/* ########################################################### */
/* This Software is licensed under the GPL licensed Version 2, */
/* please read http://www.gnu.org/copyleft/gpl.html.           */
/* ########################################################### */

/* ************************************************************************* */
/* Custom fgetc/ungetc implementation able to unget more than one character. */
/* ************************************************************************* */

#include <stdio.h>
#include "fgetc.h"

enum
{
  GETC_BUFF_SIZE = 16
};

static char getc_buffer[GETC_BUFF_SIZE] = { '\0' };

static long next_buffer_pos = 0; /* Next free position in the getc buffer. */

/* ======================================== */
/* Gets a (possibly pushed-back) character. */
/* ======================================== */
int
my_fgetc(FILE * input)
{
  return (next_buffer_pos > 0) ? getc_buffer[--next_buffer_pos] : fgetc(input);
}

/* =============================== */
/* Pushes character back on input. */
/* =============================== */
void
my_ungetc(int c)
{
  if (next_buffer_pos >= GETC_BUFF_SIZE)
    fprintf(stderr, "Error: cannot push back more than %d characters\n",
            GETC_BUFF_SIZE);
  else
    getc_buffer[next_buffer_pos++] = c;
}