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+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+import (
+ "reflect"
+ "sync"
+ "text/template/parse"
+)
+
+// common holds the information shared by related templates.
+type common struct {
+ tmpl map[string]*Template // Map from name to defined templates.
+ muTmpl sync.RWMutex // protects tmpl
+ option option
+ // We use two maps, one for parsing and one for execution.
+ // This separation makes the API cleaner since it doesn't
+ // expose reflection to the client.
+ muFuncs sync.RWMutex // protects parseFuncs and execFuncs
+ parseFuncs FuncMap
+ execFuncs map[string]reflect.Value
+}
+
+// Template is the representation of a parsed template. The *parse.Tree
+// field is exported only for use by html/template and should be treated
+// as unexported by all other clients.
+type Template struct {
+ name string
+ *parse.Tree
+ *common
+ leftDelim string
+ rightDelim string
+}
+
+// New allocates a new, undefined template with the given name.
+func New(name string) *Template {
+ t := &Template{
+ name: name,
+ }
+ t.init()
+ return t
+}
+
+// Name returns the name of the template.
+func (t *Template) Name() string {
+ return t.name
+}
+
+// New allocates a new, undefined template associated with the given one and with the same
+// delimiters. The association, which is transitive, allows one template to
+// invoke another with a {{template}} action.
+//
+// Because associated templates share underlying data, template construction
+// cannot be done safely in parallel. Once the templates are constructed, they
+// can be executed in parallel.
+func (t *Template) New(name string) *Template {
+ t.init()
+ nt := &Template{
+ name: name,
+ common: t.common,
+ leftDelim: t.leftDelim,
+ rightDelim: t.rightDelim,
+ }
+ return nt
+}
+
+// init guarantees that t has a valid common structure.
+func (t *Template) init() {
+ if t.common == nil {
+ c := new(common)
+ c.tmpl = make(map[string]*Template)
+ c.parseFuncs = make(FuncMap)
+ c.execFuncs = make(map[string]reflect.Value)
+ t.common = c
+ }
+}
+
+// Clone returns a duplicate of the template, including all associated
+// templates. The actual representation is not copied, but the name space of
+// associated templates is, so further calls to Parse in the copy will add
+// templates to the copy but not to the original. Clone can be used to prepare
+// common templates and use them with variant definitions for other templates
+// by adding the variants after the clone is made.
+func (t *Template) Clone() (*Template, error) {
+ nt := t.copy(nil)
+ nt.init()
+ if t.common == nil {
+ return nt, nil
+ }
+ t.muTmpl.RLock()
+ defer t.muTmpl.RUnlock()
+ for k, v := range t.tmpl {
+ if k == t.name {
+ nt.tmpl[t.name] = nt
+ continue
+ }
+ // The associated templates share nt's common structure.
+ tmpl := v.copy(nt.common)
+ nt.tmpl[k] = tmpl
+ }
+ t.muFuncs.RLock()
+ defer t.muFuncs.RUnlock()
+ for k, v := range t.parseFuncs {
+ nt.parseFuncs[k] = v
+ }
+ for k, v := range t.execFuncs {
+ nt.execFuncs[k] = v
+ }
+ return nt, nil
+}
+
+// copy returns a shallow copy of t, with common set to the argument.
+func (t *Template) copy(c *common) *Template {
+ return &Template{
+ name: t.name,
+ Tree: t.Tree,
+ common: c,
+ leftDelim: t.leftDelim,
+ rightDelim: t.rightDelim,
+ }
+}
+
+// AddParseTree associates the argument parse tree with the template t, giving
+// it the specified name. If the template has not been defined, this tree becomes
+// its definition. If it has been defined and already has that name, the existing
+// definition is replaced; otherwise a new template is created, defined, and returned.
+func (t *Template) AddParseTree(name string, tree *parse.Tree) (*Template, error) {
+ t.init()
+ t.muTmpl.Lock()
+ defer t.muTmpl.Unlock()
+ nt := t
+ if name != t.name {
+ nt = t.New(name)
+ }
+ // Even if nt == t, we need to install it in the common.tmpl map.
+ if t.associate(nt, tree) || nt.Tree == nil {
+ nt.Tree = tree
+ }
+ return nt, nil
+}
+
+// Templates returns a slice of defined templates associated with t.
+func (t *Template) Templates() []*Template {
+ if t.common == nil {
+ return nil
+ }
+ // Return a slice so we don't expose the map.
+ t.muTmpl.RLock()
+ defer t.muTmpl.RUnlock()
+ m := make([]*Template, 0, len(t.tmpl))
+ for _, v := range t.tmpl {
+ m = append(m, v)
+ }
+ return m
+}
+
+// Delims sets the action delimiters to the specified strings, to be used in
+// subsequent calls to Parse, ParseFiles, or ParseGlob. Nested template
+// definitions will inherit the settings. An empty delimiter stands for the
+// corresponding default: {{ or }}.
+// The return value is the template, so calls can be chained.
+func (t *Template) Delims(left, right string) *Template {
+ t.init()
+ t.leftDelim = left
+ t.rightDelim = right
+ return t
+}
+
+// Funcs adds the elements of the argument map to the template's function map.
+// It must be called before the template is parsed.
+// It panics if a value in the map is not a function with appropriate return
+// type or if the name cannot be used syntactically as a function in a template.
+// It is legal to overwrite elements of the map. The return value is the template,
+// so calls can be chained.
+func (t *Template) Funcs(funcMap FuncMap) *Template {
+ t.init()
+ t.muFuncs.Lock()
+ defer t.muFuncs.Unlock()
+ addValueFuncs(t.execFuncs, funcMap)
+ addFuncs(t.parseFuncs, funcMap)
+ return t
+}
+
+// Lookup returns the template with the given name that is associated with t.
+// It returns nil if there is no such template or the template has no definition.
+func (t *Template) Lookup(name string) *Template {
+ if t.common == nil {
+ return nil
+ }
+ t.muTmpl.RLock()
+ defer t.muTmpl.RUnlock()
+ return t.tmpl[name]
+}
+
+// Parse parses text as a template body for t.
+// Named template definitions ({{define ...}} or {{block ...}} statements) in text
+// define additional templates associated with t and are removed from the
+// definition of t itself.
+//
+// Templates can be redefined in successive calls to Parse.
+// A template definition with a body containing only white space and comments
+// is considered empty and will not replace an existing template's body.
+// This allows using Parse to add new named template definitions without
+// overwriting the main template body.
+func (t *Template) Parse(text string) (*Template, error) {
+ t.init()
+ t.muFuncs.RLock()
+ trees, err := parse.Parse(t.name, text, t.leftDelim, t.rightDelim, t.parseFuncs, builtins())
+ t.muFuncs.RUnlock()
+ if err != nil {
+ return nil, err
+ }
+ // Add the newly parsed trees, including the one for t, into our common structure.
+ for name, tree := range trees {
+ if _, err := t.AddParseTree(name, tree); err != nil {
+ return nil, err
+ }
+ }
+ return t, nil
+}
+
+// associate installs the new template into the group of templates associated
+// with t. The two are already known to share the common structure.
+// The boolean return value reports whether to store this tree as t.Tree.
+func (t *Template) associate(new *Template, tree *parse.Tree) bool {
+ if new.common != t.common {
+ panic("internal error: associate not common")
+ }
+ if old := t.tmpl[new.name]; old != nil && parse.IsEmptyTree(tree.Root) && old.Tree != nil {
+ // If a template by that name exists,
+ // don't replace it with an empty template.
+ return false
+ }
+ t.tmpl[new.name] = new
+ return true
+}