/*
C: The Complete Reference, 4th Ed. (Paperback)
by Herbert Schildt
ISBN: 0072121246
Publisher: McGraw-Hill Osborne Media; 4 edition (April 26, 2000)
*/
/* A circular queue example using a keyboard buffer. */
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
#define MAX 80
char buf[MAX+1];
int spos = 0;
int rpos = 0;
void qstore(char q);
char qretrieve(void);
int main(void)
{
register char ch;
int t;
buf[80] = '\0';
/* Input characters until a carriage return is typed. */
for(ch=' ',t=0; t<32000 && ch!='\r'; ++t) {
if(_kbhit()) {
ch = _getch();
qstore(ch);
}
printf("%d ", t);
if(ch == '\r') {
/* Display and empty the key buffer. */
printf("\n");
while((ch=qretrieve()) != '\0') printf("%c", ch);
printf("\n");
}
}
return 0;
}
/* Store characters in the queue. */
void qstore(char q)
{
if(spos+1==rpos || (spos+1==MAX && !rpos)) {
printf("List Full\n");
return;
}
buf[spos] = q;
spos++;
if(spos==MAX) spos = 0; /* loop back */
}
/* Retrieve a character. */
char qretrieve(void)
{
if(rpos==MAX) rpos = 0; /* loop back */
if(rpos==spos) return '\0';
rpos++;
return buf[rpos-1];
}
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