索引到信号量数组中

假设我初始化了两个全局信号量数组

semaphore empty[someNum];

和

semaphore full[someNum];

并且CCD_ 3被初始化为

const int someNum = 3;（全球）

我将有一个名为init()的方法，里面有一个for-loop来帮助索引这些数组。

for (index=0; index<someNum; index++) num[index]=0;

我的目标是使用像wait和signal这样的命令——数组中的某些信号量，例如，如果num已满，那么我不希望我的生产者在其中放置值。

在init()内部，我知道我需要初始化循环体中的所有信号量。到目前为止，我已经尝试过

empty[index] = create_semaphore(1)

full[index] = create_semaphore(0)

在我想要预处理动作wait和signal的方法内部，例如

wait(empty) ;

但我又犯了错误。我知道这是因为我使用的是数组的名称，而不是特定的信号量。

所以我的问题是，如何正确地索引到for-loop中的数组中以指定一个信号量？

感谢您的任何和所有投入！如果你有任何问题，请随时要求澄清！请耐心等待，信号量对我来说是一个新概念

注意

命令CCD_ 18存在于与该命令相关联的另一程序中。

编辑

foodPass.cpp

#include <iostream>
#include <sched.h>
#include <time.h>
#include <pthread.h>
#include <string>
#include "sem.h"
using namespace std ;
/* ######################################## */
/*             Misc Data Types              */
/* ######################################## */
     /* A data type - a struct with an int field
        to represent a child ID at the program level. */
struct threadIdType
{
  int id ;
};
/* ######################################## */
/*             Global Variables             */
/* ######################################## */
//const int numTrivets = 6 ;
const int numTrivets = 3 ;
const int numDiners = numTrivets - 1 ;
const int maxDishNames = 13 ;
//const int numDishNames = 13 ;
const int numDishNames = 5 ;
int trivet[numTrivets] ;
string dishName[maxDishNames];
      /* Here declare the semaphores and other variables you will
         need to synchronize threads. */
sim_semaphore  empty[numTrivets] ; 
sim_semaphore  full[numTrivets] ; 
      /* child_t are global variables to represent the
         dynamically-created threads. */
pthread_t child_t[numTrivets] ;
/* ######################################## */
/*      "Special"   Global Variables        */
/* ######################################## */
/* Code in sem.cpp "expects" the two variables below to be here.
   This particular program does not use "checking." */
         /* "Checking" is just a flag that you set to 1 if you want lots of
            debugging messages and set to 0 otherwise.  The semaphore code in
            sem.cpp imports "checking".  Therefore the semaphore operations
            will write lots of messages if you set checking=1.  */
int checking ;
      /* In some programs, we use the "stdoutLock" variable declared below to
         get intelligible printouts from multiple concurrent threads that write
         to the standard output.  (There has to be something to prevent the
         output of the threads from interleaving unintelligibly on the standard
         output, and we can't use semaphores if the semaphore code is writing
         messages too.)
         To print a message to standard output, a thread first locks standard
         output, then writes, then unlocks standard output.  See files sem.cpp
         or conc.cpp for examples of code that write messages in this manner.
         WARNING:  DON'T change how the locking of standard output is done
         until you've thought a WHOLE lot about the consequences.  In
         particular, using semaphores to do the job of stdoutLock can cause
         "infinite recursion" under certain circumstances.  The reason is that
         the semaphore code itself imports "stdoutLock" and writes messages
         when the "checking" variable is set to 1. */
pthread_mutex_t stdoutLock ;
/* ################################################## */
/*                         init                       */
/* ################################################## */
void init()
{
  int index ;
  srandom(time((time_t *) 0)); /* INITIALIZE RANDOM NUMBER GENERATOR */
  checking = 0 ;
       /* Initialize the "special lock" that is used only to get
          exclusive access to the screen. */
  if ( 0!=pthread_mutex_init(&stdoutLock, NULL) )
  {  cout << "MUTEX INITIALIZATION FAILURE!" << endl;
     exit(-1) ;}
    /* Initialize the trivets to indicate that each contains "no
       dish." */
  for (index=0; index<numTrivets; index++) trivet[index]=0;
    /* Here initialize the semaphores and other variables you use
       for synchronization.  */
  for (index=0; index<numTrivets; index++) full[index] = create_sim_sem(0) ;
  for (index=0; index<numTrivets; index++) empty[index] = create_sim_sem(1) ;

 /* Give some mnemonic names to the dishes.  The first name is
    used for an empty trivet.  The last name denotes the check
    (bill) for the meal.  This is coded so no changes are needed
    here as long as the value of "numDishNames" is between 2 and
    13. */
  dishName[0]="no dish";
  dishName[1]="vegetable soup" ;
  dishName[2]="bread and butter" ;
  dishName[3]="beets and chickpeas" ;
  dishName[4]="hardboiled eggs" ;
  dishName[5]="calf tongue" ;
  dishName[6]="baked potato" ;
  dishName[7]="string beans" ;
  dishName[8]="rack of lamb" ;
  dishName[9]="salad" ;
  dishName[10]="coffee" ;
  dishName[11]="flan" ;
  dishName[numDishNames-1]="check" ;
}
/* ################################################## */
/*                    DelayAsMuchAs                   */
/* ################################################## */
void delayAsMuchAs (int limit)
{
  int time, step;
  time=(int)random()%limit;
  for (step=0;step<time;step++) sched_yield() ;
}
/* ################################################## */
/*                       Server                       */
/* ################################################## */
/*
     The mother thread spawns a child thread that executes this
     function.  This function carries out the job of the server
     at the restaurant.
*/
void * Server(void * ignore)
{
  int i, j, delayLimit=100 ;
  for (i=1; i<numDishNames; i++)
  {
        /* I delay a random time before I "feel like" placing
           another dish on the table.*/
    delayAsMuchAs(delayLimit);
      /* When the trivet is available, I place the dish on the
         trivet to my right. */
       /* Here do a synchronization task.  One thing you need to
          do is be sure that you are not going to place a dish on
          a trivet that alreay has a dish on it.  *DO NOT* just
          busy-wait until you see that the trivet is empty. */
    wait_sem(empty[i]) ; 
    trivet[0]=i; // put dish #i onto trivet #0
    pthread_mutex_lock(&stdoutLock) ;
    cout << "Server places " << dishName[trivet[0]]
         << " on trivet #0." << endl ;
    pthread_mutex_unlock(&stdoutLock);
       /* Here you may want to a synchronization task --
          something that "opens the door" for diner #0 to get
          access to the new dish. */
    signal_sem(full[i]) ; 

  }
  pthread_exit ((void *)0) ;
}
/* ################################################## */
/*                         Diner                      */
/* ################################################## */
/*
     The mother thread spawns child threads that execute this
     function.  This function carries out the job of one of the
     diners at the restaurant.
*/
void * Diner(void * postnPtr)
{
       /* Type cast the parameter to recover "position" -- which
          tells me the position at which I am seated at the
          table. */
int position = ((threadIdType *)(postnPtr))->id ;
  int i, j, delayLimit=100 ;
  for (i=1; i<numDishNames; i++)
  {
        /* I delay a random time before I "feel like" picking up the next
           dish.*/
    delayAsMuchAs(delayLimit);
      /* When available, I pick up the next new dish on my left. */
       /* Here do a synchronization task.  One thing you need to
          do is be sure that there is a new dish on the trivet to
          your left now, and that the person on your left has
          "let go" of it. */
    wait_sem(full[i]); 
      /* I declare what I am doing */
    pthread_mutex_lock(&stdoutLock) ;
    cout << "Diner number "<< position ;
    if (i<numDishNames-1) cout << " enjoys ";
    else if (position<numDiners-1) cout << " examines " ;
         else cout << " examines and pays " ;
    cout << dishName[trivet[position]] << endl ;
    pthread_mutex_unlock(&stdoutLock);
        /* I delay a random time to simulate the time it takes for me to
           serve myself some of what is on the dish -- or look at the
           check. */
    delayAsMuchAs(delayLimit);
        /* When available, I place the dish on the trivet to my right. */
       /* Here do a synchronization task.  One thing you need to
          do is be sure that the trivet on your right does not
          have a dish on it now.*/
    wait_sem (empty[i]); 
    pthread_mutex_lock(&stdoutLock) ;
    cout << "Diner number "<< position << " moves "
         << dishName[trivet[position]] << " from trivet #"
         << position << " to trivet #" << position+1 << endl;
    pthread_mutex_unlock(&stdoutLock);
       /* transfer the dish on my left to trivet on my right */
    trivet[position+1]=trivet[position] ;
      /* mark trivet on my left as empty */
    trivet[position]=0;
       /* Here do a synchronization task. You have transferred a
          dish from your left to your right.  The person on your
          left will need to find out that the trivet on your left
          is now empty.  The person on your right will need to
          find out that the trivet on your right now has a new
          dish on it.  */
    signal_sem(empty[i]); 
    signal_sem(full[i]); 
  }
  delete((threadIdType *)(postnPtr)) ;
  pthread_exit ((void *) 0) ;
}
/* ################################################## */
/*                       Busser                       */
/* ################################################## */
/*
     The mother thread spawns children and then executes this
     function.  This is convenient because this function should
     be the last to exit.  This function carries out the job of
     the busser at the restaurant.
*/
void * Busser (void * ignore)
{
  int i, j, delayLimit=100 ;
  for (i=1; i<numDishNames; i++)
  {
        /* I delay a random time before I "feel like" bussing another
           dish.*/
    delayAsMuchAs(delayLimit);
      /* When another dish is on the trivet to my right I remove it. */
       /* Here do a synchronization task.  One thing you need to
          do is be sure that there is a new dish on the trivet to
          your left now, and that the person on your left has
          "let go" of it. */
    wait_sem (full[i]) ; 
    pthread_mutex_lock(&stdoutLock) ;
    cout << "Busser removes "
         << dishName[trivet[numTrivets-1]] << " from trivet #"
         << numTrivets-1<< "." << endl ;
    pthread_mutex_unlock(&stdoutLock);
    trivet[numTrivets-1]=0; // remove the dish.
       /* Here do a synchronization task. The person on your left
          will need to find out that the trivet on your left is
          now empty.  */
    signal_sem (empty[i]); 
  }
  return ignore ;
}
/* ################################################## */
/*                         Main                       */
/* ################################################## */
int main()
{
    init();
    cout << endl << endl;
    cout << "Welcome to the restaurant!" << endl ;
    cout << numDiners << " will be dining." << endl ;
    cout << "The meal will consist of " << numDishNames-2
         << " dishes." << endl;
    cout << "Bon appetite!" << endl ;
    cout << endl << endl;
    int i;
        /* This is a pointer to a struct that contains an int
          field - it is a convenient data type to use as the
          parameter to the child function.  */
    threadIdType * idPtr ;
    for (i=0; i<numDiners; i++)
    {
          /* This records the current index as this child's ID */
       idPtr = new threadIdType ;
       idPtr->id = i ;
       if (0!=pthread_create(&child_t[i], NULL, Diner, (void *) idPtr))
          {cout << "THREAD CREATION FAILURE!" << endl; exit(-1) ;}
       if (0!=pthread_detach(child_t[i]))
          {cout << "THREAD DETACHMENT FAILURE!" << endl ; exit(-1) ;}
    }
       if (0!=pthread_create(&child_t[numDiners], NULL, Server, (void *) 0))
          {cout << "THREAD CREATION FAILURE!" << endl; exit(-1) ;}
       if (0!=pthread_detach(child_t[numDiners]))
          {cout << "THREAD DETACHMENT FAILURE!" << endl ; exit(-1) ;}
    Busser((void *) 0) ;
    cout << endl << endl;
    cout << "Thank you for coming!" << endl ;
    cout << endl << endl;
    return 0 ;
}

for (index=0; index<numTrivets; index++) full[index] = create_sim_sem(0) ;
for (index=0; index<numTrivets; index++) empty[index] = create_sim_sem(1) ;