Question

I am writing to a binary file using a struct that just contains a char[32]. I basically need to format each block of data by performing various calculations on string arrays and concatenating the results. I am attempting to copy an std::string to a char array with no null termination. The more I read into this, the more confused I get. If I do:

struct block{
    char data[32];
};
block blocks[2048];
std::string buffer;

buffer = "12345678123456781234567812345678";
strcpy(blocks[0].data, buffer.c_str());

I get an error, because adding the null terminator with c_str() makes the string length 33. If I subtract one char from the string, it works, but then I have the null terminator, which I don’t want. I can successfully do the following:

strcpy(blocks[0].data, "12345678123456781234567812345678");

but I want to construct the string first, since it often involves concatenating different strings from various arrays. For instance, I can do this with std::string:

std::string buffer = stringArray1[0] + stringArray2[0];
strcpy(blocks[0].data, buffer.c_str());

but then I have the null terminator again. I’d just like to copy exactly the chars in the std::string with no null terminator.

I am using VC++ 6.0.

Answer 1

Use memcpy instead of strcpy, that’s what it’s there for:

memcpy(blocks[0].data, buffer.data(), sizeof(blocks[0].data));