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/*
* MinIO Go Library for Amazon S3 Compatible Cloud Storage
* Copyright 2015-2017 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 minio
import (
"fmt"
"io"
)
// hookReader hooks additional reader in the source stream. It is
// useful for making progress bars. Second reader is appropriately
// notified about the exact number of bytes read from the primary
// source on each Read operation.
type hookReader struct {
source io.Reader
hook io.Reader
}
// Seek implements io.Seeker. Seeks source first, and if necessary
// seeks hook if Seek method is appropriately found.
func (hr *hookReader) Seek(offset int64, whence int) (n int64, err error) {
// Verify for source has embedded Seeker, use it.
sourceSeeker, ok := hr.source.(io.Seeker)
if ok {
n, err = sourceSeeker.Seek(offset, whence)
if err != nil {
return 0, err
}
}
// Verify if hook has embedded Seeker, use it.
hookSeeker, ok := hr.hook.(io.Seeker)
if ok {
var m int64
m, err = hookSeeker.Seek(offset, whence)
if err != nil {
return 0, err
}
if n != m {
return 0, fmt.Errorf("hook seeker seeked %d bytes, expected source %d bytes", m, n)
}
}
return n, nil
}
// Read implements io.Reader. Always reads from the source, the return
// value 'n' number of bytes are reported through the hook. Returns
// error for all non io.EOF conditions.
func (hr *hookReader) Read(b []byte) (n int, err error) {
n, err = hr.source.Read(b)
if err != nil && err != io.EOF {
return n, err
}
// Progress the hook with the total read bytes from the source.
if _, herr := hr.hook.Read(b[:n]); herr != nil {
if herr != io.EOF {
return n, herr
}
}
return n, err
}
// newHook returns a io.ReadSeeker which implements hookReader that
// reports the data read from the source to the hook.
func newHook(source, hook io.Reader) io.Reader {
if hook == nil {
return source
}
return &hookReader{source, hook}
}
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