/*
 * TaskQueM.c
 *
 * Sample code for "Multithreading Applications in Win32"
 * This is from Chapter 3, Listing 3-3
 *
 * Call ThreadFunc NUM_TASKS times, using
 * no more than THREAD_POOL_SIZE threads.
 * This version uses WaitForMultipleObjects
 * to provide a more optimal solution.
 *
 * Build command: cl /MD TaskQueM.c
 */

#define WIN32_LEAN_AND_MEAN
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#include "MtVerify.h"

DWORD WINAPI ThreadFunc(LPVOID);

#define THREAD_POOL_SIZE 3
#define MAX_THREAD_INDEX THREAD_POOL_SIZE-1
#define NUM_TASKS 6

int main()
{
    HANDLE  hThrds[THREAD_POOL_SIZE];
    int     slot = 0;
    DWORD   threadId;
    int     i;
    DWORD   rc;

    for (i=1; i<=NUM_TASKS; i++)
    {
        /* Until we've used all threads in *
         * the pool, do not need to wait   *
         * for one to exit                 */
        if (i > THREAD_POOL_SIZE)
        {
            /* Wait for one thread to terminate */
            rc = WaitForMultipleObjects(
                THREAD_POOL_SIZE,
                hThrds,
                FALSE,
                INFINITE );
            slot = rc - WAIT_OBJECT_0;
            MTVERIFY( slot >= 0 
                && slot < THREAD_POOL_SIZE );
            printf("Slot %d terminated\n", slot );
            MTVERIFY( CloseHandle(hThrds[slot]) );
        }
        /* Create a new thread in the given
         * available slot */
        MTVERIFY( hThrds[slot] = CreateThread(NULL,
            0,
            ThreadFunc,
            (LPVOID)slot,
            0,
            &threadId ) );
        printf("Launched thread #%d (slot %d)\n", i, slot);
        slot++;
    }

    /* Now wait for all threads to terminate */
    rc = WaitForMultipleObjects(
        THREAD_POOL_SIZE,
        hThrds,
        TRUE,
        INFINITE );
    MTVERIFY( rc >= WAIT_OBJECT_0
             && rc < WAIT_OBJECT_0+THREAD_POOL_SIZE);
    for (slot=0; slot<THREAD_POOL_SIZE; slot++)
        MTVERIFY( CloseHandle(hThrds[slot]) );
    printf("All slots terminated\n");

    return EXIT_SUCCESS;
}

/*
 * This function just calls Sleep for
 * a random amount of time, thereby
 * simulating some task that takes time.
 *
 * The param "n" is the index into
 * the handle array, kept for informational
 * purposes.
 */
DWORD WINAPI ThreadFunc(LPVOID n)
{
    srand( GetTickCount() );

    Sleep((rand()%10)*800+500);
    printf("Slot %d idle\n", n);
    return ((DWORD)n);
}