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forgejo/modules/charset/escape.go

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// Copyright 2021 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
package charset
import (
"bytes"
"fmt"
"io"
"strings"
"unicode"
"unicode/utf8"
"golang.org/x/text/unicode/bidi"
)
// EscapeStatus represents the findings of the unicode escaper
type EscapeStatus struct {
Escaped bool
HasError bool
HasBadRunes bool
HasControls bool
HasSpaces bool
HasMarks bool
HasBIDI bool
BadBIDI bool
HasRTLScript bool
HasLTRScript bool
}
// Or combines two EscapeStatus structs into one representing the conjunction of the two
func (status EscapeStatus) Or(other EscapeStatus) EscapeStatus {
st := status
st.Escaped = st.Escaped || other.Escaped
st.HasError = st.HasError || other.HasError
st.HasBadRunes = st.HasBadRunes || other.HasBadRunes
st.HasControls = st.HasControls || other.HasControls
st.HasSpaces = st.HasSpaces || other.HasSpaces
st.HasMarks = st.HasMarks || other.HasMarks
st.HasBIDI = st.HasBIDI || other.HasBIDI
st.BadBIDI = st.BadBIDI || other.BadBIDI
st.HasRTLScript = st.HasRTLScript || other.HasRTLScript
st.HasLTRScript = st.HasLTRScript || other.HasLTRScript
return st
}
// EscapeControlString escapes the unicode control sequences in a provided string and returns the findings as an EscapeStatus and the escaped string
func EscapeControlString(text string) (EscapeStatus, string) {
sb := &strings.Builder{}
escaped, _ := EscapeControlReader(strings.NewReader(text), sb)
return escaped, sb.String()
}
// EscapeControlBytes escapes the unicode control sequences a provided []byte and returns the findings as an EscapeStatus and the escaped []byte
func EscapeControlBytes(text []byte) (EscapeStatus, []byte) {
buf := &bytes.Buffer{}
escaped, _ := EscapeControlReader(bytes.NewReader(text), buf)
return escaped, buf.Bytes()
}
// EscapeControlReader escapes the unicode control sequences a provided Reader writing the escaped output to the output and returns the findings as an EscapeStatus and an error
func EscapeControlReader(text io.Reader, output io.Writer) (escaped EscapeStatus, err error) {
buf := make([]byte, 4096)
readStart := 0
var n int
var writePos int
lineHasBIDI := false
lineHasRTLScript := false
lineHasLTRScript := false
readingloop:
for err == nil {
n, err = text.Read(buf[readStart:])
bs := buf[:n+readStart]
i := 0
for i < len(bs) {
r, size := utf8.DecodeRune(bs[i:])
// Now handle the codepoints
switch {
case r == utf8.RuneError:
if writePos < i {
if _, err = output.Write(bs[writePos:i]); err != nil {
escaped.HasError = true
return
}
writePos = i
}
// runes can be at most 4 bytes - so...
if len(bs)-i <= 3 {
// if not request more data
copy(buf, bs[i:])
readStart = n - i
writePos = 0
continue readingloop
}
// this is a real broken rune
escaped.HasBadRunes = true
escaped.Escaped = true
if err = writeBroken(output, bs[i:i+size]); err != nil {
escaped.HasError = true
return
}
writePos += size
case r == '\n':
if lineHasBIDI && !lineHasRTLScript && lineHasLTRScript {
escaped.BadBIDI = true
}
lineHasBIDI = false
lineHasRTLScript = false
lineHasLTRScript = false
case r == '\r' || r == '\t' || r == ' ':
// These are acceptable control characters and space characters
case unicode.IsSpace(r):
escaped.HasSpaces = true
escaped.Escaped = true
if writePos < i {
if _, err = output.Write(bs[writePos:i]); err != nil {
escaped.HasError = true
return
}
}
if err = writeEscaped(output, r); err != nil {
escaped.HasError = true
return
}
writePos = i + size
case unicode.Is(unicode.Bidi_Control, r):
escaped.Escaped = true
escaped.HasBIDI = true
if writePos < i {
if _, err = output.Write(bs[writePos:i]); err != nil {
escaped.HasError = true
return
}
}
lineHasBIDI = true
if err = writeEscaped(output, r); err != nil {
escaped.HasError = true
return
}
writePos = i + size
case unicode.Is(unicode.C, r):
escaped.Escaped = true
escaped.HasControls = true
if writePos < i {
if _, err = output.Write(bs[writePos:i]); err != nil {
escaped.HasError = true
return
}
}
if err = writeEscaped(output, r); err != nil {
escaped.HasError = true
return
}
writePos = i + size
case unicode.Is(unicode.M, r):
escaped.Escaped = true
escaped.HasMarks = true
if writePos < i {
if _, err = output.Write(bs[writePos:i]); err != nil {
escaped.HasError = true
return
}
}
if err = writeEscaped(output, r); err != nil {
escaped.HasError = true
return
}
writePos = i + size
default:
p, _ := bidi.Lookup(bs[i : i+size])
c := p.Class()
if c == bidi.R || c == bidi.AL {
lineHasRTLScript = true
escaped.HasRTLScript = true
} else if c == bidi.L {
lineHasLTRScript = true
escaped.HasLTRScript = true
}
}
i += size
}
if n > 0 {
// we read something...
// write everything unwritten
if writePos < i {
if _, err = output.Write(bs[writePos:i]); err != nil {
escaped.HasError = true
return
}
}
// reset the starting positions for the next read
readStart = 0
writePos = 0
}
}
if readStart > 0 {
// this means that there is an incomplete or broken rune at 0-readStart and we read nothing on the last go round
escaped.Escaped = true
escaped.HasBadRunes = true
if err = writeBroken(output, buf[:readStart]); err != nil {
escaped.HasError = true
return
}
}
if err == io.EOF {
if lineHasBIDI && !lineHasRTLScript && lineHasLTRScript {
escaped.BadBIDI = true
}
err = nil
return
}
escaped.HasError = true
return
}
func writeBroken(output io.Writer, bs []byte) (err error) {
_, err = fmt.Fprintf(output, `<span class="broken-code-point">&lt;%X&gt;</span>`, bs)
return
}
func writeEscaped(output io.Writer, r rune) (err error) {
_, err = fmt.Fprintf(output, `<span class="escaped-code-point" data-escaped="[U+%04X]"><span class="char">%c</span></span>`, r, r)
return
}