Question

我试图在Java中使用O_direct而不是Linux中的JNI。这是java部分：

public class jnitest {
    static {
        System.loadLibrary("jnitest"); // Load native library at runtime
                                       // hello.dll (Windows) or libhello.so (Unixes)
    }
    private native void test();
    private native void write(String path, byte[] chunkpayload);
    public static void main(String[] args) {
        try{
            jnitest t=new jnitest();
            byte[] chunk=new byte[5];
            chunk[0]=1;
            chunk[1]=2;
            chunk[2]=3;
            chunk[3]=4;
            chunk[4]=5;
            String s="outtest";
            t.write(s,chunk);
        }catch(Exception e){
            System.out.println("fehler lol");
        }
    }
}

这是C部分：

#define _GNU_SOURCE
#include <jni.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include "jnitest.h"
#define BLOCKSIZE 512

JNIEXPORT void JNICALL Java_jnitest_write(JNIEnv *env, jobject obj, jstring jpath, jbyteArray jchunkpayload){
    const char *path=(*env)->GetStringUTFChars(env, jpath, 0);
    printf("path=%s \n",path);
    (*env)->ReleaseStringUTFChars(env, jpath, path);
    int len = (*env)->GetArrayLength (env,jchunkpayload);
    printf("lenght= %d \n",len);
    unsigned char* payload =(*env)->GetByteArrayElements(env,jchunkpayload,0);
    int i=0;
    for(i=0;i<len-1;i++){
        printf("%02x \n",(int)payload[i]);  
    }
    void *buffer; 
    int fd = open(path, O_SYNC|O_APPEND|O_CREAT|O_DIRECT);
    posix_memalign(&buffer,BLOCKSIZE,BLOCKSIZE);
    memcpy(buffer,payload,len);
    write(fd,buffer,BLOCKSIZE);
    printf("writen to file\n");
    (*env)->ReleaseByteArrayElements(env,jchunkpayload,payload,JNI_ABORT);
    free(buffer);
    return;
}

JNIEXPORT void JNICALL Java_jnitest_test(JNIEnv *env, jobject obj){
    printf("test\n");
    return;
}

程序不会失败，但数据永远不会被写入。我知道我可以使用JNA，但我想使用JNI。有人有一个使用O_direct在JNI上用java编写字节数组的工作示例吗？

Java使用O_direct在JNI上编写字节数组

0 个答案: