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Groovy example source code file (UnicodeEscapingReader.java)

This example Groovy source code file (UnicodeEscapingReader.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Groovy tags/keywords

a, charscanner, charscanner, dummylexer, io, ioexception, ioexception, override, reader, reader, stringbuffer, token, token, tokenstreamexception, unicodeescapingreader

The Groovy UnicodeEscapingReader.java source code

/*
 * Copyright 2003-2007 the original author or authors.
 *
 * Licensed 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 org.codehaus.groovy.antlr;

import java.io.IOException;
import java.io.Reader;

import antlr.CharScanner;
import antlr.Token;
import antlr.TokenStreamException;

/**
 * Translates GLS-defined unicode escapes into characters. Throws an exception
 * in the event of an invalid unicode escape being detected.
 *
 * <p>No attempt has been made to optimize this class for speed or
 * space.</p>
 *
 * @version $Revision: 21731 $
 */
public class UnicodeEscapingReader extends Reader {

    private final Reader reader;
    private CharScanner lexer;
    private boolean hasNextChar = false;
    private int nextChar;
    private final SourceBuffer sourceBuffer;
    private int previousLine;
    private int numUnicodeEscapesFound = 0;
    private int numUnicodeEscapesFoundOnCurrentLine = 0;

    private static class DummyLexer extends CharScanner {
        final private Token t = new Token();
        public Token nextToken() throws TokenStreamException {
            return t;
        }
        @Override
        public int getColumn() {
            return 0;
        }
        @Override
        public int getLine() {
            return 0;
        }
    }
    
    /**
     * Constructor.
     * @param reader The reader that this reader will filter over.
     */
    public UnicodeEscapingReader(Reader reader,SourceBuffer sourceBuffer) {
        this.reader = reader;
        this.sourceBuffer = sourceBuffer;
        this.lexer = new DummyLexer();
    }

    /**
     * Sets the lexer that is using this reader. Must be called before the
     * lexer is used.
     */
    public void setLexer(CharScanner lexer) {
        this.lexer = lexer;
    }

    /**
     * Reads characters from the underlying reader.
     * @see java.io.Reader#read(char[],int,int)
     */
    public int read(char cbuf[], int off, int len) throws IOException {
        int c = 0;
        int count = 0;
        while (count < len && (c = read())!= -1) {
            cbuf[off + count] = (char) c;
            count++;
        }
        return (count == 0 && c == -1) ? -1 : count;
    }

    /**
     * Gets the next character from the underlying reader,
     * translating escapes as required.
     * @see java.io.Reader#close()
     */
    public int read() throws IOException {
        if (hasNextChar) {
            hasNextChar = false;
            write(nextChar);
            return nextChar;
        }

        if (previousLine != lexer.getLine()) {
            // new line, so reset unicode escapes
            numUnicodeEscapesFoundOnCurrentLine = 0;
            previousLine = lexer.getLine();
        }
        
        int c = reader.read();
        if (c != '\\') {
            write(c);
            return c;
        }

        // Have one backslash, continue if next char is 'u'
        c = reader.read();
        if (c != 'u') {
            hasNextChar = true;
            nextChar = c;
            write('\\');
            return '\\';
        }

        // Swallow multiple 'u's
        int numberOfUChars = 0;
        do {
            numberOfUChars++;
            c = reader.read();
        } while (c == 'u');

        // Get first hex digit
        checkHexDigit(c);
        StringBuffer charNum = new StringBuffer();
        charNum.append((char) c);

        // Must now be three more hex digits
        for (int i = 0; i < 3; i++) {
            c = reader.read();
            checkHexDigit(c);
            charNum.append((char) c);
        }
        int rv = Integer.parseInt(charNum.toString(), 16);
        write(rv);
        
        numUnicodeEscapesFound += 4 + numberOfUChars;
        numUnicodeEscapesFoundOnCurrentLine += 4 + numberOfUChars;

        return rv;
    }
    private void write(int c) {
        if (sourceBuffer != null) {sourceBuffer.write(c);}
    }
    /**
     * Checks that the given character is indeed a hex digit.
     */
    private void checkHexDigit(int c) throws IOException {
        if (c >= '0' && c <= '9') {
            return;
        }
        if (c >= 'a' && c <= 'f') {
            return;
        }
        if (c >= 'A' && c <= 'F') {
            return;
        }
        // Causes the invalid escape to be skipped
        hasNextChar = true;
        nextChar = c;
        throw new IOException("Did not find four digit hex character code."
                + " line: " + lexer.getLine() + " col:" + lexer.getColumn());
    }

    public int getUnescapedUnicodeColumnCount() {
        return numUnicodeEscapesFoundOnCurrentLine;
    }

    public int getUnescapedUnicodeOffsetCount() {
        return numUnicodeEscapesFound;
    }

    /**
     * Closes this reader by calling close on the underlying reader.
     * @see java.io.Reader#close()
     */
    public void close() throws IOException {
        reader.close();
    }
}

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