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/* MIX simulator, copyright 1994 by Darius Bacon */
#include "mix.h"
#ifndef CELL_H
#define CELL_H
/* --- Call this before anything else --- */
void precompute_field_data(void);
/*
* MIX values ---
*
* Currently represented as a long. (A long must have >= 31 bits.)
* Bit 30 is the sign, higher bits are 0, and bits 0-29 are the magnitude.
* (If we made the high bit the sign, would it be a little faster to check?)
* Each MIX 'byte' is a 6-bit substring of the magnitude.
*
* Other reps which might make sense:
* array of bytes
* pair (sign, magnitude)
* 1's-complement???
* (a kind of halfway house between 2's-complement and sign/magnitude)
* (alas, field operations would be more work...)
* Unfortunately, in several places I've made the convenient assumption that
* the magnitude of a MIX cell can be converted to a C long int; that would
* be wrong for, e.g., a decimal MIX machine if a long int is only 32 bits.
*/
typedef long Cell;
typedef unsigned Byte; /* 0..63 */
/* These are to allow symbol.c to convert a Cell to or from a unique string
representation. We could just as easily use unparse() if we defined a
complementary parse() function. */
#define cell_to_long(c) (c)
#define long_to_cell(l) (l)
/* Largest possible magnitude of a Cell */
#define CELL_MAX ((1L << 30) - 1)
/* Largest possible magnitude of an index register (i.e., 2 bytes) */
#define INDEX_MAX ((1L << 12) - 1)
#define zero ((Cell) 0)
#define the_sign_bit (1L << 30)
#define negative(cell) ( (cell) ^ the_sign_bit )
#define sign_bit(cell) ( (cell) & the_sign_bit )
#define magnitude(cell) ( (cell) & (the_sign_bit - 1) )
#define is_negative(cell) ( sign_bit(cell) != 0 )
Cell ulong_to_cell(unsigned long n);
Byte make_field_spec(unsigned L, unsigned R);
void assert_valid_field(Cell field_spec);
/*** should separate into fast/safe versions */
Cell field(Byte field_spec, Cell cell);
Cell set_field(Cell value, Byte field_spec, Cell into);
Byte get_byte(unsigned field, Cell cell);
Cell set_byte(Byte value, unsigned field, Cell into);
extern Flag overflow;
Cell add(Cell x, Cell y);
Cell sub(Cell x, Cell y);
void multiply(Cell x, Cell y, Cell *high_word, Cell *low_word);
Cell mul(Cell x, Cell y);
void divide(Cell n1, Cell n0, Cell d, Cell *quotient, Cell *remainder);
Cell slash(Cell x, Cell y); /* the name 'div' is taken... */
void shift_left(Cell A, Cell X, unsigned long count, Cell *pA, Cell *pX);
void shift_right(Cell A, Cell X, unsigned long count, Cell *pA, Cell *pX);
void shift_left_circular(Cell A, Cell X, unsigned count, Cell *pA, Cell *pX);
/* Break a cell into its component fields. */
#define destructure_cell(cell, A, I, F, C) \
do { \
Cell temp_ = (cell); \
Cell sign_ = sign_bit(temp_); \
C = temp_ & 63; \
F = (temp_ >>= 6) & 63; \
I = (temp_ >>= 6) & 63; \
A = sign_ | (4095 & (temp_ >> 6)); \
} while (0)
/* --- Printable representation --- */
void print_cell(Cell cell);
void unparse_cell(char *buffer, Cell cell); /* Pre: 12 <= sizeof(buffer) */
/* --- Addresses --- */
typedef unsigned Address;
Cell address_to_cell(Address addr);
Address cell_to_address(Cell cell);
#endif
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