Getting first byte in a char* buffer

Question

I have a char* buffer and I am interested in looking at the first byte in the char* buffer, what is the most optimal way to go about this.

EDIT: Based on the negative votes I might want to explain why this question, I am aware of methods but in the code base that I have been looking for getting first byte people do all kinds of crazy things like do a copy of the buffer , copy it to a stream and then do a get.

Answer 1

Just use

char firstByte = buffer[0];

Answer 2

char* c_ptr;
char first_char;

first_char = c_ptr[0];

Answer 3

Or this:

char firstByte = *buffer;

For clarification, there's no difference between *buffer and buffer[0], since the latter is really just shorthand for *(buffer + 0*sizeof(char)), and any compiler is going to be smart enough to replace that with *(buffer+0) and then *buffer. So the choice is really whichever is clearest in the context you are using it, not how efficient each one is.

Answer 4

char first = someCharPtr[0];

or

char first = *someCharPtr;

Answer 5

char *buffer = {'h','e','l','l','o','\0'};

or:

char *buffer = "hello";

or:

char buffer[6] = {'h','e','l','l','o','\0'};

and to get the first byte:

char firstChar = buffer[0];

or:

char firstChar = *buffer; // since the buffer pointer points to the first element in the array

Answer 6

If you're determined to micro-optimize, you should know that every compiler made in this millennium should produce exactly the same machine code for "c = *buffer" and "c = buffer[0]".

Answer 7

Good for x86 platforms...

char firstByte;

__asm {
   mov al, [buffer]
   mov [firstByte], al
}

Answer 8

Just as a clarification of what several people have mentioned--that:

buffer[0]

is equivalent to

*(buffer + 0*sizeof(char))

That's not technically true if you assume that's literal C code (i.e. not pseudo code), although that's what the compiler is doing for you.

Because of pointer arithmetic, when you add an integer to a pointer, it is automatically multiplied by sizeof(*pointer), so it should really be:

*(buffer + 0)

Although, since sizeof(char) is defined to be 1, it is actually equivalent in this case.