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/*
* Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "aligned_malloc.h"
#include <assert.h>
#include <memory.h>
#ifdef ANDROID
#include <stdlib.h>
#endif
#if WEBRTC_MAC
#include <malloc/malloc.h>
#else
#include <malloc.h>
#endif
#if _WIN32
#include <windows.h>
#else
#include <stdint.h>
#endif
#include "typedefs.h"
// Ok reference on memory alignment:
// http://stackoverflow.com/questions/227897/solve-the-memory-alignment-in-c-interview-question-that-stumped-me
namespace webrtc
{
// TODO (hellner) better to create just one memory block and
// interpret the first sizeof(AlignedMemory) bytes as
// an AlignedMemory struct.
struct AlignedMemory
{
void* alignedBuffer;
void* memoryPointer;
};
void* AlignedMalloc(size_t size, size_t alignment)
{
if(alignment == 0)
{
// Don't allow alignment 0 since it's undefined.
return NULL;
}
// Make sure that the alignment is an integer power of two or fail.
if(alignment & (alignment - 1))
{
return NULL;
}
AlignedMemory* returnValue = new AlignedMemory();
if(returnValue == NULL)
{
return NULL;
}
// The memory is aligned towards the lowest address that so only
// alignment - 1 bytes needs to be allocated.
// A pointer to AlignedMemory must be stored so that it can be retreived for
// deletion, ergo the sizeof(uintptr_t).
returnValue->memoryPointer = malloc(size + sizeof(uintptr_t) +
alignment - 1);
if(returnValue->memoryPointer == NULL)
{
delete returnValue;
return NULL;
}
// Alligning after the sizeof(header) bytes will leave room for the header
// in the same memory block.
uintptr_t alignStartPos = (uintptr_t)returnValue->memoryPointer;
alignStartPos += sizeof(uintptr_t);
// The buffer should be aligned with 'alignment' bytes. The - 1 guarantees
// that we align towards the lowest address.
uintptr_t alignedPos = (alignStartPos + alignment - 1) & ~(alignment - 1);
// alignedPos is the address sought for.
returnValue->alignedBuffer = (void*)alignedPos;
// Store the address to the AlignedMemory struct in the header so that a
// it's possible to reclaim all memory.
uintptr_t headerPos = alignedPos;
headerPos -= sizeof(uintptr_t);
void* headerPtr = (void*) headerPos;
uintptr_t headerValue = (uintptr_t)returnValue;
memcpy(headerPtr,&headerValue,sizeof(uintptr_t));
return returnValue->alignedBuffer;
}
void AlignedFree(void* memBlock)
{
if(memBlock == NULL)
{
return;
}
uintptr_t alignedPos = (uintptr_t)memBlock;
uintptr_t headerPos = alignedPos - sizeof(uintptr_t);
// Read out the address of the AlignedMemory struct from the header.
uintptr_t* headerPtr = (uintptr_t*)headerPos;
AlignedMemory* deleteMemory = (AlignedMemory*) *headerPtr;
if(deleteMemory->memoryPointer != NULL)
{
free(deleteMemory->memoryPointer);
}
delete deleteMemory;
}
} // namespace webrtc
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