hash.c

int hashc(char* p, int sz)
{
    if (!sz)
        return 0;
    sz /= sizeof(char);
    int h = 1;
    for (int i = 0; i < sz; ++i)
        h = 31 * h + *(p + i);
    return h;
}

int hashs(short* p, int sz)
{
    if (!sz)
        return 0;
    sz /= sizeof(short);
    int h = 1;
    for (int i = 0; i < sz; ++i)
        h = 31 * h + *(p + i);
    return h;
}

int hashi(int* p, int sz)
{
    if (!sz)
        return 0;
    sz /= sizeof(int);
    int h = 1;
    for (int i = 0; i < sz; ++i)
        h = 31 * h + *(p + i);
    return h;
}

int hashl(long long* p, int sz)
{
    if (!sz)
        return 0;
    sz /= sizeof(long long);
    int h = 1;
    for (int i = 0; i < sz; ++i)
        h = 31 * h + *(p + i);
    return h;
}

main.c

#include <stdio.h>

void main()
{
    char      a[] = { 65, 66, 67, 68 };
    short     b[] = { 65, 66, 67, 68 };
    int       c[] = { 65, 66, 67, 68 };
    long long d[] = { 65, 66, 67, 68 };
    char      e[] = "ABCD";
    wchar_t   f[] = L"ABCD";
    // These yields the same result
    printf("%d\n", hashc(a, sizeof(a)));
    printf("%d\n", hashs(b, sizeof(b)));
    printf("%d\n", hashi(c, sizeof(c)));
    printf("%d\n", hashl(d, sizeof(d)));
    printf("%d\n", hashc(e, sizeof(e) - sizeof(char)));
    printf("%d\n", hashs(f, sizeof(f) - sizeof(short)));
}