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// Copyright (c) 2021 Tulir Asokan
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
// Package binary implements encoding and decoding documents in WhatsApp's binary XML format.
package binary
import (
"fmt"
)
// Attrs is a type alias for the attributes of an XML element (Node).
type Attrs = map[string]interface{}
// Node represents an XML element.
type Node struct {
Tag string // The tag of the element.
Attrs Attrs // The attributes of the element.
Content interface{} // The content inside the element. Can be nil, a list of Nodes, or a byte array.
}
// GetChildren returns the Content of the node as a list of nodes. If the content is not a list of nodes, this returns nil.
func (n *Node) GetChildren() []Node {
if n.Content == nil {
return nil
}
children, ok := n.Content.([]Node)
if !ok {
return nil
}
return children
}
// GetChildrenByTag returns the same list as GetChildren, but filters it by tag first.
func (n *Node) GetChildrenByTag(tag string) (children []Node) {
for _, node := range n.GetChildren() {
if node.Tag == tag {
children = append(children, node)
}
}
return
}
// GetOptionalChildByTag finds the first child with the given tag and returns it.
// Each provided tag will recurse in, so this is useful for getting a specific nested element.
func (n *Node) GetOptionalChildByTag(tags ...string) (val Node, ok bool) {
val = *n
Outer:
for _, tag := range tags {
for _, child := range val.GetChildren() {
if child.Tag == tag {
val = child
continue Outer
}
}
// If no matching children are found, return false
return
}
// All iterations of loop found a matching child, return it
ok = true
return
}
// GetChildByTag does the same thing as GetOptionalChildByTag, but returns the Node directly without the ok boolean.
func (n *Node) GetChildByTag(tags ...string) Node {
node, _ := n.GetOptionalChildByTag(tags...)
return node
}
// Marshal encodes an XML element (Node) into WhatsApp's binary XML representation.
func Marshal(n Node) ([]byte, error) {
w := newEncoder()
w.writeNode(n)
return w.getData(), nil
}
// Unmarshal decodes WhatsApp's binary XML representation into a Node.
func Unmarshal(data []byte) (*Node, error) {
r := newDecoder(data)
n, err := r.readNode()
if err != nil {
return nil, err
} else if r.index != len(r.data) {
return n, fmt.Errorf("%d leftover bytes after decoding", len(r.data)-r.index)
}
return n, nil
}
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