prwlock.cpp

一个ftp搜索引擎的源代码

#include "prwlock.h"
#include <fcntl.h>
#include <errno.h>

#define write_lock(fd, offset, whence, len) \
            lock_reg(fd, F_SETLKW, F_WRLCK, offset, whence, len)

#define read_lock(fd, offset, whence, len) \
            lock_reg(fd, F_SETLKW, F_RDLCK, offset, whence, len)

#define un_lock(fd, offset, whence, len) \
            lock_reg(fd, F_SETLK, F_UNLCK, offset, whence, len)

int lock_reg(int fd, int cmd, int type, off_t offset, int whence, off_t len)
{
    struct flock    lock;

    lock.l_type = type;     /* F_RDLCK, F_WRLCK, F_UNLCK */
    lock.l_start = offset;  /* byte offset, relative to l_whence */
    lock.l_whence = whence; /* SEEK_SET, SEEK_CUR, SEEK_END */
    lock.l_len = len;       /* #bytes (0 means to EOF) */

    return( fcntl(fd, cmd, &lock) );    /* -1 upon error */
}

int Prwlock::wlock(int fd)
{
	int ret;
	while((ret=write_lock(fd,0,SEEK_SET,0)) < 0)
	{
		if(errno == EINTR)
		{
			continue;
		}
		else 
		{
			return ret;
		}
	}
	return ret;
}

int Prwlock::rlock(int fd)
{	
	int ret;
	while((ret=read_lock(fd,0,SEEK_SET,0)) < 0)
	{
		if(errno == EINTR)
		{
			continue;
		}
		else 
		{
			return ret;
		}
	}
	return ret;
}

int Prwlock::unlock(int fd)
{
	return un_lock(fd,0,SEEK_SET,0);
}