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76 lines
1.4 KiB
76 lines
1.4 KiB
#define _POSIX_C_SOURCE 200809l
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#define _DEFAULT_SOURCE
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#include <stdlib.h>
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#include <stdint.h>
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#include <string.h>
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#include "hash.h"
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#define MAXSIZE 4096
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static unsigned int hash(unsigned int code)
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{
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// identity map the ascii range
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if (code < 128) return code;
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return (uint32_t)((uint64_t)(code*2654435761)>>32);
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}
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struct hm_ref * hm_create(unsigned int size)
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{
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if (!size || size > MAXSIZE)
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return NULL;
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// round to the greater power of two
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size = 1<<__builtin_clz(size);
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// FIXME: check for intger overflow here
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struct hm_ref *h = malloc(sizeof(struct hm_ref)+sizeof(struct hm_entry)*size);
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if (h) {
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h->items = 0;
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h->size = size;
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memset(h->bucket, 0, sizeof(struct hm_ref)*size);
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}
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return h;
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}
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void hm_destroy(struct hm_ref *hm)
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{
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free(hm);
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}
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static struct hm_entry * lookup(struct hm_ref *hm, unsigned int code)
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{
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// fast modulo operation for power-of-2 size
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unsigned int mask = hm->size - 1;
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unsigned int i = hash(code);
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for (unsigned int j = 1; ; i += j++) {
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if (!hm->bucket[i&mask].code || hm->bucket[i].code == code)
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return &(hm->bucket[i&mask]);
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}
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return NULL;
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}
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struct hm_entry * hm_search(struct hm_ref *hm, unsigned int code)
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{
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struct hm_entry *r = lookup(hm, code);
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if (r) {
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if (r->code == code)
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return r;
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return NULL;
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}
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return r;
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}
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struct hm_entry * hm_insert(struct hm_ref *hm, struct hm_entry *entry)
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{
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struct hm_entry *r = lookup(hm, entry->code);
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if (r) *r = *entry;
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return r;
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}
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