CoreFoundation/Collections.subproj/CFBasicHashFindBucket.m

/*	CFBasicHashFindBucket.m
	Copyright (c) 2009-2016, Apple Inc. and the Swift project authors
 
	Portions Copyright (c) 2014-2016 Apple Inc. and the Swift project authors
	Licensed under Apache License v2.0 with Runtime Library Exception
	See http://swift.org/LICENSE.txt for license information
	See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
	Responsibility: Christopher Kane
*/


#if !defined(FIND_BUCKET_NAME) || !defined(FIND_BUCKET_HASH_STYLE) || !defined(FIND_BUCKET_FOR_REHASH) || !defined(FIND_BUCKET_FOR_INDIRECT_KEY)
#error All of FIND_BUCKET_NAME, FIND_BUCKET_HASH_STYLE, FIND_BUCKET_FOR_REHASH, and FIND_BUCKET_FOR_INDIRECT_KEY must be defined before #including this file.
#endif


// During rehashing of a mutable CFBasicHash, we know that there are no
// deleted slots and the keys have already been uniqued. When rehashing,
// if key_hash is non-0, we use it as the hash code.
static
#if FIND_BUCKET_FOR_REHASH
CFIndex
#else
CFBasicHashBucket
#endif
FIND_BUCKET_NAME (CFConstBasicHashRef ht, uintptr_t stack_key
#if FIND_BUCKET_FOR_REHASH
, uintptr_t key_hash
#endif
) {
    uint8_t num_buckets_idx = ht->bits.num_buckets_idx;
    uintptr_t num_buckets = __CFBasicHashTableSizes[num_buckets_idx];
#if FIND_BUCKET_FOR_REHASH
    CFHashCode hash_code = key_hash ? key_hash : __CFBasicHashHashKey(ht, stack_key);
#else
    CFHashCode hash_code = __CFBasicHashHashKey(ht, stack_key);
#endif

#if FIND_BUCKET_HASH_STYLE == 1	// __kCFBasicHashLinearHashingValue
    // Linear probing, with c = 1
    // probe[0] = h1(k)
    // probe[i] = (h1(k) + i * c) mod num_buckets, i = 1 .. num_buckets - 1
    // h1(k) = k mod num_buckets
#if defined(__arm__)
    uintptr_t h1 = __CFBasicHashFold(hash_code, num_buckets_idx);
#else
    uintptr_t h1 = hash_code % num_buckets;
#endif
#elif FIND_BUCKET_HASH_STYLE == 2	// __kCFBasicHashDoubleHashingValue
    // Double hashing
    // probe[0] = h1(k)
    // probe[i] = (h1(k) + i * h2(k)) mod num_buckets, i = 1 .. num_buckets - 1
    // h1(k) = k mod num_buckets
    // h2(k) = floor(k / num_buckets) mod num_buckets
#if defined(__arm__)
    uintptr_t h1 = __CFBasicHashFold(hash_code, num_buckets_idx);
    uintptr_t h2 = __CFBasicHashFold(hash_code / num_buckets, num_buckets_idx);
#else
    uintptr_t h1 = hash_code % num_buckets;
    uintptr_t h2 = (hash_code / num_buckets) % num_buckets;
#endif
    if (0 == h2) h2 = num_buckets - 1;
#elif FIND_BUCKET_HASH_STYLE == 3	// __kCFBasicHashExponentialHashingValue
    // Improved exponential hashing
    // probe[0] = h1(k)
    // probe[i] = (h1(k) + pr(k)^i * h2(k)) mod num_buckets, i = 1 .. num_buckets - 1
    // h1(k) = k mod num_buckets
    // h2(k) = floor(k / num_buckets) mod num_buckets
    // note: h2(k) has the effect of rotating the sequence if it is constant
    // note: pr(k) is any primitive root of num_buckets, varying this gives different sequences
#if defined(__arm__)
    uintptr_t h1 = __CFBasicHashFold(hash_code, num_buckets_idx);
    uintptr_t h2 = __CFBasicHashFold(hash_code / num_buckets, num_buckets_idx);
#else
    uintptr_t h1 = hash_code % num_buckets;
    uintptr_t h2 = (hash_code / num_buckets) % num_buckets;
#endif
    if (0 == h2) h2 = num_buckets - 1;
    uintptr_t pr = __CFBasicHashPrimitiveRoots[num_buckets_idx];
#endif

    COCOA_HASHTABLE_PROBING_START(ht, num_buckets);
    CFBasicHashValue *keys = (ht->bits.keys_offset) ? __CFBasicHashGetKeys(ht) : __CFBasicHashGetValues(ht);
#if !FIND_BUCKET_FOR_REHASH
    uintptr_t *hashes = (__CFBasicHashHasHashCache(ht)) ? __CFBasicHashGetHashes(ht) : NULL;
#endif
    CFIndex deleted_idx = kCFNotFound;
    uintptr_t probe = h1;
#if FIND_BUCKET_HASH_STYLE == 3	// __kCFBasicHashExponentialHashingValue
    uintptr_t acc = pr;
#endif
    for (CFIndex idx = 0; idx < num_buckets; idx++) {
        uintptr_t curr_key = keys[probe].neutral;
        if (curr_key == 0UL) {
            COCOA_HASHTABLE_PROBE_EMPTY(ht, probe);
#if FIND_BUCKET_FOR_REHASH
            CFIndex result = (kCFNotFound == deleted_idx) ? probe : deleted_idx;
#else
            CFBasicHashBucket result;
            result.idx = (kCFNotFound == deleted_idx) ? probe : deleted_idx;
            result.count = 0;
#endif
            COCOA_HASHTABLE_PROBING_END(ht, idx + 1);
            return result;
#if !FIND_BUCKET_FOR_REHASH
        } else if (curr_key == ~0UL) {
            COCOA_HASHTABLE_PROBE_DELETED(ht, probe);
            if (kCFNotFound == deleted_idx) {
                deleted_idx = probe;
            }
        } else {
            COCOA_HASHTABLE_PROBE_VALID(ht, probe);
            if (__CFBasicHashSubABZero == curr_key) curr_key = 0UL;
            if (__CFBasicHashSubABOne == curr_key) curr_key = ~0UL;
#if FIND_BUCKET_FOR_INDIRECT_KEY
            // curr_key holds the value coming in here
            curr_key = __CFBasicHashGetIndirectKey(ht, curr_key);
#endif
            if (curr_key == stack_key || ((!hashes || hashes[probe] == hash_code) && __CFBasicHashTestEqualKey(ht, curr_key, stack_key))) {
                COCOA_HASHTABLE_PROBING_END(ht, idx + 1);
#if FIND_BUCKET_FOR_REHASH
                CFIndex result = probe;
#else
                CFBasicHashBucket result;
                result.idx = probe;
                result.weak_value = __CFBasicHashGetValue(ht, probe);
                result.weak_key = curr_key;
                result.count = (ht->bits.counts_offset) ? __CFBasicHashGetSlotCount(ht, probe) : 1;
#endif
                return result;
            }
#endif
        }

#if FIND_BUCKET_HASH_STYLE == 1	// __kCFBasicHashLinearHashingValue
        probe += 1;
        if (num_buckets <= probe) {
            probe -= num_buckets;
        }
#elif FIND_BUCKET_HASH_STYLE == 2	// __kCFBasicHashDoubleHashingValue
        probe += h2;
        if (num_buckets <= probe) {
            probe -= num_buckets;
        }
#elif FIND_BUCKET_HASH_STYLE == 3	// __kCFBasicHashExponentialHashingValue
        probe = h1 + h2 * acc;
        if (num_buckets <= probe) {
#if defined(__arm__)
            probe = __CFBasicHashFold(probe, num_buckets_idx);
#else
            probe = probe % num_buckets;
#endif
        }
        acc = acc * pr;
        if (num_buckets <= acc) {
#if defined(__arm__)
            acc = __CFBasicHashFold(acc, num_buckets_idx);
#else
            acc = acc % num_buckets;
#endif
        }
#endif

    }
    COCOA_HASHTABLE_PROBING_END(ht, num_buckets);
#if FIND_BUCKET_FOR_REHASH
    CFIndex result = deleted_idx;
#else
    CFBasicHashBucket result;
    result.idx = deleted_idx;
    result.count = 0;
#endif
    return result; // all buckets full or deleted, return first deleted element which was found
}

#undef FIND_BUCKET_NAME
#undef FIND_BUCKET_HASH_STYLE
#undef FIND_BUCKET_FOR_REHASH
#undef FIND_BUCKET_FOR_INDIRECT_KEY