Print chars' counts as C array of ints

count_chars.c

/* Print chars' counts as C array of ints */

#include <stdio.h>

// https://en.wikipedia.org/wiki/C_preprocessor#Token_stringification
#define xstr(s) str(s)
#define str(s) #s

#define NLETTERS 256
#define BUFSIZE (1024 * 1024)
#define NVALUES_IN_LINE 5

void initializeTable(int* table) {
    int l;
    for (l = 0; l < NLETTERS; l++) {
        table[l] = 0;
    }
}

void countLetters(int* table, const char* text, size_t length) {
    size_t i;
    for (i = 0; i < length; i++) {
        unsigned char l = text[i];
        table[l] += 1;
    }
}

void countFile(int* table, FILE* f) {
    size_t nread;
    char buffer[BUFSIZE];
    while (nread = fread(buffer, 1, BUFSIZE, f)) {
        countLetters(table, buffer, nread);
    }
}

void printTable(const int* table, FILE* f, const char* table_name) {
    fprintf(f, "static const int %s[" xstr(NLETTERS) "] = {\n", table_name);
    size_t l;
    for (l = 0; l < NLETTERS; l++) {
        int count = table[l];
        char space = ((l + 1) % NVALUES_IN_LINE == 0) ? '\n' : ' ';
        fprintf(f, "%d,%c", count, space);
    }
    fprintf(f, "\n};\n");
}

int main(int argc, char** argv) {
    int table[NLETTERS];
    initializeTable(table);
    countFile(table, stdin);
    printTable(table, stdout, "count_letters");
    return 0;
}