Created
October 7, 2013 21:18
-
-
Save jstedfast/6875129 to your computer and use it in GitHub Desktop.
Email address validator
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
// | |
// EmailValidator.cs | |
// | |
// Author: Jeffrey Stedfast <[email protected]> | |
// | |
// Copyright (c) 2013 Xamarin Inc. | |
// | |
// Permission is hereby granted, free of charge, to any person obtaining a copy | |
// of this software and associated documentation files (the "Software"), to deal | |
// in the Software without restriction, including without limitation the rights | |
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
// copies of the Software, and to permit persons to whom the Software is | |
// furnished to do so, subject to the following conditions: | |
// | |
// The above copyright notice and this permission notice shall be included in | |
// all copies or substantial portions of the Software. | |
// | |
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | |
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | |
// THE SOFTWARE. | |
using System; | |
namespace EmailValidation | |
{ | |
public static class EmailValidator | |
{ | |
const string AtomCharacters = "!#$%&'*+-/=?^_`{|}~"; | |
static bool IsLetterOrDigit (char c) | |
{ | |
return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9'); | |
} | |
static bool IsAtom (char c) | |
{ | |
return IsLetterOrDigit (c) || AtomCharacters.IndexOf (c) != -1; | |
} | |
static bool IsDomain (char c) | |
{ | |
return IsLetterOrDigit (c) || c == '-'; | |
} | |
static bool SkipAtom (string text, ref int index) | |
{ | |
int startIndex = index; | |
while (index < text.Length && IsAtom (text[index])) | |
index++; | |
return index > startIndex; | |
} | |
static bool SkipSubDomain (string text, ref int index) | |
{ | |
if (!IsDomain (text[index]) || text[index] == '-') | |
return false; | |
index++; | |
while (index < text.Length && IsDomain (text[index])) | |
index++; | |
return true; | |
} | |
static bool SkipDomain (string text, ref int index) | |
{ | |
if (!SkipSubDomain (text, ref index)) | |
return false; | |
while (index < text.Length && text[index] == '.') { | |
index++; | |
if (index == text.Length) | |
return false; | |
if (!SkipSubDomain (text, ref index)) | |
return false; | |
} | |
return true; | |
} | |
static bool SkipQuoted (string text, ref int index) | |
{ | |
bool escaped = false; | |
// skip over leading '"' | |
index++; | |
while (index < text.Length) { | |
if (text[index] == (byte) '\\') { | |
escaped = !escaped; | |
} else if (!escaped) { | |
if (text[index] == (byte) '"') | |
break; | |
} else { | |
escaped = false; | |
} | |
index++; | |
} | |
if (index >= text.Length || text[index] != (byte) '"') | |
return false; | |
index++; | |
return true; | |
} | |
static bool SkipWord (string text, ref int index) | |
{ | |
if (text[index] == (byte) '"') | |
return SkipQuoted (text, ref index); | |
return SkipAtom (text, ref index); | |
} | |
static bool SkipIPv4Literal (string text, ref int index) | |
{ | |
int groups = 0; | |
while (index < text.Length && groups < 4) { | |
int startIndex = index; | |
int value = 0; | |
while (index < text.Length && text[index] >= '0' && text[index] <= '9') { | |
value = (value * 10) + (text[index] - '0'); | |
index++; | |
} | |
if (index == startIndex || index - startIndex > 3 || value > 255) | |
return false; | |
groups++; | |
if (groups < 4 && index < text.Length && text[index] == '.') | |
index++; | |
} | |
return groups == 4; | |
} | |
static bool IsHexDigit (char c) | |
{ | |
return (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f') || (c >= '0' && c <= '9'); | |
} | |
// This needs to handle the following forms: | |
// | |
// IPv6-addr = IPv6-full / IPv6-comp / IPv6v4-full / IPv6v4-comp | |
// IPv6-hex = 1*4HEXDIG | |
// IPv6-full = IPv6-hex 7(":" IPv6-hex) | |
// IPv6-comp = [IPv6-hex *5(":" IPv6-hex)] "::" [IPv6-hex *5(":" IPv6-hex)] | |
// ; The "::" represents at least 2 16-bit groups of zeros | |
// ; No more than 6 groups in addition to the "::" may be | |
// ; present | |
// IPv6v4-full = IPv6-hex 5(":" IPv6-hex) ":" IPv4-address-literal | |
// IPv6v4-comp = [IPv6-hex *3(":" IPv6-hex)] "::" | |
// [IPv6-hex *3(":" IPv6-hex) ":"] IPv4-address-literal | |
// ; The "::" represents at least 2 16-bit groups of zeros | |
// ; No more than 4 groups in addition to the "::" and | |
// ; IPv4-address-literal may be present | |
static bool SkipIPv6Literal (string text, ref int index) | |
{ | |
bool compact = false; | |
int colons = 0; | |
while (index < text.Length) { | |
int startIndex = index; | |
while (index < text.Length && IsHexDigit (text[index])) | |
index++; | |
if (index >= text.Length) | |
break; | |
if (index > startIndex && colons > 2 && text[index] == '.') { | |
// IPv6v4 | |
index = startIndex; | |
if (!SkipIPv4Literal (text, ref index)) | |
return false; | |
break; | |
} | |
int count = index - startIndex; | |
if (count > 4) | |
return false; | |
if (text[index] != ':') | |
break; | |
startIndex = index; | |
while (index < text.Length && text[index] == ':') | |
index++; | |
count = index - startIndex; | |
if (count > 2) | |
return false; | |
if (count == 2) { | |
if (compact) | |
return false; | |
compact = true; | |
colons += 2; | |
} else { | |
colons++; | |
} | |
} | |
if (colons < 2) | |
return false; | |
if (compact) | |
return colons < 6; | |
return colons < 7; | |
} | |
public static bool Validate (string email) | |
{ | |
int index = 0; | |
if (!SkipWord (email, ref index) || index >= email.Length) | |
return false; | |
while (index < email.Length && email[index] == '.') { | |
index++; | |
if (!SkipWord (email, ref index) || index >= email.Length) | |
return false; | |
} | |
if (index + 1 >= email.Length || email[index++] != '@') | |
return false; | |
if (email[index] != '[') { | |
// domain | |
if (!SkipDomain (email, ref index)) | |
return false; | |
return index == email.Length; | |
} | |
// address literal | |
index++; | |
// we need at least 8 more characters | |
if (index + 8 >= email.Length) | |
return false; | |
var ipv6 = email.Substring (index, 5); | |
if (ipv6.ToLowerInvariant () == "ipv6:") { | |
index += "IPv6:".Length; | |
if (!SkipIPv6Literal (email, ref index)) | |
return false; | |
} else { | |
if (!SkipIPv4Literal (email, ref index)) | |
return false; | |
} | |
if (index >= email.Length || email[index++] != ']') | |
return false; | |
return index == email.Length; | |
} | |
} | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment