core/jni/android_util_FileObserver.cpp

/* //device/libs/android_runtime/android_util_FileObserver.cpp
**
** Copyright 2006, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License"); 
** you may not use this file except in compliance with the License. 
** You may obtain a copy of the License at 
**
**     http://www.apache.org/licenses/LICENSE-2.0 
**
** Unless required by applicable law or agreed to in writing, software 
** distributed under the License is distributed on an "AS IS" BASIS, 
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
** See the License for the specific language governing permissions and 
** limitations under the License.
*/

#include "JNIHelp.h"
#include "jni.h"
#include "utils/Log.h"
#include "utils/misc.h"
#include "android_runtime/AndroidRuntime.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <errno.h>

#ifdef HAVE_INOTIFY
#include <sys/inotify.h>
#endif

namespace android {

static jmethodID method_onEvent;

static jint android_os_fileobserver_init(JNIEnv* env, jobject object)
{
#ifdef HAVE_INOTIFY

    return (jint)inotify_init();    

#else // HAVE_INOTIFY

    return -1;

#endif // HAVE_INOTIFY
}

static void android_os_fileobserver_observe(JNIEnv* env, jobject object, jint fd)
{
#ifdef HAVE_INOTIFY
 
    char event_buf[512];
    struct inotify_event* event;
         
    while (1)
    {
        int event_pos = 0;
        int num_bytes = read(fd, event_buf, sizeof(event_buf));
        
        if (num_bytes < (int)sizeof(*event))
        {
            if (errno == EINTR)
                continue;

            ALOGE("***** ERROR! android_os_fileobserver_observe() got a short event!");
            return;
        }
        
        while (num_bytes >= (int)sizeof(*event))
        {
            int event_size;
            event = (struct inotify_event *)(event_buf + event_pos);

            jstring path = NULL;
            
            if (event->len > 0)
            {
                path = env->NewStringUTF(event->name);
            }

            env->CallVoidMethod(object, method_onEvent, event->wd, event->mask, path);
            if (env->ExceptionCheck()) {
                env->ExceptionDescribe();
                env->ExceptionClear();
            }
            if (path != NULL)
            {
                env->DeleteLocalRef(path);
            }

            event_size = sizeof(*event) + event->len;
            num_bytes -= event_size;
            event_pos += event_size;
        }
    }
    
#endif // HAVE_INOTIFY
}

static jint android_os_fileobserver_startWatching(JNIEnv* env, jobject object, jint fd, jstring pathString, jint mask)
{
    int res = -1;
    
#ifdef HAVE_INOTIFY
   
    if (fd >= 0)
    {
        const char* path = env->GetStringUTFChars(pathString, NULL);
        
        res = inotify_add_watch(fd, path, mask);
        
        env->ReleaseStringUTFChars(pathString, path);
    }

#endif // HAVE_INOTIFY
    
    return res;
}

static void android_os_fileobserver_stopWatching(JNIEnv* env, jobject object, jint fd, jint wfd)
{
#ifdef HAVE_INOTIFY

    inotify_rm_watch((int)fd, (uint32_t)wfd);

#endif // HAVE_INOTIFY
}

static JNINativeMethod sMethods[] = {
     /* name, signature, funcPtr */
    { "init", "()I", (void*)android_os_fileobserver_init },
    { "observe", "(I)V", (void*)android_os_fileobserver_observe },
    { "startWatching", "(ILjava/lang/String;I)I", (void*)android_os_fileobserver_startWatching },
    { "stopWatching", "(II)V", (void*)android_os_fileobserver_stopWatching }
    
};

int register_android_os_FileObserver(JNIEnv* env)
{
    jclass clazz;

    clazz = env->FindClass("android/os/FileObserver$ObserverThread");

    if (clazz == NULL)
	{
        ALOGE("Can't find android/os/FileObserver$ObserverThread");
        return -1;
    }

    method_onEvent = env->GetMethodID(clazz, "onEvent", "(IILjava/lang/String;)V");
    if (method_onEvent == NULL)
    {
        ALOGE("Can't find FileObserver.onEvent(int, int, String)");
        return -1;
    }

    return AndroidRuntime::registerNativeMethods(env, "android/os/FileObserver$ObserverThread", sMethods, NELEM(sMethods));
}

} /* namespace android */