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Diffstat (limited to '')
| -rw-r--r-- | sal/rtl/hash.cxx | 241 |
1 files changed, 241 insertions, 0 deletions
diff --git a/sal/rtl/hash.cxx b/sal/rtl/hash.cxx new file mode 100644 index 000000000..4fed60889 --- /dev/null +++ b/sal/rtl/hash.cxx @@ -0,0 +1,241 @@ +/* -*- 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> + +namespace { + +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); + +static StringHashTable * getHashTable() +{ + static StringHashTable* pInternPool = rtl_str_hash_new(1024); + 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: */ |