libzmq/bindings/java/Context.cpp

/*
    Copyright (c) 2007-2010 iMatix Corporation

    This file is part of 0MQ.

    0MQ is free software; you can redistribute it and/or modify it under
    the terms of the Lesser GNU General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    0MQ 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
    Lesser GNU General Public License for more details.

    You should have received a copy of the Lesser GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <assert.h>
#include <errno.h>

#include "../c/zmq.h"

#include "org_zmq_Context.h"

/** Handle to Java's Context::contextHandle. */
static jfieldID ctx_handle_fid = NULL;

/**
 * Make sure we have a valid pointer to Java's Context::contextHandle.
 */
static void ensure_context (JNIEnv *env, jobject obj)
{
    if (ctx_handle_fid == NULL) {
        jclass cls = env->GetObjectClass (obj);
        assert (cls);
        ctx_handle_fid = env->GetFieldID (cls, "contextHandle", "J");
        assert (ctx_handle_fid);
        env->DeleteLocalRef (cls);
    }
}

/**
 * Get the value of Java's Context::contextHandle.
 */
static void *get_context (JNIEnv *env, jobject obj)
{
    ensure_context (env, obj);
    void *s = (void*) env->GetLongField (obj, ctx_handle_fid);
    return s;
}

/**
 * Set the value of Java's Context::contextHandle.
 */
static void put_context (JNIEnv *env, jobject obj, void *s)
{
    ensure_context (env, obj);
    env->SetLongField (obj, ctx_handle_fid, (jlong) s);
}

/**
 * Raise an exception that includes 0MQ's error message.
 */
static void raise_exception (JNIEnv *env, int err)
{
    //  Get exception class.
    jclass exception_class = env->FindClass ("java/lang/Exception");
    assert (exception_class);

    //  Get text description of the exception.
    const char *err_msg = zmq_strerror (err);

    //  Raise the exception.
    int rc = env->ThrowNew (exception_class, err_msg);
    env->DeleteLocalRef (exception_class);

    assert (rc == 0);
}

/**
 * Called to construct a Java Context object.
 */
JNIEXPORT void JNICALL Java_org_zmq_Context_construct (JNIEnv *env,
    jobject obj, jint app_threads, jint io_threads, jint flags)
{
    void *c = get_context (env, obj);
    assert (!c);

    c = zmq_init (app_threads, io_threads, flags);
    put_context (env, obj, c);

    if (!c) {
        raise_exception (env, errno);
        return;
    }
}

/**
 * Called to destroy a Java Context object.
 */
JNIEXPORT void JNICALL Java_org_zmq_Context_finalize (JNIEnv *env,
    jobject obj)
{
    void *c = get_context (env, obj);
    assert (c);

    int rc = zmq_term (c);
    put_context (env, obj, NULL);
    assert (rc == 0);
}