imgproxy/processing/svg/parser/escape.go

package svgparser

import (
	"bufio"
	"unicode/utf8"
)

var (
	escQuot = []byte(""")
	escApos = []byte("'")
	escAmp  = []byte("&")
	escLT   = []byte("<")
	escGT   = []byte(">")
	escTab  = []byte("	")
	escNL   = []byte("
")
	escCR   = []byte("
")
	escFFFD = []byte("\uFFFD") // Unicode replacement character
)

// escapeString writes an escaped version of a string to the writer.
// It's a copy of xml.EscapeText with changed escape replacements.
func escapeString(w *bufio.Writer, s string) error {
	var esc []byte
	last := 0
	for i := 0; i < len(s); {
		r, width := utf8.DecodeRuneInString(s[i:])
		i += width
		switch r {
		case '"':
			esc = escQuot
		case '\'':
			esc = escApos
		case '&':
			esc = escAmp
		case '<':
			esc = escLT
		case '>':
			esc = escGT
		case '\t':
			esc = escTab
		case '\n':
			esc = escNL
		case '\r':
			esc = escCR
		default:
			if !isInCharacterRange(r) || (r == 0xFFFD && width == 1) {
				esc = escFFFD
				break
			}
			continue
		}
		if _, err := w.WriteString(s[last : i-width]); err != nil {
			return err
		}
		if _, err := w.Write(esc); err != nil {
			return err
		}
		last = i
	}
	if _, err := w.WriteString(s[last:]); err != nil {
		return err
	}
	return nil
}

func isInCharacterRange(r rune) bool {
	return r == 0x09 ||
		r == 0x0A ||
		r == 0x0D ||
		r >= 0x20 && r <= 0xD7FF ||
		r >= 0xE000 && r <= 0xFFFD ||
		r >= 0x10000 && r <= 0x10FFFF
}