1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/gfx/skia/trunk/src/effects/gradients/SkClampRange.cpp Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,165 @@
1.4 +
1.5 +/*
1.6 + * Copyright 2011 Google Inc.
1.7 + *
1.8 + * Use of this source code is governed by a BSD-style license that can be
1.9 + * found in the LICENSE file.
1.10 + */
1.11 +
1.12 +
1.13 +#include "SkClampRange.h"
1.14 +
1.15 +/*
1.16 + * returns [0..count] for the number of steps (<= count) for which x0 <= edge
1.17 + * given each step is followed by x0 += dx
1.18 + */
1.19 +static int chop(int64_t x0, SkFixed edge, int64_t x1, int64_t dx, int count) {
1.20 + SkASSERT(dx > 0);
1.21 + SkASSERT(count >= 0);
1.22 +
1.23 + if (x0 >= edge) {
1.24 + return 0;
1.25 + }
1.26 + if (x1 <= edge) {
1.27 + return count;
1.28 + }
1.29 + int64_t n = (edge - x0 + dx - 1) / dx;
1.30 + SkASSERT(n >= 0);
1.31 + SkASSERT(n <= count);
1.32 + return (int)n;
1.33 +}
1.34 +
1.35 +static bool overflows_fixed(int64_t x) {
1.36 + return x < -SK_FixedMax || x > SK_FixedMax;
1.37 +}
1.38 +
1.39 +void SkClampRange::initFor1(SkFixed fx) {
1.40 + fCount0 = fCount1 = fCount2 = 0;
1.41 + if (fx <= 0) {
1.42 + fCount0 = 1;
1.43 + } else if (fx < 0xFFFF) {
1.44 + fCount1 = 1;
1.45 + fFx1 = fx;
1.46 + } else {
1.47 + fCount2 = 1;
1.48 + }
1.49 +}
1.50 +
1.51 +void SkClampRange::init(SkFixed fx0, SkFixed dx0, int count, int v0, int v1) {
1.52 + SkASSERT(count > 0);
1.53 +
1.54 + fV0 = v0;
1.55 + fV1 = v1;
1.56 + fOverflowed = false;
1.57 +
1.58 + // special case 1 == count, as it is slightly common for skia
1.59 + // and avoids us ever calling divide or 64bit multiply
1.60 + if (1 == count) {
1.61 + this->initFor1(fx0);
1.62 + return;
1.63 + }
1.64 +
1.65 + int64_t fx = fx0;
1.66 + int64_t dx = dx0;
1.67 + // start with ex equal to the last computed value
1.68 + int64_t ex = fx + (count - 1) * dx;
1.69 + fOverflowed = overflows_fixed(ex);
1.70 +
1.71 + if ((uint64_t)(fx | ex) <= 0xFFFF) {
1.72 + fCount0 = fCount2 = 0;
1.73 + fCount1 = count;
1.74 + fFx1 = fx0;
1.75 + return;
1.76 + }
1.77 + if (fx <= 0 && ex <= 0) {
1.78 + fCount1 = fCount2 = 0;
1.79 + fCount0 = count;
1.80 + return;
1.81 + }
1.82 + if (fx >= 0xFFFF && ex >= 0xFFFF) {
1.83 + fCount0 = fCount1 = 0;
1.84 + fCount2 = count;
1.85 + return;
1.86 + }
1.87 +
1.88 + int extraCount = 0;
1.89 +
1.90 + // now make ex be 1 past the last computed value
1.91 + ex += dx;
1.92 + fOverflowed = overflows_fixed(ex);
1.93 + // now check for over/under flow
1.94 + if (fOverflowed) {
1.95 + int originalCount = count;
1.96 + int64_t ccount;
1.97 + bool swap = dx < 0;
1.98 + if (swap) {
1.99 + dx = -dx;
1.100 + fx = -fx;
1.101 + }
1.102 + ccount = (SK_FixedMax - fx + dx - 1) / dx;
1.103 + if (swap) {
1.104 + dx = -dx;
1.105 + fx = -fx;
1.106 + }
1.107 + SkASSERT(ccount > 0 && ccount <= SK_FixedMax);
1.108 +
1.109 + count = (int)ccount;
1.110 + if (0 == count) {
1.111 + this->initFor1(fx0);
1.112 + if (dx > 0) {
1.113 + fCount2 += originalCount - 1;
1.114 + } else {
1.115 + fCount0 += originalCount - 1;
1.116 + }
1.117 + return;
1.118 + }
1.119 + extraCount = originalCount - count;
1.120 + ex = fx + dx * count;
1.121 + }
1.122 +
1.123 + bool doSwap = dx < 0;
1.124 +
1.125 + if (doSwap) {
1.126 + ex -= dx;
1.127 + fx -= dx;
1.128 + SkTSwap(fx, ex);
1.129 + dx = -dx;
1.130 + }
1.131 +
1.132 +
1.133 + fCount0 = chop(fx, 0, ex, dx, count);
1.134 + count -= fCount0;
1.135 + fx += fCount0 * dx;
1.136 + SkASSERT(fx >= 0);
1.137 + SkASSERT(fCount0 == 0 || (fx - dx) < 0);
1.138 + fCount1 = chop(fx, 0xFFFF, ex, dx, count);
1.139 + count -= fCount1;
1.140 + fCount2 = count;
1.141 +
1.142 +#ifdef SK_DEBUG
1.143 + fx += fCount1 * dx;
1.144 + SkASSERT(fx <= ex);
1.145 + if (fCount2 > 0) {
1.146 + SkASSERT(fx >= 0xFFFF);
1.147 + if (fCount1 > 0) {
1.148 + SkASSERT(fx - dx < 0xFFFF);
1.149 + }
1.150 + }
1.151 +#endif
1.152 +
1.153 + if (doSwap) {
1.154 + SkTSwap(fCount0, fCount2);
1.155 + SkTSwap(fV0, fV1);
1.156 + dx = -dx;
1.157 + }
1.158 +
1.159 + if (fCount1 > 0) {
1.160 + fFx1 = fx0 + fCount0 * (int)dx;
1.161 + }
1.162 +
1.163 + if (dx > 0) {
1.164 + fCount2 += extraCount;
1.165 + } else {
1.166 + fCount0 += extraCount;
1.167 + }
1.168 +}
