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htable
hash table routines
Rusty Russell <rusty@rustcorp.com.au>
A hash table is an efficient structure for looking up keys. This version grows with usage and allows efficient deletion.
#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)
{
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;
unsigned 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 < 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;
}
LGPL (v2.1 or any later version)