C memcpy unsigned char转1个元素unsigned char数组进行校验和计算

Question

有一个字符数组 ACKbuffer[2] 所以我首先将我想要的元素转换为 unsigned char 但是当我尝试将它 memcpy 转换为 unsigned char数组。

//first element is checksum
unsigned char ack_csum;
ack_csum = (unsigned char)ACKbuffer[0];
//second element is ACK which needs to be run through checksum 
//in a checksum function that accepts unsigned char array as parameter
unsigned char ACK_actual = (unsigned char)ACKbuffer[1];
unsigned char ACK [1];
memcpy(ACK, ACK_actual, 1);

错误：

note: expected ‘const void * restrict’ but argument is of type ‘unsigned char’
 extern void *memcpy (void *__restrict __dest, const void *__restrict __src,
              ^~~~~~
swap_client.c: In function ‘swap_write’:
swap_client.c:185:17: warning: passing argument 2 of ‘memcpy’ makes pointer from integer without a cast [-Wint-conversion]
     memcpy(ACK, ACK_actual, 1);

我也试过另一种方法，但我得到 invalid initializer:

unsigned char ACK_actual = (unsigned char)ACKbuffer[1];
unsigned char ACK [1] = ACK_actual;

理想情况下，我希望我的 ACK 数组保存来自 ACKbuffer 的值。

Answer 1

在memcpy的这个调用中

memcpy(ACK, ACK_actual, 1);

变量 ACK_actual 的类型为 unsigned char

unsigned char ACK_actual = (unsigned char)ACKbuffer[1];

但是函数需要一个指针类型。

随便写

memcpy(ACK, ACKbuffer + 1, 1);

至于第二个代码片段你应该这样写

unsigned char ACK_actual = (unsigned char)ACKbuffer[1];
unsigned char ACK [1] = { ACK_actual };

C memcpy unsigned char转1个元素unsigned char数组进行校验和计算

C memcpy unsigned char to 1 element unsigned char array for checksum calculation

c

memcpy

unsigned-char