xref: /plan9-contrib/sys/src/cmd/gs/src/gxarith.h (revision 593dc095aefb2a85c828727bbfa9da139a49bdf4)

/* Copyright (C) 1990, 1993, 1994, 1996, 1998 Aladdin Enterprises.  All rights reserved.

  This software is provided AS-IS with no warranty, either express or
  implied.

  This software is distributed under license and may not be copied,
  modified or distributed except as expressly authorized under the terms
  of the license contained in the file LICENSE in this distribution.

  For more information about licensing, please refer to
  http://www.ghostscript.com/licensing/. For information on
  commercial licensing, go to http://www.artifex.com/licensing/ or
  contact Artifex Software, Inc., 101 Lucas Valley Road #110,
  San Rafael, CA  94903, U.S.A., +1(415)492-9861.
*/

#ifndef gxarith_INCLUDED
#  define gxarith_INCLUDED

/* $Id: gxarith.h,v 1.5 2002/06/16 08:45:43 lpd Exp $ */
/* Arithmetic macros for Ghostscript library */

/* Define an in-line abs function, good for any signed numeric type. */
#define any_abs(x) ((x) < 0 ? -(x) : (x))

/* Compute M modulo N.  Requires N > 0; guarantees 0 <= imod(M,N) < N, */
/* regardless of the whims of the % operator for negative operands. */
int imod(int m, int n);

/* Compute the GCD of two integers. */
int igcd(int x, int y);

/*
 * Given A, B, and M, compute X such that A*X = B mod M, 0 < X < M.
 * Requires: M > 0, 0 < A < M, 0 < B < M, gcd(A, M) | gcd(A, B).
 */
int idivmod(int a, int b, int m);

/*
 * Compute floor(log2(N)).  Requires N > 0.
 */
int ilog2(int n);

/* Test whether an integral value fits in a given number of bits. */
/* This works for all integral types. */
#define fits_in_bits(i, n)\
  (sizeof(i) <= sizeof(int) ? fits_in_ubits((i) + (1 << ((n) - 1)), (n) + 1) :\
   fits_in_ubits((i) + (1L << ((n) - 1)), (n) + 1))
#define fits_in_ubits(i, n) (((i) >> (n)) == 0)

/*
 * There are some floating point operations that can be implemented
 * very efficiently on machines that have no floating point hardware,
 * assuming IEEE representation and no range overflows.
 * We define straightforward versions of them here, and alternate versions
 * for no-floating-point machines in gxfarith.h.
 */
/* Test floating point values against constants. */
#define is_fzero(f) ((f) == 0.0)
#define is_fzero2(f1,f2) ((f1) == 0.0 && (f2) == 0.0)
#define is_fneg(f) ((f) < 0.0)
#define is_fge1(f) ((f) >= 1.0)
/* Test whether a floating point value fits in a given number of bits. */
#define f_fits_in_bits(f, n)\
  ((f) >= -2.0 * (1L << ((n) - 2)) && (f) < 2.0 * (1L << ((n) - 2)))
#define f_fits_in_ubits(f, n)\
  ((f) >= 0 && (f) < 4.0 * (1L << ((n) - 2)))

/*
 * Define a macro for computing log2(n), where n=1,2,4,...,128.
 * Because some compilers limit the total size of a statement,
 * this macro must only mention n once.  The macro should really
 * only be used with compile-time constant arguments, but it will work
 * even if n is an expression computed at run-time.
 */
#define small_exact_log2(n)\
 ((uint)(05637042010L >> ((((n) % 11) - 1) * 3)) & 7)

/*
 * The following doesn't give rise to a macro, but is used in several
 * places in Ghostscript.  We observe that if M = 2^n-1 and V < M^2,
 * then the quotient Q and remainder R can be computed as:
 *              Q = V / M = (V + (V >> n) + 1) >> n;
 *              R = V % M = (V + (V / M)) & M = V - (Q << n) + Q.
 */

#endif /* gxarith_INCLUDED */