python LInux下使用ctypes操作内存
# _*_ coding:UTF-8import sysimport timeimport osimport ctypesimport ctypes.utildef ctypes_alloc_aligned(size, alignment): buf_size = size + (alignment - 1) #先使用bytearray函数分配一块内存 raw_memory = bytearray(buf_size) #然后从raw_memory创建一个ctypes对象 ctypes_raw_type = (ctypes.c_char * buf_size) ctypes_raw_memory = ctypes_raw_type.from_buffer(raw_memory) #通过ctypes对象的addressof获得内存指针的值 raw_address = ctypes.addressof(ctypes_raw_memory) offset = raw_address % alignment #通过内存地址可以得出，对齐内存的偏移量 offset_to_aligned = (alignment - offset) % alignment ctypes_aligned_type = (ctypes.c_char * (buf_size - offset_to_aligned)) #通过内存的偏移量，创建对齐内存的ctype对象 ctypes_aligned_memory = ctypes_aligned_type.from_buffer(raw_memory, offset_to_aligned) return ctypes_aligned_memorylibc = ctypes.CDLL(ctypes.util.find_library('c'))#获得一块4k对齐的内存buf =ctypes_alloc_aligned(1024*1024, 4096)#direct io的方式打开块设备文件#fd = os.open('/dev/loop0', os.O_RDWR|os.O_DIRECT)fd = os.open('./loop0', os.O_RDWR|os.O_DIRECT)#fd = open('d:/test.txt', 'a')#print(dir(libc))err_code = libc.read(ctypes.c_int(fd), buf, ctypes.c_int(1024*1024))#把directIO读出的数据放到python的一个字符串变量中：data = buf.raw[0:err_code]#写数据libc.memset(buf, ctypes.c_int(0), ctypes.c_int(1024*1024))libc.write(ctypes.c_int(fd), buf, ctypes.c_int(1024*1024))os.close(fd)

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