jdk-24/test/jdk/java/lang/instrument/NamedBuffer.java

/*
 * Copyright (c) 2003, 2019, 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.
 *
 * 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.
 */

import  java.io.*;

/*
 * Copyright 2003 Wily Technology, Inc.
 */

public class NamedBuffer
{
    private final String    fName;
    private final byte[]    fBuffer;

    public
    NamedBuffer(    String  name,
                    byte[]  buffer)
        {
        fName =     name;
        fBuffer =   buffer;
        }

    public
    NamedBuffer(    String      name,
                    InputStream stream)
        throws IOException
        {
        this(   name,
                loadBufferFromStream(stream));
        }

    public String
    getName()
        {
        return fName;
        }

    public byte[]
    getBuffer()
        {
        return fBuffer;
        }

    public static byte[]
    loadBufferFromStream(InputStream stream)
        throws IOException
    {
        // hack for now, just assume the stream will fit in our reasonable size buffer.
        // if not, panic
        int bufferLimit = 200 * 1024;
        byte[]  readBuffer = new byte[bufferLimit];
        int actualSize = stream.read(readBuffer);
        if ( actualSize >= bufferLimit )
            {
            // if there might be more bytes, just surrender
            throw new IOException("too big for buffer");
            }

        byte[] resultBuffer = new byte[actualSize];
        System.arraycopy(   readBuffer,
                            0,
                            resultBuffer,
                            0,
                            actualSize);
        return resultBuffer;
    }

    static final String DEST = System.getProperty("test.classes");
    static final boolean VERBOSE = false;

    static boolean checkMatch(byte[] buf, byte[] name, int begIdx) {
        if (buf.length < name.length + begIdx) {
            return false;
        }
        for (int i = 0; i < name.length; i++) {
            if (buf[i + begIdx] != name[i]) {
                return false;
            }
        }
        return true;
    }

    // This function reads a class file from disk and replaces the first character of
    // the name with the one passed as "replace".  Then goes through the bytecodes to
    // replace all instances of the name of the class with the new name.  The
    // redefinition tests use this to redefine Host$ classes with precompiled class files
    // Xost.java, Yost.java and Zost.java.
    static byte[]
    bytesForHostClass(char replace, String className) throws Throwable {
        String tail = className.substring(1);
        String origClassName = "" + replace + tail;
        File clsfile = new File(DEST + "/" + origClassName + ".class");

        if (VERBOSE) {
            System.out.println("   Reading bytes from " + clsfile);
        }
        byte[] buf = null;
        try (FileInputStream str = new FileInputStream(clsfile)) {
            buf = loadBufferFromStream(str);
        }

        boolean found = false;
        int dollarSignIdx = className.indexOf('$');
        int ptrnLen = (dollarSignIdx == -1) ? className.length() : dollarSignIdx;
        byte[] ptrnBytes = origClassName.substring(0, ptrnLen).getBytes();
        byte firstByte = className.getBytes()[0];

        for (int i = 0; i < buf.length - ptrnLen; i++) {
            if (checkMatch(buf, ptrnBytes, i)) {
                if (VERBOSE) {
                    System.out.println("Appear to have found " + origClassName + " starting at " + i);
                }
                buf[i] = firstByte;
                found = true;
            }
        }
        if (!found) {
            throw new Error("Could not locate '" + ptrnBytes + "' name in byte array");
        }
        return buf;
    }
}