open62541/src/server/ua_nodestore_hash.inc

typedef UA_UInt32 hash_t;

static hash_t mod(hash_t h, hash_t size) { return h % size; }
static hash_t mod2(hash_t h, hash_t size) { return 1 + (h % (size - 2)); }

/* Based on Murmur-Hash 3 by Austin Appleby (public domain, freely usable) */
static hash_t hash_array(const UA_Byte *data, UA_UInt32 len, UA_UInt32 seed) {
    if(data == UA_NULL)
        return 0;

    const int32_t   nblocks = len / 4;
    const uint32_t *blocks;
    static const uint32_t c1 = 0xcc9e2d51;
    static const uint32_t c2 = 0x1b873593;
    static const uint32_t r1 = 15;
    static const uint32_t r2 = 13;
    static const uint32_t m  = 5;
    static const uint32_t n  = 0xe6546b64;
    hash_t hash = seed;
    /* Somce compilers emit a warning when casting from a byte array to ints. */
#if ((__GNUC__ == 4 && __GNUC_MINOR__ >= 6) || __GNUC__ > 4 || defined(__clang__))
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wcast-align"
#endif
    blocks = (const uint32_t *)data;
#if ((__GNUC__ == 4 && __GNUC_MINOR__ >= 6) || __GNUC__ > 4 || defined(__clang__))
#pragma GCC diagnostic pop
#endif
    for(int32_t i = 0;i < nblocks;i++) {
        uint32_t k = blocks[i];
        k    *= c1;
        k     = (k << r1) | (k >> (32 - r1));
        k    *= c2;
        hash ^= k;
        hash  = ((hash << r2) | (hash >> (32 - r2))) * m + n;
    }

    const uint8_t *tail = (const uint8_t *)(data + nblocks * 4);
    uint32_t       k1   = 0;
    switch(len & 3) {
    case 3:
        k1 ^= tail[2] << 16;
    case 2:
        k1 ^= tail[1] << 8;
    case 1:
        k1   ^= tail[0];
        k1   *= c1;
        k1    = (k1 << r1) | (k1 >> (32 - r1));
        k1   *= c2;
        hash ^= k1;
    }

    hash ^= len;
    hash ^= (hash >> 16);
    hash *= 0x85ebca6b;
    hash ^= (hash >> 13);
    hash *= 0xc2b2ae35;
    hash ^= (hash >> 16);
    return hash;
}

static hash_t hash(const UA_NodeId *n) {
    switch(n->identifierType) {
    case UA_NODEIDTYPE_NUMERIC:
        /*  Knuth's multiplicative hashing */
        return (n->identifier.numeric + n->namespaceIndex) * 2654435761;   // mod(2^32) is implicit
    case UA_NODEIDTYPE_STRING:
        return hash_array(n->identifier.string.data, n->identifier.string.length, n->namespaceIndex);
    case UA_NODEIDTYPE_GUID:
        return hash_array((const UA_Byte *)&(n->identifier.guid), sizeof(UA_Guid), n->namespaceIndex);
    case UA_NODEIDTYPE_BYTESTRING:
        return hash_array((const UA_Byte *)n->identifier.byteString.data, n->identifier.byteString.length, n->namespaceIndex);
    default:
        UA_assert(UA_FALSE);
        return 0;
    }
}