C++ pass memory allocated / array by reference - c++

Question

SOLVED
I am writing a interface to an existing lib that handles struct bwords (see code below), and would like to offer the possibility to call some check functions on the bword itself, or on a string of bytes (a bword member) :
#include <cstdio>
typedef unsigned char byte;
typedef unsigned short ushort;
typedef struct bwordSt { ushort nbLetters; byte *L; } bword;
template<typename T, size_t N>
ushort checkBwL(T (&wL)[N], ushort wSz) {
return 0;
}
ushort checkBwL(const byte* const &wL, ushort wSz) {
return 0;
}
ushort checkBw(const bword &bw) {
return checkBwL(bw.L, bw.nbLetters);
}
int main() {
ushort n;
byte fL[2] = {0, 1};
n = checkBwL(fL, 2); // calls the template function
bword bW = {2, new byte[3]};
bW.L[0] = 0; bW.L[1] = 1; bW.L[2] = 2;
n = checkBwL(bW.L, 3); // calls the non-template function
n = checkBw(bW); // calls the non-template function
return n;
}
The string of bytes can be huge, so I'd like to pass by reference. And I did it.
The only way I found to offer a uniform interface was to duplicate the code of the base check function (checkBwL) in a template (for arrays[byte]) and an overload (for byte*), which is ugly and forces me to maintain two basically identical (big) functions.
Any way around this ?
SOLUTION
No need for the template function, just don't forget the const before the & in argument specification const byte* const &wL

Answer 1

The key to success is delegation:
#include <cstdio>
typedef unsigned char byte;
typedef unsigned short ushort;
typedef struct bwordSt { ushort nbLetters; byte *L; } bword;
ushort check_impl(ushort length, const byte* buffer)
{
// do your actual checking here
return 0;
}
template<typename T, size_t N>
auto checkBw(T (&wL)[N], ushort wSz) -> ushort
{
return wSz == (N * sizeof(T)) && // assuming no null terminator
check_impl(wSz, reinterpret_cast<const byte*>(wL));
}
ushort checkBw(const byte* const &wL, ushort wSz) {
return check_impl(wSz, wL);
}
ushort checkBw(const bword &bw) {
return check_impl(bw.nbLetters, bw.L);
}
int main() {
ushort n;
byte fL[2] = {0, 1};
n = checkBw(fL, 2); // calls the template function
bword bW = {2, new byte[3]};
bW.L[0] = 0; bW.L[1] = 1; bW.L[2] = 2;
n = checkBw(bW.L, 3); // calls the non-template function
n = checkBw(bW); // calls the non-template function
return n;
}