博赞的记忆矩阵sem3是什么?看不懂!

首先你得掌握基本记忆系统,SEM3在基本记忆系统的扩充.100个基本记忆图像是最基本的.比方说,3276 按千位、百位、十位个位（0-99基本记忆图像）其中,十位个位76是基本记忆图像,千位3,百位2是扩充.理解以上内容后,将各...

/*编译命令：gcc -o shm shm.c -g */

2

3#include<sys/sem.h>

4#include<sys/ipc.h>

5

6#define SEGSIZE 1024

7#define READTIME 1

8

9union semum

10{

11int val

12struct semid_ds *buf

13unsigned short *array

14}arg

15

16/* 创建信号量 */

17int sem_creat(key_t key)

18{

19union semun sem

20int semid

21sem.val = 0

22semid = semget(key, 1, IPC_CREAT | 0666)

23

24if (semid == -1)

25{

26printf("Create semaphore error\n")

27exit(-1)

28}

29

30semctl(semid, 0, SETVAL, sem)

31

32return semid

33}

34

35/* 删除信号量*/

36int del_sem(int semid)

37{

38union semun sem

39sem.val = 0

40semctl(semid, 0, IPC_RMID, sem)

41}

42

43/* 信号量的P操作，使得信号量的值加1 */

44int p(int semid)

45{

46struct sembuf sops = {0,

47 +1,

48 IPC_NOWAIT

49 }

50

51return (semop(semid, &sops, 1))

52}

53

54/* 信号量的v操作，使得信号量的值减1 */

55int v(int semid)

56{

57struct sembuf sops = {0,

58 -1,

59 IPC_NOWAIT

60 }

61

62return (semop(semid, &sops, 1))

63}

64

65/* server主程序 */

66int main(int argc, char **argv)

67{

68key_tkey

69int shmid, semid

70char *shm

71char msg[7] = "-data-"

72char i

73struct semid_ds buf

74

75key = ftok("/", 0)

76shmid = shmget(key, SEGSIZE, IPC_CREAT|0604)

77

78if shmid == -1)

79{

80printf(" create shared memory error\n")

81return -1

82}

83

84shm = (char *)shmat(shmid, 0, 0)

85if (-1 == (int)shm)

86{

87printf(" attach shared memory error\n")

88return -1

89}

90

91semid = sem_creat(key)

92

93for (i = 0i <= 3i++)

94{

95sleep(1)

96p(semid)

97sleep(READTIME)

98msg[5] = '0' + i

99memcpy(shm,msg,sizeof(msg))

100sleep(58)

101v(semid)

102}

103

104shmdt(shm)

105

106shmctl(shmid,IPC_RMID,&buf)

107

108del_sem(semid)

109

110return 0

111

112}

113

114

115

116

117

118

119

120

121

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