lock.c

一个linux下的ftp程序。它是使用文件传输协议的一系列程序的集合。

#include <string.h>
#include <stdio.h>
#include "lock.h"

/* ************ Locking functions ***************** */
#ifndef FSP_NOLOCKING

static char code_str[] =
    "0123456789:_ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

static void make_key_string(	FSP_LOCK *lock,
                                unsigned long server_addr,
			   	unsigned long server_port)
{
  unsigned long v1, v2;
  char *p;

  strcpy(lock->key_string,FSP_KEY_PREFIX);
  for(p = lock->key_string; *p; p++);
  v1 = server_addr;
  v2 = server_port;

  *p++ = code_str[v1 & 0x3f]; v1 >>= 6;
  *p++ = code_str[v1 & 0x3f]; v1 >>= 6;
  *p++ = code_str[v1 & 0x3f]; v1 >>= 6;
  v1 = v1 | (v2 << (32-3*6));
  *p++ = code_str[v1 & 0x3f]; v1 >>= 6;
  *p++ = code_str[v1 & 0x3f]; v1 >>= 6;
  *p++ = code_str[v1 & 0x3f]; v1 >>= 6;
  *p++ = code_str[v1 & 0x3f]; v1 >>= 6;
  *p++ = code_str[v1 & 0x3f]; v1 >>= 6;
  *p   = 0;
}
#endif

/********************************************************************/
/******* For those systems that has SysV shared memory + semop ******/
/********************************************************************/
#ifdef FSP_USE_SHAREMEM_AND_SEMOP

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/sem.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>

#ifdef _SEM_SEMUN_UNDEFINED
union semun
{
  int val;
  struct semid_ds *buf;
  unsigned short int *array;
  struct seminfo *__buf;
};
#endif

unsigned short client_get_key (FSP_LOCK *lock)
{
  struct sembuf sem;
  sem.sem_num = 0;
  sem.sem_op = -1;
  sem.sem_flg = SEM_UNDO;
  
  if(semop(lock->lock_sem,&sem,1) == -1 )
  {
      perror("semop lock");
  }
  return(*lock->share_key);
}

void client_set_key (FSP_LOCK *lock,unsigned short key)
{
  struct sembuf sem;

  sem.sem_num = 0;
  sem.sem_op  = 1;
  sem.sem_flg = SEM_UNDO;

  *lock->share_key = key;
  if(semop(lock->lock_sem,&sem,1) == -1) {
    perror("semop unlock");
  }
}

int client_init_key (FSP_LOCK *lock,
                            unsigned long server_addr,
			    unsigned short server_port)
{
  mode_t omask;
  key_t lock_key;
  int fd;
  union semun sun;
  struct sembuf sem;

  make_key_string(lock,server_addr,server_port);

  omask = umask(0);
  fd = open(lock->key_string,O_RDWR|O_CREAT,0666);
  umask(omask);
  close(fd);

  if((lock_key = ftok(lock->key_string,238)) == -1) {
    perror("ftok");
    return -1;
  }

  if((lock->lock_shm = shmget(lock_key,2*sizeof(unsigned int),IPC_CREAT|0666)) == -1) {
    perror("shmget");
    return -1;
  }

  if(!(lock->share_key = (unsigned int *) shmat(lock->lock_shm,NULL,0))) {
    perror("shmat");
    return -1;
  }

  if((lock->lock_sem = semget(lock_key,0,0)) == -1) {
      /* create a new semaphore and init it */
      if((lock->lock_sem = semget(lock_key,2,IPC_CREAT|0666)) == -1) {
	  perror("semget");
	  return -1;
      }
      /* we need to init this semaphore */
      sun.val=1;
      if(semctl(lock->lock_sem,0,SETVAL,sun) == -1)
      {
	  perror("semctl setval");
	  return -1;
      }
  }

  /* increase in use counter */
  sem.sem_num = 1;
  sem.sem_op = 1;
  sem.sem_flg = SEM_UNDO;

  if(semop(lock->lock_sem,&sem,1) == -1) {
      perror("semop incuse");
  }

  return 0;
}

void client_destroy_key(FSP_LOCK *lock)
{
    int rc;
    struct sembuf sem;
    
    if (shmdt(lock->share_key) < 0)
    {
	perror("shmdt");
	return;
    }
    /* check if we are only one process holding lock */
    rc = semctl(lock->lock_sem,1,GETVAL);
    if (rc == 1)
    {
	/* safe to destroy */
	if (
	     (semctl(lock->lock_sem,0,IPC_RMID) < 0) ||
	     (shmctl(lock->lock_shm,IPC_RMID,NULL) < 0) ||
	     (unlink(lock->key_string) < 0) )
	    rc=0;/* ignore cleanup errors */
    }
    else 
	if(rc > 1)
	{
	      /* we need to decrease sem. */
	      sem.sem_num = 1;
	      sem.sem_op = -1;
	      sem.sem_flg = SEM_UNDO;

	      if(semop(lock->lock_sem,&sem,1) == -1) {
		  perror("semop decuse");
	      }
	}
}
#endif


/********************************************************************/
/******* For those who do not want to use locking *******************/
/********************************************************************/
#ifdef FSP_NOLOCKING

unsigned short client_get_key (FSP_LOCK *lock)
{
    return lock->share_key;
}

void client_set_key (FSP_LOCK *lock,unsigned short key)
{
    lock->share_key=key;
}

int client_init_key (FSP_LOCK *lock,
                            unsigned long server_addr,
			    unsigned short server_port)
{
    return 0;
}

void client_destroy_key(FSP_LOCK *lock)
{
    return;
}
#endif

/********************************************************************/
/******* For those systems that has lockf function call *************/
/********************************************************************/
#ifdef FSP_USE_LOCKF

#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

unsigned short client_get_key (FSP_LOCK *lock)
{
     unsigned int okey;

     if (lockf(lock->lock_fd, F_LOCK, sizeof(okey)) < 0)
     {
	    perror("lockf");
     }

     if (read(lock->lock_fd, &okey, sizeof(okey)) < 0)
     {
	    perror("readlk");
     }

     if (lseek(lock->lock_fd, 0L, 0) < 0)
     {
            perror("seek");
     }

    return(okey);
}

void client_set_key (FSP_LOCK *lock,unsigned short nkey)
{
    unsigned int key;

    key=nkey;

    if (write(lock->lock_fd, &key, sizeof(key)) < 0)
    {
	perror("write");
    }
    if (lseek(lock->lock_fd, 0L, 0) < 0)
    {
	perror("seek");
    }
    if (lockf(lock->lock_fd, F_ULOCK, sizeof(key)) < 0)
    {
	perror("unlockf");
    }
}

int client_init_key (FSP_LOCK *lock,
                            unsigned long server_addr,
			    unsigned short server_port)
{
    mode_t omask;

    make_key_string(lock,server_addr, server_port);

    omask = umask(0);
    lock->lock_fd = open(lock->key_string, O_RDWR | O_CREAT, 0666);
    (void)umask(omask);

    if(lock->lock_fd < 0)
	return -1;
    else
	return 0;	
}

void
client_destroy_key(FSP_LOCK *lock)
{
    (void)close(lock->lock_fd);
}
#endif