Coroutine Examples

A

This appendix shows the full text of the two sample programs discussed in Chapter 2, "The Coroutine Library".

Code Example A-1 counts the number of '0' characters in a string using cooperating tasks.

Code Example A-1 Zero-Counter Program

// Simple zero-char counter program

#include <task.h>

#include <iostream.h>

class getLine : public task {

public:

getLine();

};

getLine::getLine()

{

char* tmpbuf = new char[512];

cout << "Enter string: ";

cin >> tmpbuf;

resultis((int)tmpbuf);

}

class countZero : public task {

public:

countZero(getLine*);

};

countZero::countZero(getLine *g)

{

char *s, c;

int i = 0;

s = (char*)g->result();

while( c = *s++)

if( c == `0' )

i++;

resultis(i);

}

int main()

{

getLine g;

countZero c(&g);

cout << "Count result = "

<< c.result() << "\n";

thistask->resultis(0);

return 0;

}

Code Example A-2 does the same, but illustrates the use of queues. The program loops forever, requiring a keyboard interrupt to terminate. It also never deletes the objects it allocates with new, and is thus not realistic.

Code Example A-2 Zero-Counter Using Queues

// Zero-counter program using queues

#include <task.h>

#include <iostream.h>

class getLine : public task {

public:

getLine(qhead*, qtail*);

};

class countZero : public task {

public:

countZero(qhead*, qtail*);

};

class lineHolder : public object {

public:

char *line;

lineHolder(char* s) : line(s) { }

};

class numZero : public object {

public:

int zero;

numZero(int count) : zero(count) { }

};

getLine::getLine(qhead* countQ, qtail* lineQ)

{

numZero *qdata;

while( 1 ) {

cout << "Enter a string, ^C to end session: ";

char tmpbuf[512];

cin >> tmpbuf;

lineQ->put(new lineHolder(tmpbuf));

qdata = (numZero*) countQ->get();

cout << "Count of zeroes = " << qdata->zero << "\n";

};

resultis(1); // never gets here

}

countZero::countZero(qhead *lineQ, qtail *countQ)

{

char c;

lineHolder *inmessage;

while( 1 ) {

inmessage = (lineHolder*)lineQ->get();

char *s = inmessage->line;

int i = 0;

while( c = *s++ )

if( c == `0' )

i++;

numZero *num = new numZero(i);

countQ->put(num);

}

resultis(1); // never gets here

}

int main()

{

qhead *stringQhead = new qhead;

qtail *stringQtail = stringQhead->tail();

qhead *countQhead = new qhead;

qtail *countQtail = countQhead->tail();

countZero counter(stringQhead, countQtail);

getLine g(countQhead, stringQtail);

thistask->resultis(0);

return 0;

}