mix-bytes

mix-bytes.c

#!/usr/bin/env C -m
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

void mix_bytes(const char *in_even_fname, const char *in_odd_fname, int bytes)
{
  int c;
  FILE *fin_odd, *fin_even;
  fin_even = fopen(in_even_fname, "rb");
  if (!fin_even)
  {
    fprintf(stderr, "Couldn't open %s.\n", in_even_fname);
    return;
  }
  fin_odd = fopen(in_odd_fname, "rb");
  if (!fin_odd)
  {
    fprintf(stderr, "Couldn't open %s.\n", in_odd_fname);
    fclose(fin_even);
    return;
  }

  do
  {
    for (int i = 0; i < bytes; i++)
    {
      c = fgetc(fin_even);
      if (c != EOF)
      {
        fputc(c, stdout);
      }
    }

    for (int i = 0; i < bytes; i++)
    {
      c = fgetc(fin_odd);
      if (c != EOF)
      {
        fputc(c, stdout);
      }
    }
  } while (c != EOF);

  fclose(fin_even);
  fclose(fin_odd);
}

void usage()
{
  printf("Usage: mix-bytes\n");
  printf("  mix-bytes in.even in.odd <bytes per> > out\n");
}

int main(int argc, char **argv)
{
  int bytes = 1;

  if (argc > 3) {
    bytes = atoi(argv[3]);
  }

  if (argc < 3)
  {
    usage();
    return 0;
  }
  mix_bytes(argv[1], argv[2], bytes);

  return 0;
}