有人可以查看我的代码并告诉我我是否在正确的轨道上......似乎我有点迷失..如果你看到我的错误，请告诉我们..
我要做的是使用我自己的信号量和GCD解决有界缓冲区。
提前致谢..
sema.c
void procure( Semaphore *semaphore ) {
pthread_mutex_lock(semaphore->mutex1);
while(semaphore->value <= 0)
pthread_cond_wait(&semaphore->condition, semaphore->mutex1);
semaphore->value--;
pthread_mutex_unlock(semaphore->mutex1);
}
void vacate( Semaphore *semaphore ) {
pthread_mutex_lock(semaphore->mutex1);
semaphore->value++;
pthread_cond_signal(&semaphore->condition);
pthread_mutex_unlock(semaphore->mutex1);
}
void init ( Semaphore *semaphore ){
semaphore->value = 1;
pthread_mutex_t myMutex;
semaphore->mutex1 = &myMutex;
pthread_mutex_init( semaphore->mutex1, NULL);
}
void destroy ( Semaphore *semaphore ) {
pthread_mutex_destroy(semaphore->mutex1);
}
和main.c
struct variables {
Semaphore *sem;
};
struct variables vars;
void constructer (int *buffer, int *in, int *out) {
init(vars.sem);
}
void deconstructer () {
destroy(vars.sem);
}
int rand_num_gen() {
uint_fast16_t buffer;
int file;
int *rand;
file = open("/dev/random", O_RDONLY);
while( 1 ) {
read(file, &buffer, sizeof(buffer));
printf("16 bit number: %hu\n", buffer );
*rand = (int) buffer;
close(file);
break;
}
return *rand;
}
void put_buffer( int* buffer, int* in, int* out ) {
buffer[*in] = rand_num_gen(); // produce
procure(vars.sem); // wait here
*in = (*in + 1) % BUF_SIZE;
vacate(vars.sem);
}
void get_buffer( int* buffer, int* in, int* out ) {
int value;
procure(vars.sem);
value = buffer[*out];
vacate(vars.sem);
*out = (*out + 1) % BUF_SIZE;
}
int main (void) {
int *in, *out, *buffer;
constructer(buffer, in, out);
dispatch_queue_t producer, consumer;
producer = dispatch_queue_create("put_buffer", NULL);
consumer = dispatch_queue_create("get_buffer", NULL);
dispatch_async(producer,
^{
int i;
do
{
put_buffer( buffer, in, out );
dispatch_async(consumer,
^{
get_buffer( buffer, in, out );
if (i == RUN_LENGTH) exit(EXIT_SUCCESS);
});
}
while (i < RUN_LENGTH);
});
dispatch_main();
deconstructer();
exit (0);
}
答案 0 :(得分：2)
您的代码有错误。在init函数中，您将局部变量的地址分配给semaphore->mutex1，当函数返回时，该地址将无效。稍后您仍然使用此地址，因此这会导致未定义的行为。
您必须直接在信号量中为互斥锁分配内存（不带指针），或者通过malloc分配内存。
<强>更新
您的程序有很多错误，您应该选择一个更容易的主题来学习有关内存管理的基本概念，如何分配，使用和引用缓冲区，进行正确的错误处理等。这是一个略微编辑的版本你的代码。它仍然不起作用，但可能有一些你应该遵循的想法。
#include <limits.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
void procure(Semaphore *semaphore) {
pthread_mutex_lock(semaphore->mutex1);
while (semaphore->value <= 0)
pthread_cond_wait(&semaphore->condition, semaphore->mutex1);
semaphore->value--;
pthread_mutex_unlock(semaphore->mutex1);
}
void vacate(Semaphore *semaphore) {
pthread_mutex_lock(semaphore->mutex1);
semaphore->value++;
pthread_cond_signal(&semaphore->condition);
pthread_mutex_unlock(semaphore->mutex1);
}
struct variables {
mutex_t sem_mutex;
Semaphore sem;
};
struct variables vars;
void constructor(int *buffer, int *in, int *out) {
vars.sem.value = 1;
vars.sem.mutex1 = &vars.sem_mutex;
pthread_mutex_init(vars.sem.mutex1, NULL);
}
void deconstructor() {
pthread_mutex_destroy(&semaphore->mutex1);
}
int rand_num_gen() {
const char *randomfile = "/dev/random";
unsigned char buffer[2]; // Changed: always treat files as byte sequences.
FILE *f = fopen(randomfile, "rb");
// Changed: using stdio instead of raw POSIX file access,
// since the API is much simpler; you don't have to care
// about interrupting signals or partial reads.
if (f == NULL) { // Added: error handling
fprintf(stderr, "E: cannot open %s\n", randomfile);
exit(EXIT_FAILURE);
}
if (fread(buffer, 1, 2, f) != 2) { // Added: error handling
fprintf(stderr, "E: cannot read from %s\n", randomfile);
exit(EXIT_FAILURE);
}
fclose(f);
int number = (buffer[0] << CHAR_BIT) | buffer[1];
// Changed: be independent of the endianness of the system.
// This doesn't matter for random number generators but is
// still an important coding style.
printf("DEBUG: random number: %x\n", (unsigned int) number);
return number;
}
void put_buffer( int* buffer, int* in, int* out ) {
buffer[*in] = rand_num_gen(); // produce
procure(&vars.sem); // wait here
*in = (*in + 1) % BUF_SIZE;
vacate(&vars.sem);
}
void get_buffer( int* buffer, int* in, int* out ) {
int value;
procure(&vars.sem);
value = buffer[*out];
vacate(&vars.sem);
*out = (*out + 1) % BUF_SIZE;
}
int main (void) {
int inindex = 0, outindex = 0;
int buffer[BUF_SIZE];
constructor(buffer, &inindex, &outindex);
// Changed: provided an actual buffer and actual variables
// for the indices into the buffer.
dispatch_queue_t producer, consumer;
producer = dispatch_queue_create("put_buffer", NULL);
consumer = dispatch_queue_create("get_buffer", NULL);
dispatch_async(producer, ^{
int i;
do {
put_buffer(buffer, &inindex, &outindex);
dispatch_async(consumer, ^{
get_buffer(buffer, &inindex, &outindex);
if (i == RUN_LENGTH) exit(EXIT_SUCCESS);
});
} while (i < RUN_LENGTH);
});
dispatch_main();
deconstructor();
exit (0);
}
正如我所说，我没有抓到所有的错误。