Sample Multithread C Program
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Bounce.c is a sample multithread program that creates a new thread each time the letter a or A is typed. Each thread bounces a happy face of a different color around the screen. Up to 32 threads can be created. The program's normal termination occurs when q or Q is typed. For information about compiling and linking Bounce.c, see Compiling and Linking Multithread Programs.
Example
Code
// sample_multithread_c_program.c
// compile with: /c
//
// Bounce - Creates a new thread each time the letter 'a' is typed.
// Each thread bounces a happy face of a different color around
// the screen. All threads are terminated when the letter 'Q' is
// entered.
//
#include <windows.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <conio.h>
#include <process.h>
#define MAX_THREADS 32
// The function getrandom returns a random number between
// min and max, which must be in integer range.
#define getrandom( min, max ) (SHORT)((rand() % (int)(((max) + 1) - \
(min))) + (min))
int main( void ); // Thread 1: main
void KbdFunc( void ); // Keyboard input, thread dispatch
void BounceProc( void * MyID ); // Threads 2 to n: display
void ClearScreen( void ); // Screen clear
void ShutDown( void ); // Program shutdown
void WriteTitle( int ThreadNum ); // Display title bar information
HANDLE hConsoleOut; // Handle to the console
HANDLE hRunMutex; // "Keep Running" mutex
HANDLE hScreenMutex; // "Screen update" mutex
int ThreadNr; // Number of threads started
CONSOLE_SCREEN_BUFFER_INFO csbiInfo; // Console information
int main() // Thread One
{
// Get display screen information & clear the screen.
hConsoleOut = GetStdHandle( STD_OUTPUT_HANDLE );
GetConsoleScreenBufferInfo( hConsoleOut, &csbiInfo );
ClearScreen();
WriteTitle( 0 );
// Create the mutexes and reset thread count.
hScreenMutex = CreateMutex( NULL, FALSE, NULL ); // Cleared
hRunMutex = CreateMutex( NULL, TRUE, NULL ); // Set
ThreadNr = 0;
// Start waiting for keyboard input to dispatch threads or exit.
KbdFunc();
// All threads done. Clean up handles.
CloseHandle( hScreenMutex );
CloseHandle( hRunMutex );
CloseHandle( hConsoleOut );
}
void ShutDown( void ) // Shut down threads
{
while ( ThreadNr > 0 )
{
// Tell thread to die and record its death.
ReleaseMutex( hRunMutex );
ThreadNr--;
}
// Clean up display when done
WaitForSingleObject( hScreenMutex, INFINITE );
ClearScreen();
}
void KbdFunc( void ) // Dispatch and count threads.
{
int KeyInfo;
do
{
KeyInfo = _getch();
if ( tolower( KeyInfo ) == 'a' &&
ThreadNr < MAX_THREADS )
{
ThreadNr++;
_beginthread( BounceProc, 0, &ThreadNr );
WriteTitle( ThreadNr );
}
} while( tolower( KeyInfo ) != 'q' );
ShutDown();
}
void BounceProc( void *pMyID )
{
char MyCell, OldCell;
WORD MyAttrib, OldAttrib;
char BlankCell = 0x20;
COORD Coords, Delta;
COORD Old = {0,0};
DWORD Dummy;
char *MyID = (char*)pMyID;
// Generate update increments and initial
// display coordinates.
srand( (unsigned int) *MyID * 3 );
Coords.X = getrandom( 0, csbiInfo.dwSize.X - 1 );
Coords.Y = getrandom( 0, csbiInfo.dwSize.Y - 1 );
Delta.X = getrandom( -3, 3 );
Delta.Y = getrandom( -3, 3 );
// Set up "happy face" & generate color
// attribute from thread number.
if( *MyID > 16)
MyCell = 0x01; // outline face
else
MyCell = 0x02; // solid face
MyAttrib = *MyID & 0x0F; // force black background
do
{
// Wait for display to be available, then lock it.
WaitForSingleObject( hScreenMutex, INFINITE );
// If we still occupy the old screen position, blank it out.
ReadConsoleOutputCharacter( hConsoleOut, &OldCell, 1,
Old, &Dummy );
ReadConsoleOutputAttribute( hConsoleOut, &OldAttrib, 1,
Old, &Dummy );
if (( OldCell == MyCell ) && (OldAttrib == MyAttrib))
WriteConsoleOutputCharacter( hConsoleOut, &BlankCell, 1,
Old, &Dummy );
// Draw new face, then clear screen lock
WriteConsoleOutputCharacter( hConsoleOut, &MyCell, 1,
Coords, &Dummy );
WriteConsoleOutputAttribute( hConsoleOut, &MyAttrib, 1,
Coords, &Dummy );
ReleaseMutex( hScreenMutex );
// Increment the coordinates for next placement of the block.
Old.X = Coords.X;
Old.Y = Coords.Y;
Coords.X += Delta.X;
Coords.Y += Delta.Y;
// If we are about to go off the screen, reverse direction
if( Coords.X < 0 || Coords.X >= csbiInfo.dwSize.X )
{
Delta.X = -Delta.X;
Beep( 400, 50 );
}
if( Coords.Y < 0 || Coords.Y > csbiInfo.dwSize.Y )
{
Delta.Y = -Delta.Y;
Beep( 600, 50 );
}
}
// Repeat while RunMutex is still taken.
while ( WaitForSingleObject( hRunMutex, 75L ) == WAIT_TIMEOUT );
}
void WriteTitle( int ThreadNum )
{
enum {
sizeOfNThreadMsg = 80
};
char NThreadMsg[sizeOfNThreadMsg];
sprintf_s( NThreadMsg, sizeOfNThreadMsg,
"Threads running: %02d. Press 'A' "
"to start a thread,'Q' to quit.", ThreadNum );
SetConsoleTitle( NThreadMsg );
}
void ClearScreen( void )
{
DWORD dummy;
COORD Home = { 0, 0 };
FillConsoleOutputCharacter( hConsoleOut, ' ',
csbiInfo.dwSize.X * csbiInfo.dwSize.Y,
Home, &dummy );
}
Input
a
q