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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"
"fmt"
"io"
"net/url"
"reflect"
"strings"
"unicode"
"unicode/utf8"
)
// 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 error. In that case, if the second (error)
// argument evaluates to non-nil during execution, execution terminates and
// Execute returns that error.
type FuncMap map[string]interface{}
var builtins = FuncMap{
"and": and,
"html": HTMLEscaper,
"index": index,
"js": JSEscaper,
"len": length,
"not": not,
"or": or,
"print": fmt.Sprint,
"printf": fmt.Sprintf,
"println": fmt.Sprintln,
"urlquery": URLQueryEscaper,
}
var builtinFuncs = createValueFuncs(builtins)
// createValueFuncs turns a FuncMap into a map[string]reflect.Value
func createValueFuncs(funcMap FuncMap) map[string]reflect.Value {
m := make(map[string]reflect.Value)
addValueFuncs(m, funcMap)
return m
}
// addValueFuncs adds to values the functions in funcs, converting them to reflect.Values.
func addValueFuncs(out map[string]reflect.Value, in FuncMap) {
for name, fn := range in {
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))
}
out[name] = v
}
}
// addFuncs adds to values the functions in funcs. It does no checking of the input -
// call addValueFuncs first.
func addFuncs(out, in FuncMap) {
for name, fn := range in {
out[name] = fn
}
}
// 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 error.
switch {
case typ.NumOut() == 1:
return true
case typ.NumOut() == 2 && typ.Out(1) == errorType:
return true
}
return false
}
// findFunction looks for a function in the template, and global map.
func findFunction(name string, tmpl *Template) (reflect.Value, bool) {
if tmpl != nil && tmpl.common != nil {
if fn := tmpl.execFuncs[name]; fn.IsValid() {
return fn, true
}
}
if fn := builtinFuncs[name]; fn.IsValid() {
return fn, true
}
return reflect.Value{}, false
}
// Indexing.
// index returns the result of indexing its first argument by the following
// arguments. Thus "index x 1 2 3" is, in Go syntax, x[1][2][3]. Each
// indexed item must be a map, slice, or array.
func index(item interface{}, indices ...interface{}) (interface{}, error) {
v := reflect.ValueOf(item)
for _, i := range indices {
index := reflect.ValueOf(i)
var isNil bool
if v, isNil = indirect(v); isNil {
return nil, fmt.Errorf("index of nil pointer")
}
switch v.Kind() {
case reflect.Array, reflect.Slice:
var x int64
switch index.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
x = index.Int()
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
x = int64(index.Uint())
default:
return nil, fmt.Errorf("cannot index slice/array with type %s", index.Type())
}
if x < 0 || x >= int64(v.Len()) {
return nil, fmt.Errorf("index out of range: %d", x)
}
v = v.Index(int(x))
case reflect.Map:
if !index.Type().AssignableTo(v.Type().Key()) {
return nil, fmt.Errorf("%s is not index type for %s", index.Type(), v.Type())
}
if x := v.MapIndex(index); x.IsValid() {
v = x
} else {
v = reflect.Zero(v.Type().Key())
}
default:
return nil, fmt.Errorf("can't index item of type %s", index.Type())
}
}
return v.Interface(), nil
}
// Length
// length returns the length of the item, with an error if it has no defined length.
func length(item interface{}) (int, error) {
v, isNil := indirect(reflect.ValueOf(item))
if isNil {
return 0, fmt.Errorf("len of nil pointer")
}
switch v.Kind() {
case reflect.Array, reflect.Chan, reflect.Map, reflect.Slice, reflect.String:
return v.Len(), nil
}
return 0, fmt.Errorf("len of type %s", v.Type())
}
// Boolean logic.
func truth(a interface{}) bool {
t, _ := isTrue(reflect.ValueOf(a))
return t
}
// and computes the Boolean AND of its arguments, returning
// the first false argument it encounters, or the last argument.
func and(arg0 interface{}, args ...interface{}) interface{} {
if !truth(arg0) {
return arg0
}
for i := range args {
arg0 = args[i]
if !truth(arg0) {
break
}
}
return arg0
}
// or computes the Boolean OR of its arguments, returning
// the first true argument it encounters, or the last argument.
func or(arg0 interface{}, args ...interface{}) interface{} {
if truth(arg0) {
return arg0
}
for i := range args {
arg0 = args[i]
if truth(arg0) {
break
}
}
return arg0
}
// not returns the Boolean negation of its argument.
func not(arg interface{}) (truth bool) {
truth, _ = isTrue(reflect.ValueOf(arg))
return !truth
}
// HTML escaping.
var (
htmlQuot = []byte("&#34;") // shorter than "&quot;"
htmlApos = []byte("&#39;") // shorter than "&apos;"
htmlAmp = []byte("&amp;")
htmlLt = []byte("&lt;")
htmlGt = []byte("&gt;")
)
// 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 html []byte
switch c {
case '"':
html = htmlQuot
case '\'':
html = htmlApos
case '&':
html = htmlAmp
case '<':
html = htmlLt
case '>':
html = htmlGt
default:
continue
}
w.Write(b[last:i])
w.Write(html)
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)
}
// JavaScript escaping.
var (
jsLowUni = []byte(`\u00`)
hex = []byte("0123456789ABCDEF")
jsBackslash = []byte(`\\`)
jsApos = []byte(`\'`)
jsQuot = []byte(`\"`)
jsLt = []byte(`\x3C`)
jsGt = []byte(`\x3E`)
)
// JSEscape writes to w the escaped JavaScript equivalent of the plain text data b.
func JSEscape(w io.Writer, b []byte) {
last := 0
for i := 0; i < len(b); i++ {
c := b[i]
if !jsIsSpecial(rune(c)) {
// fast path: nothing to do
continue
}
w.Write(b[last:i])
if c < utf8.RuneSelf {
// Quotes, slashes and angle brackets get quoted.
// Control characters get written as \u00XX.
switch c {
case '\\':
w.Write(jsBackslash)
case '\'':
w.Write(jsApos)
case '"':
w.Write(jsQuot)
case '<':
w.Write(jsLt)
case '>':
w.Write(jsGt)
default:
w.Write(jsLowUni)
t, b := c>>4, c&0x0f
w.Write(hex[t : t+1])
w.Write(hex[b : b+1])
}
} else {
// Unicode rune.
r, size := utf8.DecodeRune(b[i:])
if unicode.IsPrint(r) {
w.Write(b[i : i+size])
} else {
fmt.Fprintf(w, "\\u%04X", r)
}
i += size - 1
}
last = i + 1
}
w.Write(b[last:])
}
// JSEscapeString returns the escaped JavaScript equivalent of the plain text data s.
func JSEscapeString(s string) string {
// Avoid allocation if we can.
if strings.IndexFunc(s, jsIsSpecial) < 0 {
return s
}
var b bytes.Buffer
JSEscape(&b, []byte(s))
return b.String()
}
func jsIsSpecial(r rune) bool {
switch r {
case '\\', '\'', '"', '<', '>':
return true
}
return r < ' ' || utf8.RuneSelf <= r
}
// JSEscaper returns the escaped JavaScript equivalent of the textual
// representation of its arguments.
func JSEscaper(args ...interface{}) string {
ok := false
var s string
if len(args) == 1 {
s, ok = args[0].(string)
}
if !ok {
s = fmt.Sprint(args...)
}
return JSEscapeString(s)
}
// URLQueryEscaper returns the escaped value of the textual representation of
// its arguments in a form suitable for embedding in a URL query.
func URLQueryEscaper(args ...interface{}) string {
s, ok := "", false
if len(args) == 1 {
s, ok = args[0].(string)
}
if !ok {
s = fmt.Sprint(args...)
}
return url.QueryEscape(s)
}