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

#include "CAL16.mem.h"

#define MAXBYTEADDR 65535

/* Memory state of the machine */
static unsigned char mem[MAXBYTEADDR];

int toInt (FILE *);
int fromChar (char);

/* Fill memory with the contents of a file */
void fillMem (FILE *in) {
  int n;
  int wordAddr;
  for (wordAddr=0; (n=toInt(in))>=0; wordAddr++) {
    toMem (wordAddr*2, n);
  }
}

/*
 *	Return the word of memory at addresses byteAddr and byteAddr+1.
 */
unsigned int fromMem (unsigned int byteAddr) {
  byteAddr = byteAddr & 0xffff;
  if (byteAddr & 1) {
    fprintf (stderr, "Load alignment error: address = %x\n", byteAddr);
    exit (1);
  }
  return (mem[byteAddr] << 8) | mem[byteAddr+1];
}

/*
 *	Store the given value at the addresses byteAddr and byteAddr+1.
 */
void toMem (unsigned int byteAddr, unsigned int value) {
  byteAddr = byteAddr & 0xffff;
  if (byteAddr & 1) {
    fprintf (stderr, "Store alignment error: address = %x\n", byteAddr);
    exit (1);
  }
  mem[byteAddr] = value >> 8;
  mem[byteAddr+1] = value & 0xff;
}

/*
 *	Return the integer representation of the four-character string of hex digits.
 */
int toInt (FILE *in) {
  char line[6];
  int k, digitVal, result;
  char *linesRemain;
  linesRemain = (char *) fgets (line, 6, in);
  if (!linesRemain) {
    return -1;
  }
  for (k=0; k<4; k++) {
    if (line[k] == '\n') {
      fprintf (stderr, "Line '%s' not four characters long.\n", line);
      exit (1);
    }
  }
  if (line[4] != '\n') {
    fprintf (stderr, "Line '%s' not four characters long.\n", line);
    exit (1);
  }
  for (result=0, k=0; k<4; k++) {
    digitVal = fromChar (line[k]);
    result = result * 16 + digitVal;
  }
  return result;
}

/*
 *	Return the binary value represented by the hex digit c.
 */
int fromChar (char c) {
  if (c >= 'A' && c <= 'F') {
    c = c - 'A' + 'a';
  }
  switch (c) {
  case '0': case '1': case '2': case '3': case '4': 
  case '5': case '6': case '7': case '8': case '9':
    return c - '0';
  case 'a': case 'b': case 'c': case 'd': case 'e': case 'f':
    return 10 + c - 'a';
  default:
    fprintf (stderr, "%c isn't a hex digit\n", c);
    exit (1);
  }
}