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/* Copyright (C) 2020 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. */
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <sys/random.h>
struct entry {
uint8_t pubkey[32];
uint64_t some_member;
uint32_t some_other_member;
struct entry *next;
};
enum { ENTRY_BUCKETS_POW2 = 1 << 17 };
static uint64_t hash_v[4];
static __attribute__((constructor)) void init_hash_v(void)
{
assert(!getentropy(&hash_v, sizeof(hash_v) / 2));
hash_v[0] ^= 0x736f6d6570736575ULL;
hash_v[1] ^= 0x646f72616e646f6dULL;
hash_v[2] = hash_v[0] ^ 0x736f6d6570736575ULL ^ 0x6c7967656e657261ULL;
hash_v[3] = hash_v[1] ^ 0x646f72616e646f6dULL ^ 0x7465646279746573ULL;
}
static unsigned int pubkey_bucket(uint8_t key[32])
{
uint64_t first, second, third, forth;
uint64_t v0 = hash_v[0];
uint64_t v1 = hash_v[1];
uint64_t v2 = hash_v[2];
uint64_t v3 = hash_v[3];
memcpy(&first, &key[0], sizeof(first));
memcpy(&second, &key[8], sizeof(second));
memcpy(&third, &key[16], sizeof(third));
memcpy(&forth, &key[24], sizeof(forth));
#define SIPROUND ( \
v0 += v1, \
v1 = ((v1 << (13 & 63)) | (v1 >> ((-13) & 63))),\
v1 ^= v0, \
v0 = ((v0 << (32 & 63)) | (v0 >> ((-32) & 63))),\
v2 += v3, \
v3 = ((v3 << (16 & 63)) | (v3 >> ((-16) & 63))),\
v3 ^= v2, \
v0 += v3, \
v3 = ((v3 << (21 & 63)) | (v3 >> ((-21) & 63))),\
v3 ^= v0, \
v2 += v1, \
v1 = ((v1 << (17 & 63)) | (v1 >> ((-17) & 63))),\
v1 ^= v2, \
v2 = ((v2 << (32 & 63)) | (v2 >> ((-32) & 63))))
v3 ^= first;
SIPROUND;
SIPROUND;
v0 ^= first;
v3 ^= second;
SIPROUND;
SIPROUND;
v0 ^= second;
v3 ^= third;
SIPROUND;
SIPROUND;
v0 ^= third;
v3 ^= forth;
SIPROUND;
SIPROUND;
v0 ^= forth;
v3 ^= 32ULL << 56;
SIPROUND;
SIPROUND;
v0 ^= 32ULL << 56;
v2 ^= 0xFF;
SIPROUND;
SIPROUND;
SIPROUND;
SIPROUND;
#undef SIPROUND
return (v0 ^ v1 ^ v2 ^ v3) & (ENTRY_BUCKETS_POW2 - 1);
}
static struct entry *entry_buckets[ENTRY_BUCKETS_POW2];
static struct entry *find_entry(uint8_t key[32])
{
struct entry *entry;
for (entry = entry_buckets[pubkey_bucket(key)]; entry; entry = entry->next) {
if (!memcmp(entry->pubkey, key, 32))
return entry;
}
return NULL;
}
static struct entry *find_or_insert_entry(uint8_t key[32])
{
struct entry **entry;
for (entry = &entry_buckets[pubkey_bucket(key)]; *entry; entry = &(*entry)->next) {
if (!memcmp((*entry)->pubkey, key, 32))
return *entry;
}
*entry = calloc(1, sizeof(**entry));
assert(*entry);
memcpy((*entry)->pubkey, key, 32);
return *entry;
}
/* Just a small test */
int main(int argc, char *argv[])
{
uint8_t key[32] = { 0 };
int i;
for (i = 0; i < 1 << 20; ++i) {
struct entry *entry;
memcpy(key, &i, sizeof(i));
entry = find_or_insert_entry(key);
entry->some_member = i ^ 0xffffffff;
}
for (i = 0; i < 1 << 20; ++i) {
struct entry *entry;
memcpy(key, &i, sizeof(i));
entry = find_entry(key);
assert(entry);
assert(entry->some_member == i ^ 0xffffffff);
}
return 0;
}
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