我写了一个简单的程序,用memcpy测试从字节缓冲区向结构体复制字节。然而,我没有得到预期的结果。
我分配了一个100字节的缓冲区,并设置值为0、1、2…99。然后将字节复制到一个16字节的结构体中。
在某个地方,字节0x01丢失了。我正在努力理解发生了什么。
#include <stdio.h>
#include <stdint.h>
struct Test {
uint8_t a;
uint16_t b;
uint32_t c;
uint64_t d;
uint8_t e;
};
int main(int argc, char** argv) {
uint8_t buffer[100];
for (uint8_t i = 0; i < 100; i++) {
buffer[i] = i;
}
struct Test test;
memcpy(&test, buffer, sizeof(struct Test));
printf("A is %ld and should be %ld\n", test.a, 0x00);
printf("B is %ld and should be %ld\n", test.b, 0x0201);
printf("C is %ld and should be %ld\n", test.c, 0x06050403);
printf("D is %ld and should be %ld\n", test.d, 0x1413121110090807);
printf("E is %ld and should be %ld\n", test.e, 0x15);
}
我得到了一个结果:
A is 0 and should be 0
B is 770 and should be 513
C is 117835012 and should be 100992003
D is 1084818905618843912 and should be 1446519769808832519
E is 16 and should be 21
770(B 值)是字节 0302,而不是 0201(int 513)。
%lx
,那么效果会更容易看到。 - Weather Vane