com.antsdb.saltedfish.sql.vdm.ExprUtil.java Source code

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Here is the source code for com.antsdb.saltedfish.sql.vdm.ExprUtil.java

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/*-------------------------------------------------------------------------------------------------
 _______ __   _ _______ _______ ______  ______
 |_____| | \  |    |    |______ |     \ |_____]
 |     | |  \_|    |    ______| |_____/ |_____]
    
 Copyright (c) 2016, antsdb.com and/or its affiliates. All rights reserved. *-xguo0<@
    
 This program is free software: you can redistribute it and/or modify it under the terms of the
 GNU Affero General Public License, version 3, as published by the Free Software Foundation.
    
 You should have received a copy of the GNU Affero General Public License along with this program.
 If not, see <https://www.gnu.org/licenses/agpl-3.0.txt>
-------------------------------------------------------------------------------------------------*/
package com.antsdb.saltedfish.sql.vdm;

import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;

import org.apache.commons.lang.UnhandledException;
import org.apache.commons.lang.exception.NestableRuntimeException;
import org.apache.commons.lang.text.StrBuilder;

/**
 * 
 * @author wgu0
 */
public final class ExprUtil {
    /**
     * <p>Unescapes any Java literals found in the <code>String</code>.
     * For example, it will turn a sequence of <code>'\'</code> and
     * <code>'n'</code> into a newline character, unless the <code>'\'</code>
     * is preceded by another <code>'\'</code>.</p>
     * 
     * @param str  the <code>String</code> to unescape, may be null
     * @return a new unescaped <code>String</code>, <code>null</code> if null string input
     */
    public static String unescape(String str) {
        if (str == null) {
            return null;
        }
        try {
            StringWriter writer = new StringWriter(str.length());
            unescapeJava(writer, str);
            return writer.toString();
        } catch (IOException ioe) {
            // this should never ever happen while writing to a StringWriter
            throw new UnhandledException(ioe);
        }

    }

    /**
     * <p>Unescapes any Java literals found in the <code>String</code> to a
     * <code>Writer</code>.</p>
     *
     * <p>For example, it will turn a sequence of <code>'\'</code> and
     * <code>'n'</code> into a newline character, unless the <code>'\'</code>
     * is preceded by another <code>'\'</code>.</p>
     * 
     * <p>A <code>null</code> string input has no effect.</p>
     * 
     * @see http://dev.mysql.com/doc/refman/5.7/en/string-literals.html
     * 
     * @param out  the <code>Writer</code> used to output unescaped characters
     * @param str  the <code>String</code> to unescape, may be null
     * @throws IllegalArgumentException if the Writer is <code>null</code>
     * @throws IOException if error occurs on underlying Writer
     */
    public static void unescapeJava(Writer out, String str) throws IOException {
        if (out == null) {
            throw new IllegalArgumentException("The Writer must not be null");
        }
        if (str == null) {
            return;
        }
        int sz = str.length();
        StrBuilder unicode = new StrBuilder(4);
        boolean hadSlash = false;
        boolean inUnicode = false;
        for (int i = 0; i < sz; i++) {
            char ch = str.charAt(i);
            if (inUnicode) {
                // if in unicode, then we're reading unicode
                // values in somehow
                unicode.append(ch);
                if (unicode.length() == 4) {
                    // unicode now contains the four hex digits
                    // which represents our unicode character
                    try {
                        int value = Integer.parseInt(unicode.toString(), 16);
                        out.write((char) value);
                        unicode.setLength(0);
                        inUnicode = false;
                        hadSlash = false;
                    } catch (NumberFormatException nfe) {
                        throw new NestableRuntimeException("Unable to parse unicode value: " + unicode, nfe);
                    }
                }
                continue;
            }
            if (hadSlash) {
                // handle an escaped value
                hadSlash = false;
                switch (ch) {
                case '0':
                    out.write(0);
                    break;
                case '\'':
                    out.write('\'');
                    break;
                case '\"':
                    out.write('"');
                    break;
                case 'b':
                    out.write('\b');
                    break;
                case 'n':
                    out.write('\n');
                    break;
                case 'r':
                    out.write('\r');
                    break;
                case 't':
                    out.write('\t');
                    break;
                case 'Z':
                    out.write(26);
                    break;
                case '\\':
                    out.write('\\');
                    break;
                case '%':
                    out.write('%');
                    break;
                case '_':
                    out.write('_');
                    break;
                case 'u': {
                    // uh-oh, we're in unicode country....
                    inUnicode = true;
                    break;
                }
                default:
                    out.write(ch);
                }
                continue;
            } else if (ch == '\\') {
                hadSlash = true;
                continue;
            }
            out.write(ch);
        }
        if (hadSlash) {
            // then we're in the weird case of a \ at the end of the
            // string, let's output it anyway.
            out.write('\\');
        }
    }

}