Better caldav support (#73)

vendor/github.com/beevik/etree/helpers.go

@@ -0,0 +1,276 @@
+// Copyright 2015-2019 Brett Vickers.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package etree
+
+import (
+	"bufio"
+	"io"
+	"strings"
+	"unicode/utf8"
+)
+
+// A simple stack
+type stack struct {
+	data []interface{}
+}
+
+func (s *stack) empty() bool {
+	return len(s.data) == 0
+}
+
+func (s *stack) push(value interface{}) {
+	s.data = append(s.data, value)
+}
+
+func (s *stack) pop() interface{} {
+	value := s.data[len(s.data)-1]
+	s.data[len(s.data)-1] = nil
+	s.data = s.data[:len(s.data)-1]
+	return value
+}
+
+func (s *stack) peek() interface{} {
+	return s.data[len(s.data)-1]
+}
+
+// A fifo is a simple first-in-first-out queue.
+type fifo struct {
+	data       []interface{}
+	head, tail int
+}
+
+func (f *fifo) add(value interface{}) {
+	if f.len()+1 >= len(f.data) {
+		f.grow()
+	}
+	f.data[f.tail] = value
+	if f.tail++; f.tail == len(f.data) {
+		f.tail = 0
+	}
+}
+
+func (f *fifo) remove() interface{} {
+	value := f.data[f.head]
+	f.data[f.head] = nil
+	if f.head++; f.head == len(f.data) {
+		f.head = 0
+	}
+	return value
+}
+
+func (f *fifo) len() int {
+	if f.tail >= f.head {
+		return f.tail - f.head
+	}
+	return len(f.data) - f.head + f.tail
+}
+
+func (f *fifo) grow() {
+	c := len(f.data) * 2
+	if c == 0 {
+		c = 4
+	}
+	buf, count := make([]interface{}, c), f.len()
+	if f.tail >= f.head {
+		copy(buf[0:count], f.data[f.head:f.tail])
+	} else {
+		hindex := len(f.data) - f.head
+		copy(buf[0:hindex], f.data[f.head:])
+		copy(buf[hindex:count], f.data[:f.tail])
+	}
+	f.data, f.head, f.tail = buf, 0, count
+}
+
+// countReader implements a proxy reader that counts the number of
+// bytes read from its encapsulated reader.
+type countReader struct {
+	r     io.Reader
+	bytes int64
+}
+
+func newCountReader(r io.Reader) *countReader {
+	return &countReader{r: r}
+}
+
+func (cr *countReader) Read(p []byte) (n int, err error) {
+	b, err := cr.r.Read(p)
+	cr.bytes += int64(b)
+	return b, err
+}
+
+// countWriter implements a proxy writer that counts the number of
+// bytes written by its encapsulated writer.
+type countWriter struct {
+	w     io.Writer
+	bytes int64
+}
+
+func newCountWriter(w io.Writer) *countWriter {
+	return &countWriter{w: w}
+}
+
+func (cw *countWriter) Write(p []byte) (n int, err error) {
+	b, err := cw.w.Write(p)
+	cw.bytes += int64(b)
+	return b, err
+}
+
+// isWhitespace returns true if the byte slice contains only
+// whitespace characters.
+func isWhitespace(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if c := s[i]; c != ' ' && c != '\t' && c != '\n' && c != '\r' {
+			return false
+		}
+	}
+	return true
+}
+
+// spaceMatch returns true if namespace a is the empty string
+// or if namespace a equals namespace b.
+func spaceMatch(a, b string) bool {
+	switch {
+	case a == "":
+		return true
+	default:
+		return a == b
+	}
+}
+
+// spaceDecompose breaks a namespace:tag identifier at the ':'
+// and returns the two parts.
+func spaceDecompose(str string) (space, key string) {
+	colon := strings.IndexByte(str, ':')
+	if colon == -1 {
+		return "", str
+	}
+	return str[:colon], str[colon+1:]
+}
+
+// Strings used by indentCRLF and indentLF
+const (
+	indentSpaces = "\r\n                                                                "
+	indentTabs   = "\r\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t"
+)
+
+// indentCRLF returns a CRLF newline followed by n copies of the first
+// non-CRLF character in the source string.
+func indentCRLF(n int, source string) string {
+	switch {
+	case n < 0:
+		return source[:2]
+	case n < len(source)-1:
+		return source[:n+2]
+	default:
+		return source + strings.Repeat(source[2:3], n-len(source)+2)
+	}
+}
+
+// indentLF returns a LF newline followed by n copies of the first non-LF
+// character in the source string.
+func indentLF(n int, source string) string {
+	switch {
+	case n < 0:
+		return source[1:2]
+	case n < len(source)-1:
+		return source[1 : n+2]
+	default:
+		return source[1:] + strings.Repeat(source[2:3], n-len(source)+2)
+	}
+}
+
+// nextIndex returns the index of the next occurrence of sep in s,
+// starting from offset.  It returns -1 if the sep string is not found.
+func nextIndex(s, sep string, offset int) int {
+	switch i := strings.Index(s[offset:], sep); i {
+	case -1:
+		return -1
+	default:
+		return offset + i
+	}
+}
+
+// isInteger returns true if the string s contains an integer.
+func isInteger(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if (s[i] < '0' || s[i] > '9') && !(i == 0 && s[i] == '-') {
+			return false
+		}
+	}
+	return true
+}
+
+type escapeMode byte
+
+const (
+	escapeNormal escapeMode = iota
+	escapeCanonicalText
+	escapeCanonicalAttr
+)
+
+// escapeString writes an escaped version of a string to the writer.
+func escapeString(w *bufio.Writer, s string, m escapeMode) {
+	var esc []byte
+	last := 0
+	for i := 0; i < len(s); {
+		r, width := utf8.DecodeRuneInString(s[i:])
+		i += width
+		switch r {
+		case '&':
+			esc = []byte("&amp;")
+		case '<':
+			esc = []byte("&lt;")
+		case '>':
+			if m == escapeCanonicalAttr {
+				continue
+			}
+			esc = []byte("&gt;")
+		case '\'':
+			if m != escapeNormal {
+				continue
+			}
+			esc = []byte("&apos;")
+		case '"':
+			if m == escapeCanonicalText {
+				continue
+			}
+			esc = []byte("&quot;")
+		case '\t':
+			if m != escapeCanonicalAttr {
+				continue
+			}
+			esc = []byte("&#x9;")
+		case '\n':
+			if m != escapeCanonicalAttr {
+				continue
+			}
+			esc = []byte("&#xA;")
+		case '\r':
+			if m == escapeNormal {
+				continue
+			}
+			esc = []byte("&#xD;")
+		default:
+			if !isInCharacterRange(r) || (r == 0xFFFD && width == 1) {
+				esc = []byte("\uFFFD")
+				break
+			}
+			continue
+		}
+		w.WriteString(s[last : i-width])
+		w.Write(esc)
+		last = i
+	}
+	w.WriteString(s[last:])
+}
+
+func isInCharacterRange(r rune) bool {
+	return r == 0x09 ||
+		r == 0x0A ||
+		r == 0x0D ||
+		r >= 0x20 && r <= 0xD7FF ||
+		r >= 0xE000 && r <= 0xFFFD ||
+		r >= 0x10000 && r <= 0x10FFFF
+}