mailaddress.java

基于UDP的可靠邮件系统

	 * @return the hashcode.
	 */
	public int hashCode() {
		return toString().toLowerCase(Locale.US).hashCode();
	}

	private String parseQuotedLocalPart(String address) throws Exception {
		StringBuffer resultSB = new StringBuffer();
		resultSB.append('\"');
		pos++;
		// <quoted-string> ::= """ <qtext> """
		// <qtext> ::= "\" <x> | "\" <x> <qtext> | <q> | <q> <qtext>
		while (true) {
			if (address.charAt(pos) == '\"') {
				resultSB.append('\"');
				// end of quoted string... move forward
				pos++;
				break;
			}
			if (address.charAt(pos) == '\\') {
				resultSB.append('\\');
				pos++;
				// <x> ::= any one of the 128 ASCII characters (no exceptions)
				char x = address.charAt(pos);
				if (x < 0 || x > 127) {
					throw new Exception(
							"Invalid \\ syntaxed character at position "
									+ (pos + 1));
				}
				resultSB.append(x);
				pos++;
			} else {
				// <q> ::= any one of the 128 ASCII characters except <CR>,
				// <LF>, quote ("), or backslash (\)
				char q = address.charAt(pos);
				if (q <= 0 || q == '\n' || q == '\r' || q == '\"' || q == '\\') {
					throw new Exception(
							"Unquoted local-part (user account) must be one of the 128 ASCI characters exception <CR>, <LF>, quote (\"), or backslash (\\) at position "
									+ (pos + 1));
				}
				resultSB.append(q);
				pos++;
			}
		}
		return resultSB.toString();
	}

	private String parseUnquotedLocalPart(String address) throws Exception {
		StringBuffer resultSB = new StringBuffer();
		// <dot-string> ::= <string> | <string> "." <dot-string>
		boolean lastCharDot = false;
		while (true) {
			// <string> ::= <char> | <char> <string>
			// <char> ::= <c> | "\" <x>
			if (address.charAt(pos) == '\\') {
				resultSB.append('\\');
				pos++;
				// <x> ::= any one of the 128 ASCII characters (no exceptions)
				char x = address.charAt(pos);
				if (x < 0 || x > 127) {
					throw new Exception(
							"Invalid \\ syntaxed character at position "
									+ (pos + 1));
				}
				resultSB.append(x);
				pos++;
				lastCharDot = false;
			} else if (address.charAt(pos) == '.') {
				resultSB.append('.');
				pos++;
				lastCharDot = true;
			} else if (address.charAt(pos) == '@') {
				// End of local-part
				break;
			} else {
				// <c> ::= any one of the 128 ASCII characters, but not any
				// <special> or <SP>
				// <special> ::= "<" | ">" | "(" | ")" | "[" | "]" | "\" | "."
				// | "," | ";" | ":" | "@" """ | the control
				// characters (ASCII codes 0 through 31 inclusive and
				// 127)
				// <SP> ::= the space character (ASCII code 32)
				char c = address.charAt(pos);
				if (c <= 31 || c >= 127 || c == ' ') {
					throw new Exception(
							"Invalid character in local-part (user account) at position "
									+ (pos + 1));
				}
				for (int i = 0; i < SPECIAL.length; i++) {
					if (c == SPECIAL[i]) {
						throw new Exception(
								"Invalid character in local-part (user account) at position "
										+ (pos + 1));
					}
				}
				resultSB.append(c);
				pos++;
				lastCharDot = false;
			}
		}
		if (lastCharDot) {
			throw new Exception(
					"local-part (user account) ended with a \".\", which is invalid.");
		}
		return resultSB.toString();
	}

	private String parseNumber(String address) throws Exception {
		// <number> ::= <d> | <d> <number>

		StringBuffer resultSB = new StringBuffer();
		// We keep the position from the class level pos field
		while (true) {
			if (pos >= address.length()) {
				break;
			}
			// <d> ::= any one of the ten digits 0 through 9
			char d = address.charAt(pos);
			if (d == '.') {
				break;
			}
			if (d < '0' || d > '9') {
				throw new Exception(
						"In domain, did not find a number in # address at position "
								+ (pos + 1));
			}
			resultSB.append(d);
			pos++;
		}
		return resultSB.toString();
	}

	private String parseDotNum(String address) throws Exception {
		// throw away all irrelevant '\' they're not necessary for escaping of
		// '.' or digits, and are illegal as part of the domain-literal
		while (address.indexOf("\\") > -1) {
			address = address.substring(0, address.indexOf("\\"))
					+ address.substring(address.indexOf("\\") + 1);
		}
		StringBuffer resultSB = new StringBuffer();
		// we were passed the string with pos pointing the the [ char.
		// take the first char ([), put it in the result buffer and increment
		// pos
		resultSB.append(address.charAt(pos));
		pos++;

		// <dotnum> ::= <snum> "." <snum> "." <snum> "." <snum>
		for (int octet = 0; octet < 4; octet++) {
			// <snum> ::= one, two, or three digits representing a decimal
			// integer value in the range 0 through 255
			// <d> ::= any one of the ten digits 0 through 9
			StringBuffer snumSB = new StringBuffer();
			for (int digits = 0; digits < 3; digits++) {
				char d = address.charAt(pos);
				if (d == '.') {
					break;
				}
				if (d == ']') {
					break;
				}
				if (d < '0' || d > '9') {
					throw new Exception("Invalid number at position "
							+ (pos + 1));
				}
				snumSB.append(d);
				pos++;
			}
			if (snumSB.toString().length() == 0) {
				throw new Exception("Number not found at position " + (pos + 1));
			}
			try {
				int snum = Integer.parseInt(snumSB.toString());
				if (snum > 255) {
					throw new Exception("Invalid number at position "
							+ (pos + 1));
				}
			} catch (NumberFormatException nfe) {
				throw new Exception("Invalid number at position " + (pos + 1));
			}
			resultSB.append(snumSB.toString());
			if (address.charAt(pos) == ']') {
				if (octet < 3) {
					throw new Exception("End of number reached too quickly at "
							+ (pos + 1));
				} else {
					break;
				}
			}
			if (address.charAt(pos) == '.') {
				resultSB.append('.');
				pos++;
			}
		}
		if (address.charAt(pos) != ']') {
			throw new Exception(
					"Did not find closing bracket \"]\" in domain at position "
							+ (pos + 1));
		}
		resultSB.append(']');
		pos++;
		return resultSB.toString();
	}

	private String parseDomainName(String address) throws Exception {
		StringBuffer resultSB = new StringBuffer();
		// <name> ::= <a> <ldh-str> <let-dig>
		// <ldh-str> ::= <let-dig-hyp> | <let-dig-hyp> <ldh-str>
		// <let-dig> ::= <a> | <d>
		// <let-dig-hyp> ::= <a> | <d> | "-"
		// <a> ::= any one of the 52 alphabetic characters A through Z
		// in upper case and a through z in lower case
		// <d> ::= any one of the ten digits 0 through 9

		// basically, this is a series of letters, digits, and hyphens,
		// but it can't start with a digit or hypthen
		// and can't end with a hyphen

		// in practice though, we should relax this as domain names can start
		// with digits as well as letters. So only check that doesn't start
		// or end with hyphen.
		while (true) {
			if (pos >= address.length()) {
				break;
			}
			char ch = address.charAt(pos);
			if ((ch >= '0' && ch <= '9') || (ch >= 'a' && ch <= 'z')
					|| (ch >= 'A' && ch <= 'Z') || (ch == '-')) {
				resultSB.append(ch);
				pos++;
				continue;
			}
			if (ch == '.') {
				break;
			}
			throw new Exception("Invalid character at " + pos);
		}
		String result = resultSB.toString();
		if (result.startsWith("-") || result.endsWith("-")) {
			throw new Exception(
					"Domain name cannot begin or end with a hyphen \"-\" at position "
							+ (pos + 1));
		}
		return result;
	}
}