#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include "ipc_msg.h"


int file_exists(char *filename)
{
  struct stat   buffer;   
  return (stat (filename, &buffer) == 0);
}
/**
 * @brief 发送目标文件描述符
 * @param fd		传递信息的 UNIX 域 文件描述符
 * @param fd_to_send	待发送的文件描述符
 */
int  send_fd_args_sendmsg(int  fd, int fd_to_send, pid_t pid, void **ppdata, int len)
{
	struct iovec iov[1];
	struct msghdr msg;
  int control_len = 0;  
  int ret = 0;
  memfd_data_st memfd_data;
	struct cmsghdr cm;			/* 这是辅助数据头部结构体，文件描述符就是通过这个结构体以及后面的数据部分发送的 */
  
   control_len = CMSG_SPACE(sizeof(memfd_data_st) + len);
   char * recv_buf = (char *)malloc(control_len); 

   if(NULL != recv_buf)
   {
        return -1;
   }   

	iov[0].iov_base = recv_buf;
	iov[0].iov_len = 1;
	msg.msg_name = NULL;
	msg.msg_namelen = 0;
	msg.msg_iov = iov;
	msg.msg_iovlen = 1;

  memfd_data.memfd = fd_to_send;
  memfd_data.pid = pid;
  memfd_data.data = *ppdata;
  memfd_data.len = len;
  

	cm.cmsg_len = control_len;	/* 辅助数据的字节数，包扩头部和真正的数据 */
	cm.cmsg_level = SOL_SOCKET;	/* 表示原始协议级别，与 setsockopt 的 level 参数相同 */
	cm.cmsg_type = SCM_RIGHTS;	/* 控制信息类型，SCM_RIGHTS 表示传送的内容是访问权 */
	*(memfd_data_st*)CMSG_DATA(&cm) = memfd_data;/* 设置真正数据部分为我们想发送的文件描述符 */
	msg.msg_control = &cm;		/* 设置辅助数据 */
	msg.msg_controllen = control_len;

	ret = sendmsg(fd, &msg, 0);
  free(recv_buf);
  return ret;
}

/**
 * @brief 发送目标文件描述符
 * @param fd		传递信息的 UNIX 域 文件描述符
 * @param fd_to_send	待发送的文件描述符
 */
int  send_fd_sendmsg(int  fd, memfd_data_st** ppmemfd_data)
{
  memfd_data_st *ptr_memfd_data = *ppmemfd_data; 
  return send_fd_args_sendmsg(fd, ptr_memfd_data->memfd, ptr_memfd_data->pid, &ptr_memfd_data->data, ptr_memfd_data->len);
}

/**
 * @brief 接受文件描述符
 * @param fd 传递信息的 UNIX 域 文件描述符
 */
int recv_fd_recvmsg(int  fd, memfd_data_st** ppmemfd_data)
{
  struct iovec iov[1];
  struct msghdr msg;
  char recv_buf[MAX_LEN];
  int ret = -1; 
  int control_len = 0;
  struct cmsghdr cm;

  iov[0].iov_base = recv_buf;
	iov[0].iov_len = 1;
	msg.msg_name = NULL;
	msg.msg_namelen = 0;
	msg.msg_iov = iov;
	msg.msg_iovlen = 1;

  control_len = CMSG_SPACE(sizeof(memfd_data_st) + MAX_LEN);

	msg.msg_control = &cm;
	msg.msg_controllen = control_len;

	ret = recvmsg(fd, &msg, 0);
  if(ret < 0)
  {
    ret = -1;
  }
  
  int off = offsetof(memfd_data_st, len);
  int len = *(int*)((char *)CMSG_DATA(&cm) + off);
  control_len = CMSG_SPACE(sizeof(memfd_data_st) + len);
  *ppmemfd_data = (memfd_data_st *)malloc(control_len);
  if(*ppmemfd_data == NULL)
  {
      return -1;
  }
  memset(*ppmemfd_data, 0, control_len);
  memcpy(*ppmemfd_data, CMSG_DATA(&cm),  control_len);
  return ret;
}