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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)<--- Consider using std::find_if algorithm instead of a raw loop.
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: */
|