/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package javax.mail.internet;
/**
* @version $Rev$ $Date$
*/
public class HeaderTokenizer {
public static class Token {
// Constant values from J2SE 1.4 API Docs (Constant values)
public static final int ATOM = -1;
public static final int COMMENT = -3;
public static final int EOF = -4;
public static final int QUOTEDSTRING = -2;
private int _type;
private String _value;
public Token(int type, String value) {
_type = type;
_value = value;
}
public int getType() {
return _type;
}
public String getValue() {
return _value;
}
}
private static final Token EOF = new Token(Token.EOF, null);
// characters not allowed in MIME
public static final String MIME = "()<>@,;:\\\"\t []/?=";
// charaters not allowed in RFC822
public static final String RFC822 = "()<>@,;:\\\"\t .[]";
private static final String WHITE = " \t\n\r";
private String _delimiters;
private String _header;
private boolean _skip;
private int pos;
public HeaderTokenizer(String header) {
this(header, RFC822);
}
public HeaderTokenizer(String header, String delimiters) {
this(header, delimiters, true);
}
public HeaderTokenizer(String header,
String delimiters,
boolean skipComments) {
_skip = skipComments;
_header = header;
_delimiters = delimiters;
}
public String getRemainder() {
return _header.substring(pos);
}
public Token next() throws ParseException {
return readToken();
}
public Token peek() throws ParseException {
int start = pos;
try {
return readToken();
} finally {
pos = start;
}
}
/**
* Read an ATOM token from the parsed header.
*
* @return A token containing the value of the atom token.
*/
private Token readAtomicToken() {
// skip to next delimiter
int start = pos;
while (++pos < _header.length()) {
// break on the first non-atom character.
char ch = _header.charAt(pos);
if (_delimiters.indexOf(_header.charAt(pos)) != -1 || ch < 32 || ch >= 127) {
break;
}
}
return new Token(Token.ATOM, _header.substring(start, pos));
}
/**
* Read the next token from the header.
*
* @return The next token from the header. White space is skipped, and comment
* tokens are also skipped if indicated.
* @exception ParseException
*/
private Token readToken() throws ParseException {
if (pos >= _header.length()) {
return EOF;
} else {
char c = _header.charAt(pos);
// comment token...read and skip over this
if (c == '(') {
Token comment = readComment();
if (_skip) {
return readToken();
} else {
return comment;
}
// quoted literal
} else if (c == '\"') {
return readQuotedString();
// white space, eat this and find a real token.
} else if (WHITE.indexOf(c) != -1) {
eatWhiteSpace();
return readToken();
// either a CTL or special. These characters have a self-defining token type.
} else if (c < 32 || c >= 127 || _delimiters.indexOf(c) != -1) {
pos++;
return new Token((int)c, String.valueOf(c));
} else {
// start of an atom, parse it off.
return readAtomicToken();
}
}
}
/**
* Extract a substring from the header string and apply any
* escaping/folding rules to the string.
*
* @param start The starting offset in the header.
* @param end The header end offset + 1.
*
* @return The processed string value.
* @exception ParseException
*/
private String getEscapedValue(int start, int end) throws ParseException {
StringBuffer value = new StringBuffer();
for (int i = start; i < end; i++) {
char ch = _header.charAt(i);
// is this an escape character?
if (ch == '\\') {
i++;
if (i == end) {
throw new ParseException("Invalid escape character");
}
value.append(_header.charAt(i));
}
// line breaks are ignored, except for naked '\n' characters, which are consider
// parts of linear whitespace.
else if (ch == '\r') {
// see if this is a CRLF sequence, and skip the second if it is.
if (i < end - 1 && _header.charAt(i + 1) == '\n') {
i++;
}
}
else {
// just append the ch value.
value.append(ch);
}
}
return value.toString();
}
/**
* Read a comment from the header, applying nesting and escape
* rules to the content.
*
* @return A comment token with the token value.
* @exception ParseException
*/
private Token readComment() throws ParseException {
int start = pos + 1;
int nesting = 1;
boolean requiresEscaping = false;
// skip to end of comment/string
while (++pos < _header.length()) {
char ch = _header.charAt(pos);
if (ch == ')') {
nesting--;
if (nesting == 0) {
break;
}
}
else if (ch == '(') {
nesting++;
}
else if (ch == '\\') {
pos++;
requiresEscaping = true;
}
// we need to process line breaks also
else if (ch == '\r') {
requiresEscaping = true;
}
}
if (nesting != 0) {
throw new ParseException("Unbalanced comments");
}
String value;
if (requiresEscaping) {
value = getEscapedValue(start, pos);
}
else {
value = _header.substring(start, pos++);
}
return new Token(Token.COMMENT, value);
}
/**
* Parse out a quoted string from the header, applying escaping
* rules to the value.
*
* @return The QUOTEDSTRING token with the value.
* @exception ParseException
*/
private Token readQuotedString() throws ParseException {
int start = pos+1;
boolean requiresEscaping = false;
// skip to end of comment/string
while (++pos < _header.length()) {
char ch = _header.charAt(pos);
if (ch == '"') {
String value;
if (requiresEscaping) {
value = getEscapedValue(start, pos++);
}
else {
value = _header.substring(start, pos++);
}
return new Token(Token.QUOTEDSTRING, value);
}
else if (ch == '\\') {
pos++;
requiresEscaping = true;
}
// we need to process line breaks also
else if (ch == '\r') {
requiresEscaping = true;
}
}
throw new ParseException("Missing '\"'");
}
/**
* Skip white space in the token string.
*/
private void eatWhiteSpace() {
// skip to end of whitespace
while (++pos < _header.length()
&& WHITE.indexOf(_header.charAt(pos)) != -1)
;
}
}