386 lines
11 KiB
Go
386 lines
11 KiB
Go
// Copyright 2016 Google LLC
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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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package storage
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import (
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"errors"
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"fmt"
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"hash/crc32"
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"io"
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"io/ioutil"
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"net/http"
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"net/url"
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"reflect"
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"strconv"
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"strings"
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"time"
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"cloud.google.com/go/internal/trace"
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"golang.org/x/net/context"
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"google.golang.org/api/googleapi"
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)
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var crc32cTable = crc32.MakeTable(crc32.Castagnoli)
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// ReaderObjectAttrs are attributes about the object being read. These are populated
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// during the New call. This struct only holds a subset of object attributes: to
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// get the full set of attributes, use ObjectHandle.Attrs.
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//
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// Each field is read-only.
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type ReaderObjectAttrs struct {
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// Size is the length of the object's content.
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Size int64
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// ContentType is the MIME type of the object's content.
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ContentType string
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// ContentEncoding is the encoding of the object's content.
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ContentEncoding string
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// CacheControl specifies whether and for how long browser and Internet
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// caches are allowed to cache your objects.
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CacheControl string
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// LastModified is the time that the object was last modified.
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LastModified time.Time
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// Generation is the generation number of the object's content.
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Generation int64
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// Metageneration is the version of the metadata for this object at
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// this generation. This field is used for preconditions and for
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// detecting changes in metadata. A metageneration number is only
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// meaningful in the context of a particular generation of a
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// particular object.
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Metageneration int64
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}
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// NewReader creates a new Reader to read the contents of the
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// object.
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// ErrObjectNotExist will be returned if the object is not found.
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//
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// The caller must call Close on the returned Reader when done reading.
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func (o *ObjectHandle) NewReader(ctx context.Context) (*Reader, error) {
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return o.NewRangeReader(ctx, 0, -1)
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}
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// NewRangeReader reads part of an object, reading at most length bytes
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// starting at the given offset. If length is negative, the object is read
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// until the end.
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func (o *ObjectHandle) NewRangeReader(ctx context.Context, offset, length int64) (r *Reader, err error) {
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ctx = trace.StartSpan(ctx, "cloud.google.com/go/storage.Object.NewRangeReader")
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defer func() { trace.EndSpan(ctx, err) }()
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if err := o.validate(); err != nil {
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return nil, err
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}
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if offset < 0 {
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return nil, fmt.Errorf("storage: invalid offset %d < 0", offset)
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}
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if o.conds != nil {
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if err := o.conds.validate("NewRangeReader"); err != nil {
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return nil, err
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}
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}
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u := &url.URL{
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Scheme: "https",
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Host: "storage.googleapis.com",
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Path: fmt.Sprintf("/%s/%s", o.bucket, o.object),
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}
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verb := "GET"
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if length == 0 {
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verb = "HEAD"
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}
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req, err := http.NewRequest(verb, u.String(), nil)
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if err != nil {
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return nil, err
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}
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req = withContext(req, ctx)
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if o.userProject != "" {
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req.Header.Set("X-Goog-User-Project", o.userProject)
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}
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if o.readCompressed {
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req.Header.Set("Accept-Encoding", "gzip")
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}
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if err := setEncryptionHeaders(req.Header, o.encryptionKey, false); err != nil {
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return nil, err
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}
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gen := o.gen
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// Define a function that initiates a Read with offset and length, assuming we
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// have already read seen bytes.
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reopen := func(seen int64) (*http.Response, error) {
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start := offset + seen
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if length < 0 && start > 0 {
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req.Header.Set("Range", fmt.Sprintf("bytes=%d-", start))
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} else if length > 0 {
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// The end character isn't affected by how many bytes we've seen.
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req.Header.Set("Range", fmt.Sprintf("bytes=%d-%d", start, offset+length-1))
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}
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// We wait to assign conditions here because the generation number can change in between reopen() runs.
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req.URL.RawQuery = conditionsQuery(gen, o.conds)
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var res *http.Response
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err = runWithRetry(ctx, func() error {
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res, err = o.c.hc.Do(req)
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if err != nil {
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return err
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}
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if res.StatusCode == http.StatusNotFound {
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res.Body.Close()
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return ErrObjectNotExist
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}
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if res.StatusCode < 200 || res.StatusCode > 299 {
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body, _ := ioutil.ReadAll(res.Body)
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res.Body.Close()
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return &googleapi.Error{
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Code: res.StatusCode,
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Header: res.Header,
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Body: string(body),
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}
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}
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if start > 0 && length != 0 && res.StatusCode != http.StatusPartialContent {
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res.Body.Close()
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return errors.New("storage: partial request not satisfied")
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}
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// If a generation hasn't been specified, and this is the first response we get, let's record the
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// generation. In future requests we'll use this generation as a precondition to avoid data races.
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if gen < 0 && res.Header.Get("X-Goog-Generation") != "" {
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gen64, err := strconv.ParseInt(res.Header.Get("X-Goog-Generation"), 10, 64)
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if err != nil {
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return err
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}
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gen = gen64
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}
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return nil
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})
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if err != nil {
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return nil, err
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}
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return res, nil
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}
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res, err := reopen(0)
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if err != nil {
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return nil, err
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}
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var (
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size int64 // total size of object, even if a range was requested.
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checkCRC bool
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crc uint32
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)
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if res.StatusCode == http.StatusPartialContent {
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cr := strings.TrimSpace(res.Header.Get("Content-Range"))
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if !strings.HasPrefix(cr, "bytes ") || !strings.Contains(cr, "/") {
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return nil, fmt.Errorf("storage: invalid Content-Range %q", cr)
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}
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size, err = strconv.ParseInt(cr[strings.LastIndex(cr, "/")+1:], 10, 64)
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if err != nil {
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return nil, fmt.Errorf("storage: invalid Content-Range %q", cr)
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}
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} else {
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size = res.ContentLength
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// Check the CRC iff all of the following hold:
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// - We asked for content (length != 0).
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// - We got all the content (status != PartialContent).
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// - The server sent a CRC header.
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// - The Go http stack did not uncompress the file.
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// - We were not served compressed data that was uncompressed on download.
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// The problem with the last two cases is that the CRC will not match -- GCS
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// computes it on the compressed contents, but we compute it on the
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// uncompressed contents.
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if length != 0 && !goHTTPUncompressed(res) && !uncompressedByServer(res) {
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crc, checkCRC = parseCRC32c(res)
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}
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}
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remain := res.ContentLength
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body := res.Body
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if length == 0 {
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remain = 0
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body.Close()
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body = emptyBody
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}
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var metaGen int64
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if res.Header.Get("X-Goog-Generation") != "" {
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metaGen, err = strconv.ParseInt(res.Header.Get("X-Goog-Metageneration"), 10, 64)
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if err != nil {
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return nil, err
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}
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}
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var lm time.Time
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if res.Header.Get("Last-Modified") != "" {
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lm, err = http.ParseTime(res.Header.Get("Last-Modified"))
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if err != nil {
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return nil, err
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}
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}
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attrs := ReaderObjectAttrs{
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Size: size,
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ContentType: res.Header.Get("Content-Type"),
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ContentEncoding: res.Header.Get("Content-Encoding"),
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CacheControl: res.Header.Get("Cache-Control"),
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LastModified: lm,
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Generation: gen,
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Metageneration: metaGen,
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}
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return &Reader{
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Attrs: attrs,
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body: body,
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size: size,
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remain: remain,
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wantCRC: crc,
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checkCRC: checkCRC,
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reopen: reopen,
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}, nil
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}
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func uncompressedByServer(res *http.Response) bool {
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// If the data is stored as gzip but is not encoded as gzip, then it
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// was uncompressed by the server.
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return res.Header.Get("X-Goog-Stored-Content-Encoding") == "gzip" &&
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res.Header.Get("Content-Encoding") != "gzip"
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}
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func parseCRC32c(res *http.Response) (uint32, bool) {
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const prefix = "crc32c="
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for _, spec := range res.Header["X-Goog-Hash"] {
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if strings.HasPrefix(spec, prefix) {
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c, err := decodeUint32(spec[len(prefix):])
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if err == nil {
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return c, true
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}
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}
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}
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return 0, false
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}
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var emptyBody = ioutil.NopCloser(strings.NewReader(""))
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// Reader reads a Cloud Storage object.
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// It implements io.Reader.
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//
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// Typically, a Reader computes the CRC of the downloaded content and compares it to
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// the stored CRC, returning an error from Read if there is a mismatch. This integrity check
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// is skipped if transcoding occurs. See https://cloud.google.com/storage/docs/transcoding.
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type Reader struct {
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Attrs ReaderObjectAttrs
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body io.ReadCloser
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seen, remain, size int64
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checkCRC bool // should we check the CRC?
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wantCRC uint32 // the CRC32c value the server sent in the header
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gotCRC uint32 // running crc
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reopen func(seen int64) (*http.Response, error)
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}
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// Close closes the Reader. It must be called when done reading.
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func (r *Reader) Close() error {
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return r.body.Close()
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}
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func (r *Reader) Read(p []byte) (int, error) {
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n, err := r.readWithRetry(p)
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if r.remain != -1 {
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r.remain -= int64(n)
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}
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if r.checkCRC {
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r.gotCRC = crc32.Update(r.gotCRC, crc32cTable, p[:n])
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// Check CRC here. It would be natural to check it in Close, but
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// everybody defers Close on the assumption that it doesn't return
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// anything worth looking at.
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if err == io.EOF {
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if r.gotCRC != r.wantCRC {
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return n, fmt.Errorf("storage: bad CRC on read: got %d, want %d",
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r.gotCRC, r.wantCRC)
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}
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}
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}
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return n, err
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}
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func (r *Reader) readWithRetry(p []byte) (int, error) {
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n := 0
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for len(p[n:]) > 0 {
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m, err := r.body.Read(p[n:])
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n += m
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r.seen += int64(m)
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if !shouldRetryRead(err) {
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return n, err
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}
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// Read failed, but we will try again. Send a ranged read request that takes
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// into account the number of bytes we've already seen.
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res, err := r.reopen(r.seen)
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if err != nil {
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// reopen already retries
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return n, err
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}
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r.body.Close()
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r.body = res.Body
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}
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return n, nil
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}
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func shouldRetryRead(err error) bool {
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if err == nil {
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return false
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}
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return strings.HasSuffix(err.Error(), "INTERNAL_ERROR") && strings.Contains(reflect.TypeOf(err).String(), "http2")
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}
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// Size returns the size of the object in bytes.
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// The returned value is always the same and is not affected by
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// calls to Read or Close.
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//
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// Deprecated: use Reader.Attrs.Size.
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func (r *Reader) Size() int64 {
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return r.Attrs.Size
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}
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// Remain returns the number of bytes left to read, or -1 if unknown.
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func (r *Reader) Remain() int64 {
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return r.remain
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}
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// ContentType returns the content type of the object.
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//
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// Deprecated: use Reader.Attrs.ContentType.
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func (r *Reader) ContentType() string {
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return r.Attrs.ContentType
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}
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// ContentEncoding returns the content encoding of the object.
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//
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// Deprecated: use Reader.Attrs.ContentEncoding.
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func (r *Reader) ContentEncoding() string {
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return r.Attrs.ContentEncoding
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}
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// CacheControl returns the cache control of the object.
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//
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// Deprecated: use Reader.Attrs.CacheControl.
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func (r *Reader) CacheControl() string {
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return r.Attrs.CacheControl
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}
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// LastModified returns the value of the Last-Modified header.
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//
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// Deprecated: use Reader.Attrs.LastModified.
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func (r *Reader) LastModified() (time.Time, error) {
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return r.Attrs.LastModified, nil
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}
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