alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Java example source code file (SharedMemoryConnection.c)

This example Java source code file (SharedMemoryConnection.c) 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

id_to_connection, java_com_sun_tools_jdi_sharedmemoryconnection_close0, java_com_sun_tools_jdi_sharedmemoryconnection_receivebyte0, java_com_sun_tools_jdi_sharedmemoryconnection_receivepacket0, java_com_sun_tools_jdi_sharedmemoryconnection_sendbyte0, java_com_sun_tools_jdi_sharedmemoryconnection_sendpacket0, jdwptransport_flags_reply, jnicall, jnienv, jniexport, null, sharedmemoryconnection, sys_ok, unable

The SharedMemoryConnection.c Java example source code

/*
 * Copyright (c) 1999, 2003, 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.
 */
#include <string.h>
#include <stdlib.h>
#include <stddef.h>
#include <jni.h>
#include "SharedMemory.h"
#include "com_sun_tools_jdi_SharedMemoryConnection.h"
#include "jdwpTransport.h"
#include "shmemBase.h"
#include "sys.h"

/*
 * JNI interface to the shared memory transport. These JNI methods
 * call the base shared memory support to do the real work.
 *
 * That is, this is the front-ends interface to our shared memory
 * communication code.
 */

/*
 * Cached architecture
 */
static int byte_ordering_known;
static int is_big_endian;


/*
 * Returns 1 if big endian architecture
 */
static int isBigEndian() {
    if (!byte_ordering_known) {
        unsigned int i = 0xff000000;
        if (((char *)(&i))[0] != 0) {
            is_big_endian = 1;
        } else {
            is_big_endian = 0;
        }
        byte_ordering_known = 1;
    }
    return is_big_endian;
}

/*
 * Convert to big endian
 */
static jint intToBigInt(jint i) {
    unsigned int b[4];
    if (isBigEndian()) {
        return i;
    }
    b[0] = (i >> 24) & 0xff;
    b[1] = (i >> 16) & 0xff;
    b[2] = (i >> 8) & 0xff;
    b[3] = i & 0xff;

    /*
     * It doesn't matter that jint is signed as we are or'ing
     * and hence end up with the correct bits.
     */
    return (b[3] << 24) | (b[2] << 16) | (b[1] << 8) | b[0];
}

/*
 * Convert unsigned short to big endian
 */
static unsigned short shortToBigShort(unsigned short s) {
    unsigned int b[2];
    if (isBigEndian()) {
        return s;
    }
    b[0] = (s >> 8) & 0xff;
    b[1] = s & 0xff;
    return (b[1] << 8) + b[0];
}

/*
 * Create a byte[] from a packet struct. All data in the byte array
 * is JDWP packet suitable for wire transmission. That is, all fields,
 * and data are in big-endian format as required by the JDWP
 * specification.
 */
static jbyteArray
packetToByteArray(JNIEnv *env, jdwpPacket *str)
{
    jbyteArray array;
    jsize data_length;
    jint total_length;
    jint tmpInt;

    total_length = str->type.cmd.len;
    data_length = total_length - 11;

    /* total packet length is header + data */
    array = (*env)->NewByteArray(env, total_length);
    if ((*env)->ExceptionOccurred(env)) {
        return NULL;
    }

    /* First 4 bytes of packet are the length (in big endian format) */
    tmpInt = intToBigInt((unsigned int)total_length);
    (*env)->SetByteArrayRegion(env, array, 0, 4, (const jbyte *)&tmpInt);

    /* Next 4 bytes are the id field */
    tmpInt = intToBigInt(str->type.cmd.id);
    (*env)->SetByteArrayRegion(env, array, 4, 4, (const jbyte *)&tmpInt);

    /* next byte is the flags */
    (*env)->SetByteArrayRegion(env, array, 8, 1, (const jbyte *)&(str->type.cmd.flags));

    /* next two bytes are either the error code or the command set/command */
    if (str->type.cmd.flags & JDWPTRANSPORT_FLAGS_REPLY) {
        short s = shortToBigShort(str->type.reply.errorCode);
        (*env)->SetByteArrayRegion(env, array, 9, 2, (const jbyte *)&(s));
    } else {
        (*env)->SetByteArrayRegion(env, array, 9, 1, (const jbyte *)&(str->type.cmd.cmdSet));
        (*env)->SetByteArrayRegion(env, array, 10, 1, (const jbyte *)&(str->type.cmd.cmd));
    }

    /* finally the data */

    if (data_length > 0) {
        (*env)->SetByteArrayRegion(env, array, 11,
                                   data_length, str->type.cmd.data);
        if ((*env)->ExceptionOccurred(env)) {
            return NULL;
        }
    }

    return array;
}

/*
 * Fill a packet struct from a byte array. The byte array is a
 * JDWP packet suitable for wire transmission. That is, all fields,
 * and data are in big-endian format as required by the JDWP
 * specification. We thus need to convert the fields from big
 * endian to the platform endian.
 *
 * The jbyteArray provided to this function is assumed to
 * of a length than is equal or greater than the length of
 * the JDWP packet that is contains.
 */
static void
byteArrayToPacket(JNIEnv *env, jbyteArray b, jdwpPacket *str)
{
    jsize total_length, data_length;
    jbyte *data;
    unsigned char pktHeader[11]; /* sizeof length + id + flags + cmdSet + cmd */

    /*
     * Get the packet header
     */
    (*env)->GetByteArrayRegion(env, b, 0, sizeof(pktHeader), pktHeader);

    total_length = (int)pktHeader[3] | ((int)pktHeader[2] << 8) |
                   ((int)pktHeader[1] << 16) | ((int)pktHeader[0] << 24);
    /*
     * The id field is in big endian (also errorCode field in the case
     * of reply packets).
     */
    str->type.cmd.id = (int)pktHeader[7] | ((int)pktHeader[6] << 8) |
                       ((int)pktHeader[5] << 16) | ((int)pktHeader[4] << 24);

    str->type.cmd.flags = (jbyte)pktHeader[8];

    if (str->type.cmd.flags & JDWPTRANSPORT_FLAGS_REPLY) {
        str->type.reply.errorCode = (int)pktHeader[9] + ((int)pktHeader[10] << 8);
    } else {
        /* command packet */
        str->type.cmd.cmdSet = (jbyte)pktHeader[9];
        str->type.cmd.cmd = (jbyte)pktHeader[10];
    }

    /*
     * The length of the JDWP packet is 11 + data
     */
    data_length = total_length - 11;

    if (data_length == 0) {
        data = NULL;
    } else {
        data = malloc(data_length);
        if (data == NULL) {
            throwException(env, "java/lang/OutOfMemoryError",
                           "Unable to allocate command data buffer");
            return;
        }

        (*env)->GetByteArrayRegion(env, b, 11, /*sizeof(CmdPacket)+4*/ data_length, data);
        if ((*env)->ExceptionOccurred(env)) {
            free(data);
            return;
        }
    }

    str->type.cmd.len = total_length;
    str->type.cmd.data = data;
}

static void
freePacketData(jdwpPacket *packet)
{
    if (packet->type.cmd.len > 0) {
        free(packet->type.cmd.data);
    }
}

/*
 * Class:     com_sun_tools_jdi_SharedMemoryConnection
 * Method:    close0
 * Signature: (J)V
 */
JNIEXPORT void JNICALL Java_com_sun_tools_jdi_SharedMemoryConnection_close0
  (JNIEnv *env, jobject thisObject, jlong id)
{
    SharedMemoryConnection *connection = ID_TO_CONNECTION(id);
    shmemBase_closeConnection(connection);
}

/*
 * Class:     com_sun_tools_jdi_SharedMemoryConnection
 * Method:    receiveByte0
 * Signature: (J)B
 */
JNIEXPORT jbyte JNICALL Java_com_sun_tools_jdi_SharedMemoryConnection_receiveByte0
  (JNIEnv *env, jobject thisObject, jlong id)
{
    SharedMemoryConnection *connection = ID_TO_CONNECTION(id);
    jbyte b = 0;
    jint rc;

    rc = shmemBase_receiveByte(connection, &b);
    if (rc != SYS_OK) {
        throwShmemException(env, "shmemBase_receiveByte failed", rc);
    }

    return b;
}

/*
 * Class:     com_sun_tools_jdi_SharedMemoryConnection
 * Method:    receivePacket0
 * Signature: (JLcom/sun/tools/jdi/Packet;)V
 */
JNIEXPORT jbyteArray JNICALL Java_com_sun_tools_jdi_SharedMemoryConnection_receivePacket0
  (JNIEnv *env, jobject thisObject, jlong id)
{
    SharedMemoryConnection *connection = ID_TO_CONNECTION(id);
    jdwpPacket packet;
    jint rc;

    rc = shmemBase_receivePacket(connection, &packet);
    if (rc != SYS_OK) {
        throwShmemException(env, "shmemBase_receivePacket failed", rc);
        return NULL;
    } else {
        jbyteArray array = packetToByteArray(env, &packet);

        /* Free the packet even if there was an exception above */
        freePacketData(&packet);
        return array;
    }
}

/*
 * Class:     com_sun_tools_jdi_SharedMemoryConnection
 * Method:    sendByte0
 * Signature: (JB)V
 */
JNIEXPORT void JNICALL Java_com_sun_tools_jdi_SharedMemoryConnection_sendByte0
  (JNIEnv *env, jobject thisObject, jlong id, jbyte b)
{
    SharedMemoryConnection *connection = ID_TO_CONNECTION(id);
    jint rc;

    rc = shmemBase_sendByte(connection, b);
    if (rc != SYS_OK) {
        throwShmemException(env, "shmemBase_sendByte failed", rc);
    }
}

/*
 * Class:     com_sun_tools_jdi_SharedMemoryConnection
 * Method:    sendPacket0
 * Signature: (JLcom/sun/tools/jdi/Packet;)V
 */
JNIEXPORT void JNICALL Java_com_sun_tools_jdi_SharedMemoryConnection_sendPacket0
  (JNIEnv *env, jobject thisObject, jlong id, jbyteArray b)
{
    SharedMemoryConnection *connection = ID_TO_CONNECTION(id);
    jdwpPacket packet;
    jint rc;

    byteArrayToPacket(env, b, &packet);
    if ((*env)->ExceptionOccurred(env)) {
        return;
    }

    rc = shmemBase_sendPacket(connection, &packet);
    if (rc != SYS_OK) {
        throwShmemException(env, "shmemBase_sendPacket failed", rc);
    }
    freePacketData(&packet);
}

Other Java examples (source code examples)

Here is a short list of links related to this Java SharedMemoryConnection.c source code file:

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2024 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.