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request_pagination.go
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/
request_pagination.go
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package aws
import (
"sync/atomic"
"github.com/aws/aws-sdk-go-v2/internal/awsutil"
)
// A Pager provides paginating of SDK API operations which are paginatable.
// Generally you should not use this type directly, but use the "Pages" API
// operations method to automatically perform pagination for you. Such as,
// "S3.ListObjectsPages", and "S3.ListObjectsPagesWithContext" methods.
//
// Pagier differs from a Paginator type in that pagination is the type that
// does the pagination between API operations, and Paginator defines the
// configuration that will be used per page request.
//
// for p.Next() {
// data := p.CurrentPage().(*s3.ListObjectsOutput)
// // process the page's data
// }
// return p.Err()
//
// See service client API operation Pages methods for examples how the SDK will
// use the Pager type.
type Pager struct {
// Function to return a Request value for each pagination request.
// Any configuration or handlers that need to be applied to the request
// prior to getting the next page should be done here before the request
// returned.
//
// NewRequest should always be built from the same API operations. It is
// undefined if different API operations are returned on subsequent calls.
NewRequest func() (*Request, error)
started bool
nextTokens []interface{}
err error
curPage interface{}
}
// hasNextPage will return true if Pager is able to determine that the API
// operation has additional pages. False will be returned if there are no more
// pages remaining.
//
// Will always return true if Next has not been called yet.
func (p *Pager) hasNextPage() bool {
return !(p.started && len(p.nextTokens) == 0)
}
// Err returns the error Pager encountered when retrieving the next page.
func (p *Pager) Err() error {
return p.err
}
// CurrentPage returns the current page. Page should only be called after a successful
// call to Next. It is undefined what Page will return if Page is called after
// Next returns false.
func (p *Pager) CurrentPage() interface{} {
return p.curPage
}
// Next will attempt to retrieve the next page for the API operation. When a page
// is retrieved true will be returned. If the page cannot be retrieved, or there
// are no more pages false will be returned.
//
// Use the Page method to retrieve the current page data. The data will need
// to be cast to the API operation's output type.
//
// Use the Err method to determine if an error occurred if Page returns false.
func (p *Pager) Next() bool {
if !p.hasNextPage() {
return false
}
req, err := p.NewRequest()
if err != nil {
p.err = err
return false
}
if p.started {
for i, intok := range req.Operation.InputTokens {
awsutil.SetValueAtPath(req.Params, intok, p.nextTokens[i])
}
}
p.started = true
err = req.Send()
if err != nil {
p.err = err
return false
}
p.nextTokens = req.nextPageTokens()
p.curPage = req.Data
return true
}
// A Paginator is the configuration data that defines how an API operation
// should be paginated. This type is used by the API service models to define
// the generated pagination config for service APIs.
//
// The Pager type is what provides iterating between pages of an API. It
// is only used to store the token metadata the SDK should use for performing
// pagination.
type Paginator struct {
InputTokens []string
OutputTokens []string
LimitToken string
TruncationToken string
}
// nextPageTokens returns the tokens to use when asking for the next page of data.
func (r *Request) nextPageTokens() []interface{} {
if r.Operation.Paginator == nil {
return nil
}
if r.Operation.TruncationToken != "" {
tr, _ := awsutil.ValuesAtPath(r.Data, r.Operation.TruncationToken)
if len(tr) == 0 {
return nil
}
switch v := tr[0].(type) {
case *bool:
if !BoolValue(v) {
return nil
}
case bool:
if v == false {
return nil
}
}
}
tokens := []interface{}{}
tokenAdded := false
for _, outToken := range r.Operation.OutputTokens {
vs, _ := awsutil.ValuesAtPath(r.Data, outToken)
if len(vs) == 0 {
tokens = append(tokens, nil)
continue
}
v := vs[0]
switch tv := v.(type) {
case *string:
if len(StringValue(tv)) == 0 {
tokens = append(tokens, nil)
continue
}
case string:
if len(tv) == 0 {
tokens = append(tokens, nil)
continue
}
}
tokenAdded = true
tokens = append(tokens, v)
}
if !tokenAdded {
return nil
}
return tokens
}
// Ensure a deprecated item is only logged once instead of each time its used.
func logDeprecatedf(logger Logger, flag *int32, msg string) {
if logger == nil {
return
}
if atomic.CompareAndSwapInt32(flag, 0, 1) {
logger.Log(msg)
}
}
var (
logDeprecatedHasNextPage int32
logDeprecatedNextPage int32
logDeprecatedEachPage int32
)