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An embeddable C Preprocessor for the JVM.
There is a newer version: 1.4.14
/*
 * Anarres C Preprocessor
 * Copyright (c) 2007-2008, Shevek
 *
 * 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.anarres.cpp;

import java.io.IOException;
import java.util.Iterator;
import java.util.List;

import static org.anarres.cpp.Token.*;

/* This source should always be active, since we don't expand macros
 * in any inactive context. */
/* pp */ class MacroTokenSource extends Source {

    private final Macro macro;
    private final Iterator tokens;	/* Pointer into the macro.  */

    private final List args;	/* { unexpanded, expanded } */

    private Iterator arg;	/* "current expansion" */

    /* pp */ MacroTokenSource(Macro m, List args) {
        this.macro = m;
        this.tokens = m.getTokens().iterator();
        this.args = args;
        this.arg = null;
    }

    @Override
    /* pp */ boolean isExpanding(Macro m) {
        /* When we are expanding an arg, 'this' macro is not
         * being expanded, and thus we may re-expand it. */
        if (/* XXX this.arg == null && */this.macro == m)
            return true;
        return super.isExpanding(m);
    }

    /* XXX Called from Preprocessor [ugly]. */
    /* pp */ static void escape(StringBuilder buf, CharSequence cs) {
        for (int i = 0; i < cs.length(); i++) {
            char c = cs.charAt(i);
            switch (c) {
                case '\\':
                    buf.append("\\\\");
                    break;
                case '"':
                    buf.append("\\\"");
                    break;
                case '\n':
                    buf.append("\\n");
                    break;
                case '\r':
                    buf.append("\\r");
                    break;
                default:
                    buf.append(c);
            }
        }
    }

    private void concat(StringBuilder buf, Argument arg) {
        Iterator it = arg.iterator();
        while (it.hasNext()) {
            Token tok = it.next();
            buf.append(tok.getText());
        }
    }

    private Token stringify(Token pos, Argument arg) {
        StringBuilder buf = new StringBuilder();
        concat(buf, arg);
        // System.out.println("Concat: " + arg + " -> " + buf);
        StringBuilder str = new StringBuilder("\"");
        escape(str, buf);
        str.append("\"");
        // System.out.println("Escape: " + buf + " -> " + str);
        return new Token(STRING,
                pos.getLine(), pos.getColumn(),
                str.toString(), buf.toString());
    }


    /* At this point, we have consumed the first M_PASTE.
     * @see Macro#addPaste(Token) */
    private void paste(Token ptok)
            throws IOException,
            LexerException {
        StringBuilder buf = new StringBuilder();
        Token err = null;
        /* We know here that arg is null or expired,
         * since we cannot paste an expanded arg. */

        int count = 2;
        for (int i = 0; i < count; i++) {
            if (!tokens.hasNext()) {
                /* XXX This one really should throw. */
                error(ptok.getLine(), ptok.getColumn(),
                        "Paste at end of expansion");
                buf.append(' ').append(ptok.getText());
                break;
            }
            Token tok = tokens.next();
            // System.out.println("Paste " + tok);
            switch (tok.getType()) {
                case M_PASTE:
                    /* One extra to paste, plus one because the
                     * paste token didn't count. */
                    count += 2;
                    ptok = tok;
                    break;
                case M_ARG:
                    int idx = ((Integer) tok.getValue()).intValue();
                    concat(buf, args.get(idx));
                    break;
                /* XXX Test this. */
                case CCOMMENT:
                case CPPCOMMENT:
                    break;
                default:
                    buf.append(tok.getText());
                    break;
            }
        }

        /* Push and re-lex. */
        /*
         StringBuilder		src = new StringBuilder();
         escape(src, buf);
         StringLexerSource	sl = new StringLexerSource(src.toString());
         */
        StringLexerSource sl = new StringLexerSource(buf.toString());

        /* XXX Check that concatenation produces a valid token. */
        arg = new SourceIterator(sl);
    }

    public Token token()
            throws IOException,
            LexerException {
        for (;;) {
            /* Deal with lexed tokens first. */

            if (arg != null) {
                if (arg.hasNext()) {
                    Token tok = arg.next();
                    /* XXX PASTE -> INVALID. */
                    assert tok.getType() != M_PASTE :
                            "Unexpected paste token";
                    return tok;
                }
                arg = null;
            }

            if (!tokens.hasNext())
                return new Token(EOF, -1, -1, "");	/* End of macro. */

            Token tok = tokens.next();
            int idx;
            switch (tok.getType()) {
                case M_STRING:
                    /* Use the nonexpanded arg. */
                    idx = ((Integer) tok.getValue()).intValue();
                    return stringify(tok, args.get(idx));
                case M_ARG:
                    /* Expand the arg. */
                    idx = ((Integer) tok.getValue()).intValue();
                    // System.out.println("Pushing arg " + args.get(idx));
                    arg = args.get(idx).expansion();
                    break;
                case M_PASTE:
                    paste(tok);
                    break;
                default:
                    return tok;
            }
        } /* for */

    }

    @Override
    public String toString() {
        StringBuilder buf = new StringBuilder();
        buf.append("expansion of ").append(macro.getName());
        Source parent = getParent();
        if (parent != null)
            buf.append(" in ").append(String.valueOf(parent));
        return buf.toString();
    }
}