上一小节介绍了Binder系统的框架,为了加深理解,这小节别写一个示例程序,最要有以下程序c文件
1.test_server.c:
提供“hello”服务,
提供函数:void sayhello(void),int sayhello_to(char *name)。
下面我们开始编写test_server.c。
test_server.c
首先我们复制文件SDK\frameworks\native\cmds\servicemanager\bctest.c重命令为test_server.c,上小节多次提到该文件为一个半成品,我们在现有的基础上进行修改。存放在文件夹APP_0003_binder_C_App下。然后打开test_server.c,编写如下:
/* Copyright 2008 The Android Open Source Project
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <linux/types.h>
#include <stdbool.h>
#include "binder.h"
#include "test_server.h"
#include <sys/types.h>
#define ALOGI(x...) fprintf(stderr, "svcmgr: " x)
#define ALOGE(x...) fprintf(stderr, "svcmgr: " x)
uint32_t svcmgr_lookup(struct binder_state *bs, uint32_t target, const char *name)
{
uint32_t handle;
unsigned iodata[512/4];
struct binder_io msg, reply;
bio_init(&msg, iodata, sizeof(iodata), 4);
bio_put_uint32(&msg, 0); // strict mode header
bio_put_string16_x(&msg, SVC_MGR_NAME);
bio_put_string16_x(&msg, name);
if (binder_call(bs, &msg, &reply, target, SVC_MGR_CHECK_SERVICE))
return 0;
handle = bio_get_ref(&reply);
if (handle)
binder_acquire(bs, handle);
binder_done(bs, &msg, &reply);
return handle;
}
int svcmgr_publish(struct binder_state *bs, uint32_t target, const char *name, void *ptr)
{
int status;
unsigned iodata[512/4];
struct binder_io msg, reply;
bio_init(&msg, iodata, sizeof(iodata), 4);
bio_put_uint32(&msg, 0); // strict mode header
bio_put_string16_x(&msg, SVC_MGR_NAME);
bio_put_string16_x(&msg, name);
bio_put_obj(&msg, ptr);
if (binder_call(bs, &msg, &reply, target, SVC_MGR_ADD_SERVICE))
return -1;
status = bio_get_uint32(&reply);
binder_done(bs, &msg, &reply);
return status;
}
unsigned token;
void sayhello(void)
{
static int cnt = 0;
fprintf(stderr,"say hello : %d\n", cnt++);
}
int sayhello_to(char *name)
{
static int cnt = 0;
fprintf(stderr,"say hello to %s : %d\n", name, cnt++);
return cnt;
}
int hello_service_handler(struct binder_state *bs,
struct binder_transaction_data *txn,
struct binder_io *msg,
struct binder_io *reply)
{
/*根据txn->code知道要调用那一个函数
*如果需要参数,可以从msg取出
*如果要返回结果,可以把结果放入reply
*/
/*提供两个函数:sayhello,sayhello_to
*/
uint16_t *s;
char name[512] = {0};
size_t len;
uint32_t handle;
uint32_t strict_policy;
int i = 0;
//ALOGI("target=%p code=%d pid=%d uid=%d\n",
// (void*) txn->target.ptr, txn->code, txn->sender_pid, txn->sender_euid);
if (txn->target.ptr != BINDER_SERVICE_MANAGER)
return -1;
if (txn->code == PING_TRANSACTION)
return 0;
// Equivalent to Parcel::enforceInterface(), reading the RPC
// header with the strict mode policy mask and the interface name.
// Note that we ignore the strict_policy and don't propagate it
// further (since we do no outbound RPCs anyway).
strict_policy = bio_get_uint32(msg);
switch(txn->code) {
case HELLO_SVR_CMD_SAYHELLO:
sayhello();
break;
case HELLO_SVR_CMD_SAYHELLO_TO:
/*从msg里取出字符串*/
s = bio_get_string16(msg, &len);
if (s == NULL) {
return -1;
}
for(i=0; i<len; i++)
name[i] = s[i];
name[i] = '\0';
/*处理*/
i = sayhello_to(name);
/*把结果放入reply*/
bio_put_uint32(reply,i);
break;
case SVC_MGR_ADD_SERVICE:
break;
case SVC_MGR_LIST_SERVICES:
break;
default:
ALOGE("unknown code %d\n", txn->code);
return -1;
}
bio_put_uint32(reply, 0);
return 0;
}
int main(int argc, char **argv)
{
struct binder_state *bs;
uint32_t svcmgr = BINDER_SERVICE_MANAGER;
uint32_t handle;
int ret;
bs = binder_open(128*1024);
if (!bs) {
fprintf(stderr, "failed to open binder driver\n");
return -1;
}
/*add server*/
//向进程svcmgr注册一个"hello"服务
ret = svcmgr_publish(bs,svcmgr,"hello","123");
if (!ret) {
fprintf(stderr, "failed to publish hello service\n");
return -1;
}
ret = svcmgr_publish(bs,svcmgr,"goodbye","1234");
if (!ret) {
fprintf(stderr, "failed to publish goodbye service\n");
return -1;
}
#if 0
while(1){
/*read data*/
/*parse data,and process*/
/*reply*/
}
#endif
binder_loop(bs, hello_service_handler);
return 0;
}
简述代码的流程如下
main(int argc, char **argv) //从main函数开始
bs = binder_open(128*1024); //打开binder驱动
svcmgr_publish(bs,svcmgr,"hello",NULL)
下面我们再编写 test_client.c
test_client.c
/* Copyright 2008 The Android Open Source Project
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <linux/types.h>
#include <stdbool.h>
#include "binder.h"
#include "test_server.h"
#include <sys/types.h>
uint32_t svcmgr_lookup(struct binder_state *bs, uint32_t target, const char *name)
{
uint32_t handle;
unsigned iodata[512/4];
struct binder_io msg, reply;
bio_init(&msg, iodata, sizeof(iodata), 4);
bio_put_uint32(&msg, 0); // strict mode header
bio_put_string16_x(&msg, SVC_MGR_NAME);
bio_put_string16_x(&msg, name);
if (binder_call(bs, &msg, &reply, target, SVC_MGR_CHECK_SERVICE))
return 0;
handle = bio_get_ref(&reply);
if (handle)
binder_acquire(bs, handle);
binder_done(bs, &msg, &reply);
return handle;
}
int svcmgr_publish(struct binder_state *bs, uint32_t target, const char *name, void *ptr)
{
int status;
unsigned iodata[512/4];
struct binder_io msg, reply;
bio_init(&msg, iodata, sizeof(iodata), 4);
bio_put_uint32(&msg, 0); // strict mode header
bio_put_string16_x(&msg, SVC_MGR_NAME);
bio_put_string16_x(&msg, name);
bio_put_obj(&msg, ptr);
if (binder_call(bs, &msg, &reply, target, SVC_MGR_ADD_SERVICE))
return -1;
status = bio_get_uint32(&reply);
binder_done(bs, &msg, &reply);
return status;
}
struct binder_state *g_bs;
uint32_t g_handle;
void sayhello(void)
{
unsigned iodata[512/4];
struct binder_io msg, reply;
/*构造一个binder_io*/
bio_init(&msg, iodata, sizeof(iodata), 4);
bio_put_uint32(&msg, 0); // strict mode header(此处必须填写一个0)
/*放入参数*/
/*调用binder_call*/
if (binder_call(g_bs, &msg, &reply, g_handle, HELLO_SVR_CMD_SAYHELLO))
return ;
/*从reply中解析出返回值*/
binder_done(g_bs, &msg, &reply);
}
int sayhello_to(char *name)
{
unsigned iodata[512/4];
struct binder_io msg, reply;
int ret;
/*构造一个binder_io*/
bio_init(&msg, iodata, sizeof(iodata), 4);
bio_put_uint32(&msg, 0); // strict mode header(此处必须填写一个0)
/*放入参数*/
bio_put_string16_x(&msg, name);
/*调用binder_call*/
if (binder_call(g_bs, &msg, &reply, g_handle, HELLO_SVR_CMD_SAYHELLO_TO))
return 0;
/*从reply中解析出返回值*/
ret = bio_get_uint32(&reply);
binder_done(g_bs, &msg, &reply);
return ret;
}
/*程序如何运行
* ./test_client hello
* ./test_client hello <name>
*/
unsigned token;
int main(int argc, char **argv)
{
struct binder_state *bs;
uint32_t svcmgr = BINDER_SERVICE_MANAGER;
uint32_t handle;
int ret;
bs = binder_open(128*1024);
if (!bs) {
fprintf(stderr, "failed to open binder driver\n");
return -1;
}
g_bs = bs;
/*get service(服务)*/
handle = svcmgr_lookup(bs, svcmgr, "hello");
if (!handle){
fprintf(stderr,"failed to get hello service\n");
return -1;
}
g_handle = handle;
/*send data to server(服务器)*/
if(argc == 2){
sayhello();
}else if(argc == 3){
ret = sayhello_to(argv[2]);
fprintf(stderr,"get ret of sayhello_to %d\n",ret);
}
binder_release(bs, handle);
return 0;
}
程序编译
编写好程序之后,我们肯定需要去编译,那么我们应该怎么编译呢?我们cd到SDK/frameworks\native\cmds\servicemanager\目录下,然后假装修改一下binder.c,退出保存之后,执行命令如下:
source build/envsetup.sh
lunch rk3399_all-userdebug
mmm ./ showcommands