1 /* -*- Mode: c; tab-width: 8; c-basic-offset: 4; indent-tabs-mode: t; -*- */
2 /* Cairo - a vector graphics library with display and print output
4 * Copyright © 2007 Mozilla Corporation
6 * This library is free software; you can redistribute it and/or
7 * modify it either under the terms of the GNU Lesser General Public
8 * License version 2.1 as published by the Free Software Foundation
9 * (the "LGPL") or, at your option, under the terms of the Mozilla
10 * Public License Version 1.1 (the "MPL"). If you do not alter this
11 * notice, a recipient may use your version of this file under either
12 * the MPL or the LGPL.
14 * You should have received a copy of the LGPL along with this library
15 * in the file COPYING-LGPL-2.1; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
17 * You should have received a copy of the MPL along with this library
18 * in the file COPYING-MPL-1.1
20 * The contents of this file are subject to the Mozilla Public License
21 * Version 1.1 (the "License"); you may not use this file except in
22 * compliance with the License. You may obtain a copy of the License at
23 * http://www.mozilla.org/MPL/
25 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
26 * OF ANY KIND, either express or implied. See the LGPL or the MPL for
27 * the specific language governing rights and limitations.
29 * The Original Code is the cairo graphics library.
31 * The Initial Developer of the Original Code is Mozilla Foundation
34 * Vladimir Vukicevic <vladimir@pobox.com>
37 #ifndef CAIRO_FIXED_PRIVATE_H
38 #define CAIRO_FIXED_PRIVATE_H
40 #include "cairo-fixed-type-private.h"
42 #include "cairo-wideint-private.h"
46 #if (CAIRO_FIXED_BITS != 32)
47 # error CAIRO_FIXED_BITS must be 32, and the type must be a 32-bit type.
48 # error To remove this limitation, you will have to fix the tesselator.
51 #define CAIRO_FIXED_ONE ((cairo_fixed_t)(1 << CAIRO_FIXED_FRAC_BITS))
52 #define CAIRO_FIXED_ONE_DOUBLE ((double)(1 << CAIRO_FIXED_FRAC_BITS))
53 #define CAIRO_FIXED_EPSILON ((cairo_fixed_t)(1))
55 #define CAIRO_FIXED_ERROR_DOUBLE (1. / (2 * CAIRO_FIXED_ONE_DOUBLE))
57 #define CAIRO_FIXED_FRAC_MASK ((cairo_fixed_t)(((cairo_fixed_unsigned_t)(-1)) >> (CAIRO_FIXED_BITS - CAIRO_FIXED_FRAC_BITS)))
58 #define CAIRO_FIXED_WHOLE_MASK (~CAIRO_FIXED_FRAC_MASK)
60 static inline cairo_fixed_t
61 _cairo_fixed_from_int (int i)
63 return i << CAIRO_FIXED_FRAC_BITS;
66 /* This is the "magic number" approach to converting a double into fixed
67 * point as described here:
69 * http://www.stereopsis.com/sree/fpu2006.html (an overview)
70 * http://www.d6.com/users/checker/pdfs/gdmfp.pdf (in detail)
72 * The basic idea is to add a large enough number to the double that the
73 * literal floating point is moved up to the extent that it forces the
74 * double's value to be shifted down to the bottom of the mantissa (to make
75 * room for the large number being added in). Since the mantissa is, at a
76 * given moment in time, a fixed point integer itself, one can convert a
77 * float to various fixed point representations by moving around the point
78 * of a floating point number through arithmetic operations. This behavior
79 * is reliable on most modern platforms as it is mandated by the IEEE-754
80 * standard for floating point arithmetic.
82 * For our purposes, a "magic number" must be carefully selected that is
83 * both large enough to produce the desired point-shifting effect, and also
84 * has no lower bits in its representation that would interfere with our
85 * value at the bottom of the mantissa. The magic number is calculated as
88 * (2 ^ (MANTISSA_SIZE - FRACTIONAL_SIZE)) * 1.5
91 * - MANTISSA_SIZE for 64-bit doubles is 52
92 * - FRACTIONAL_SIZE for 16.16 fixed point is 16
94 * Although this approach provides a very large speedup of this function
95 * on a wide-array of systems, it does come with two caveats:
97 * 1) It uses banker's rounding as opposed to arithmetic rounding.
98 * 2) It doesn't function properly if the FPU is in single-precision
102 /* The 16.16 number must always be available */
103 #define CAIRO_MAGIC_NUMBER_FIXED_16_16 (103079215104.0)
105 #if CAIRO_FIXED_BITS <= 32
106 #define CAIRO_MAGIC_NUMBER_FIXED ((1LL << (52 - CAIRO_FIXED_FRAC_BITS)) * 1.5)
108 /* For 32-bit fixed point numbers */
109 static inline cairo_fixed_t
110 _cairo_fixed_from_double (double d)
117 u.d = d + CAIRO_MAGIC_NUMBER_FIXED;
118 #ifdef FLOAT_WORDS_BIGENDIAN
126 # error Please define a magic number for your fixed point type!
127 # error See cairo-fixed-private.h for details.
130 static inline cairo_fixed_t
131 _cairo_fixed_from_26_6 (uint32_t i)
133 #if CAIRO_FIXED_FRAC_BITS > 6
134 return i << (CAIRO_FIXED_FRAC_BITS - 6);
136 return i >> (6 - CAIRO_FIXED_FRAC_BITS);
140 static inline cairo_fixed_t
141 _cairo_fixed_from_16_16 (uint32_t i)
143 #if CAIRO_FIXED_FRAC_BITS > 16
144 return i << (CAIRO_FIXED_FRAC_BITS - 16);
146 return i >> (16 - CAIRO_FIXED_FRAC_BITS);
151 _cairo_fixed_to_double (cairo_fixed_t f)
153 return ((double) f) / CAIRO_FIXED_ONE_DOUBLE;
157 _cairo_fixed_is_integer (cairo_fixed_t f)
159 return (f & CAIRO_FIXED_FRAC_MASK) == 0;
162 static inline cairo_fixed_t
163 _cairo_fixed_floor (cairo_fixed_t f)
165 return f & ~CAIRO_FIXED_FRAC_MASK;
168 static inline cairo_fixed_t
169 _cairo_fixed_ceil (cairo_fixed_t f)
171 return _cairo_fixed_floor (f + CAIRO_FIXED_FRAC_MASK);
174 static inline cairo_fixed_t
175 _cairo_fixed_round (cairo_fixed_t f)
177 return _cairo_fixed_floor (f + (CAIRO_FIXED_FRAC_MASK+1)/2);
180 static inline cairo_fixed_t
181 _cairo_fixed_round_down (cairo_fixed_t f)
183 return _cairo_fixed_floor (f + CAIRO_FIXED_FRAC_MASK/2);
187 _cairo_fixed_integer_part (cairo_fixed_t f)
189 return f >> CAIRO_FIXED_FRAC_BITS;
193 _cairo_fixed_integer_round (cairo_fixed_t f)
195 return _cairo_fixed_integer_part (f + (CAIRO_FIXED_FRAC_MASK+1)/2);
199 _cairo_fixed_integer_round_down (cairo_fixed_t f)
201 return _cairo_fixed_integer_part (f + CAIRO_FIXED_FRAC_MASK/2);
205 _cairo_fixed_fractional_part (cairo_fixed_t f)
207 return f & CAIRO_FIXED_FRAC_MASK;
211 _cairo_fixed_integer_floor (cairo_fixed_t f)
214 return f >> CAIRO_FIXED_FRAC_BITS;
216 return -((-f - 1) >> CAIRO_FIXED_FRAC_BITS) - 1;
220 _cairo_fixed_integer_ceil (cairo_fixed_t f)
223 return ((f - 1)>>CAIRO_FIXED_FRAC_BITS) + 1;
225 return - (-f >> CAIRO_FIXED_FRAC_BITS);
228 /* A bunch of explicit 16.16 operators; we need these
229 * to interface with pixman and other backends that require
230 * 16.16 fixed point types.
232 static inline cairo_fixed_16_16_t
233 _cairo_fixed_to_16_16 (cairo_fixed_t f)
235 #if (CAIRO_FIXED_FRAC_BITS == 16) && (CAIRO_FIXED_BITS == 32)
237 #elif CAIRO_FIXED_FRAC_BITS > 16
238 /* We're just dropping the low bits, so we won't ever got over/underflow here */
239 return f >> (CAIRO_FIXED_FRAC_BITS - 16);
241 cairo_fixed_16_16_t x;
243 /* Handle overflow/underflow by clamping to the lowest/highest
244 * value representable as 16.16
246 if ((f >> CAIRO_FIXED_FRAC_BITS) < INT16_MIN) {
248 } else if ((f >> CAIRO_FIXED_FRAC_BITS) > INT16_MAX) {
251 x = f << (16 - CAIRO_FIXED_FRAC_BITS);
258 static inline cairo_fixed_16_16_t
259 _cairo_fixed_16_16_from_double (double d)
266 u.d = d + CAIRO_MAGIC_NUMBER_FIXED_16_16;
267 #ifdef FLOAT_WORDS_BIGENDIAN
275 _cairo_fixed_16_16_floor (cairo_fixed_16_16_t f)
280 return -((-f - 1) >> 16) - 1;
284 _cairo_fixed_16_16_to_double (cairo_fixed_16_16_t f)
286 return ((double) f) / (double) (1 << 16);
289 #if CAIRO_FIXED_BITS == 32
291 static inline cairo_fixed_t
292 _cairo_fixed_mul (cairo_fixed_t a, cairo_fixed_t b)
294 cairo_int64_t temp = _cairo_int32x32_64_mul (a, b);
295 return _cairo_int64_to_int32(_cairo_int64_rsl (temp, CAIRO_FIXED_FRAC_BITS));
298 /* computes round (a * b / c) */
299 static inline cairo_fixed_t
300 _cairo_fixed_mul_div (cairo_fixed_t a, cairo_fixed_t b, cairo_fixed_t c)
302 cairo_int64_t ab = _cairo_int32x32_64_mul (a, b);
303 cairo_int64_t c64 = _cairo_int32_to_int64 (c);
304 return _cairo_int64_to_int32 (_cairo_int64_divrem (ab, c64).quo);
307 /* computes floor (a * b / c) */
308 static inline cairo_fixed_t
309 _cairo_fixed_mul_div_floor (cairo_fixed_t a, cairo_fixed_t b, cairo_fixed_t c)
311 return _cairo_int64_32_div (_cairo_int32x32_64_mul (a, b), c);
315 static inline cairo_fixed_t
316 _cairo_edge_compute_intersection_y_for_x (const cairo_point_t *p1,
317 const cairo_point_t *p2,
330 y += _cairo_fixed_mul_div_floor (x - p1->x, p2->y - p1->y, dx);
335 static inline cairo_fixed_t
336 _cairo_edge_compute_intersection_x_for_y (const cairo_point_t *p1,
337 const cairo_point_t *p2,
350 x += _cairo_fixed_mul_div_floor (y - p1->y, p2->x - p1->x, dy);
356 # error Please define multiplication and other operands for your fixed-point type size
359 #endif /* CAIRO_FIXED_PRIVATE_H */