12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879 | // Copyright (C) 2020 The Qt Company Ltd.// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only#include"qmalloc.h"#include"qplatformdefs.h"#include <stdlib.h>#include <string.h>/* Define the container allocation functions in a separate file, so that our users can easily override them.*/ QT_BEGIN_NAMESPACE void*qMallocAligned(size_t size,size_t alignment){returnqReallocAligned(nullptr, size,0, alignment);}void*qReallocAligned(void*oldptr,size_t newsize,size_t oldsize,size_t alignment){// fake an aligned allocationvoid*actualptr = oldptr ?static_cast<void**>(oldptr)[-1] :nullptr;if(alignment <=sizeof(void*)) {// special, fast casevoid**newptr =static_cast<void**>(realloc(actualptr, newsize +sizeof(void*)));if(!newptr)returnnullptr;if(newptr == actualptr) {// realloc succeeded without reallocatingreturn oldptr;}*newptr = newptr;return newptr +1;}// malloc returns pointers aligned at least at sizeof(size_t) boundaries// but usually more (8- or 16-byte boundaries).// So we overallocate by alignment-sizeof(size_t) bytes, so we're guaranteed to find a// somewhere within the first alignment-sizeof(size_t) that is properly aligned.// However, we need to store the actual pointer, so we need to allocate actually size +// alignment anyway. qptrdiff oldoffset = oldptr ?static_cast<char*>(oldptr) -static_cast<char*>(actualptr) :0;void*real =realloc(actualptr, newsize + alignment);if(!real)returnnullptr; quintptr faked =reinterpret_cast<quintptr>(real) + alignment; faked &= ~(alignment -1);void**faked_ptr =reinterpret_cast<void**>(faked);if(oldptr) { qptrdiff newoffset =reinterpret_cast<char*>(faked_ptr) -static_cast<char*>(real);if(oldoffset != newoffset)memmove(faked_ptr,static_cast<char*>(real) + oldoffset,qMin(oldsize, newsize));}// now save the value of the real pointer at faked-sizeof(void*)// by construction, alignment > sizeof(void*) and is a power of 2, so// faked-sizeof(void*) is properly aligned for a pointer faked_ptr[-1] = real;return faked_ptr;}voidqFreeAligned(void*ptr){if(!ptr)return;void**ptr2 =static_cast<void**>(ptr);free(ptr2[-1]);} QT_END_NAMESPACE
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