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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #define LOG_TAG "simplejni native.cpp"
     18 #include <utils/Log.h>
     19 
     20 #include <stdio.h>
     21 
     22 #include "jni.h"
     23 
     24 static jint
     25 add(JNIEnv *env, jobject thiz, jint a, jint b) {
     26 int result = a + b;
     27     ALOGI("%d + %d = %d", a, b, result);
     28     return result;
     29 }
     30 
     31 static const char *classPathName = "com/example/android/simplejni/Native";
     32 
     33 static JNINativeMethod methods[] = {
     34   {"add", "(II)I", (void*)add },
     35 };
     36 
     37 /*
     38  * Register several native methods for one class.
     39  */
     40 static int registerNativeMethods(JNIEnv* env, const char* className,
     41     JNINativeMethod* gMethods, int numMethods)
     42 {
     43     jclass clazz;
     44 
     45     clazz = env->FindClass(className);
     46     if (clazz == NULL) {
     47         ALOGE("Native registration unable to find class '%s'", className);
     48         return JNI_FALSE;
     49     }
     50     if (env->RegisterNatives(clazz, gMethods, numMethods) < 0) {
     51         ALOGE("RegisterNatives failed for '%s'", className);
     52         return JNI_FALSE;
     53     }
     54 
     55     return JNI_TRUE;
     56 }
     57 
     58 /*
     59  * Register native methods for all classes we know about.
     60  *
     61  * returns JNI_TRUE on success.
     62  */
     63 static int registerNatives(JNIEnv* env)
     64 {
     65   if (!registerNativeMethods(env, classPathName,
     66                  methods, sizeof(methods) / sizeof(methods[0]))) {
     67     return JNI_FALSE;
     68   }
     69 
     70   return JNI_TRUE;
     71 }
     72 
     73 
     74 // ----------------------------------------------------------------------------
     75 
     76 /*
     77  * This is called by the VM when the shared library is first loaded.
     78  */
     79 
     80 typedef union {
     81     JNIEnv* env;
     82     void* venv;
     83 } UnionJNIEnvToVoid;
     84 
     85 jint JNI_OnLoad(JavaVM* vm, void* reserved)
     86 {
     87     UnionJNIEnvToVoid uenv;
     88     uenv.venv = NULL;
     89     jint result = -1;
     90     JNIEnv* env = NULL;
     91 
     92     ALOGI("JNI_OnLoad");
     93 
     94     if (vm->GetEnv(&uenv.venv, JNI_VERSION_1_4) != JNI_OK) {
     95         ALOGE("ERROR: GetEnv failed");
     96         goto bail;
     97     }
     98     env = uenv.env;
     99 
    100     if (registerNatives(env) != JNI_TRUE) {
    101         ALOGE("ERROR: registerNatives failed");
    102         goto bail;
    103     }
    104 
    105     result = JNI_VERSION_1_4;
    106 
    107 bail:
    108     return result;
    109 }
    110