/
rsm.go
132 lines (117 loc) · 3.58 KB
/
rsm.go
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// Copyright 2021 The Mellium Contributors.
// Use of this source code is governed by the BSD 2-clause
// license that can be found in the LICENSE file.
//go:generate go run ../internal/genfeature
// Package paging implements result set management.
package paging // import "mellium.im/xmpp/paging"
import (
"encoding/xml"
"mellium.im/xmlstream"
)
// Namespaces used by this package.
const (
NS = "http://jabber.org/protocol/rsm"
)
// Iter provides a mechanism for iterating over the children of an XML element.
// Successive calls to Next will step through each child, returning its start
// element and a reader that is limited to the remainder of the child.
//
// If the results indicate that there is another page of data, the paging child
// is skipped and the various paging methods will return queries that can be
// used to fetch the next and/or previous pages.
type Iter struct {
iter *xmlstream.Iter
nextPageSet *RequestNext
prevPageSet *RequestPrev
curSet *Set
err error
max uint64
}
// NewIter returns a new iterator that iterates over the children of the most
// recent start element already consumed from r.
func NewIter(r xml.TokenReader, max uint64) *Iter {
return WrapIter(xmlstream.NewIter(r), max)
}
// WrapIter returns a new iterator that supports paging from an existing
// xmlstream.Iter.
func WrapIter(iter *xmlstream.Iter, max uint64) *Iter {
return &Iter{
iter: iter,
max: max,
}
}
// Close indicates that we are finished with the given iterator. Calling it
// multiple times has no effect.
//
// If the underlying TokenReader is also an io.Closer, Close calls the readers
// Close method.
func (i *Iter) Close() error {
return i.iter.Close()
}
// Current returns a reader over the most recent child.
func (i *Iter) Current() (*xml.StartElement, xml.TokenReader) {
return i.iter.Current()
}
// Err returns the last error encountered by the iterator (if any).
func (i *Iter) Err() error {
if i.err != nil {
return i.err
}
return i.iter.Err()
}
// Next returns true if there are more items to decode.
func (i *Iter) Next() bool {
if i.err != nil {
return false
}
hasNext := i.iter.Next()
if hasNext {
start, r := i.iter.Current()
if start != nil && start.Name.Local == "set" && start.Name.Space == NS {
i.nextPageSet = nil
i.prevPageSet = nil
i.curSet = &Set{}
i.err = xml.NewTokenDecoder(xmlstream.MultiReader(xmlstream.Token(*start), r)).Decode(i.curSet)
if i.err != nil {
return false
}
if i.curSet.First.ID != "" {
i.prevPageSet = &RequestPrev{
Before: i.curSet.First.ID,
Max: i.max,
}
}
if i.curSet.Last != "" {
i.nextPageSet = &RequestNext{
After: i.curSet.Last,
Max: i.max,
}
}
return i.Next()
}
}
return hasNext
}
// NextPage returns a value that can be used to construct a new iterator that
// queries for the next page.
//
// It is only guaranteed to be set once iteration is finished, or when the
// iterator is closed without error and may be nil.
func (i *Iter) NextPage() *RequestNext {
return i.nextPageSet
}
// PreviousPage returns a value that can be used to construct a new iterator that
// queries for the previous page.
//
// It is only guaranteed to be set once iteration is finished, or when the
// iterator is closed without error and may be nil.
func (i *Iter) PreviousPage() *RequestPrev {
return i.prevPageSet
}
// CurrentPage returns information about the current page.
//
// It is only guaranteed to be set once iteration is finished, or when the
// iterator is closed without error and may be nil.
func (i *Iter) CurrentPage() *Set {
return i.curSet
}