Add link metadata fetching package

vendor/github.com/golang-commonmark/markdown/byteutil/byteutil.go

@@ -0,0 +1,160 @@
+// Copyright 2015 The 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 byteutil provides various operations on bytes and byte strings.
+package byteutil
+
+var (
+	digit     [256]bool
+	hexdigit  [256]bool
+	letter    [256]bool
+	uppercase [256]bool
+	lowercase [256]bool
+	alphanum  [256]bool
+	tolower   [256]byte
+	toupper   [256]byte
+)
+
+func init() {
+	for _, b := range "0123456789" {
+		digit[b] = true
+	}
+	for _, b := range "0123456789abcdefABCDEF" {
+		hexdigit[b] = true
+	}
+	for _, b := range "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ" {
+		letter[b] = true
+	}
+	for _, b := range "abcdefghijklmnopqrstuvwxyz" {
+		lowercase[b] = true
+	}
+	for _, b := range "ABCDEFGHIJKLMNOPQRSTUVWXYZ" {
+		uppercase[b] = true
+	}
+	for _, b := range "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ" {
+		alphanum[b] = true
+	}
+	for i := 0; i < 256; i++ {
+		tolower[i] = byte(i)
+		toupper[i] = byte(i)
+	}
+	for _, b := range "ABCDEFGHIJKLMNOPQRSTUVWXYZ" {
+		tolower[b] = byte(b) - 'A' + 'a'
+	}
+	for _, b := range "abcdefghijklmnopqrstuvwxyz" {
+		toupper[b] = byte(b) - 'a' + 'A'
+	}
+}
+
+func IsDigit(b byte) bool {
+	return digit[b]
+}
+
+func IsHexDigit(b byte) bool {
+	return hexdigit[b]
+}
+
+func IsLetter(b byte) bool {
+	return letter[b]
+}
+
+func IsLowercaseLetter(b byte) bool {
+	return lowercase[b]
+}
+
+func IsUppercaseLetter(b byte) bool {
+	return uppercase[b]
+}
+
+func IsAlphaNum(b byte) bool {
+	return alphanum[b]
+}
+
+func ToLower(s string) string {
+	if s == "" {
+		return ""
+	}
+
+	hasUpper := false
+	for i := 0; i < len(s); i++ {
+		if uppercase[s[i]] {
+			hasUpper = true
+			break
+		}
+	}
+	if !hasUpper {
+		return s
+	}
+
+	buf := make([]byte, len(s))
+	for i := 0; i < len(s); i++ {
+		buf[i] = tolower[s[i]]
+	}
+	return string(buf)
+}
+
+func ToUpper(s string) string {
+	if s == "" {
+		return ""
+	}
+
+	hasLower := false
+	for i := 0; i < len(s); i++ {
+		if lowercase[s[i]] {
+			hasLower = true
+			break
+		}
+	}
+	if !hasLower {
+		return s
+	}
+
+	buf := make([]byte, len(s))
+	for i := 0; i < len(s); i++ {
+		buf[i] = toupper[s[i]]
+	}
+	return string(buf)
+}
+
+func ByteToLower(b byte) byte {
+	return tolower[b]
+}
+
+func ByteToUpper(b byte) byte {
+	return toupper[b]
+}
+
+func IndexAny(s, chars string) int {
+	var t [256]bool
+	for i := 0; i < len(chars); i++ {
+		t[chars[i]] = true
+	}
+	for i := 0; i < len(s); i++ {
+		if t[s[i]] {
+			return i
+		}
+	}
+	return -1
+}
+
+func IndexAnyTable(s string, t *[256]bool) int {
+	for i := 0; i < len(s); i++ {
+		if t[s[i]] {
+			return i
+		}
+	}
+	return -1
+}
+
+func Unhex(d byte) byte {
+	switch {
+	case digit[d]:
+		return d - '0'
+	case uppercase[d]:
+		return d - 'A' + 10
+	case lowercase[d]:
+		return d - 'a' + 10
+	}
+	panic("unhex: not hex digit")
+}