python中malloc创建的space如何赋值?
How to assign a value to the space created by malloc in python?
我试图将一个值(字节)分配给由 malloc 在 python (Ubuntu 18.04 linux) 中创建的 space 但不知道如何...
dllc = CDLL("lib.so.6")
malloc = dll.malloc
malloc.restype = c_void_p
malloc.argtypes = (c_size_t,)
#initialize a pointer using malloc and allocate a space of size 1032
ptr = malloc(1032)
#here is the sample value of size 1032 in bytes
value = b'xxxxxxxxxxxxxxxxx......xxxxxxxx'
我实际上尝试使用 memcpy 复制值,但结果值与原始值不一样...
memcpy = dllc.memcpy
memcpy.restype = c_void_p
memcpy.argtype = (c_void_p, c_void_p, c_size_t)
#copy value to the space referenced by ptr
memcpy(ptr, id(value), 1032)
当我取消引用指针时,值与分配的值不同
import ctypes
#dereference the pointer but the value doesn't match
ctypes.cast(ptr, ctypes.py_object).value
有人可以帮忙吗...
您不应该使用 id
,因为您可以将字节缓冲区传递给 memcpy
。
我在 windows,所以只有第一行不同,但其余代码应该有效:
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import ctypes
def main():
dll = ctypes.CDLL("msvcrt")
malloc = dll.malloc
malloc.restype = ctypes.c_void_p
malloc.argtypes = (ctypes.c_size_t, )
memcpy = dll.memcpy
memcpy.restype = ctypes.c_void_p
memcpy.argtypes = (ctypes.c_void_p, ctypes.c_void_p, ctypes.c_size_t)
alloc_size = 1032
ptr = malloc(alloc_size)
value = b"A" + b"X" * 1030 + b"B"
assert len(value) == alloc_size
# note that ctypes has a memmove method.
# ctypes.memmove(ptr, value, alloc_size)
memcpy(ptr, value, alloc_size)
# cast the pointer to a char*
pchar = ctypes.cast(ptr, ctypes.c_char_p)
# print the first, some of the in-between and the last bytes.
print(pchar.value[0], pchar.value[1:10], pchar.value[alloc_size - 1])
if __name__ == "__main__":
main()
输出:
65 b'XXXXXXXXX' 66
还要注意 ctypes 有一个 memmove
(所以你不需要 memcpy
)。
我试图将一个值(字节)分配给由 malloc 在 python (Ubuntu 18.04 linux) 中创建的 space 但不知道如何...
dllc = CDLL("lib.so.6")
malloc = dll.malloc
malloc.restype = c_void_p
malloc.argtypes = (c_size_t,)
#initialize a pointer using malloc and allocate a space of size 1032
ptr = malloc(1032)
#here is the sample value of size 1032 in bytes
value = b'xxxxxxxxxxxxxxxxx......xxxxxxxx'
我实际上尝试使用 memcpy 复制值,但结果值与原始值不一样...
memcpy = dllc.memcpy
memcpy.restype = c_void_p
memcpy.argtype = (c_void_p, c_void_p, c_size_t)
#copy value to the space referenced by ptr
memcpy(ptr, id(value), 1032)
当我取消引用指针时,值与分配的值不同
import ctypes
#dereference the pointer but the value doesn't match
ctypes.cast(ptr, ctypes.py_object).value
有人可以帮忙吗...
您不应该使用 id
,因为您可以将字节缓冲区传递给 memcpy
。
我在 windows,所以只有第一行不同,但其余代码应该有效:
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import ctypes
def main():
dll = ctypes.CDLL("msvcrt")
malloc = dll.malloc
malloc.restype = ctypes.c_void_p
malloc.argtypes = (ctypes.c_size_t, )
memcpy = dll.memcpy
memcpy.restype = ctypes.c_void_p
memcpy.argtypes = (ctypes.c_void_p, ctypes.c_void_p, ctypes.c_size_t)
alloc_size = 1032
ptr = malloc(alloc_size)
value = b"A" + b"X" * 1030 + b"B"
assert len(value) == alloc_size
# note that ctypes has a memmove method.
# ctypes.memmove(ptr, value, alloc_size)
memcpy(ptr, value, alloc_size)
# cast the pointer to a char*
pchar = ctypes.cast(ptr, ctypes.c_char_p)
# print the first, some of the in-between and the last bytes.
print(pchar.value[0], pchar.value[1:10], pchar.value[alloc_size - 1])
if __name__ == "__main__":
main()
输出:
65 b'XXXXXXXXX' 66
还要注意 ctypes 有一个 memmove
(所以你不需要 memcpy
)。