encoding/xml: predefine xml name space prefix
Also change prefix generation to use more human-friendly prefixes.
Fixes #5040.
R=golang-dev, r, bradfitz
CC=golang-dev
https://golang.org/cl/7777047
diff --git a/src/pkg/encoding/xml/marshal.go b/src/pkg/encoding/xml/marshal.go
index 052e101..47b0017 100644
--- a/src/pkg/encoding/xml/marshal.go
+++ b/src/pkg/encoding/xml/marshal.go
@@ -126,6 +126,70 @@
depth int
indentedIn bool
putNewline bool
+ attrNS map[string]string // map prefix -> name space
+ attrPrefix map[string]string // map name space -> prefix
+}
+
+// createAttrPrefix finds the name space prefix attribute to use for the given name space,
+// defining a new prefix if necessary. It returns the prefix and whether it is new.
+func (p *printer) createAttrPrefix(url string) (prefix string, isNew bool) {
+ if prefix = p.attrPrefix[url]; prefix != "" {
+ return prefix, false
+ }
+
+ // The "http://www.w3.org/XML/1998/namespace" name space is predefined as "xml"
+ // and must be referred to that way.
+ // (The "http://www.w3.org/2000/xmlns/" name space is also predefined as "xmlns",
+ // but users should not be trying to use that one directly - that's our job.)
+ if url == xmlURL {
+ return "xml", false
+ }
+
+ // Need to define a new name space.
+ if p.attrPrefix == nil {
+ p.attrPrefix = make(map[string]string)
+ p.attrNS = make(map[string]string)
+ }
+
+ // Pick a name. We try to use the final element of the path
+ // but fall back to _.
+ prefix = strings.TrimRight(url, "/")
+ if i := strings.LastIndex(prefix, "/"); i >= 0 {
+ prefix = prefix[i+1:]
+ }
+ if prefix == "" || !isName([]byte(prefix)) || strings.Contains(prefix, ":") {
+ prefix = "_"
+ }
+ if strings.HasPrefix(prefix, "xml") {
+ // xmlanything is reserved.
+ prefix = "_" + prefix
+ }
+ if p.attrNS[prefix] != "" {
+ // Name is taken. Find a better one.
+ for p.seq++; ; p.seq++ {
+ if id := prefix + "_" + strconv.Itoa(p.seq); p.attrNS[id] == "" {
+ prefix = id
+ break
+ }
+ }
+ }
+
+ p.attrPrefix[url] = prefix
+ p.attrNS[prefix] = url
+
+ p.WriteString(`xmlns:`)
+ p.WriteString(prefix)
+ p.WriteString(`="`)
+ EscapeText(p, []byte(url))
+ p.WriteString(`" `)
+
+ return prefix, true
+}
+
+// deleteAttrPrefix removes an attribute name space prefix.
+func (p *printer) deleteAttrPrefix(prefix string) {
+ delete(p.attrPrefix, p.attrNS[prefix])
+ delete(p.attrNS, prefix)
}
// marshalValue writes one or more XML elements representing val.
@@ -212,17 +276,11 @@
}
p.WriteByte(' ')
if finfo.xmlns != "" {
- p.WriteString("xmlns:")
- p.seq++
- id := "_" + strconv.Itoa(p.seq)
- p.WriteString(id)
- p.WriteString(`="`)
- // TODO: EscapeString, to avoid the allocation.
- if err := EscapeText(p, []byte(finfo.xmlns)); err != nil {
- return err
+ prefix, created := p.createAttrPrefix(finfo.xmlns)
+ if created {
+ defer p.deleteAttrPrefix(prefix)
}
- p.WriteString(`" `)
- p.WriteString(id)
+ p.WriteString(prefix)
p.WriteByte(':')
}
p.WriteString(finfo.name)
