1 files changed, 113 insertions, 0 deletions
diff --git a/base/gxfrac.h b/base/gxfrac.h
new file mode 100644
index 00000000..620d9eb1
--- /dev/null
+++ b/base/gxfrac.h
@@ -0,0 +1,113 @@
+/* Copyright (C) 2001-2019 Artifex Software, Inc.
+   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.
+
+   Refer to licensing information at http://www.artifex.com or contact
+   Artifex Software, Inc.,  1305 Grant Avenue - Suite 200, Novato,
+   CA 94945, U.S.A., +1(415)492-9861, for further information.
+*/
+
+
+/* Fraction representation for Ghostscript */
+
+#ifndef gxfrac_INCLUDED
+#  define gxfrac_INCLUDED
+
+/*
+ * Represent a fraction in [0.0..1.0].  Note that the 1.0 endpoint is
+ * included.  Since undercolor removal requires a signed frac, we limit
+ * fracs to 15 bits rather than 16.
+ */
+typedef short frac;
+typedef short signed_frac;
+
+#define arch_log2_sizeof_frac ARCH_LOG2_SIZEOF_SHORT
+#define arch_sizeof_frac ARCH_SIZEOF_SHORT
+#define frac_bits 15
+#define frac_0 ((frac)0)
+
+/*
+ * Normally one would represent a fractional value of this kind as a short
+ * integer, in [-32767..32767].  Unfortunately, this approach cannot
+ * represent any of the common values like 1/2, 1/3, or 1/5 exactly, causing
+ * rounding errors.  Instead, we opt for using the range [-32760..32760],
+ * which allows exact representation of almost all commonly used fractions
+ * (e.g., N/360 for 0<=N<=360).
+ */
+#define frac_1_0bits 3
+#define frac_1 ((frac)0x7ff8)
+#define frac_1_long ((long)frac_1)
+#define frac_1_float ((float)frac_1)
+/* Conversion between fracs and floats. */
+#define frac2float(fr) ((fr) / frac_1_float)
+#define float2frac(fl) ((frac)(((fl) + 0.5 / frac_1_float) * frac_1_float))
+
+/*
+ * Conversion between unsigned fracs and bytes (or, in general,
+ * shorter integers) representing fractions. This is highly dependent
+ * on the definition of frac_1 above.
+ */
+#define _frac2s(fr)\
+  (((fr) >> (frac_bits - frac_1_0bits)) + (fr))
+#define frac2bits(fr, nb)\
+  ((uint)(_frac2s(fr) >> (frac_bits - (nb))))
+#define frac2byte(fr) ((byte)frac2bits(fr, 8))
+/* bits2frac requires frac_bits / 2 <= nb <= frac_bits. */
+#define bits2frac(v, nb) ((frac)(\
+  ((frac)(v) << (frac_bits - (nb))) +\
+   ((v) >> ((nb) * 2 - frac_bits)) -\
+   ((v) >> ((nb) - frac_1_0bits)) ))
+#define byte2frac(b) bits2frac(b, 8)
+/* Produce a result that is guaranteed to convert back to a frac */
+/* not exceeding the original value fr. */
+#define frac2bits_floor(fr, nb)\
+  ((uint)((_frac2s(fr) - (_frac2s(fr) >> (nb))) >> (frac_bits - (nb))))
+/*
+ * Conversion between fracs and unsigned shorts.
+ */
+#define ushort_bits (ARCH_SIZEOF_SHORT * 8)
+#define frac2ushort(fr) ((ushort)(\
+  ((fr) << (ushort_bits - frac_bits)) +\
+  ((fr) >> (frac_bits * 2 - ushort_bits - frac_1_0bits)) ))
+#define ushort2frac(us) ((frac)(\
+  ((us) >> (ushort_bits - frac_bits)) -\
+  ((us) >> (ushort_bits - frac_1_0bits)) ))
+
+/*
+ * Conversion between frac31s and unsigned shorts.
+ */
+#define ushort_bits (ARCH_SIZEOF_SHORT * 8)
+#define frac31_bits 31
+#if 0
+#define frac312ushort(fr) ((ushort)(\
+  ((fr) >> (frac31_bits - ushort_bits)) +\
+  ((fr) >> (frac31_bits - ushort_bits + frac_bits - frac_1_0bits)) ))
+#define ushort2frac31(us) ((frac31)(\
+  ((us) << (frac31_bits - ushort_bits)) -\
+  ((us) << (frac31_bits - ushort_bits - frac_bits + frac_1_0bits)) ))
+#else
+#define frac312ushort(fr) ((ushort)((fr) >> (frac31_bits - ushort_bits)))
+#define ushort2frac31(us) ((frac31)((us) << (frac31_bits - ushort_bits)))
+#endif
+
+/*
+ * Compute the quotient Q = floor(P / frac_1),
+ * where P is the (ulong) product of a uint or ushort V and a frac F.
+ * See gxarith.h for the underlying algorithm.
+ */
+#define frac_1_quo(p)\
+  ( (((p) >> frac_1_0bits) + ((p) >> frac_bits) + 1) >> (frac_bits - frac_1_0bits) )
+/*
+ * Compute the remainder similarly, having already computed the quotient.
+ * This is, of course, P - Q * frac_1.
+ */
+#define frac_1_rem(p, q)\
+  ((frac)( (uint)(p) - ((q) << frac_bits) + ((q) << frac_1_0bits) ))
+
+#endif /* gxfrac_INCLUDED */