have read it to the end
if r.eof && r.original != nil {
if r.current == r.original {
// Start = only what we've read already
start = r.next
}
r.original.Close()
r.original = nil
}
// Rewind back to the start
r.next = new(bytes.Buffer)
r.current = start
return nil
}