p10-1.c

来自「SUN Solaris8平台下进程间通信」· C语言 代码 · 共 44 行

#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <stdlib.h>
pid_t lock_test(int fd, int type, off_t offset, int whence, off_t len)
{
    struct flock  flock_to_test;
    flock_to_test.l_type = type;
    flock_to_test.l_whence = whence;
    flock_to_test.l_start = offset;
    flock_to_test.l_len = len;
    flock_to_test.l_pid = -1;
    if (fcntl(fd, F_GETLK, &flock_to_test) < 0){
       fprintf(stderr, "F_GETLK failed\n");
       exit(EXIT_FAILURE);
    }
    if (flock_to_test.l_type == F_UNLCK)
       return(0);   
    return(flock_to_test.l_pid);
}
int lock_region(int fd, int cmd, int type, off_t offset, int whence, off_t len)
{
    struct flock  flock;
    flock.l_type =type;
    flock.l_whence = whence;
    flock.l_start = offset;
    flock.l_len = len;
    return(fcntl(fd, cmd, &flock));
}
#define READ_LOCK(FD, OFFSET,WHENCE,LEN)    \
              lock_region(FD, F_SETLK, F_RDLCK, OFFSET, WHENCE, LEN)
#define WRITE_LOCK(FD,OFFSET,WHENCE,LEN)   \
              lock_region(FD, F_SETLK, F_WRLCK, OFFSET, WHENCE, LEN)
#define UN_LOCK(FD,OFFSET,WHENCE,LEN)       \
              lock_region(FD, F_SETLK, F_UNLCK, OFFSET, WHENCE, LEN)
#define READW_LOCK(FD, OFFSET,WHENCE,LEN)   \
              lock_region(FD, F_SETLKW, F_RDLCK, OFFSET, WHENCE, LEN)
#define WRITEW_LOCK(FD,OFFSET,WHENCE,LEN)   \
              lock_region(FD, F_SETLKW, F_WRLCK, OFFSET, WHENCE, LEN)
#define IS_READLOCK(FD,OFFSET,WHENCE,LEN)   \
              lock_test(FD, F_RDLCK, OFFSET, WHENCE, LEN)
#define IS_WRITELOCK(FD,OFFSET,WHENCE,LEN)  \
              lock_test(FD, F_WRLCK, OFFSET, WHENCE, LEN)