©2004 by Marc J. Rochkind. All rights reserved. Portions marked "Open Source" may be copied under license.

 

                 

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c5/t2.c

Go to the documentation of this file.

/*
    Thread example (background sorting; no mutexes)
    AUP2, Sec. 5.17 (not in book)

    Copyright 2003 by Marc J. Rochkind. All rights reserved.
    May be copied only for purposes and under conditions described
    on the Web page www.basepath.com/aup/copyright.htm.

    The Example Files are provided "as is," without any warranty;
    without even the implied warranty of merchantability or fitness
    for a particular purpose. The author and his publisher are not
    responsible for any damages, direct or incidental, resulting
    from the use or non-use of these Example Files.

    The Example Files may contain defects, and some contain deliberate
    coding mistakes that were included for educational reasons.
    You are responsible for determining if and how the Example Files
    are to be used.

*/
#include "defs.h"
#include <pthread.h>

#define MAX_ENTRIES 100

struct dict {
    int d_nentries;
    char *d_entry[MAX_ENTRIES];
    bool d_issorted;
};

static int compar(const void *x, const void *y)
{
    return strcmp(*(char **)x, *(char **)y);
}

static void *sorter(void *arg)
{
    struct dict *d = arg;

    while (true) {
        if (!d->d_issorted) {
            qsort(d->d_entry, d->d_nentries, sizeof(char *), compar);
            d->d_issorted = true;
        }
        sleep(1);
    }
}

int main(void)
{
    struct dict dictionary;
    pthread_t tid;
    char word[100];
    int i;
    size_t wordlen;

    dictionary.d_nentries = 0;
    dictionary.d_issorted = true;
    ec_rv( pthread_create(&tid, NULL, sorter, &dictionary) )
    while (!feof(stdin)) {
        printf("Word? ");
        if (fgets(word, sizeof(word), stdin) == NULL && ferror(stdin))
            EC_FAIL
        if (word[0] == '-') {
            if (dictionary.d_issorted)
                for (i = 0; i < dictionary.d_nentries; i++)
                    printf("\t%s\n", dictionary.d_entry[i]);
            else
                printf("Not sorted -- try again later\n");
            continue;
        }
        wordlen = strlen(word);
        if (word[wordlen - 1] == '\n')
            word[--wordlen] = '\0';
        if (dictionary.d_nentries >= MAX_ENTRIES) {
            errno = E2BIG;
            EC_FAIL
        }
        ec_null( dictionary.d_entry[dictionary.d_nentries] =
          malloc(wordlen + 1) )
        strcpy(dictionary.d_entry[dictionary.d_nentries], word);
        /*
            Make entry visible to sorter. Value of d_issorted is
            unknown.
        */
        dictionary.d_nentries++;
        /*
            Force sort. May be a redundant one because sort may
            occur between previous statement and next. In this case
            an extra sort will occur later.
        */
        dictionary.d_issorted = false;
    }
    return EXIT_SUCCESS;

EC_CLEANUP_BGN
    return EXIT_FAILURE;
EC_CLEANUP_END
}

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