30分求帮忙将以下C代码转写为Python代码

void coder(unsigned char* in, unsigned char *out, int size, unsigned char key, unsigned char step, int block, int limit){ unsigned char *i_itr = in; unsigned char *o_itr = out; unsigned char *o_base; int addup; int i; addup = size % block; if(addup >= block / 4) addup = 0; addup += size % 2; size -= addup; while(size > 0 && limit > 0) { if(size < block) block = size; o_base = o_itr; o_itr = o_itr + block - 1; for(i = (block + 1) / 2; i > 0; --i, ++i_itr) { *o_itr = *i_itr ^ key; o_itr -= 2; key += step; } o_itr = o_base + block - 2; for(i = block / 2; i > 0; --i, ++i_itr) { *o_itr = *i_itr ^ key; o_itr -= 2; key += step; } size -= block; o_itr = o_base + block; limit -= block; } size += addup; if(size > 0) memcpy(o_itr, i_itr, size);}变量名如果没有必要请不要改变，谢谢帮忙的朋友。我知道变量是不需要预定义的，我说的只是变量的名字尽量不要改变啊，如果实在需要改也没有关系的。另外这套程序不过是一个解密算法而已，全是符号是可想而知的吧。