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gfx/skia/trunk/src/effects/gradients/SkClampRange.cpp@b8a032363ba2 (annotated)

gfx/skia/trunk/src/effects/gradients/SkClampRange.cpp

Thu, 22 Jan 2015 13:21:57 +0100

author

Michael Schloh von Bennewitz <michael@schloh.com>

date

Thu, 22 Jan 2015 13:21:57 +0100

branch

TOR_BUG_9701

changeset 15

b8a032363ba2

permissions

-rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

michael@0	1
michael@0	2	/*
michael@0	3	* Copyright 2011 Google Inc.
michael@0	4	*
michael@0	5	* Use of this source code is governed by a BSD-style license that can be
michael@0	6	* found in the LICENSE file.
michael@0	7	*/
michael@0	8
michael@0	9
michael@0	10	#include "SkClampRange.h"
michael@0	11
michael@0	12	/*
michael@0	13	* returns [0..count] for the number of steps (<= count) for which x0 <= edge
michael@0	14	* given each step is followed by x0 += dx
michael@0	15	*/
michael@0	16	static int chop(int64_t x0, SkFixed edge, int64_t x1, int64_t dx, int count) {
michael@0	17	SkASSERT(dx > 0);
michael@0	18	SkASSERT(count >= 0);
michael@0	19
michael@0	20	if (x0 >= edge) {
michael@0	21	return 0;
michael@0	22	}
michael@0	23	if (x1 <= edge) {
michael@0	24	return count;
michael@0	25	}
michael@0	26	int64_t n = (edge - x0 + dx - 1) / dx;
michael@0	27	SkASSERT(n >= 0);
michael@0	28	SkASSERT(n <= count);
michael@0	29	return (int)n;
michael@0	30	}
michael@0	31
michael@0	32	static bool overflows_fixed(int64_t x) {
michael@0	33	return x < -SK_FixedMax || x > SK_FixedMax;
michael@0	34	}
michael@0	35
michael@0	36	void SkClampRange::initFor1(SkFixed fx) {
michael@0	37	fCount0 = fCount1 = fCount2 = 0;
michael@0	38	if (fx <= 0) {
michael@0	39	fCount0 = 1;
michael@0	40	} else if (fx < 0xFFFF) {
michael@0	41	fCount1 = 1;
michael@0	42	fFx1 = fx;
michael@0	43	} else {
michael@0	44	fCount2 = 1;
michael@0	45	}
michael@0	46	}
michael@0	47
michael@0	48	void SkClampRange::init(SkFixed fx0, SkFixed dx0, int count, int v0, int v1) {
michael@0	49	SkASSERT(count > 0);
michael@0	50
michael@0	51	fV0 = v0;
michael@0	52	fV1 = v1;
michael@0	53	fOverflowed = false;
michael@0	54
michael@0	55	// special case 1 == count, as it is slightly common for skia
michael@0	56	// and avoids us ever calling divide or 64bit multiply
michael@0	57	if (1 == count) {
michael@0	58	this->initFor1(fx0);
michael@0	59	return;
michael@0	60	}
michael@0	61
michael@0	62	int64_t fx = fx0;
michael@0	63	int64_t dx = dx0;
michael@0	64	// start with ex equal to the last computed value
michael@0	65	int64_t ex = fx + (count - 1) * dx;
michael@0	66	fOverflowed = overflows_fixed(ex);
michael@0	67
michael@0	68	if ((uint64_t)(fx | ex) <= 0xFFFF) {
michael@0	69	fCount0 = fCount2 = 0;
michael@0	70	fCount1 = count;
michael@0	71	fFx1 = fx0;
michael@0	72	return;
michael@0	73	}
michael@0	74	if (fx <= 0 && ex <= 0) {
michael@0	75	fCount1 = fCount2 = 0;
michael@0	76	fCount0 = count;
michael@0	77	return;
michael@0	78	}
michael@0	79	if (fx >= 0xFFFF && ex >= 0xFFFF) {
michael@0	80	fCount0 = fCount1 = 0;
michael@0	81	fCount2 = count;
michael@0	82	return;
michael@0	83	}
michael@0	84
michael@0	85	int extraCount = 0;
michael@0	86
michael@0	87	// now make ex be 1 past the last computed value
michael@0	88	ex += dx;
michael@0	89	fOverflowed = overflows_fixed(ex);
michael@0	90	// now check for over/under flow
michael@0	91	if (fOverflowed) {
michael@0	92	int originalCount = count;
michael@0	93	int64_t ccount;
michael@0	94	bool swap = dx < 0;
michael@0	95	if (swap) {
michael@0	96	dx = -dx;
michael@0	97	fx = -fx;
michael@0	98	}
michael@0	99	ccount = (SK_FixedMax - fx + dx - 1) / dx;
michael@0	100	if (swap) {
michael@0	101	dx = -dx;
michael@0	102	fx = -fx;
michael@0	103	}
michael@0	104	SkASSERT(ccount > 0 && ccount <= SK_FixedMax);
michael@0	105
michael@0	106	count = (int)ccount;
michael@0	107	if (0 == count) {
michael@0	108	this->initFor1(fx0);
michael@0	109	if (dx > 0) {
michael@0	110	fCount2 += originalCount - 1;
michael@0	111	} else {
michael@0	112	fCount0 += originalCount - 1;
michael@0	113	}
michael@0	114	return;
michael@0	115	}
michael@0	116	extraCount = originalCount - count;
michael@0	117	ex = fx + dx * count;
michael@0	118	}
michael@0	119
michael@0	120	bool doSwap = dx < 0;
michael@0	121
michael@0	122	if (doSwap) {
michael@0	123	ex -= dx;
michael@0	124	fx -= dx;
michael@0	125	SkTSwap(fx, ex);
michael@0	126	dx = -dx;
michael@0	127	}
michael@0	128
michael@0	129
michael@0	130	fCount0 = chop(fx, 0, ex, dx, count);
michael@0	131	count -= fCount0;
michael@0	132	fx += fCount0 * dx;
michael@0	133	SkASSERT(fx >= 0);
michael@0	134	SkASSERT(fCount0 == 0 || (fx - dx) < 0);
michael@0	135	fCount1 = chop(fx, 0xFFFF, ex, dx, count);
michael@0	136	count -= fCount1;
michael@0	137	fCount2 = count;
michael@0	138
michael@0	139	#ifdef SK_DEBUG
michael@0	140	fx += fCount1 * dx;
michael@0	141	SkASSERT(fx <= ex);
michael@0	142	if (fCount2 > 0) {
michael@0	143	SkASSERT(fx >= 0xFFFF);
michael@0	144	if (fCount1 > 0) {
michael@0	145	SkASSERT(fx - dx < 0xFFFF);
michael@0	146	}
michael@0	147	}
michael@0	148	#endif
michael@0	149
michael@0	150	if (doSwap) {
michael@0	151	SkTSwap(fCount0, fCount2);
michael@0	152	SkTSwap(fV0, fV1);
michael@0	153	dx = -dx;
michael@0	154	}
michael@0	155
michael@0	156	if (fCount1 > 0) {
michael@0	157	fFx1 = fx0 + fCount0 * (int)dx;
michael@0	158	}
michael@0	159
michael@0	160	if (dx > 0) {
michael@0	161	fCount2 += extraCount;
michael@0	162	} else {
michael@0	163	fCount0 += extraCount;
michael@0	164	}
michael@0	165	}