hashtable_eastl.cpp

/*
Copyright (C) 2009-2010 Electronic Arts, Inc.  All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

1.  Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.
2.  Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.
3.  Neither the name of Electronic Arts, Inc. ("EA") nor the names of
    its contributors may be used to endorse or promote products derived
    from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY ELECTRONIC ARTS AND ITS CONTRIBUTORS "AS IS" AND ANY
EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL ELECTRONIC ARTS OR ITS CONTRIBUTORS BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

// EASTL/hashtable.cpp
//
// Copyright (c) 2005, Electronic Arts. All rights reserved.
// Written and maintained by Paul Pedriana.



#include <stk_util/util/hashtable_eastl.h>
#include <stk_util/util/utility_eastl.h>
#include <math.h>  // Not all compilers support <cmath> and std::ceil(), which we need below.
#include <stddef.h>


#ifdef _MSC_VER
    #pragma warning(disable: 4267)  // 'argument' : conversion from 'size_t' to 'const uint32_t', possible loss of data. This is a bogus warning resulting from a bug in VC++.
#endif


namespace eastl
{

    EASTL_API void* gpEmptyBucketArray[2] = { NULL, (void*)uintptr_t(~0) };



    const uint32_t gPrimeNumberArray[] =
    {
        2u, 3u, 5u, 7u, 11u, 13u, 17u, 19u, 23u, 29u, 31u,
        37u, 41u, 43u, 47u, 53u, 59u, 61u, 67u, 71u, 73u, 79u,
        83u, 89u, 97u, 103u, 109u, 113u, 127u, 137u, 139u, 149u,
        157u, 167u, 179u, 193u, 199u, 211u, 227u, 241u, 257u,
        277u, 293u, 313u, 337u, 359u, 383u, 409u, 439u, 467u,
        503u, 541u, 577u, 619u, 661u, 709u, 761u, 823u, 887u,
        953u, 1031u, 1109u, 1193u, 1289u, 1381u, 1493u, 1613u,
        1741u, 1879u, 2029u, 2179u, 2357u, 2549u, 2753u, 2971u,
        3209u, 3469u, 3739u, 4027u, 4349u, 4703u, 5087u, 5503u,
        5953u, 6427u, 6949u, 7517u, 8123u, 8783u, 9497u, 10273u,
        11113u, 12011u, 12983u, 14033u, 15173u, 16411u, 17749u,
        19183u, 20753u, 22447u, 24281u, 26267u, 28411u, 30727u,
        33223u, 35933u, 38873u, 42043u, 45481u, 49201u, 53201u,
        57557u, 62233u, 67307u, 72817u, 78779u, 85229u, 92203u,
        99733u, 107897u, 116731u, 126271u, 136607u, 147793u,
        159871u, 172933u, 187091u, 202409u, 218971u, 236897u,
        256279u, 277261u, 299951u, 324503u, 351061u, 379787u,
        410857u, 444487u, 480881u, 520241u, 562841u, 608903u,
        658753u, 712697u, 771049u, 834181u, 902483u, 976369u,
        1056323u, 1142821u, 1236397u, 1337629u, 1447153u, 1565659u,
        1693859u, 1832561u, 1982627u, 2144977u, 2320627u, 2510653u,
        2716249u, 2938679u, 3179303u, 3439651u, 3721303u, 4026031u,
        4355707u, 4712381u, 5098259u, 5515729u, 5967347u, 6456007u,
        6984629u, 7556579u, 8175383u, 8844859u, 9569143u, 10352717u,
        11200489u, 12117689u, 13109983u, 14183539u, 15345007u,
        16601593u, 17961079u, 19431899u, 21023161u, 22744717u,
        24607243u, 26622317u, 28802401u, 31160981u, 33712729u,
        36473443u, 39460231u, 42691603u, 46187573u, 49969847u,
        54061849u, 58488943u, 63278561u, 68460391u, 74066549u,
        80131819u, 86693767u, 93793069u, 101473717u, 109783337u,
        118773397u, 128499677u, 139022417u, 150406843u, 162723577u,
        176048909u, 190465427u, 206062531u, 222936881u, 241193053u,
        260944219u, 282312799u, 305431229u, 330442829u, 357502601u,
        386778277u, 418451333u, 452718089u, 489790921u, 529899637u,
        573292817u, 620239453u, 671030513u, 725980837u, 785430967u,
        849749479u, 919334987u, 994618837u, 1076067617u, 1164186217u,
        1259520799u, 1362662261u, 1474249943u, 1594975441u,
        1725587117u, 1866894511u, 2019773507u, 2185171673u,
        2364114217u, 2557710269u, 2767159799u, 2993761039u,
        3238918481u, 3504151727u, 3791104843u, 4101556399u,
        4294967291u,
        4294967291u // Sentinel so we don't have to test result of lower_bound
    };


    const uint32_t kPrimeCount = (sizeof(gPrimeNumberArray) / sizeof(gPrimeNumberArray[0]) - 1);


    uint32_t prime_rehash_policy::GetPrevBucketCountOnly(uint32_t nBucketCountHint)
    {
        const uint32_t nPrime = *(eastl::upper_bound(gPrimeNumberArray, gPrimeNumberArray + kPrimeCount, nBucketCountHint) - 1);
        return nPrime;
    }


    uint32_t prime_rehash_policy::GetPrevBucketCount(uint32_t nBucketCountHint) const
    {
        const uint32_t nPrime = *(eastl::upper_bound(gPrimeNumberArray, gPrimeNumberArray + kPrimeCount, nBucketCountHint) - 1);

        mnNextResize = (uint32_t)ceil(nPrime * mfMaxLoadFactor);
        return nPrime;
    }


    uint32_t prime_rehash_policy::GetNextBucketCount(uint32_t nBucketCountHint) const
    {
        const uint32_t nPrime = *eastl::lower_bound(gPrimeNumberArray, gPrimeNumberArray + kPrimeCount, nBucketCountHint);

        mnNextResize = (uint32_t)ceil(nPrime * mfMaxLoadFactor);
        return nPrime;
    }


    uint32_t prime_rehash_policy::GetBucketCount(uint32_t nElementCount) const
    {
        const uint32_t nMinBucketCount = (uint32_t)(nElementCount / mfMaxLoadFactor);
        const uint32_t nPrime          = *eastl::lower_bound(gPrimeNumberArray, gPrimeNumberArray + kPrimeCount, nMinBucketCount);

        mnNextResize = (uint32_t)ceil(nPrime * mfMaxLoadFactor);
        return nPrime;
    }


    eastl::pair<bool, uint32_t>
    prime_rehash_policy::GetRehashRequired(uint32_t nBucketCount, uint32_t nElementCount, uint32_t nElementAdd) const
    {
        if((nElementCount + nElementAdd) > mnNextResize) // It is significant that we specify > next resize and not >= next resize.
        {
            if(nBucketCount == 1) // We force rehashing to occur if the bucket count is < 2.
                nBucketCount = 0;

            float fMinBucketCount = (nElementCount + nElementAdd) / mfMaxLoadFactor;

            if(fMinBucketCount > (float)nBucketCount)
            {
                fMinBucketCount       = eastl::max_alt(fMinBucketCount, mfGrowthFactor * nBucketCount);
                const uint32_t nPrime = *eastl::lower_bound(gPrimeNumberArray, gPrimeNumberArray + kPrimeCount, (uint32_t)fMinBucketCount);
                mnNextResize          = (uint32_t)ceil(nPrime * mfMaxLoadFactor);

                return eastl::pair<bool, uint32_t>(true, nPrime);
            }
            else
            {
                mnNextResize = (uint32_t)ceil(nBucketCount * mfMaxLoadFactor);
                return eastl::pair<bool, uint32_t>(false, (uint32_t)0);
            }
        }

        return eastl::pair<bool, uint32_t>(false, (uint32_t)0);
    }


} // namespace eastl