/*
 * Scenario 3: stdio Buffering
 * ===========================
 * This version uses fgetc() which is buffered by stdio.
 * It reads byte-by-byte in C code, but stdio buffers internally.
 *
 * Compile: gcc -O2 -o read_stdio read_stdio.c
 *
 * EXERCISES:
 * 1. Run: time ./read_stdio testfile
 * 2. Compare: strace -c ./read_stdio testfile
 * 3. Notice fewer syscalls than read_slow, but more than read_fast
 * 4. Why? Default stdio buffer is ~4KB, we use 64KB in read_fast
 */

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

int main(int argc, char *argv[]) {
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <filename>\n", argv[0]);
        return 1;
    }

    FILE *fp = fopen(argv[1], "rb");
    if (!fp) {
        perror("fopen");
        return 1;
    }

    int c;
    unsigned long byte_count = 0;
    unsigned long checksum = 0;

    /* fgetc is buffered internally by stdio */
    while ((c = fgetc(fp)) != EOF) {
        byte_count++;
        checksum += (unsigned char)c;
    }

    fclose(fp);

    printf("Read %lu bytes\n", byte_count);
    printf("Checksum: %lu\n", checksum);

    return 0;
}