    /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
    /*
     * This file is part of the LibreOffice project.
     *
     * This Source Code Form is subject to the terms of the Mozilla Public
     * License, v. 2.0. If a copy of the MPL was not distributed with this
     * file, You can obtain one at http://mozilla.org/MPL/2.0/.
     *
     * This file incorporates work covered by the following license notice:
     *
     *   Licensed to the Apache Software Foundation (ASF) under one or more
     *   contributor license agreements. See the NOTICE file distributed
     *   with this work for additional information regarding copyright
     *   ownership. The ASF licenses this file to you under the Apache
     *   License, Version 2.0 (the "License"); you may not use this file
     *   except in compliance with the License. You may obtain a copy of
     *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
     */

    #include <sal/config.h>

    #include <stdlib.h>

    #include "hash.hxx"
    #include "strimp.hxx"
    #include <osl/diagnose.h>
    #include <sal/macros.h>

    struct StringHashTableImpl {
        sal_uInt32    nEntries;
        sal_uInt32    nSize;
        rtl_uString **pData;
    };

    typedef StringHashTableImpl StringHashTable;

    // Only for use in the implementation
    static StringHashTable *rtl_str_hash_new(sal_uInt32 nSize);
    static void rtl_str_hash_free(StringHashTable *pHash);

    StringHashTable * getHashTable()
    {
        static StringHashTable *pInternPool = nullptr;
        if (!pInternPool)
        {
            static StringHashTable* pHash = rtl_str_hash_new(1024);
            pInternPool = pHash;
        }
        return pInternPool;
    }

    // Better / smaller / faster hash set ....

    // TODO: add bottom bit-set list terminator to string list

    static sal_uInt32 getNextSize(sal_uInt32 nSize)
    {
        // Sedgewick - Algorithms in C P577.
        static const sal_uInt32 nPrimes[] = { 1021, 2039, 4093, 8191, 16381, 32749,
                                              65521, 131071,262139, 524287, 1048573,
                                              2097143, 4194301, 8388593, 16777213,
                                              33554393, 67108859, 134217689 };

        for (sal_uInt32 nPrime : nPrimes)
        {
            if (nPrime > nSize)
                return nPrime;
        }
        return nSize * 2;
    }

    static sal_uInt32 hashString(rtl_uString *pString)
    {
        return static_cast<sal_uInt32>(rtl_ustr_hashCode_WithLength(pString->buffer,
                                                         pString->length));
    }

    static StringHashTable * rtl_str_hash_new(sal_uInt32 nSize)
    {
        StringHashTable *pHash = static_cast<StringHashTable *>(malloc(sizeof(StringHashTable)));

        pHash->nEntries = 0;
        pHash->nSize = getNextSize (nSize);
        pHash->pData = static_cast< rtl_uString ** >(calloc(sizeof(rtl_uString *), pHash->nSize));

        return pHash;
    }

    static void rtl_str_hash_free(StringHashTable *pHash)
    {
        if (!pHash)
            return;

        if (pHash->pData)
            free(pHash->pData);

        free(pHash);
    }

    static void
    rtl_str_hash_insert_nonequal(StringHashTable   *pHash,
                                 rtl_uString       *pString)
    {
        sal_uInt32 nHash = hashString(pString);
        sal_uInt32 n;

        n = nHash % pHash->nSize;
        while (pHash->pData[n])
        {
            n++;
            if (n >= pHash->nSize)
                n = 0;
        }
        pHash->pData[n] = pString;
    }

    static void rtl_str_hash_resize(sal_uInt32 nNewSize)
    {
        sal_uInt32 i;
        StringHashTable *pNewHash;
        StringHashTable *pHash = getHashTable();

        OSL_ASSERT(nNewSize > pHash->nEntries);

        pNewHash = rtl_str_hash_new(nNewSize);

        for (i = 0; i < pHash->nSize; i++)
        {
            if (pHash->pData[i])
                rtl_str_hash_insert_nonequal(pNewHash, pHash->pData[i]);
        }

        pNewHash->nEntries = pHash->nEntries;
        free(pHash->pData);
        *pHash = *pNewHash;
        pNewHash->pData = nullptr;
        rtl_str_hash_free(pNewHash);
    }

    static bool compareEqual(rtl_uString *pStringA, rtl_uString *pStringB)
    {
        if (pStringA == pStringB)
            return true;

        if (pStringA->length != pStringB->length)
            return false;

        return !rtl_ustr_compare_WithLength( pStringA->buffer, pStringA->length,
                                             pStringB->buffer, pStringB->length);
    }

    rtl_uString * rtl_str_hash_intern (
                    rtl_uString *pString,
                    int         can_return)
    {
        sal_uInt32 nHash = hashString(pString);
        sal_uInt32 n;
        rtl_uString *pHashStr;

        StringHashTable *pHash = getHashTable();

        // Should we resize ?
        if (pHash->nEntries >= pHash->nSize/2)
            rtl_str_hash_resize(getNextSize(pHash->nSize));

        n = nHash % pHash->nSize;
        while ((pHashStr = pHash->pData[n]))
        {
            if (compareEqual(pHashStr, pString))
            {
                rtl_uString_acquire(pHashStr);
                return pHashStr;
            }

            n++;
            if (n >= pHash->nSize)
                n = 0;
        }

        if (!can_return)
        {
            rtl_uString *pCopy = nullptr;
            rtl_uString_newFromString( &pCopy, pString );
            pString = pCopy;

            if (!pString)
                return nullptr;
        }

        if (!SAL_STRING_IS_STATIC(pString))
            pString->refCount |= SAL_STRING_INTERN_FLAG;

        pHash->pData[n] = pString;
        pHash->nEntries++;

        return pString;
    }

    void rtl_str_hash_remove(rtl_uString *pString)
    {
        sal_uInt32 n;
        sal_uInt32 nHash = hashString(pString);
        rtl_uString *pHashStr;

        StringHashTable *pHash = getHashTable();

        n = nHash % pHash->nSize;
        while ((pHashStr = pHash->pData[n]))
        {
            if (compareEqual(pHashStr, pString))
                break;

            n++;

            if (n >= pHash->nSize)
                n = 0;
        }

        OSL_ASSERT(pHash->pData[n]);
        if (!pHash->pData[n])
            return;

        pHash->pData[n++] = nullptr;
        pHash->nEntries--;

        if (n >= pHash->nSize)
            n = 0;

        while ((pHashStr = pHash->pData[n]))
        {
            pHash->pData[n] = nullptr;
            // FIXME: rather unsophisticated and N^2 in chain-length, but robust.
            rtl_str_hash_insert_nonequal(pHash, pHashStr);
            n++;

            if (n >= pHash->nSize)
                n = 0;
        }
        // FIXME: Should we down-size ?
    }

    /* vim:set shiftwidth=4 softtabstop=4 expandtab: */

↑ V522 There might be dereferencing of a potential null pointer 'pHash'. Check lines: 82, 80.

↑ V522 Dereferencing of the null pointer 'pHash' might take place. The potential null pointer is passed into 'rtl_str_hash_insert_nonequal' function. Inspect the first argument. Check lines: 107, 130.