Question

我正在尝试在android ndk项目中使用canutils。包canutils通常编译成可执行文件，但我还没有找到一种方法来在ndk项目中包含这些可执行文件。所以我现在正在做的只是加载这样的共享库：

static{
System.loadLibrary("cansend");
}
public native void cansend();

我已经改变了android-mk来构建共享库。

我的c代码看起来像这个cansend.c作为一个例子：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <net/if.h>
#include <sys/ioctl.h>
#include <sys/socket.h>

#include <linux/can.h>
#include <linux/can/raw.h>

#include "lib.h"

int main(int argc, char **argv)
{
int s; /* can raw socket */ 
int required_mtu;
int mtu;
int enable_canfd = 1;
struct sockaddr_can addr;
struct canfd_frame frame;
struct ifreq ifr;

/* check command line options */
if (argc != 3) {
    fprintf(stderr, "Usage: %s <device> <can_frame>.\n", argv[0]);
    return 1;
}

/* parse CAN frame */
required_mtu = parse_canframe(argv[2], &frame);
if (!required_mtu){
    fprintf(stderr, "\nWrong CAN-frame format! Try:\n\n");
    fprintf(stderr, "    <can_id>#{R|data}          for CAN 2.0 frames\n");
    fprintf(stderr, "    <can_id>##<flags>{data}    for CAN FD frames\n\n");
    fprintf(stderr, "<can_id> can have 3 (SFF) or 8 (EFF) hex chars\n");
    fprintf(stderr, "{data} has 0..8 (0..64 CAN FD) ASCII hex-values (optionally");
    fprintf(stderr, " seperated by '.')\n");
    fprintf(stderr, "<flags> a single ASCII Hex value (0 .. F) which defines");
    fprintf(stderr, " canfd_frame.flags\n\n");
    fprintf(stderr, "e.g. 5A1#11.2233.44556677.88 / 123#DEADBEEF / 5AA# / ");
    fprintf(stderr, "123##1 / 213##311\n     1F334455#1122334455667788 / 123#R ");
    fprintf(stderr, "for remote transmission request.\n\n");
    return 1;
}

/* open socket */
if ((s = socket(PF_CAN, SOCK_RAW, CAN_RAW)) < 0) {
    perror("socket");
    return 1;
}

addr.can_family = AF_CAN;

strcpy(ifr.ifr_name, argv[1]);
if (ioctl(s, SIOCGIFINDEX, &ifr) < 0) {
    perror("SIOCGIFINDEX");
    return 1;
}
addr.can_ifindex = ifr.ifr_ifindex;

if (required_mtu > CAN_MTU) {

    /* check if the frame fits into the CAN netdevice */
    if (ioctl(s, SIOCGIFMTU, &ifr) < 0) {
        perror("SIOCGIFMTU");
        return 1;
    }
    mtu = ifr.ifr_mtu;

    if (mtu != CANFD_MTU) {
        printf("CAN interface ist not CAN FD capable - sorry.\n");
        return 1;
    }

    /* interface is ok - try to switch the socket into CAN FD mode */
    if (setsockopt(s, SOL_CAN_RAW, CAN_RAW_FD_FRAMES,
               &enable_canfd, sizeof(enable_canfd))){
        printf("error when enabling CAN FD support\n");
        return 1;
    }

    /* ensure discrete CAN FD length values 0..8, 12, 16, 20, 24, 32, 64 */
    frame.len = can_dlc2len(can_len2dlc(frame.len));
}

/* disable default receive filter on this RAW socket */
/* This is obsolete as we do not read from the socket at all, but for */
/* this reason we can remove the receive list in the Kernel to save a */
/* little (really a very little!) CPU usage.                          */
setsockopt(s, SOL_CAN_RAW, CAN_RAW_FILTER, NULL, 0);

if (bind(s, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
    perror("bind");
    return 1;
}

/* send frame */
if (write(s, &frame, required_mtu) != required_mtu) {
    perror("write");
    return 1;
}

close(s);

return 0;
}

我希望能够在我的android-ndk项目中使用这个cansend方法。我是否需要调整c代码并从代码中创建共享库，或者我是否需要使用可执行文件并调用并以某种方式将其包含在我的项目中以便能够使用它？

Answer 1

重命名主要功能或在其周围放置另一个包装器。如果您希望将本机函数命名为cansend()，那么您的包装函数应该是这样的：

#ifdef __cplusplus
extern "C" {
#endif

JNIEXPORT 
void
Java_com_aaa_bbb_ccc_cansend( JNIEnv* env, jobject thiz);

#ifdef __cplusplus
}
#endif

此处，com_aaa_bbb_ccc来自您的java代码的包名，其中包含public native void cansend();。

例如，如果您的包名称为com.example.test，则您的函数名称将为：

Java_com_example_test_cansend();

在android ndk项目中使用c可执行文件/方法

1 个答案: