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Java example source code file (Spp.java)

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

Learn more about this Java project at its project page.

Java - Java tags/keywords

error, gn_key, gn_no, gn_yes, key, map, matcher, mis\-matched, regex, set, string, stringbuffer, text, this, util, var

The Spp.java Java example source code

/*
 * Copyright (c) 2008, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package build.tools.spp;

import java.util.*;
import java.util.regex.*;

/*
 * Spp: A simple regex-based stream preprocessor based on Mark Reinhold's
 *      sed-based spp.sh
 *
 * Usage: java build.tools.spp.Spp [-be] [-Kkey] -Dvar=value ... <in >out
 *
 * Source-file constructs
 *
 *   Meaningful only at beginning of line, works with any number of keys:
 *
 *    #if[key]              Includes text between #if/#end if -Kkey specified,
 *    #else[key]            otherwise changes text to blank lines; key test
 *    #end[key]             may be negated by prefixing !, e.g., #if[!key]
 *
 *    #begin                If -be is specified then lines up to and including
 *    #end                  #begin, and from #end to EOF, are deleted
 *
 *    #warn                 Changed into warning that file is generated
 *
 *    // ##                 Changed into blank line
 *
 *  Meaningful anywhere in line
 *
 *    {#if[key]?yes}        Expands to yes if -Kkey specified
 *    {#if[key]?yes:no}     Expands to yes if -Kkey, otherwise no
 *    {#if[!key]?yes}       Expands to yes if -Kother
 *    {#if[!key]?yes:no}    Expands to yes if -Kother, otherwise no
 *    $var$                 Expands to value if -Dvar=value given
 *
 *    yes, no must not contain whitespace
 *
 * @author Xueming Shen
 */

public class Spp {
    public static void main(String args[]) throws Exception {
        Map<String, String> vars = new HashMap();
        Set<String> keys = new HashSet();
        boolean be = false;

        for (String arg:args) {
            if (arg.startsWith("-D")) {
                int i = arg.indexOf('=');
                vars.put(arg.substring(2, i),arg.substring(i+1));
            } else if (arg.startsWith("-K")) {
                keys.add(arg.substring(2));
            } else if ("-be".equals(arg)) {
                be = true;
            } else {
                System.err.println("Usage: java build.tools.spp.Spp [-be] [-Kkey] -Dvar=value ... <in >out");
                System.exit(-1);
            }
        }

        StringBuffer out = new StringBuffer();
        new Spp().spp(new Scanner(System.in),
                      out, "",
                      keys, vars, be,
                      false);
        System.out.print(out.toString());
    }

    static final String LNSEP = System.getProperty("line.separator");
    static final String KEY = "([a-zA-Z0-9]+)";
    static final String VAR = "([a-zA-Z0-9_\\-]+)";
    static final String TEXT = "([a-zA-Z0-9&;,.<>/#() \\$]+)"; // $ -- hack embedded $var$

    static final int GN_NOT = 1;
    static final int GN_KEY = 2;
    static final int GN_YES = 3;
    static final int GN_NO  = 5;
    static final int GN_VAR = 6;

    Matcher ifkey = Pattern.compile("^#if\\[(!)?" + KEY + "\\]").matcher("");
    Matcher elsekey = Pattern.compile("^#else\\[(!)?" + KEY + "\\]").matcher("");
    Matcher endkey = Pattern.compile("^#end\\[(!)?" + KEY + "\\]").matcher("");
    Matcher  vardef = Pattern.compile("\\{#if\\[(!)?" + KEY + "\\]\\?" + TEXT + "(:"+ TEXT + ")?\\}|\\$" + VAR + "\\$").matcher("");
    Matcher  vardef2 = Pattern.compile("\\$" + VAR + "\\$").matcher("");

    void append(StringBuffer buf, String ln,
                Set<String> keys, Map vars) {
        vardef.reset(ln);
        while (vardef.find()) {
            String repl = "";
            if (vardef.group(GN_VAR) != null)
                repl = vars.get(vardef.group(GN_VAR));
            else {
                boolean test = keys.contains(vardef.group(GN_KEY));
                if (vardef.group(GN_NOT) != null)
                    test = !test;
                repl = test?vardef.group(GN_YES):vardef.group(GN_NO);
                if (repl == null)
                    repl = "";
                else {  // embedded $var$
                    while (vardef2.reset(repl).find()) {
                        repl = vardef2.replaceFirst(vars.get(vardef2.group(1)));
                    }
                }
            }
            vardef.appendReplacement(buf, repl);
        }
        vardef.appendTail(buf);
    }

    // return true if #end[key], #end or EOF reached
    boolean spp(Scanner in, StringBuffer buf, String key,
                Set<String> keys, Map vars,
                boolean be, boolean skip) {
        while (in.hasNextLine()) {
            String ln = in.nextLine();
            if (be) {
                if (ln.startsWith("#begin")) {
                    buf.setLength(0);      //clean up to this line
                    continue;
                }
                if (ln.equals("#end")) {
                    while (in.hasNextLine())
                        in.nextLine();
                    return true;           //discard the rest to EOF
                }
            }
            if (ifkey.reset(ln).find()) {
                String k = ifkey.group(GN_KEY);
                boolean test = keys.contains(k);
                if (ifkey.group(GN_NOT) != null)
                    test = !test;
                buf.append(LNSEP);
                if (!spp(in, buf, k, keys, vars, be, skip || !test)) {
                    spp(in, buf, k, keys, vars, be, skip || test);
                }
                continue;
            }
            if (elsekey.reset(ln).find()) {
                if (!key.equals(elsekey.group(GN_KEY))) {
                    throw new Error("Mis-matched #if-else-end at line <" + ln + ">");
                }
                buf.append(LNSEP);
                return false;
            }
            if (endkey.reset(ln).find()) {
                if (!key.equals(endkey.group(GN_KEY))) {
                    throw new Error("Mis-matched #if-else-end at line <" + ln + ">");
                }
                buf.append(LNSEP);
                return true;
            }
            if (ln.startsWith("#warn")) {
                ln = "// -- This file was mechanically generated: Do not edit! -- //";
            } else if (ln.trim().startsWith("// ##")) {
                ln = "";
            }
            if (!skip) {
                append(buf, ln, keys, vars);
            }
            buf.append(LNSEP);
        }
        return true;
    }
}

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