Convert array of char[] to byte[] and vice versa? C++

Question

What is the best way to convert an array of chars to bytes and vice versa?

Solution:

void CharToByte(char* chars, byte* bytes, unsigned int count){
          


        

Answer 1

There is no byte type in C++, and according to the Standard:

Edit:

1.7:

A byte is at least large enough to contain any member of the basic execution character set and is composed of a contiguous sequence of bits, the number of which is implementation-defined.

5.3.3:

sizeof(char), sizeof(signed char) and sizeof(unsigned char) are 1; the result of sizeof applied to any other fundamental type (3.9.1) is implementation-defined.

Answer 2

There is no byte type in C++. You could typedef 'unsigned char' to 'byte' if that makes it nicer. Really thats all a byte is in C++ - an unsigned char. Aside from that, yes I would cast... but this cast is better:

unsigned_char_arr[i]= static_cast<unsigned char>(char_arr[i]);

or... just use the char array and cast it when it needs to be interpreted as an unsigned char...

Answer 3

In almost every C++ implementation you'll come across, a char is exactly a byte an octet. This is not guaranteed by the C++ standard, but it's practically always the case. A char is always at least 8 bits large, and the exact number of bits is given by the preprocessor constant CHAR_BIT. Also, the sizeof() operator tells you the size of an object/type in terms of the number of chars, not the number of bytes octets, so if you were on some weird system with a 16-bit char and a 32-bit int, then sizeof(int) would be 2, not 4.

EDIT: Replaced byte by octet. A char is guaranteed to be a byte by the C standard, but a byte is not guaranteed to be an octet, which is exactly 8 bits. If you've ever read any French technical literature, they always use 'octet' instead of 'byte', and they have kilooctets (KO), megaoctets (MO), etc. instead of kilbytes and megabytes.

Answer 4

The type char is one of the few types that has a size guaranteed by the ANSI standard and that size is 1 byte. As far as I know C does not directly define the type byte. However it would be just short of insane to have a type named byte which is not in fact a byte in size. Therefore a simple cast should do the trick.