我正在尝试在中声明一个常量变量C++；
#include <iostream>
#include <pthread.h>
#include <stdlib.h>
using namespace std;
//
// declare the mutex
//
static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
//
// AVOID NEGATIVE NUMBERS
//
unsigned int MAXSIZE = 0;
unsigned int head = 0;
unsigned int tail = 0;
//
// return a empty circular queue
//
int* initialize(int size){
MAXSIZE = size;
pthread_mutex_lock( &mutex );
int* queue = new int[ MAXSIZE ];
// initialize each position to zero ( explicitly )
for(int i = 0; i < MAXSIZE; i++){
queue[i] = 0;
}
pthread_mutex_unlock( &mutex );
return queue;
}
//
// enqueue number into the queue
// returns the position it was stored
//
void* enqueue( void* local_queue, void* local_data ){
// ASSERT ONLY ONE THREAD EACH TIME
pthread_mutex_lock( &mutex );
// convert back to int
int data = *((int*)(&local_data));
int* queue = (int*)local_queue;
queue[tail] = data;
tail = (tail+1) % MAXSIZE;
pthread_mutex_unlock( &mutex );
cout << "Tail: " << tail << endl;
}
//
// dequeue, given the queue
//
void* dequeue( void* queue ){
int temp;
pthread_mutex_lock( &mutex );
int* local_queue = ( int* )queue;
temp = local_queue[ head ];
head = ( head + 1 ) % MAXSIZE;
pthread_mutex_unlock( &mutex );
cout << "Removed: " << temp << endl;
}
//
// print the queue as it is
//
void* display( void* local_queue ){
pthread_mutex_lock( &mutex );
int* queue = (int*)local_queue;
if( head == tail ){
cout << "Queue underflow" << endl;
}
else{
//
// prints each element in the queue
//
for( unsigned int i = head; i < tail; i = (i+1) % MAXSIZE ){
cout << queue[i] << endl;
}
}
pthread_mutex_unlock( &mutex );
}
//
// delete the memory allocated to the queue
//
void remove( int* queue){
delete queue;
}
//
// explain the user how to run the program
//
void usage(){
cout << "Usage: " << endl;
cout << " ./queue [size] [elements]" << endl;
cout << "ex: ./queue 5 0 1 2 3 4 5" << endl;
}
//
// main function, the tests are done in the for loop
//
int main( int argc, char* argv[] ){
pthread_t threads[5];
if(argc < 2){
cout << "Args must be at least 1 " << endl;
usage();
return -1;
}
for(size_t j = 0; j < 5; j++){
unsigned int size = atoi( argv[1] );
cout << "Size: " << size << endl;
int* queue = initialize(size);
for(size_t i = 2; i < argc; i++){
enqueue( queue, (void*)atoi( argv[i] ) );
}
pthread_create( &threads[j], NULL, dequeue, (void*)queue );
// make sure memory is freed
// finally end the thread
pthread_join( threads[j], NULL );
remove(queue);
}
return 0;
}
我想unsigned int MAXSIZE = 0;声明为const unsigned int MAXSIZE;所以我可以在runtime. 我知道它可以在 的构造函数中完成class，但是我想知道是否有一种方法可以初始化MAXSIZE用户size给出的方法。MAXSIZE用于实现在数组中实现的循环队列，所以MAXSIZE声明为const避免被更改进而影响circular队列的操作很重要。谢谢。*我希望我能澄清我的问题，以获得更准确的答案。为了完整性和社区的利益，我已将所有代码添加到问题中。*