99 lines
3.2 KiB
C++
99 lines
3.2 KiB
C++
/*
|
|
* 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 "rtc_base/memory/aligned_malloc.h"
|
|
|
|
#include <stdlib.h> // for free, malloc
|
|
#include <string.h> // for memcpy
|
|
|
|
#include "rtc_base/checks.h"
|
|
|
|
#ifdef _WIN32
|
|
#include <windows.h>
|
|
#else
|
|
#include <stdint.h>
|
|
#endif
|
|
|
|
// Reference on memory alignment:
|
|
// http://stackoverflow.com/questions/227897/solve-the-memory-alignment-in-c-interview-question-that-stumped-me
|
|
namespace webrtc {
|
|
|
|
uintptr_t GetRightAlign(uintptr_t start_pos, size_t alignment) {
|
|
// The pointer should be aligned with `alignment` bytes. The - 1 guarantees
|
|
// that it is aligned towards the closest higher (right) address.
|
|
return (start_pos + alignment - 1) & ~(alignment - 1);
|
|
}
|
|
|
|
// Alignment must be an integer power of two.
|
|
bool ValidAlignment(size_t alignment) {
|
|
if (!alignment) {
|
|
return false;
|
|
}
|
|
return (alignment & (alignment - 1)) == 0;
|
|
}
|
|
|
|
void* GetRightAlign(const void* pointer, size_t alignment) {
|
|
if (!pointer) {
|
|
return NULL;
|
|
}
|
|
if (!ValidAlignment(alignment)) {
|
|
return NULL;
|
|
}
|
|
uintptr_t start_pos = reinterpret_cast<uintptr_t>(pointer);
|
|
return reinterpret_cast<void*>(GetRightAlign(start_pos, alignment));
|
|
}
|
|
|
|
void* AlignedMalloc(size_t size, size_t alignment) {
|
|
if (size == 0) {
|
|
return NULL;
|
|
}
|
|
if (!ValidAlignment(alignment)) {
|
|
return NULL;
|
|
}
|
|
|
|
// The memory is aligned towards the lowest address that so only
|
|
// alignment - 1 bytes needs to be allocated.
|
|
// A pointer to the start of the memory must be stored so that it can be
|
|
// retreived for deletion, ergo the sizeof(uintptr_t).
|
|
void* memory_pointer = malloc(size + sizeof(uintptr_t) + alignment - 1);
|
|
RTC_CHECK(memory_pointer) << "Couldn't allocate memory in AlignedMalloc";
|
|
|
|
// Aligning after the sizeof(uintptr_t) bytes will leave room for the header
|
|
// in the same memory block.
|
|
uintptr_t align_start_pos = reinterpret_cast<uintptr_t>(memory_pointer);
|
|
align_start_pos += sizeof(uintptr_t);
|
|
uintptr_t aligned_pos = GetRightAlign(align_start_pos, alignment);
|
|
void* aligned_pointer = reinterpret_cast<void*>(aligned_pos);
|
|
|
|
// Store the address to the beginning of the memory just before the aligned
|
|
// memory.
|
|
uintptr_t header_pos = aligned_pos - sizeof(uintptr_t);
|
|
void* header_pointer = reinterpret_cast<void*>(header_pos);
|
|
uintptr_t memory_start = reinterpret_cast<uintptr_t>(memory_pointer);
|
|
memcpy(header_pointer, &memory_start, sizeof(uintptr_t));
|
|
|
|
return aligned_pointer;
|
|
}
|
|
|
|
void AlignedFree(void* mem_block) {
|
|
if (mem_block == NULL) {
|
|
return;
|
|
}
|
|
uintptr_t aligned_pos = reinterpret_cast<uintptr_t>(mem_block);
|
|
uintptr_t header_pos = aligned_pos - sizeof(uintptr_t);
|
|
|
|
// Read out the address of the AlignedMemory struct from the header.
|
|
uintptr_t memory_start_pos = *reinterpret_cast<uintptr_t*>(header_pos);
|
|
void* memory_start = reinterpret_cast<void*>(memory_start_pos);
|
|
free(memory_start);
|
|
}
|
|
|
|
} // namespace webrtc
|