A very simple hash function. Take input from stdin.

The perl version is available here.

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

int main() {
    int             count = 0;  /* number of characters seen */
    FILE *in_file;  /* input */
    int modulus = 256;

    int ch;
    int total = 0;

    in_file = fdopen(0, "r"); /* 0 is stdin */
    if (in_file == NULL) {
        printf("Error input%s\n");
        exit(8);
    }

    while (1) {
        ch = fgetc(in_file);
        if ((ch == EOF) || (ch == 10))
            break;
        ++count;
        printf("\n%c %d",ch, ch);
        total += ch;
        total = total % modulus;
    }
    printf("\nNumber of characters of input is %d\n", count);
    printf("\nResult : %d\n", total);
    fclose(in_file);
    return (0);
}

The result of the code


CGs-MacBook:Desktop chika$ ./a.out
elliptic curve cryptography

e 101
l 108
l 108
i 105
p 112
t 116
i 105
c 99
32
c 99
u 117
r 114
v 118
e 101
32
c 99
r 114
y 121
p 112
t 116
o 111
g 103
r 114
a 97
p 112
h 104
y 121
Number of characters of input is 27

Result : 231


For a slight different input:

Elliptic curve cryptography

E 69
l 108
l 108
i 105
p 112
t 116
i 105
c 99
32
c 99
u 117
r 114
v 118
e 101
32
c 99
r 114
y 121
p 112
t 116
o 111
g 103
r 114
a 97
p 112
h 104
y 121
Number of characters of input is 27

Result : 199