com.github.simy4.xpath.parser.XPathLexer Maven / Gradle / Ivy
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Convenient utility to build XML models by evaluating XPath expressions
package com.github.simy4.xpath.parser;
import com.github.simy4.xpath.parser.Token.Type;
import com.github.simy4.xpath.util.ReadOnlyIterator;
class XPathLexer extends ReadOnlyIterator {
private final String xpath;
private int cursor;
XPathLexer(String xpath) {
this.xpath = xpath;
}
@Override
public boolean hasNext() {
return cursor < xpath.length();
}
@Override
public Token next() {
Token token;
do {
final char ch = charAt(1);
switch (ch) {
case '"':
case '\'':
token = literal();
break;
case '/':
token = token2('/', Type.SLASH, Type.DOUBLE_SLASH);
break;
case '[':
token = new Token(Type.LEFT_BRACKET, xpath, cursor, cursor + 1);
cursor += 1;
break;
case ']':
token = new Token(Type.RIGHT_BRACKET, xpath, cursor, cursor + 1);
cursor += 1;
break;
case '+':
token = new Token(Type.PLUS, xpath, cursor, cursor + 1);
cursor += 1;
break;
case '-':
token = new Token(Type.MINUS, xpath, cursor, cursor + 1);
cursor += 1;
break;
case '<':
case '>':
token = relationalOperator();
break;
case '=':
token = new Token(Type.EQUALS, xpath, cursor, cursor + 1);
cursor += 1;
break;
case '!':
if ('=' == charAt(2)) {
token = new Token(Type.NOT_EQUALS, xpath, cursor, cursor + 2);
cursor += 2;
} else {
token = null;
}
break;
case '@':
token = new Token(Type.AT, xpath, cursor, cursor + 1);
cursor += 1;
break;
case ':':
token = token2(':', Type.COLON, Type.DOUBLE_COLON);
break;
case '*':
token = new Token(Type.STAR, xpath, cursor, cursor + 1);
cursor += 1;
break;
case '.':
switch (charAt(2)) {
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
token = number();
break;
default:
token = token2('.', Type.DOT, Type.DOUBLE_DOT);
break;
}
break;
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
token = number();
break;
case ' ':
case '\t':
case '\r':
case '\n':
token = whitespace();
break;
default:
if (isXmlStartCharacter(ch)) {
token = identifier();
} else {
token = null;
}
break;
}
if (token == null) {
token = hasNext()
? new Token(Type.ERROR, xpath, cursor, xpath.length())
: new Token(Type.EOF, xpath, 0, 0);
}
} while (token.getType() == Type.SKIP);
return token;
}
private Token literal() {
final char match = charAt(1);
final int start = cursor += 1;
Token token = null;
while (null == token && hasNext()) {
if (match == charAt(1)) {
token = new Token(Type.LITERAL, xpath, start, cursor);
}
cursor += 1;
}
return token;
}
private Token identifier() {
final int start = cursor;
while (hasNext()) {
if (isXmlCharacter(charAt(1))) {
cursor += 1;
} else {
break;
}
}
return new Token(Type.IDENTIFIER, xpath, start, cursor);
}
private Token number() {
final int start = cursor;
boolean periodAllowed = true;
loop: while (true) {
switch (charAt(1)) {
case '.':
if (periodAllowed) {
periodAllowed = false;
cursor += 1;
} else {
break loop;
}
break;
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
cursor += 1;
break;
default:
break loop;
}
}
return new Token(Type.DOUBLE, xpath, start, cursor);
}
private Token relationalOperator() {
final Token token;
switch (charAt(1)) {
case '<':
if ('=' == charAt(2)) {
token = new Token(Type.LESS_THAN_OR_EQUALS, xpath, cursor, cursor + 2);
cursor += 1;
} else {
token = new Token(Type.LESS_THAN, xpath, cursor, cursor + 1);
}
cursor += 1;
break;
case '>':
if ('=' == charAt(2)) {
token = new Token(Type.GREATER_THAN_OR_EQUALS, xpath, cursor, cursor + 2);
cursor += 1;
} else {
token = new Token(Type.GREATER_THAN, xpath, cursor, cursor + 1);
}
cursor += 1;
break;
default:
token = null;
break;
}
return token;
}
private Token whitespace() {
loop: while (true) {
switch (charAt(1)) {
case ' ':
case '\t':
case '\r':
case '\n':
cursor += 1;
break;
default:
break loop;
}
}
return new Token(Type.SKIP, xpath, 0, 0);
}
private Token token2(char ch, short if1, short if2) {
final Token token;
if (charAt(2) == ch) {
token = new Token(if2, xpath, cursor, cursor + 2);
cursor += 2;
} else {
token = new Token(if1, xpath, cursor, cursor + 1);
cursor += 1;
}
return token;
}
private char charAt(int i) {
final int pos = cursor + i - 1;
return pos >= xpath.length() ? (char) -1 : xpath.charAt(pos);
}
private boolean isXmlStartCharacter(char ch) {
return Character.isLetter(ch) || '_' == ch;
}
private boolean isXmlCharacter(char ch) {
return isXmlStartCharacter(ch) || Character.isDigit(ch) || '-' == ch || '.' == ch;
}
}
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