Browse Source Download (without any required ccan dependencies)

Module:

htable

Summary:

hash table routines

Author:

Rusty Russell <rusty@rustcorp.com.au>

Dependencies:

Description:

A hash table is an efficient structure for looking up keys. This version grows with usage and allows efficient deletion.

Example:

#include <ccan/htable/htable.h>
#include <ccan/hash/hash.h>
#include <stdio.h>
#include <err.h>
#include <string.h>

struct name_to_digit {
        const char *name;
        unsigned int val;
};

static struct name_to_digit map[] = {
        { "zero", 0},
        { "one", 1 },
        { "two", 2 },
        { "three", 3 },
        { "four", 4 },
        { "five", 5 },
        { "six", 6 },
        { "seven", 7 },
        { "eight", 8 },
        { "nine", 9 }
};

// Wrapper for rehash function pointer.
static size_t rehash(const void *e, void *unused)
{
        (void)unused;
        return hash_string(((struct name_to_digit *)e)->name);
}

// Comparison function.
static bool streq(const void *e, void *string)
{
        return strcmp(((struct name_to_digit *)e)->name, string) == 0;
}

// We let them add their own aliases, eg. --alias=v=5
static void add_alias(struct htable *ht, const char *alias)
{
        char *eq;
        struct name_to_digit *n;

        n = malloc(sizeof(*n));
        n->name = strdup(alias);

        eq = strchr(n->name, '=');
        if (!eq || ((n->val = atoi(eq+1)) == 0 && !strcmp(eq+1, "0")))
                errx(1, "Usage: --alias=<name>=<value>");
        *eq = '\0';
        htable_add(ht, hash_string(n->name), n);
}

int main(int argc, char *argv[])
{
        struct htable ht;
        int i;
        unsigned long val;

        if (argc < 2)
                errx(1, "Usage: %s [--alias=<name>=<val>]... <str>...",
                     argv[0]);

        // Create and populate hash table.
        htable_init(&ht, rehash, NULL);
        for (i = 0; i < (int)(sizeof(map)/sizeof(map[0])); i++)
                htable_add(&ht, hash_string(map[i].name), &map[i]);

        // Add any aliases to the hash table.
        for (i = 1; i < argc; i++) {
                if (!strncmp(argv[i], "--alias=", strlen("--alias=")))
                        add_alias(&ht, argv[i] + strlen("--alias="));
                else
                        break;
        }

        // Find the other args in the hash table.
        for (val = 0; i < argc; i++) {
                struct name_to_digit *n;
                n = htable_get(&ht, hash_string(argv[i]),
                               streq, argv[i]);
                if (!n)
                        errx(1, "Invalid digit name %s", argv[i]);
                // Append it to the value we are building up.
                val *= 10;
                val += n->val;
        }
        printf("%lu\n", val);
        return 0;
}

License:

LGPL (v2.1 or any later version)