January 01, 2003
Multithreaded Programming with the Command Pattern
Multithreaded Programming with the Command Pattern
Listing 3 This app reads messages from a queue by using a thread pool
#include <iostream>
#include <string>
#include <vector>
#include <windows.h>
HANDLE condition;
HANDLE mutex;
std::vector < std::string > queue;
void thread_entry ()
{
for ( ;; )
{
WaitForSingleObject ( mutex, INFINITE );
if ( queue.empty () )
{
ReleaseMutex ( mutex );
std::cout << "thread going to sleep" << std::endl;
WaitForSingleObject ( condition, INFINITE );
WaitForSingleObject ( mutex, INFINITE );
std::cout << "thread awake" << std::endl;
}
if ( queue.empty () )
{
std::cout << "work queue is empty" << std::endl;
ReleaseMutex ( mutex );
continue;
}
std::string message = queue.back ();
queue.pop_back ();
ReleaseMutex ( mutex );
std::cout << message << std::endl;
Sleep ( 1 );
}
}
int main ()
{
HANDLE threads[ 3 ];
std::string messages[ 10 ] = { "hello", "goodbye", "test", "check",
"one", "two", "james", "way-way",
"here", "there" };
mutex = CreateMutex ( NULL, FALSE, NULL );
condition = CreateEvent ( NULL, FALSE, FALSE, NULL );
for ( int i = 3; i > 0; --i )
{
threads[ i - 1 ] = CreateThread ( NULL, 0,
( LPTHREAD_START_ROUTINE ) thread_entry,
NULL, 0, NULL );
}
for ( int index = 10; index > 0; --index )
{
WaitForSingleObject ( mutex, INFINITE );
queue.push_back ( messages[ index - 1 ] );
SetEvent ( condition );
ReleaseMutex ( mutex );
}
WaitForSingleObject ( threads[ 0 ], INFINITE );
return ( 0 );
}
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