Python结构中的动态数组和结构 [英] Dynamic arrays and structures in structures in python

问题描述

我正在尝试使用ctypes在python中实现此C结构：

I am trying to implement this C structures in python using ctypes:

struct _rows {
    int cols_count;
    char *cols[];
}

struct _unit {
    int rows_count;
    struct _rows *rows;
}

int my_func(struct _unit *param);

问题是_rows.cols是动态大小的char指针数组，而_unit.rows是动态的_rows结构的大小数组。如何在python中使用ctypes实现此功能？

Problem is that _rows.cols is a dynamically sized array of char pointer and _unit.rows is a dynamically sized array of _rows structure. How can I implement this using ctypes in python?

我能够定义一个函数，该函数将返回具有可变数量的char指针的_rows结构：

I was able to define a function that will return a _rows structure with variable number of char pointers:

def get_row(cols):
    class Row(ctypes.Structure):
        _fields_ = [("cols_count", ctypes.c_int), 
                    ("cols", ctypes.c_char_p * cols)
                   ]

我不知道该怎么办做nex，这有点模糊，ctypes文档也无济于事。

I don't know what to do nex, it's all a bit fuzzy and ctypes documentation isn't helping.

推荐答案

我正在对OP想要，如果有更简单的方法可以做到，我会建议您，但这就是我想出的：

I'm making some assumptions about what the OP wants, and I'd love suggestions if there is an easier way to do this, but this is what I came up with:

import string
from ctypes import Structure,c_int,c_char_p,POINTER,cast,pointer,byref,CDLL

class Row(Structure):
    _fields_ = [('cols_count', c_int), 
                ('cols', POINTER(c_char_p))]
    def __init__(self,cols):
        self.cols_count = cols
        # Allocate an array of character pointers
        pc = (c_char_p * cols)()
        self.cols = cast(pc,POINTER(c_char_p))            

class Unit(Structure):
    _fields_ = [('rows_count', c_int),
                ('rows',POINTER(Row))]
    def __init__(self,rows,cols):
        self.rows_count = rows
        # Allocate an array of Row structures.
        # This does NOT call __init__.
        pr = (Row * rows)()
        # Call init manually with the column size.
        for r in pr:
            r.__init__(cols)
        self.rows = cast(pr,POINTER(Row))

unit = Unit(2,3)

# Stuff some strings ('aaaaa','bbbbb',etc.)
for i in xrange(unit.rows_count):
    for j in xrange(unit.rows[i].cols_count):
        unit.rows[i].cols[j] = string.ascii_lowercase[i*5+j]*5

dll = CDLL('test.dll')
dll.my_func(byref(unit))

test.c

test.c

#include <stdio.h>

struct _rows {
    int cols_count;
    char **cols;
};

struct _unit {
    int rows_count;
    struct _rows *rows;
};

__declspec(dllexport) int my_func(struct _unit *param)
{
    int i,j;
    for(i=0;i<param->rows_count;i++)
        for(j=0;j<param->rows[i].cols_count;j++)
            printf("%d,%d = %s\n",i,j,param->rows[i].cols[j]);
    return 0;
}

makefile

与Visual Studio 2010一起编译。

makefile

Compiled with Visual Studio 2010.

test.dll: test.c
    cl /W4 /LD test.c

输出

Output

0,0 = aaaaa
0,1 = bbbbb
0,2 = ccccc
1,0 = fffff
1,1 = ggggg
1,2 = hhhhh

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