87 lines
2.4 KiB
Go
87 lines
2.4 KiB
Go
// Copyright 2016 Google Inc. All Rights Reserved.
|
|
//
|
|
// 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 storage
|
|
|
|
import (
|
|
"fmt"
|
|
"hash/crc32"
|
|
"io"
|
|
)
|
|
|
|
var crc32cTable = crc32.MakeTable(crc32.Castagnoli)
|
|
|
|
// Reader reads a Cloud Storage object.
|
|
// It implements io.Reader.
|
|
type Reader struct {
|
|
body io.ReadCloser
|
|
remain, size int64
|
|
contentType string
|
|
contentEncoding string
|
|
cacheControl string
|
|
checkCRC bool // should we check the CRC?
|
|
wantCRC uint32 // the CRC32c value the server sent in the header
|
|
gotCRC uint32 // running crc
|
|
}
|
|
|
|
// Close closes the Reader. It must be called when done reading.
|
|
func (r *Reader) Close() error {
|
|
return r.body.Close()
|
|
}
|
|
|
|
func (r *Reader) Read(p []byte) (int, error) {
|
|
n, err := r.body.Read(p)
|
|
if r.remain != -1 {
|
|
r.remain -= int64(n)
|
|
}
|
|
if r.checkCRC {
|
|
r.gotCRC = crc32.Update(r.gotCRC, crc32cTable, p[:n])
|
|
// Check CRC here. It would be natural to check it in Close, but
|
|
// everybody defers Close on the assumption that it doesn't return
|
|
// anything worth looking at.
|
|
if r.remain == 0 && r.gotCRC != r.wantCRC {
|
|
return n, fmt.Errorf("storage: bad CRC on read: got %d, want %d",
|
|
r.gotCRC, r.wantCRC)
|
|
}
|
|
}
|
|
return n, err
|
|
}
|
|
|
|
// Size returns the size of the object in bytes.
|
|
// The returned value is always the same and is not affected by
|
|
// calls to Read or Close.
|
|
func (r *Reader) Size() int64 {
|
|
return r.size
|
|
}
|
|
|
|
// Remain returns the number of bytes left to read, or -1 if unknown.
|
|
func (r *Reader) Remain() int64 {
|
|
return r.remain
|
|
}
|
|
|
|
// ContentType returns the content type of the object.
|
|
func (r *Reader) ContentType() string {
|
|
return r.contentType
|
|
}
|
|
|
|
// ContentEncoding returns the content encoding of the object.
|
|
func (r *Reader) ContentEncoding() string {
|
|
return r.contentEncoding
|
|
}
|
|
|
|
// CacheControl returns the cache control of the object.
|
|
func (r *Reader) CacheControl() string {
|
|
return r.cacheControl
|
|
}
|