src/pkg/template/format.go

// Copyright 2009 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.

// Template library: default formatters

package template

import (
	"bytes"
	"fmt"
	"io"
)

// StringFormatter formats into the default string representation.
// It is stored under the name "str" and is the default formatter.
// You can override the default formatter by storing your default
// under the name "" in your custom formatter map.
func StringFormatter(w io.Writer, value interface{}, format string) {
	if b, ok := value.([]byte); ok {
		w.Write(b)
		return
	}
	fmt.Fprint(w, value)
}

var (
	esc_quot = []byte(""") // shorter than """
	esc_apos = []byte("'") // shorter than "'"
	esc_amp  = []byte("&")
	esc_lt   = []byte("<")
	esc_gt   = []byte(">")
)

// HTMLEscape writes to w the properly escaped HTML equivalent
// of the plain text data s.
func HTMLEscape(w io.Writer, s []byte) {
	var esc []byte
	last := 0
	for i, c := range s {
		switch c {
		case '"':
			esc = esc_quot
		case '\'':
			esc = esc_apos
		case '&':
			esc = esc_amp
		case '<':
			esc = esc_lt
		case '>':
			esc = esc_gt
		default:
			continue
		}
		w.Write(s[last:i])
		w.Write(esc)
		last = i + 1
	}
	w.Write(s[last:])
}

// HTMLFormatter formats arbitrary values for HTML
func HTMLFormatter(w io.Writer, value interface{}, format string) {
	b, ok := value.([]byte)
	if !ok {
		var buf bytes.Buffer
		fmt.Fprint(&buf, value)
		b = buf.Bytes()
	}
	HTMLEscape(w, b)
}