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With inspiration from other libraries
/**
* Logback: the reliable, generic, fast and flexible logging framework.
* Copyright (C) 1999-2015, QOS.ch. All rights reserved.
*
* This program and the accompanying materials are dual-licensed under
* either the terms of the Eclipse Public License v1.0 as published by
* the Eclipse Foundation
*
* or (per the licensee's choosing)
*
* under the terms of the GNU Lesser General Public License version 2.1
* as published by the Free Software Foundation.
*/
package ch.qos.logback.core.pattern.parser;
import java.util.List;
import java.util.ArrayList;
import ch.qos.logback.core.CoreConstants;
import static ch.qos.logback.core.CoreConstants.CURLY_LEFT;
import static ch.qos.logback.core.CoreConstants.ESCAPE_CHAR;
import ch.qos.logback.core.pattern.util.IEscapeUtil;
import ch.qos.logback.core.pattern.util.RegularEscapeUtil;
import ch.qos.logback.core.pattern.util.RestrictedEscapeUtil;
import ch.qos.logback.core.spi.ScanException;
/**
*
* Return a steady stream of tokens.
*
*
*
* The returned tokens are one of: LITERAL, '%', FORMAT_MODIFIER, SIMPLE_KEYWORD, COMPOSITE_KEYWORD
* OPTION, LEFT_PARENTHESIS, and RIGHT_PARENTHESIS.
*
*
*
* The '\' character is used as escape. It can be used to escape '_', '%', '('
* and '('.
*
*
*
* Note that there is no EOS token returned.
*
*/
class TokenStream {
enum TokenizerState {
LITERAL_STATE, FORMAT_MODIFIER_STATE, KEYWORD_STATE, OPTION_STATE, RIGHT_PARENTHESIS_STATE
}
final String pattern;
final int patternLength;
final IEscapeUtil escapeUtil;
final IEscapeUtil optionEscapeUtil = new RestrictedEscapeUtil();
TokenizerState state = TokenizerState.LITERAL_STATE;
int pointer = 0;
// this variant should be used for testing purposes only
TokenStream(String pattern) {
this(pattern, new RegularEscapeUtil());
}
TokenStream(String pattern, IEscapeUtil escapeUtil) {
if (pattern == null || pattern.length() == 0) {
throw new IllegalArgumentException("null or empty pattern string not allowed");
}
this.pattern = pattern;
patternLength = pattern.length();
this.escapeUtil = escapeUtil;
}
List tokenize() throws ScanException {
List tokenList = new ArrayList();
StringBuffer buf = new StringBuffer();
while (pointer < patternLength) {
char c = pattern.charAt(pointer);
pointer++;
switch (state) {
case LITERAL_STATE:
handleLiteralState(c, tokenList, buf);
break;
case FORMAT_MODIFIER_STATE:
handleFormatModifierState(c, tokenList, buf);
break;
case OPTION_STATE:
processOption(c, tokenList, buf);
break;
case KEYWORD_STATE:
handleKeywordState(c, tokenList, buf);
break;
case RIGHT_PARENTHESIS_STATE:
handleRightParenthesisState(c, tokenList, buf);
break;
default:
}
}
// EOS
switch (state) {
case LITERAL_STATE:
addValuedToken(Token.LITERAL, buf, tokenList);
break;
case KEYWORD_STATE:
tokenList.add(new Token(Token.SIMPLE_KEYWORD, buf.toString()));
break;
case RIGHT_PARENTHESIS_STATE:
tokenList.add(Token.RIGHT_PARENTHESIS_TOKEN);
break;
case FORMAT_MODIFIER_STATE:
case OPTION_STATE:
throw new ScanException("Unexpected end of pattern string");
}
return tokenList;
}
private void handleRightParenthesisState(char c, List tokenList, StringBuffer buf) {
tokenList.add(Token.RIGHT_PARENTHESIS_TOKEN);
switch (c) {
case CoreConstants.RIGHT_PARENTHESIS_CHAR:
break;
case CURLY_LEFT:
state = TokenizerState.OPTION_STATE;
break;
case ESCAPE_CHAR:
escape("%{}", buf);
state = TokenizerState.LITERAL_STATE;
break;
default:
buf.append(c);
state = TokenizerState.LITERAL_STATE;
}
}
private void processOption(char c, List tokenList, StringBuffer buf) throws ScanException {
OptionTokenizer ot = new OptionTokenizer(this);
ot.tokenize(c, tokenList);
}
private void handleFormatModifierState(char c, List tokenList, StringBuffer buf) {
if (c == CoreConstants.LEFT_PARENTHESIS_CHAR) {
addValuedToken(Token.FORMAT_MODIFIER, buf, tokenList);
tokenList.add(Token.BARE_COMPOSITE_KEYWORD_TOKEN);
state = TokenizerState.LITERAL_STATE;
} else if (Character.isJavaIdentifierStart(c)) {
addValuedToken(Token.FORMAT_MODIFIER, buf, tokenList);
state = TokenizerState.KEYWORD_STATE;
buf.append(c);
} else {
buf.append(c);
}
}
private void handleLiteralState(char c, List tokenList, StringBuffer buf) {
switch (c) {
case ESCAPE_CHAR:
escape("%()", buf);
break;
case CoreConstants.PERCENT_CHAR:
addValuedToken(Token.LITERAL, buf, tokenList);
tokenList.add(Token.PERCENT_TOKEN);
state = TokenizerState.FORMAT_MODIFIER_STATE;
break;
case CoreConstants.RIGHT_PARENTHESIS_CHAR:
addValuedToken(Token.LITERAL, buf, tokenList);
state = TokenizerState.RIGHT_PARENTHESIS_STATE;
break;
default:
buf.append(c);
}
}
private void handleKeywordState(char c, List tokenList, StringBuffer buf) {
if (Character.isJavaIdentifierPart(c)) {
buf.append(c);
} else if (c == CURLY_LEFT) {
addValuedToken(Token.SIMPLE_KEYWORD, buf, tokenList);
state = TokenizerState.OPTION_STATE;
} else if (c == CoreConstants.LEFT_PARENTHESIS_CHAR) {
addValuedToken(Token.COMPOSITE_KEYWORD, buf, tokenList);
state = TokenizerState.LITERAL_STATE;
} else if (c == CoreConstants.PERCENT_CHAR) {
addValuedToken(Token.SIMPLE_KEYWORD, buf, tokenList);
tokenList.add(Token.PERCENT_TOKEN);
state = TokenizerState.FORMAT_MODIFIER_STATE;
} else if (c == CoreConstants.RIGHT_PARENTHESIS_CHAR) {
addValuedToken(Token.SIMPLE_KEYWORD, buf, tokenList);
state = TokenizerState.RIGHT_PARENTHESIS_STATE;
} else {
addValuedToken(Token.SIMPLE_KEYWORD, buf, tokenList);
if (c == ESCAPE_CHAR) {
if ((pointer < patternLength)) {
char next = pattern.charAt(pointer++);
escapeUtil.escape("%()", buf, next, pointer);
}
} else {
buf.append(c);
}
state = TokenizerState.LITERAL_STATE;
}
}
void escape(String escapeChars, StringBuffer buf) {
if ((pointer < patternLength)) {
char next = pattern.charAt(pointer++);
escapeUtil.escape(escapeChars, buf, next, pointer);
}
}
void optionEscape(String escapeChars, StringBuffer buf) {
if ((pointer < patternLength)) {
char next = pattern.charAt(pointer++);
optionEscapeUtil.escape(escapeChars, buf, next, pointer);
}
}
private void addValuedToken(int type, StringBuffer buf, List tokenList) {
if (buf.length() > 0) {
tokenList.add(new Token(type, buf.toString()));
buf.setLength(0);
}
}
}