1 /*
2 * Copyright (c) 2006-2021, RT-Thread Development Team
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 *
6 * Change Logs:
7 * Date Author Notes
8 */
9 /* The classic producer-consumer example, implemented with semaphores.
10 All integers between 0 and 9999 should be printed exactly twice,
11 once to the right of the arrow and once to the left. */
12
13 #include <stdio.h>
14 #include "pthread.h"
15 #include "semaphore.h"
16
17 #define BUFFER_SIZE 16
18
19 /* Circular buffer of integers. */
20
21 struct prodcons {
22 int buffer[BUFFER_SIZE]; /* the actual data */
23 int readpos, writepos; /* positions for reading and writing */
24 sem_t sem_read; /* number of elements available for reading */
25 sem_t sem_write; /* number of locations available for writing */
26 };
27
28 /* Initialize a buffer */
29
init(struct prodcons * b)30 void init(struct prodcons * b)
31 {
32 sem_init(&b->sem_write, 0, BUFFER_SIZE - 1);
33 sem_init(&b->sem_read, 0, 0);
34 b->readpos = 0;
35 b->writepos = 0;
36 }
37
38 /* Store an integer in the buffer */
39
put(struct prodcons * b,int data)40 void put(struct prodcons * b, int data)
41 {
42 /* Wait until buffer is not full */
43 sem_wait(&b->sem_write);
44 /* Write the data and advance write pointer */
45 b->buffer[b->writepos] = data;
46 b->writepos++;
47 if (b->writepos >= BUFFER_SIZE) b->writepos = 0;
48 /* Signal that the buffer contains one more element for reading */
49 sem_post(&b->sem_read);
50 }
51
52 /* Read and remove an integer from the buffer */
53
get(struct prodcons * b)54 int get(struct prodcons * b)
55 {
56 int data;
57 /* Wait until buffer is not empty */
58 sem_wait(&b->sem_read);
59 /* Read the data and advance read pointer */
60 data = b->buffer[b->readpos];
61 b->readpos++;
62 if (b->readpos >= BUFFER_SIZE) b->readpos = 0;
63 /* Signal that the buffer has now one more location for writing */
64 sem_post(&b->sem_write);
65 return data;
66 }
67
68 /* A test program: one thread inserts integers from 1 to 10000,
69 the other reads them and prints them. */
70
71 #define OVER (-1)
72
73 struct prodcons buffer;
74
producer(void * data)75 static void *producer(void * data)
76 {
77 int n;
78 for (n = 0; n < 10000; n++) {
79 printf("%d --->\n", n);
80 put(&buffer, n);
81 }
82 put(&buffer, OVER);
83 return NULL;
84 }
85
consumer(void * data)86 static void *consumer(void * data)
87 {
88 int d;
89 while (1) {
90 d = get(&buffer);
91 if (d == OVER) break;
92 printf("---> %d\n", d);
93 }
94 return NULL;
95 }
96
libc_ex5(void)97 int libc_ex5(void)
98 {
99 pthread_t th_a, th_b;
100 void * retval;
101
102 init(&buffer);
103 /* Create the threads */
104 pthread_create(&th_a, NULL, producer, 0);
105 pthread_create(&th_b, NULL, consumer, 0);
106 /* Wait until producer and consumer finish. */
107 pthread_join(th_a, &retval);
108 pthread_join(th_b, &retval);
109 return 0;
110 }
111 #include <finsh.h>
112 FINSH_FUNCTION_EXPORT(libc_ex5, example 5 for libc);
113
114