signaturereader.java

jboss规则引擎

/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2005 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.drools.asm.signature;

/**
 * A type signature parser to make a signature visitor visit an existing
 * signature.
 * 
 * @author Thomas Hallgren
 * @author Eric Bruneton
 */
public class SignatureReader {

    /**
     * The signature to be read.
     */
    private final String signature;

    /**
     * Constructs a {@link SignatureReader} for the given signature.
     * 
     * @param signature A <i>ClassSignature</i>, <i>MethodTypeSignature</i>,
     *        or <i>FieldTypeSignature</i>.
     */
    public SignatureReader(final String signature) {
        this.signature = signature;
    }

    /**
     * Makes the given visitor visit the signature of this
     * {@link SignatureReader}. This signature is the one specified in the
     * constructor (see {@link #SignatureReader(String) SignatureReader}). This
     * method is intended to be called on a {@link SignatureReader} that was
     * created using a <i>ClassSignature</i> (such as the
     * <code>signature</code> parameter of the
     * {@link org.drools.asm.ClassVisitor#visit ClassVisitor.visit} method)
     * or a <i>MethodTypeSignature</i> (such as the <code>signature</code>
     * parameter of the
     * {@link org.drools.asm.ClassVisitor#visitMethod ClassVisitor.visitMethod}
     * method).
     * 
     * @param v the visitor that must visit this signature.
     */
    public void accept(final SignatureVisitor v) {
        final String signature = this.signature;
        final int len = signature.length();
        int pos;
        char c;

        if ( signature.charAt( 0 ) == '<' ) {
            pos = 2;
            do {
                final int end = signature.indexOf( ':',
                                                   pos );
                v.visitFormalTypeParameter( signature.substring( pos - 1,
                                                                 end ) );
                pos = end + 1;

                c = signature.charAt( pos );
                if ( c == 'L' || c == '[' || c == 'T' ) {
                    pos = parseType( signature,
                                     pos,
                                     v.visitClassBound() );
                }

                for ( ;; ) {
                    if ( (c = signature.charAt( pos++ )) == ':' ) {
                        pos = parseType( signature,
                                         pos,
                                         v.visitInterfaceBound() );
                    } else {
                        break;
                    }
                }
            } while ( c != '>' );
        } else {
            pos = 0;
        }

        if ( signature.charAt( pos ) == '(' ) {
            pos = pos + 1;
            while ( signature.charAt( pos ) != ')' ) {
                pos = parseType( signature,
                                 pos,
                                 v.visitParameterType() );
            }
            pos = parseType( signature,
                             pos + 1,
                             v.visitReturnType() );
            while ( pos < len ) {
                pos = parseType( signature,
                                 pos + 1,
                                 v.visitExceptionType() );
            }
        } else {
            pos = parseType( signature,
                             pos,
                             v.visitSuperclass() );
            while ( pos < len ) {
                pos = parseType( signature,
                                 pos,
                                 v.visitInterface() );
            }
        }
    }

    /**
     * Makes the given visitor visit the signature of this
     * {@link SignatureReader}. This signature is the one specified in the
     * constructor (see {@link #SignatureReader(String) SignatureReader}). This
     * method is intended to be called on a {@link SignatureReader} that was
     * created using a <i>FieldTypeSignature</i>, such as the
     * <code>signature</code> parameter of the
     * {@link org.drools.asm.ClassVisitor#visitField 
     * ClassVisitor.visitField} or {@link 
     * org.drools.asm.MethodVisitor#visitLocalVariable
     * MethodVisitor.visitLocalVariable} methods.
     * 
     * @param v the visitor that must visit this signature.
     */
    public void acceptType(final SignatureVisitor v) {
        parseType( this.signature,
                   0,
                   v );
    }

    /**
     * Parses a field type signature and makes the given visitor visit it.
     * 
     * @param signature a string containing the signature that must be parsed.
     * @param pos index of the first character of the signature to parsed.
     * @param v the visitor that must visit this signature.
     * @return the index of the first character after the parsed signature.
     */
    private static int parseType(final String signature,
                                 int pos,
                                 final SignatureVisitor v) {
        char c;
        int start, end;
        boolean visited, inner;
        String name;

        switch ( c = signature.charAt( pos++ ) ) {
            case 'Z' :
            case 'C' :
            case 'B' :
            case 'S' :
            case 'I' :
            case 'F' :
            case 'J' :
            case 'D' :
            case 'V' :
                v.visitBaseType( c );
                return pos;

            case '[' :
                return parseType( signature,
                                  pos,
                                  v.visitArrayType() );

            case 'T' :
                end = signature.indexOf( ';',
                                         pos );
                v.visitTypeVariable( signature.substring( pos,
                                                          end ) );
                return end + 1;

            default : // case 'L':
                start = pos;
                visited = false;
                inner = false;
                for ( ;; ) {
                    switch ( c = signature.charAt( pos++ ) ) {
                        case '.' :
                        case ';' :
                            if ( !visited ) {
                                name = signature.substring( start,
                                                            pos - 1 );
                                if ( inner ) {
                                    v.visitInnerClassType( name );
                                } else {
                                    v.visitClassType( name );
                                }
                            }
                            if ( c == ';' ) {
                                v.visitEnd();
                                return pos;
                            }
                            start = pos;
                            visited = false;
                            inner = true;
                            break;

                        case '<' :
                            name = signature.substring( start,
                                                        pos - 1 );
                            if ( inner ) {
                                v.visitInnerClassType( name );
                            } else {
                                v.visitClassType( name );
                            }
                            visited = true;
                            top : for ( ;; ) {
                                switch ( c = signature.charAt( pos ) ) {
                                    case '>' :
                                        break top;
                                    case '*' :
                                        ++pos;
                                        v.visitTypeArgument();
                                        break;
                                    case '+' :
                                    case '-' :
                                        pos = parseType( signature,
                                                         pos + 1,
                                                         v.visitTypeArgument( c ) );
                                        break;
                                    default :
                                        pos = parseType( signature,
                                                         pos,
                                                         v.visitTypeArgument( '=' ) );
                                        break;
                                }
                            }
                    }
                }
        }
    }
}