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iter_demo.c

#include <stdio.h>
#include <string.h>
#include <assert.h>

#include "iter.h"


char *
get_next_string_in_sequence(iter *i)
{
    static char *strings[] = { "john", "jacob", "jingleheimer", "smith", 0 };
    char *result;
    
    result = strings[ ((int)(i->state)) ++];
    if (!result) i->state = 0;
    
    return result;
}

void 
simple_example()
{
    iter i={0,0};
    char *s;

    while (( s=get_next_string_in_sequence(&i) )) {
    printf("s is '%s'\n", s);
    }

}


void 
medium_example()
{
    iter i={0,0};
    char *s;

    while (( s=get_next_string_in_sequence(&i) )) {
    if (!strcmp(s, "jingleheimer")) {
        iter_reset(&i);  /* free any resources */
        break;
    }
    printf("s is '%s'\n", s);
    }

}

void 
lookahead_1_example()
{
    iter i={0,0};
    char *current=0;
    char *next;
    
    printf("The names are: ");
    do {
    next = get_next_string_in_sequence(&i);
    if (current) {
        /* do something with current, looking at next if you want  */
        if (next) {
        printf("%s, ", current);
        } else {
        printf("%s.\n", current);
        }
    }
    current = next;
    } while (current);
}

void 
general_lookahead_example()
{
    iter i={0,0};
    const int MAX_LOOKAHEAD = 16;
    char *buf[MAX_LOOKAHEAD];
    int current_index = 0;
    int buf_count = 0;
    int done = 0;
#define peek(n,m) (buf[ (n+m) % MAX_LOOKAHEAD ])

    for(;;) {
    /*  read next item into buffer */
    if (!done) {
        assert(buf_count < MAX_LOOKAHEAD);
        peek(current_index, buf_count) = get_next_string_in_sequence(&i);
        if (peek(current_index, buf_count) == 0) done = 1;
        buf_count++;
    }

    /*  user code:   "continue" for more lookahead */
    if (buf_count < 3 && !done) continue;

    printf("%s", peek(current_index, 0));

    if (done) switch(buf_count) {
    case 3: /* second to last item */
        printf(", and also "); break;
    case 2: /* last item */
        printf(".\n"); break;
    } else {
        printf(", ");
    }
         
    /*  advance current_index to next item */
    current_index = (current_index+1) % MAX_LOOKAHEAD;
    buf_count--;
    if (!peek(current_index, 0)) break;
    }
}


void 
iter_demo_driver()
{
    printf("\n\n* simple example\n\n");
    simple_example();

    printf("\n\n* medium example\n\n");
    medium_example();

    printf("\n\n* lookahead_1 example\n\n");
    lookahead_1_example();

    printf("\n\n* general_lookahead example\n\n");
    general_lookahead_example();

}

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