在python ctypes中控制内存对齐 [英] control memory alignment in python ctypes

问题描述

我正在研究使用ctypes来处理C函数，这些函数处理必须在16个字节边界上对齐的SSE（__m128）数据。

I'm looking into using ctypes for using C functions manipulating SSE (__m128) data that have to be aligned on 16 bytes boundaries.

我找不到一个控制ctypes分配的内存对齐方式的简单方法，因此，现在，我正在使ctypes调用C函数，该函数提供正确对齐的内存缓冲区。

I could not find a simple way to control the alignment of memory allocated by ctypes, so, right now, I'm making ctypes call a C function that provides a correctly aligned memory buffer.

这种方法的问题在于，我必须手动显式释放该内存以防止其泄漏。

The problem I have with this approach is that I have to manually explicitly release this memory to prevent it from being leaked.

有没有办法控制由ctypes分配的内存的对齐方式？或者有没有方法注册清除函数来释放由ctypes调用的C函数分配的内存（标准python运算符 __ del __ 除外）？

Is there a way to control the alignment of memory allocated by ctypes ? or is there a way to register a cleanup function to release memory allocated by a C function called by ctypes (apart from standard python operator __del__) ?

遵循的最佳路径是什么？

What is the best path to follow ?

推荐答案

我一直在学习一些在研究的时候，我想出了一个函数，该函数应允许我为ctypes分配任意对齐的内存，基本上是基于ctypes应该在未对齐的内存缓冲区上保留引用，同时使实例在内存中的对齐位置开始的事实。

I've been taking some time to investigate, I came up with a function that should allow me to allocate arbitrary aligned memory with ctypes, basically relying on the fact that ctypes should keep a reference on the unaligned memory buffer, while having an instance starting at an aligned position in the buffer.

仍然必须在生产环境中对此进行测试。

Still have to test this in production.

import ctypes

def ctypes_alloc_aligned(size, alignment):

  bufSize = size+(alignment-1)
  raw_memory = bytearray(bufSize)

  ctypes_raw_type = (ctypes.c_char * bufSize)
  ctypes_raw_memory = ctypes_raw_type.from_buffer(raw_memory)

  raw_address = ctypes.addressof(ctypes_raw_memory)
  offset = raw_address % alignment
  offset_to_aligned = (alignment - offset) % alignment

  ctypes_aligned_type = (ctypes.c_char * (bufSize-offset_to_aligned))
  ctypes_aligned_memory = ctypes_aligned_type.from_buffer(raw_memory, offset_to_aligned)

  return ctypes_aligned_memory

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