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85 lines
2.4 KiB
85 lines
2.4 KiB
/*
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* MinIO Go Library for Amazon S3 Compatible Cloud Storage
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* Copyright 2015-2017 MinIO, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package minio
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import (
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"fmt"
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"io"
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)
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// hookReader hooks additional reader in the source stream. It is
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// useful for making progress bars. Second reader is appropriately
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// notified about the exact number of bytes read from the primary
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// source on each Read operation.
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type hookReader struct {
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source io.Reader
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hook io.Reader
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}
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// Seek implements io.Seeker. Seeks source first, and if necessary
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// seeks hook if Seek method is appropriately found.
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func (hr *hookReader) Seek(offset int64, whence int) (n int64, err error) {
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// Verify for source has embedded Seeker, use it.
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sourceSeeker, ok := hr.source.(io.Seeker)
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if ok {
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n, err = sourceSeeker.Seek(offset, whence)
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if err != nil {
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return 0, err
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}
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}
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// Verify if hook has embedded Seeker, use it.
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hookSeeker, ok := hr.hook.(io.Seeker)
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if ok {
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var m int64
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m, err = hookSeeker.Seek(offset, whence)
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if err != nil {
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return 0, err
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}
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if n != m {
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return 0, fmt.Errorf("hook seeker seeked %d bytes, expected source %d bytes", m, n)
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}
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}
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return n, nil
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}
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// Read implements io.Reader. Always reads from the source, the return
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// value 'n' number of bytes are reported through the hook. Returns
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// error for all non io.EOF conditions.
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func (hr *hookReader) Read(b []byte) (n int, err error) {
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n, err = hr.source.Read(b)
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if err != nil && err != io.EOF {
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return n, err
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}
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// Progress the hook with the total read bytes from the source.
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if _, herr := hr.hook.Read(b[:n]); herr != nil {
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if herr != io.EOF {
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return n, herr
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}
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}
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return n, err
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}
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// newHook returns a io.ReadSeeker which implements hookReader that
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// reports the data read from the source to the hook.
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func newHook(source, hook io.Reader) io.Reader {
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if hook == nil {
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return source
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}
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return &hookReader{source, hook}
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}
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