Vendor dependencies for GCS

vendor/google.golang.org/api/iterator/iterator.go

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+// 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 iterator provides support for standard Google API iterators.
+// See https://github.com/GoogleCloudPlatform/gcloud-golang/wiki/Iterator-Guidelines.
+package iterator
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+)
+
+// Done is returned by an iterator's Next method when the iteration is
+// complete; when there are no more items to return.
+var Done = errors.New("no more items in iterator")
+
+// We don't support mixed calls to Next and NextPage because they play
+// with the paging state in incompatible ways.
+var errMixed = errors.New("iterator: Next and NextPage called on same iterator")
+
+// PageInfo contains information about an iterator's paging state.
+type PageInfo struct {
+	// Token is the token used to retrieve the next page of items from the
+	// API. You may set Token immediately after creating an iterator to
+	// begin iteration at a particular point. If Token is the empty string,
+	// the iterator will begin with the first eligible item.
+	//
+	// The result of setting Token after the first call to Next is undefined.
+	//
+	// After the underlying API method is called to retrieve a page of items,
+	// Token is set to the next-page token in the response.
+	Token string
+
+	// MaxSize is the maximum number of items returned by a call to the API.
+	// Set MaxSize as a hint to optimize the buffering behavior of the iterator.
+	// If zero, the page size is determined by the underlying service.
+	//
+	// Use Pager to retrieve a page of a specific, exact size.
+	MaxSize int
+
+	// The error state of the iterator. Manipulated by PageInfo.next and Pager.
+	// This is a latch: it starts as nil, and once set should never change.
+	err error
+
+	// If true, no more calls to fetch should be made. Set to true when fetch
+	// returns an empty page token. The iterator is Done when this is true AND
+	// the buffer is empty.
+	atEnd bool
+
+	// Function that fetches a page from the underlying service. It should pass
+	// the pageSize and pageToken arguments to the service, fill the buffer
+	// with the results from the call, and return the next-page token returned
+	// by the service. The function must not remove any existing items from the
+	// buffer. If the underlying RPC takes an int32 page size, pageSize should
+	// be silently truncated.
+	fetch func(pageSize int, pageToken string) (nextPageToken string, err error)
+
+	// Function that clears the iterator's buffer, returning any currently buffered items.
+	bufLen func() int
+
+	// Function that returns the buffer, after setting the buffer variable to nil.
+	takeBuf func() interface{}
+
+	// Set to true on first call to PageInfo.next or Pager.NextPage. Used to check
+	// for calls to both Next and NextPage with the same iterator.
+	nextCalled, nextPageCalled bool
+}
+
+// NewPageInfo exposes internals for iterator implementations.
+// It is not a stable interface.
+var NewPageInfo = newPageInfo
+
+// If an iterator can support paging, its iterator-creating method should call
+// this (via the NewPageInfo variable above).
+//
+// The fetch, bufLen and takeBuf arguments provide access to the
+// iterator's internal slice of buffered items. They behave as described in
+// PageInfo, above.
+//
+// The return value is the PageInfo.next method bound to the returned PageInfo value.
+// (Returning it avoids exporting PageInfo.next.)
+func newPageInfo(fetch func(int, string) (string, error), bufLen func() int, takeBuf func() interface{}) (*PageInfo, func() error) {
+	pi := &PageInfo{
+		fetch:   fetch,
+		bufLen:  bufLen,
+		takeBuf: takeBuf,
+	}
+	return pi, pi.next
+}
+
+// Remaining returns the number of items available before the iterator makes another API call.
+func (pi *PageInfo) Remaining() int { return pi.bufLen() }
+
+// next provides support for an iterator's Next function. An iterator's Next
+// should return the error returned by next if non-nil; else it can assume
+// there is at least one item in its buffer, and it should return that item and
+// remove it from the buffer.
+func (pi *PageInfo) next() error {
+	pi.nextCalled = true
+	if pi.err != nil { // Once we get an error, always return it.
+		// TODO(jba): fix so users can retry on transient errors? Probably not worth it.
+		return pi.err
+	}
+	if pi.nextPageCalled {
+		pi.err = errMixed
+		return pi.err
+	}
+	// Loop until we get some items or reach the end.
+	for pi.bufLen() == 0 && !pi.atEnd {
+		if err := pi.fill(pi.MaxSize); err != nil {
+			pi.err = err
+			return pi.err
+		}
+		if pi.Token == "" {
+			pi.atEnd = true
+		}
+	}
+	// Either the buffer is non-empty or pi.atEnd is true (or both).
+	if pi.bufLen() == 0 {
+		// The buffer is empty and pi.atEnd is true, i.e. the service has no
+		// more items.
+		pi.err = Done
+	}
+	return pi.err
+}
+
+// Call the service to fill the buffer, using size and pi.Token. Set pi.Token to the
+// next-page token returned by the call.
+// If fill returns a non-nil error, the buffer will be empty.
+func (pi *PageInfo) fill(size int) error {
+	tok, err := pi.fetch(size, pi.Token)
+	if err != nil {
+		pi.takeBuf() // clear the buffer
+		return err
+	}
+	pi.Token = tok
+	return nil
+}
+
+// Pageable is implemented by iterators that support paging.
+type Pageable interface {
+	// PageInfo returns paging information associated with the iterator.
+	PageInfo() *PageInfo
+}
+
+// Pager supports retrieving iterator items a page at a time.
+type Pager struct {
+	pageInfo *PageInfo
+	pageSize int
+}
+
+// NewPager returns a pager that uses iter. Calls to its NextPage method will
+// obtain exactly pageSize items, unless fewer remain. The pageToken argument
+// indicates where to start the iteration. Pass the empty string to start at
+// the beginning, or pass a token retrieved from a call to Pager.NextPage.
+//
+// If you use an iterator with a Pager, you must not call Next on the iterator.
+func NewPager(iter Pageable, pageSize int, pageToken string) *Pager {
+	p := &Pager{
+		pageInfo: iter.PageInfo(),
+		pageSize: pageSize,
+	}
+	p.pageInfo.Token = pageToken
+	if pageSize <= 0 {
+		p.pageInfo.err = errors.New("iterator: page size must be positive")
+	}
+	return p
+}
+
+// NextPage retrieves a sequence of items from the iterator and appends them
+// to slicep, which must be a pointer to a slice of the iterator's item type.
+// Exactly p.pageSize items will be appended, unless fewer remain.
+//
+// The first return value is the page token to use for the next page of items.
+// If empty, there are no more pages. Aside from checking for the end of the
+// iteration, the returned page token is only needed if the iteration is to be
+// resumed a later time, in another context (possibly another process).
+//
+// The second return value is non-nil if an error occurred. It will never be
+// the special iterator sentinel value Done. To recognize the end of the
+// iteration, compare nextPageToken to the empty string.
+//
+// It is possible for NextPage to return a single zero-length page along with
+// an empty page token when there are no more items in the iteration.
+func (p *Pager) NextPage(slicep interface{}) (nextPageToken string, err error) {
+	p.pageInfo.nextPageCalled = true
+	if p.pageInfo.err != nil {
+		return "", p.pageInfo.err
+	}
+	if p.pageInfo.nextCalled {
+		p.pageInfo.err = errMixed
+		return "", p.pageInfo.err
+	}
+	if p.pageInfo.bufLen() > 0 {
+		return "", errors.New("must call NextPage with an empty buffer")
+	}
+	// The buffer must be empty here, so takeBuf is a no-op. We call it just to get
+	// the buffer's type.
+	wantSliceType := reflect.PtrTo(reflect.ValueOf(p.pageInfo.takeBuf()).Type())
+	if slicep == nil {
+		return "", errors.New("nil passed to Pager.NextPage")
+	}
+	vslicep := reflect.ValueOf(slicep)
+	if vslicep.Type() != wantSliceType {
+		return "", fmt.Errorf("slicep should be of type %s, got %T", wantSliceType, slicep)
+	}
+	for p.pageInfo.bufLen() < p.pageSize {
+		if err := p.pageInfo.fill(p.pageSize - p.pageInfo.bufLen()); err != nil {
+			p.pageInfo.err = err
+			return "", p.pageInfo.err
+		}
+		if p.pageInfo.Token == "" {
+			break
+		}
+	}
+	e := vslicep.Elem()
+	e.Set(reflect.AppendSlice(e, reflect.ValueOf(p.pageInfo.takeBuf())))
+	return p.pageInfo.Token, nil
+}