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dex/vendor/github.com/russellhaering/goxmldsig/etreeutils/namespace.go
2017-03-21 09:27:22 -07:00

253 lines
6.3 KiB
Go

package etreeutils
import (
"errors"
"fmt"
"sort"
"github.com/beevik/etree"
)
const (
defaultPrefix = ""
xmlnsPrefix = "xmlns"
xmlPrefix = "xml"
XMLNamespace = "http://www.w3.org/XML/1998/namespace"
XMLNSNamespace = "http://www.w3.org/2000/xmlns/"
)
var (
DefaultNSContext = NSContext{
prefixes: map[string]string{
defaultPrefix: XMLNamespace,
xmlPrefix: XMLNamespace,
xmlnsPrefix: XMLNSNamespace,
},
}
EmptyNSContext = NSContext{}
ErrReservedNamespace = errors.New("disallowed declaration of reserved namespace")
ErrInvalidDefaultNamespace = errors.New("invalid default namespace declaration")
ErrTraversalHalted = errors.New("traversal halted")
)
type ErrUndeclaredNSPrefix struct {
Prefix string
}
func (e ErrUndeclaredNSPrefix) Error() string {
return fmt.Sprintf("undeclared namespace prefix: '%s'", e.Prefix)
}
type NSContext struct {
prefixes map[string]string
}
func (ctx NSContext) SubContext(el *etree.Element) (NSContext, error) {
// The subcontext should inherit existing declared prefixes
prefixes := make(map[string]string, len(ctx.prefixes)+4)
for k, v := range ctx.prefixes {
prefixes[k] = v
}
// Merge new namespace declarations on top of existing ones.
for _, attr := range el.Attr {
if attr.Space == xmlnsPrefix {
// This attribute is a namespace declaration of the form "xmlns:<prefix>"
// The 'xml' namespace may only be re-declared with the name 'http://www.w3.org/XML/1998/namespace'
if attr.Key == xmlPrefix && attr.Value != XMLNamespace {
return ctx, ErrReservedNamespace
}
// The 'xmlns' namespace may not be re-declared
if attr.Key == xmlnsPrefix {
return ctx, ErrReservedNamespace
}
prefixes[attr.Key] = attr.Value
} else if attr.Space == defaultPrefix && attr.Key == xmlnsPrefix {
// This attribute is a default namespace declaration
// The xmlns namespace value may not be declared as the default namespace
if attr.Value == XMLNSNamespace {
return ctx, ErrInvalidDefaultNamespace
}
prefixes[defaultPrefix] = attr.Value
}
}
return NSContext{prefixes: prefixes}, nil
}
// LookupPrefix attempts to find a declared namespace for the specified prefix. If the prefix
// is an empty string this will be the default namespace for this context. If the prefix is
// undeclared in this context an ErrUndeclaredNSPrefix will be returned.
func (ctx NSContext) LookupPrefix(prefix string) (string, error) {
if namespace, ok := ctx.prefixes[prefix]; ok {
return namespace, nil
}
return "", ErrUndeclaredNSPrefix{
Prefix: prefix,
}
}
func nsTraverse(ctx NSContext, el *etree.Element, handle func(NSContext, *etree.Element) error) error {
ctx, err := ctx.SubContext(el)
if err != nil {
return err
}
err = handle(ctx, el)
if err != nil {
return err
}
// Recursively traverse child elements.
for _, child := range el.ChildElements() {
err := nsTraverse(ctx, child, handle)
if err != nil {
return err
}
}
return nil
}
func detachWithNamespaces(ctx NSContext, el *etree.Element) (*etree.Element, error) {
ctx, err := ctx.SubContext(el)
if err != nil {
return nil, err
}
el = el.Copy()
// Build a new attribute list
attrs := make([]etree.Attr, 0, len(el.Attr))
// First copy over anything that isn't a namespace declaration
for _, attr := range el.Attr {
if attr.Space == xmlnsPrefix {
continue
}
if attr.Space == defaultPrefix && attr.Key == xmlnsPrefix {
continue
}
attrs = append(attrs, attr)
}
// Append all in-context namespace declarations
for prefix, namespace := range ctx.prefixes {
// Skip the implicit "xml" and "xmlns" prefix declarations
if prefix == xmlnsPrefix || prefix == xmlPrefix {
continue
}
// Also skip declararing the default namespace as XMLNamespace
if prefix == defaultPrefix && namespace == XMLNamespace {
continue
}
if prefix != defaultPrefix {
attrs = append(attrs, etree.Attr{
Space: xmlnsPrefix,
Key: prefix,
Value: namespace,
})
} else {
attrs = append(attrs, etree.Attr{
Key: xmlnsPrefix,
Value: namespace,
})
}
}
sort.Sort(SortedAttrs(attrs))
el.Attr = attrs
return el, nil
}
// NSSelectOne conducts a depth-first search for an element with the specified namespace
// and tag. If such an element is found, a new *etree.Element is returned which is a
// copy of the found element, but with all in-context namespace declarations attached
// to the element as attributes.
func NSSelectOne(el *etree.Element, namespace, tag string) (*etree.Element, error) {
var found *etree.Element
err := nsTraverse(DefaultNSContext, el, func(ctx NSContext, el *etree.Element) error {
currentNS, err := ctx.LookupPrefix(el.Space)
if err != nil {
return err
}
// Base case, el is the sought after element.
if currentNS == namespace && el.Tag == tag {
found, err = detachWithNamespaces(ctx, el)
return ErrTraversalHalted
}
return nil
})
if err != nil && err != ErrTraversalHalted {
return nil, err
}
return found, nil
}
// NSFindIterate conducts a depth-first traversal searching for elements with the
// specified tag in the specified namespace. For each such element, the passed
// handler function is invoked. If the handler function returns an error
// traversal is immediately halted. If the error returned by the handler is
// ErrTraversalHalted then nil will be returned by NSFindIterate. If any other
// error is returned by the handler, that error will be returned by NSFindIterate.
func NSFindIterate(el *etree.Element, namespace, tag string, handle func(*etree.Element) error) error {
err := nsTraverse(DefaultNSContext, el, func(ctx NSContext, el *etree.Element) error {
currentNS, err := ctx.LookupPrefix(el.Space)
if err != nil {
return err
}
// Base case, el is the sought after element.
if currentNS == namespace && el.Tag == tag {
return handle(el)
}
return nil
})
if err != nil && err != ErrTraversalHalted {
return err
}
return nil
}
// NSFindOne conducts a depth-first search for the specified element. If such an element
// is found a reference to it is returned.
func NSFindOne(el *etree.Element, namespace, tag string) (*etree.Element, error) {
var found *etree.Element
err := NSFindIterate(el, namespace, tag, func(el *etree.Element) error {
found = el
return ErrTraversalHalted
})
if err != nil {
return nil, err
}
return found, nil
}