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127 lines
4 KiB
C++
127 lines
4 KiB
C++
/*******************************************************************************
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Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013, 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/realloc.cpp
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Reallocates a chunk of memory from the dynamic memory heap.
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*******************************************************************************/
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#include <assert.h>
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#include <errno.h>
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#include <malloc.h>
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#include <stdlib.h>
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#include <string.h>
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#if __is_sortix_kernel
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#include <sortix/kernel/kernel.h>
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#endif
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#if defined(HEAP_NO_ASSERT)
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#define __heap_verify() ((void) 0)
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#undef assert
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#define assert(x) do { ((void) 0); } while ( 0 )
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#endif
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extern "C" void* realloc(void* ptr, size_t requested_size)
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{
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if ( !ptr )
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return malloc(requested_size);
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if ( !heap_size_has_bin(requested_size) )
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return errno = ENOMEM, (void*) NULL;
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// Decide how big an allocation we would like to make.
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size_t requested_chunk_outer_size = sizeof(struct heap_chunk) +
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sizeof(struct heap_chunk_post);
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size_t requested_chunk_inner_size = heap_align(requested_size);
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size_t requested_chunk_size = requested_chunk_outer_size +
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requested_chunk_inner_size;
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if ( !heap_size_has_bin(requested_chunk_size) )
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return errno = ENOMEM, (void*) NULL;
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__heap_lock();
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__heap_verify();
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// Retrieve the chunk that contains this allocation.
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struct heap_chunk* chunk = heap_data_to_chunk((uint8_t*) ptr);
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assert(chunk->chunk_magic == HEAP_CHUNK_MAGIC);
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assert(heap_chunk_to_post(chunk)->chunk_magic == HEAP_CHUNK_MAGIC);
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assert(heap_chunk_to_post(chunk)->chunk_size == chunk->chunk_size);
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// Do nothing if the chunk already has the ideal size.
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if ( chunk->chunk_size == requested_chunk_size )
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{
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__heap_verify();
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__heap_unlock();
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return heap_chunk_to_data(chunk);
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}
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// If the ideal size is smaller than the current, attempt the shrink the
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// allocation if a new chunk can be created.
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if ( requested_chunk_size < chunk->chunk_size )
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{
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assert(requested_chunk_size <= chunk->chunk_size);
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if ( heap_can_split_chunk(chunk, requested_chunk_size) )
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heap_split_chunk(chunk, requested_chunk_size);
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__heap_verify();
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__heap_unlock();
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return heap_chunk_to_data(chunk);
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}
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// TODO: What if the right neighbor is the part edge?
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// If we need to expand the chunk, attempt to combine it with its right
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// neighbor if it is large enough.
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struct heap_chunk* right;
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if ( (right = heap_chunk_right(chunk)) &&
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!heap_chunk_is_used(right) &&
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requested_chunk_size <= chunk->chunk_size + right->chunk_size )
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{
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heap_remove_chunk(right);
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heap_chunk_format((uint8_t*) chunk, chunk->chunk_size + right->chunk_size);
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assert(requested_chunk_size <= chunk->chunk_size);
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if ( heap_can_split_chunk(chunk, requested_chunk_size) )
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heap_split_chunk(chunk, requested_chunk_size);
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__heap_verify();
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__heap_unlock();
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return heap_chunk_to_data(chunk);
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}
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// It appears that we cannot retain the orignal allocation location and we
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// will have to relocate the allocation elsewhere to expand it.
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size_t orignal_ptr_size = heap_chunk_data_size(chunk);
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__heap_verify();
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__heap_unlock();
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assert(orignal_ptr_size < requested_size);
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void* result = malloc(requested_size);
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if ( !result )
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return (void*) NULL;
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memcpy(result, ptr, orignal_ptr_size);
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free(ptr);
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return result;
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}
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