/*
* 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 final int _type;
private final String _value;
public Token(final int type, final String value) {
_type = type;
_value = value;
}
public int getType() {
return _type;
}
public String getValue() {
return _value;
}
}
private static final char NUL = '\0';
private static final Token EOF = new Token(Token.EOF, null);
// characters not allowed in MIME
public static final String MIME = "()<>@,;:\\\"\t []/?=";
// characters not allowed in RFC822
public static final String RFC822 = "()<>@,;:\\\"\t .[]";
private static final String WHITE = " \t\n\r";
private final String _delimiters;
private final String _header;
private final int _headerLength;
private final boolean _skip;
private int pos;
public HeaderTokenizer(final String header) {
this(header, RFC822);
}
public HeaderTokenizer(final String header, final String delimiters) {
this(header, delimiters, true);
}
public HeaderTokenizer(final String header,
final String delimiters,
final boolean skipComments) {
_skip = skipComments;
_header = header;
_delimiters = delimiters;
_headerLength=header.length();
}
//Return the rest of the Header.
//null is returned if we are already at end of header
public String getRemainder() {
if(pos > _headerLength) {
return null;
}
return _header.substring(pos);
}
public Token next() throws ParseException {
return readToken(NUL, false);
}
/**
* Parses the next token from this String.
* If endOfAtom is not NUL, the token extends until the
* endOfAtom character is seen, or to the end of the header.
* This method is useful when parsing headers that don't
* obey the MIME specification, e.g., by failing to quote
* parameter values that contain spaces.
*
* @param endOfAtom if not NUL, character marking end of token
* @return the next Token
* @exception ParseException if the parse fails
* @since JavaMail 1.5
*/
public Token next(final char endOfAtom) throws ParseException {
return next(endOfAtom, false);
}
/**
* Parses the next token from this String.
* endOfAtom is handled as above. If keepEscapes is true,
* any backslash escapes are preserved in the returned string.
* This method is useful when parsing headers that don't
* obey the MIME specification, e.g., by failing to escape
* backslashes in the filename parameter.
*
* @param endOfAtom if not NUL, character marking end of token
* @param keepEscapes keep all backslashes in returned string?
* @return the next Token
* @exception ParseException if the parse fails
* @since JavaMail 1.5
*/
public Token next(final char endOfAtom, final boolean keepEscapes)
throws ParseException {
return readToken(endOfAtom, keepEscapes);
}
public Token peek() throws ParseException {
final int start = pos;
try {
return readToken(NUL, false);
} 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
final int start = pos;
final StringBuilder sb = new StringBuilder();
sb.append(_header.charAt(pos));
while (++pos < _headerLength) {
// break on the first non-atom character.
final 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(final char endOfAtom, final boolean keepEscapes) throws ParseException {
if (pos >= _headerLength) {
return EOF;
} else {
final char c = _header.charAt(pos);
// comment token...read and skip over this
if (c == '(') {
final Token comment = readComment(keepEscapes);
if (_skip) {
return readToken(endOfAtom, keepEscapes);
} else {
return comment;
}
// quoted literal
} else if (c == '\"') {
return readQuotedString('"', keepEscapes, 1);
// white space, eat this and find a real token.
} else if (WHITE.indexOf(c) != -1) {
eatWhiteSpace();
return readToken(endOfAtom, keepEscapes);
// either a CTL or special. These characters have a self-defining token type.
} else if (c < 32 || c >= 127 || _delimiters.indexOf(c) != -1) {
if (endOfAtom != NUL && c != endOfAtom) {
return readQuotedString(endOfAtom, keepEscapes, 0);
}
pos++;
return new Token(c, String.valueOf(c));
} else {
// start of an atom, parse it off.
if (endOfAtom != NUL && c != endOfAtom) {
return readQuotedString(endOfAtom, keepEscapes, 0);
}
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(final int start, final int end, final boolean keepEscapes) throws ParseException {
final StringBuffer value = new StringBuffer();
for (int i = start; i < end; i++) {
final char ch = _header.charAt(i);
// is this an escape character?
if (ch == '\\') {
i++;
if (i == end) {
throw new ParseException("Invalid escape character");
}
if(keepEscapes) {
value.append("\\");
}
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(final boolean keepEscapes) throws ParseException {
final int start = pos + 1;
int nesting = 1;
boolean requiresEscaping = false;
// skip to end of comment/string
while (++pos < _headerLength) {
final 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, keepEscapes);
}
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(final char endChar, final boolean keepEscapes, final int offset) throws ParseException {
final int start = pos+offset;
boolean requiresEscaping = false;
// skip to end of comment/string
while (++pos < _headerLength) {
final char ch = _header.charAt(pos);
if (ch == endChar) {
String value;
if (requiresEscaping) {
value = getEscapedValue(start, pos++, keepEscapes);
}
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 < _headerLength
&& WHITE.indexOf(_header.charAt(pos)) != -1) {
;
}
}
}