106 lines
3.2 KiB
C++
106 lines
3.2 KiB
C++
/*******************************************************************************
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Copyright(C) Jonas 'Sortie' Termansen 2012, 2014.
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This file is part of the Sortix C Library.
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The Sortix C Library is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 3 of the License, or (at your
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option) any later version.
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The Sortix C Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
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stdlib/qsort_r.cpp
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Sort an array.
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*******************************************************************************/
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#include <stdlib.h>
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#include <string.h>
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static void memswap(unsigned char* a, unsigned char* b, size_t size)
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{
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unsigned char tmp;
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for ( size_t i = 0; i < size; i++ )
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{
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tmp = a[i];
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a[i] = b[i];
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b[i] = tmp;
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}
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}
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static
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unsigned char* array_index(unsigned char* base,
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size_t element_size,
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size_t index)
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{
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return base + element_size * index;
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}
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static
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size_t partition(unsigned char* base,
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size_t element_size,
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size_t num_elements,
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size_t pivot_index,
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int (*compare)(const void*, const void*, void*),
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void* arg)
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{
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if ( pivot_index != num_elements - 1 )
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{
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unsigned char* pivot = array_index(base, element_size, pivot_index);
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unsigned char* other = array_index(base, element_size, num_elements - 1);
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memswap(pivot, other, element_size);
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pivot_index = num_elements - 1;
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}
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size_t store_index = 0;
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for ( size_t i = 0; i < num_elements - 1; i++ )
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{
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unsigned char* pivot = array_index(base, element_size, pivot_index);
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unsigned char* value = array_index(base, element_size, i);
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if ( compare(value, pivot, arg) <= 0 )
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{
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unsigned char* other = array_index(base, element_size, store_index);
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if ( value != other )
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memswap(value, other, element_size);
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store_index++;
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}
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}
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unsigned char* pivot = array_index(base, element_size, pivot_index);
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unsigned char* value = array_index(base, element_size, store_index);
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memswap(pivot, value, element_size);
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return store_index;
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}
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extern "C"
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void qsort_r(void* base_ptr,
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size_t num_elements,
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size_t element_size,
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int (*compare)(const void*, const void*, void*),
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void* arg)
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{
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unsigned char* base = (unsigned char*) base_ptr;
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if ( !element_size || num_elements < 2 )
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return;
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size_t pivot_index = num_elements / 2;
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pivot_index = partition(base, element_size, num_elements, pivot_index, compare, arg);
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if ( 2 <= pivot_index )
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qsort_r(base, pivot_index, element_size, compare, arg);
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if ( 2 <= num_elements - (pivot_index + 1) )
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qsort_r(array_index(base, element_size, pivot_index + 1),
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num_elements - (pivot_index + 1), element_size, compare, arg);
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}
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