/*
 * Copyright (c) 2014, 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 <windows.h>

#include <jni.h>
#include "jni_util.h"
#include "sun_misc_SystemRandomImpl.h"

static BOOLEAN (APIENTRY *rtlGenRandomFn)(void*, ULONG) = 0;

/*
 * Load library (increment reference count), obtain the rtlGenRandomFn
 * function pointer and return a library handle
 */
JNIEXPORT jlong JNICALL Java_sun_misc_SystemRandomImpl_init0
  (JNIEnv *env, jclass clazz)
{
    HMODULE hLib = LoadLibraryA("ADVAPI32.DLL");
    if (!hLib) {
        JNU_ThrowByName(env, "java/lang/UnsupportedOperationException", "Can't load ADVAPI32.DLL");
        return 0;
    }

    if (!rtlGenRandomFn) {
        rtlGenRandomFn = (BOOLEAN (APIENTRY *)(void*,ULONG))GetProcAddress(hLib, "SystemFunction036");
    }

    if (!rtlGenRandomFn) {
        FreeLibrary(hLib);
        JNU_ThrowByName(env, "java/lang/UnsupportedOperationException", "Can't obtain ADVAPI32!RtlGenRandom function.");
        return 0;
    }

    return (jlong)hLib;
}

/*
 * Obtain random bytes
 */
JNIEXPORT void JNICALL Java_sun_misc_SystemRandomImpl_getBytes0
  (JNIEnv *env, jclass clazz, jbyteArray randArray)
{
    jsize numBytes = (*env)->GetArrayLength(env, randArray);
    jbyte* randBytes = (*env)->GetByteArrayElements(env, randArray, NULL);
    if (randBytes == NULL) {
        JNU_ThrowByName(env, "java/lang/RuntimeException", "Can't obtain byte[] elements.");
        return;
    }

    if (!rtlGenRandomFn(randBytes, numBytes)) {
        (*env)->ReleaseByteArrayElements(env, randArray, randBytes, 0);
        JNU_ThrowByName(env, "java/lang/RuntimeException", "RtlGenRandom function failed.");
        return;
    }

    (*env)->ReleaseByteArrayElements(env, randArray, randBytes, 0);
}

/*
 * Unload the library (decrement reference count)
 */
JNIEXPORT void JNICALL Java_sun_misc_SystemRandomImpl_deinit0
  (JNIEnv *env, jclass clazz, jlong libraryHandle)
{
    FreeLibrary((HMODULE) libraryHandle);
}