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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 (
"bytes"
"io"
"fmt"
"reflect"
"strings"
)
// FuncMap is the type of the map defining the mapping from names to functions.
// Each function must have either a single return value, or two return values of
// which the second has type os.Error.
type FuncMap map[string]interface{}
var funcs = map[string]reflect.Value{
"printf": reflect.ValueOf(fmt.Sprintf),
"html": reflect.ValueOf(HTMLEscaper),
}
// addFuncs adds to values the functions in funcs, converting them to reflect.Values.
func addFuncs(values map[string]reflect.Value, funcMap FuncMap) {
for name, fn := range funcMap {
v := reflect.ValueOf(fn)
if v.Kind() != reflect.Func {
panic("value for " + name + " not a function")
}
if !goodFunc(v.Type()) {
panic(fmt.Errorf("can't handle multiple results from method/function %q", name))
}
values[name] = v
}
}
// goodFunc checks that the function or method has the right result signature.
func goodFunc(typ reflect.Type) bool {
// We allow functions with 1 result or 2 results where the second is an os.Error.
switch {
case typ.NumOut() == 1:
return true
case typ.NumOut() == 2 && typ.Out(1) == osErrorType:
return true
}
return false
}
// findFunction looks for a function in the template, set, and global map.
func findFunction(name string, tmpl *Template, set *Set) (reflect.Value, bool) {
if tmpl != nil {
if fn := tmpl.funcs[name]; fn.IsValid() {
return fn, true
}
}
if set != nil {
if fn := set.funcs[name]; fn.IsValid() {
return fn, true
}
}
if fn := funcs[name]; fn.IsValid() {
return fn, true
}
return reflect.Value{}, false
}
// HTML escaping
var (
escQuot = []byte(""") // shorter than """
escApos = []byte("'") // shorter than "'"
escAmp = []byte("&")
escLt = []byte("<")
escGt = []byte(">")
)
// HTMLEscape writes to w the escaped HTML equivalent of the plain text data b.
func HTMLEscape(w io.Writer, b []byte) {
last := 0
for i, c := range b {
var esc []byte
switch c {
case '"':
esc = escQuot
case '\'':
esc = escApos
case '&':
esc = escAmp
case '<':
esc = escLt
case '>':
esc = escGt
default:
continue
}
w.Write(b[last:i])
w.Write(esc)
last = i + 1
}
w.Write(b[last:])
}
// HTMLEscapeString returns the escaped HTML equivalent of the plain text data s.
func HTMLEscapeString(s string) string {
// Avoid allocation if we can.
if strings.IndexAny(s, `'"&<>`) < 0 {
return s
}
var b bytes.Buffer
HTMLEscape(&b, []byte(s))
return b.String()
}
// HTMLEscaper returns the escaped HTML equivalent of the textual
// representation of its arguments.
func HTMLEscaper(args ...interface{}) string {
ok := false
var s string
if len(args) == 1 {
s, ok = args[0].(string)
}
if !ok {
s = fmt.Sprint(args...)
}
return HTMLEscapeString(s)
}
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