template.concat.cpp

template.concat.cpp

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <wchar.h>

#ifndef uint_t
typedef unsigned uint_t;
#endif
typedef char CHAR;
typedef wchar_t WCHAR;

template <typename T>
uint_t StringLength(const T *str);

template <>
uint_t StringLength(const CHAR *str)
{
    return str != nullptr ? (uint_t)strlen(str) : 0;
}

template <>
uint_t StringLength(const WCHAR *str)
{
    return str != nullptr ? (uint_t)wcslen(str) : 0;
}

template <typename T>
uint_t StringsLengths(uint_t *cch, const T *head)
{
    return cch[0] = StringLength(head);
}

template <typename T, typename ...Ts>
uint_t StringsLengths(uint_t *cch, const T *head, const Ts *...tail)
{
    return StringsLengths(&cch[0], head) + StringsLengths(&cch[1], tail...);
}

template <typename T>
void CopyStrings(T *buffer, uint_t *cch, const T *head)
{
    memcpy(buffer, head, cch[0] * sizeof(T));
}

template <typename T, typename ...Ts>
void CopyStrings(T *buffer, uint_t *cch, const T *head, const Ts *...tail)
{
    CopyStrings(buffer, &cch[0], head);
    CopyStrings(buffer + cch[0], &cch[1], tail...);
}

template <typename T, typename ...Ts>
int concat(uint_t *pcch, T **ppout, const T *head, const Ts *...tail)
{
    uint_t offsets[sizeof...(tail) + 1] = {};
    uint_t cch = StringsLengths(offsets, head, tail...) + 1;

    T *pOut = (T*)malloc(cch * sizeof(T));
    if (pOut == nullptr) {
        return -ENOMEM;
    }

    CopyStrings(pOut, offsets, head, tail...);

    pOut[cch - 1] = 0;
    *pcch = cch;
    *ppout = pOut;

    return 0;
}

int main(int argc, char *argv[]) {
    const char a[] ="fdas.";
    const char b[] =  "swag.";
    char *res = NULL;
    uint_t cch = 0;

    concat(&cch, &res, "yolo.", "swag.", a, "hak", b, "fda");

    printf("%d %s\n", cch, res);
    //printf("%s\n", res);
    //concat(&res, a, b);
    //printf("%s\n", res);
    return 0;
}