c++ unsigned char memory copy
-
05-07-2021 - |
题
I need to pass an unsigned char array from one method to another, and i tried using this code:
{
unsigned char *lpBuffer = new unsigned char[182];
ReceiveSystemState(lpBuffer);
}
BOOL ReceiveSystemState(unsigned char *lpBuffer)
{
unsigned char strRecvBuffer[182] = { 0 };
//strRecvBuffer construction
memcpy(lpBuffer, strRecvBuffer, sizeof(strRecvBuffer));
return TRUE;
}
Neither of those 3 methods (used in ReceiveSystemState
) worked as i expected. After using each one of them all that it is copied is the first char from strRecvBuffer
and nothing more. The strRecvBuffer
has empty chars from element to element, but i need those as they are, because that string is a message from a hardware device and that message will be anallysed using a protocol. What do i miss here? Do i initialize lpBuffer
wrong?
EDIT: I've used a simple memcpy
method to do the job. Still the same result: all that it is copied is the first char of strRecvBuffer
.
EDIT2: Working code:
{
unsigned char *lpBuffer = new unsigned char[182];
ReceiveSystemState(lpBuffer);
for (int i = 0; i < 144; i++)
{
memcpy(&c_dateKG[i], lpBuffer + i * sizeof(unsigned char), sizeof(unsigned char) );
}
}
BOOL ReceiveSystemState(unsigned char *lpBuffer)
{
unsigned char strRecvBuffer[182] = { 0 };
//strRecvBuffer construction
memcpy(lpBuffer, strRecvBuffer, sizeof(strRecvBuffer));
return TRUE;
}
解决方案
Your code is absolutely garbage. Some notes:
Use sizeof
:
Use sizeof(static_massive_name);
or count_of_arr_elements * sizeof(arr_type);
For example:
unsigned char src[255];
unsigned char dst[255];
// fill src with random data
for (int i = 0; i < 255; ++i) {
src[i] = static_cast<unsigned char> (rand() % 255);
}
memcpy(dst, src, sizeof(dst));
// now dst will have copied values from src (random numbers)
UPDATE:
Full source code for testing:
#include <iostream>
#include <string.h>
#include <time.h>
#include <stdlib.h>
using namespace std;
void print(unsigned char* arr, size_t size) {
for (size_t i = 0; i < size; ++i) {
// see type casting (to int)!!!
cout << "arr[" << i << "] = " << (int)arr[i]<< endl;
}
}
int main() {
srand(time(0));
// unsigned char type hold values from 0 to 255
unsigned char src[15];
unsigned char dst[15];
for (int i = 0; i < 15; ++i) {
src[i] = rand() % 255;
}
memcpy(dst, src, sizeof(dst));
print(src, 15);
print(dst, 15);
return 0;
}
Result:
arr[0] = 34
arr[1] = 80
arr[2] = 183
arr[3] = 112
arr[4] = 18
arr[5] = 120
arr[6] = 183
arr[7] = 0
arr[8] = 0
arr[9] = 0
arr[10] = 0
arr[11] = 57
arr[12] = 137
arr[13] = 4
arr[14] = 8
arr[0] = 34
arr[1] = 80
arr[2] = 183
arr[3] = 112
arr[4] = 18
arr[5] = 120
arr[6] = 183
arr[7] = 0
arr[8] = 0
arr[9] = 0
arr[10] = 0
arr[11] = 57
arr[12] = 137
arr[13] = 4
arr[14] = 8