libuv源码阅读(13)--plugin

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

#include <uv.h>

#include "plugin.h"

typedef void (*init_plugin_function)();

void mfp_register(const char *name) {
    fprintf(stderr, "Registered plugin \"%s\"\n", name);
}

int main(int argc, char **argv) {
    if (argc == 1) {
        fprintf(stderr, "Usage: %s [plugin1] [plugin2] ...\n", argv[0]);
        return 0;
    }

    uv_lib_t *lib = (uv_lib_t*) malloc(sizeof(uv_lib_t));
    while (--argc) {
        fprintf(stderr, "Loading %s\n", argv[argc]);
        if (uv_dlopen(argv[argc], lib)) {
            fprintf(stderr, "Error: %s\n", uv_dlerror(lib));
            continue;
        }

        init_plugin_function init_plugin;
        if (uv_dlsym(lib, "initialize", (void **) &init_plugin)) {
            fprintf(stderr, "dlsym error: %s\n", uv_dlerror(lib));
            continue;
        }

        init_plugin();
    }

    return 0;
}

#include "plugin.h"

void initialize() {
    mfp_register("Hello World!");
}

#ifndef UVBOOK_PLUGIN_SYSTEM
#define UVBOOK_PLUGIN_SYSTEM

// Plugin authors should use this to register their plugins with mfp.
void mfp_register(const char *name);

#endif

typedef struct {
  void* handle;
  char* errmsg;
} uv_lib_t;

static int uv__dlerror(uv_lib_t* lib);

// 连接动态库 得到引用句柄
int uv_dlopen(const char* filename, uv_lib_t* lib) {
  dlerror(); /* Reset error status. */
  lib->errmsg = NULL;
  lib->handle = dlopen(filename, RTLD_LAZY);
  return lib->handle ? 0 : uv__dlerror(lib);
}


void uv_dlclose(uv_lib_t* lib) {
  uv__free(lib->errmsg);
  lib->errmsg = NULL;

  if (lib->handle) {
    /* Ignore errors. No good way to signal them without leaking memory. */
    dlclose(lib->handle);
    lib->handle = NULL;
  }
}

// 获取句柄指定方法 注意第三个参数 修改指传入ptr指针所指向 函数指针
int uv_dlsym(uv_lib_t* lib, const char* name, void** ptr) {
  dlerror(); /* Reset error status. */
  *ptr = dlsym(lib->handle, name);
  return uv__dlerror(lib);
}


const char* uv_dlerror(const uv_lib_t* lib) {
  return lib->errmsg ? lib->errmsg : "no error";
}


static int uv__dlerror(uv_lib_t* lib) {
  const char* errmsg;

  uv__free(lib->errmsg);

  errmsg = dlerror();

  if (errmsg) {
    lib->errmsg = uv__strdup(errmsg);
    return -1;
  }
  else {
    lib->errmsg = NULL;
    return 0;
  }
}