pc1.c: 使用條件變量解決生產(chǎn)者、計算者、消費(fèi)者問題
實(shí)現(xiàn)思路：設(shè)置兩個大小為4的緩沖區(qū)，第一個為生產(chǎn)者和計算著共享，第二個為計算者和消費(fèi)者共享。
1、生產(chǎn)者線程產(chǎn)生字符，將字符寫入緩沖區(qū)buffer1中，并將指針后移，當(dāng)緩沖區(qū)被寫滿是，將生產(chǎn)者線程掛起，喚醒計算者線程，等待緩沖區(qū)buffer1有空閑存儲空間的時候再喚醒生產(chǎn)者線程。
2、計算者線程從buffer1中讀取數(shù)據(jù)，并移動指針，并將讀取的數(shù)據(jù)寫入buffer2中，當(dāng)buffer1有空閑時，喚醒生產(chǎn)者進(jìn)程，當(dāng)buffer2被寫滿時喚醒消費(fèi)者進(jìn)程。
3、消費(fèi)者進(jìn)程從buffer2中讀取字符并輸出，并移動指針，當(dāng)buffer2有空閑的時候，喚醒計算者進(jìn)程。
實(shí)現(xiàn)代碼：
#include<stdio.h>
#include<pthread.h>
#include<unistd.h>#define CAPACITY 4char buffer1[
4];
char buffer2[
4];
int crea;
int comp1;
int comp2;
int cons;
int buffer1_is_empty(){
return crea==comp1;
}
int buffer1_is_full(){
return (crea+
1)%CAPACITY==comp1;
}
int buffer2_is_empty(){
return comp2==cons;
}
int buffer2_is_full(){
return (cons+
1)%CAPACITY==comp2;
}
int get_item1(){
int item;item=buffer1[comp1];comp1=(comp1+
1)%CAPACITY;
return item;
}
int get_item2(){
int item;item=buffer2[cons];cons=(cons+
1)%CAPACITY;
return item;
}
int put_item1(
int item){buffer1[crea]=item;crea=(crea+
1)%CAPACITY;
}
int put_item2(
int item){buffer2[comp2]=item;comp2=(comp2+
1)%CAPACITY;
}pthread_mutex_t mutex1;
pthread_cond_t wait_empty_buffer1;
pthread_cond_t wait_full_buffer1;pthread_mutex_t mutex2;
pthread_cond_t wait_empty_buffer2;
pthread_cond_t wait_full_buffer2;
#define ITEM_COUNT (CAPACITY *2)void *consumer(
void *arg){
int i;
int item;
for(i=
0;i<ITEM_COUNT;i++){pthread_mutex_lock(&mutex2);
while(buffer2_is_empty())pthread_cond_wait(&wait_full_buffer2,&mutex2);item=get_item2();
printf(
" consume item:%c\n",item);pthread_cond_signal(&wait_empty_buffer2);pthread_mutex_unlock(&mutex2);}
return NULL;
}
void *computer(
void *arg){
int i;
int item;
for(i=
0;i<ITEM_COUNT;i++){pthread_mutex_lock(&mutex1);
while(buffer1_is_empty())pthread_cond_wait(&wait_full_buffer1,&mutex1);item=get_item1();
printf(
" computer get item:%c\n",item);item-=
32;pthread_cond_signal(&wait_empty_buffer1);pthread_mutex_unlock(&mutex1);pthread_mutex_lock(&mutex2);
while(buffer2_is_full())pthread_cond_wait(&wait_empty_buffer2,&mutex2);put_item2(item);
printf(
" computer put item:%c\n",item);pthread_cond_signal(&wait_full_buffer2);pthread_mutex_unlock(&mutex2);}
return NULL;
}
void *create(
void *arg){
int i;
int item;
for(i=
0;i<ITEM_COUNT;i++){pthread_mutex_lock(&mutex1);
while(buffer1_is_full())pthread_cond_wait(&wait_empty_buffer1,&mutex1);item=
'a'+i;put_item1(item);
printf(
"create item:%c\n",item);pthread_cond_signal(&wait_full_buffer1);pthread_mutex_unlock(&mutex1);}
return NULL;
}
int main(){pthread_t consumer_tid;pthread_t computer_tid;pthread_mutex_init(&mutex1,NULL);pthread_mutex_init(&mutex2,NULL);pthread_cond_init(&wait_empty_buffer1,NULL);pthread_cond_init(&wait_full_buffer1,NULL);pthread_cond_init(&wait_empty_buffer2,NULL);pthread_cond_init(&wait_full_buffer2,NULL);pthread_create(&consumer_tid,NULL,consumer,NULL);pthread_create(&computer_tid,NULL,computer,NULL);create(NULL);pthread_join(consumer_tid,NULL);pthread_join(computer_tid,NULL);pthread_mutex_destroy(&mutex1);pthread_mutex_destroy(&mutex2);
return 0;
}
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