Initial Contribution

1 files changed, 334 insertions, 0 deletions

diff --git a/libcorecg/SkPoint.cpp b/libcorecg/SkPoint.cpp
new file mode 100644
index 0000000..704c2ba
--- /dev/null
+++ b/libcorecg/SkPoint.cpp
@@ -0,0 +1,334 @@
+/*
+ * Copyright (C) 2006-2008 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "SkPoint.h"
+
+void SkIPoint::rotateCW(SkIPoint* dst) const {
+    SkASSERT(dst);
+
+    // use a tmp in case this == dst
+    int32_t tmp = fX;
+    dst->fX = -fY;
+    dst->fY = tmp;
+}
+
+void SkIPoint::rotateCCW(SkIPoint* dst) const {
+    SkASSERT(dst);
+
+    // use a tmp in case this == dst
+    int32_t tmp = fX;
+    dst->fX = fY;
+    dst->fY = -tmp;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+void SkPoint::rotateCW(SkPoint* dst) const {
+    SkASSERT(dst);
+
+    // use a tmp in case this == dst
+    SkScalar tmp = fX;
+    dst->fX = -fY;
+    dst->fY = tmp;
+}
+
+void SkPoint::rotateCCW(SkPoint* dst) const {
+    SkASSERT(dst);
+
+    // use a tmp in case this == dst
+    SkScalar tmp = fX;
+    dst->fX = fY;
+    dst->fY = -tmp;
+}
+
+void SkPoint::scale(SkScalar scale, SkPoint* dst) const {
+    SkASSERT(dst);
+    dst->set(SkScalarMul(fX, scale), SkScalarMul(fY, scale));
+}
+
+#define kNearlyZero     (SK_Scalar1 / 8092)
+
+bool SkPoint::normalize() {
+    return this->setLength(fX, fY, SK_Scalar1);
+}
+
+bool SkPoint::setNormalize(SkScalar x, SkScalar y) {
+    return this->setLength(x, y, SK_Scalar1);
+}
+
+bool SkPoint::setLength(SkScalar length) {
+    return this->setLength(fX, fY, length);
+}
+
+#ifdef SK_SCALAR_IS_FLOAT
+
+SkScalar SkPoint::Length(SkScalar dx, SkScalar dy) {
+    return sk_float_sqrt(dx * dx + dy * dy);
+}
+
+bool SkPoint::setLength(float x, float y, float length) {
+    float mag = sk_float_sqrt(x * x + y * y);
+    if (mag > kNearlyZero) {
+        length /= mag;
+        fX = x * length;
+        fY = y * length;
+        return true;
+    }
+    return false;
+}
+
+#else
+
+#include "Sk64.h"
+
+SkScalar SkPoint::Length(SkScalar dx, SkScalar dy) {
+    Sk64    tmp1, tmp2;
+
+    tmp1.setMul(dx, dx);
+    tmp2.setMul(dy, dy);
+    tmp1.add(tmp2);
+
+    return tmp1.getSqrt();
+}
+
+#ifdef SK_DEBUGx
+static SkFixed fixlen(SkFixed x, SkFixed y) {
+    float fx = (float)x;
+    float fy = (float)y;
+
+    return (int)floorf(sqrtf(fx*fx + fy*fy) + 0.5f);
+}
+#endif
+
+static inline uint32_t squarefixed(unsigned x) {
+    x >>= 16;
+    return x*x;
+}
+
+#if 1   // Newton iter for setLength
+
+static inline unsigned invsqrt_iter(unsigned V, unsigned U) {
+    unsigned x = V * U >> 14;
+    x = x * U >> 14;
+    x = (3 << 14) - x;
+    x = (U >> 1) * x >> 14;
+    return x;
+}
+
+static const uint16_t gInvSqrt14GuessTable[] = {
+    0x4000, 0x3c57, 0x393e, 0x3695, 0x3441, 0x3235, 0x3061,
+    0x2ebd, 0x2d41, 0x2be7, 0x2aaa, 0x2987, 0x287a, 0x2780,
+    0x2698, 0x25be, 0x24f3, 0x2434, 0x2380, 0x22d6, 0x2235,
+    0x219d, 0x210c, 0x2083, 0x2000, 0x1f82, 0x1f0b, 0x1e99,
+    0x1e2b, 0x1dc2, 0x1d5d, 0x1cfc, 0x1c9f, 0x1c45, 0x1bee,
+    0x1b9b, 0x1b4a, 0x1afc, 0x1ab0, 0x1a67, 0x1a20, 0x19dc,
+    0x1999, 0x1959, 0x191a, 0x18dd, 0x18a2, 0x1868, 0x1830,
+    0x17fa, 0x17c4, 0x1791, 0x175e, 0x172d, 0x16fd, 0x16ce
+};
+
+#define BUILD_INVSQRT_TABLEx
+#ifdef BUILD_INVSQRT_TABLE
+static void build_invsqrt14_guess_table() {
+    for (int i = 8; i <= 63; i++) {
+        unsigned x = SkToU16((1 << 28) / SkSqrt32(i << 25));
+        printf("0x%x, ", x);
+    }
+    printf("\n");
+}
+#endif
+
+static unsigned fast_invsqrt(uint32_t x) {
+#ifdef BUILD_INVSQRT_TABLE
+    unsigned top2 = x >> 25;
+    SkASSERT(top2 >= 8 && top2 <= 63);
+
+    static bool gOnce;
+    if (!gOnce) {
+        build_invsqrt14_guess_table();
+        gOnce = true;
+    }
+#endif
+
+    unsigned V = x >> 14;   // make V .14
+
+    unsigned top = x >> 25;
+    SkASSERT(top >= 8 && top <= 63);
+    SkASSERT(top - 8 < SK_ARRAY_COUNT(gInvSqrt14GuessTable));
+    unsigned U = gInvSqrt14GuessTable[top - 8];
+    
+    U = invsqrt_iter(V, U);
+    return invsqrt_iter(V, U);
+}
+
+/*  We "normalize" x,y to be .14 values (so we can square them and stay 32bits.
+    Then we Newton-iterate this in .14 space to compute the invser-sqrt, and
+    scale by it at the end. The .14 space means we can execute our iterations
+    and stay in 32bits as well, making the multiplies much cheaper than calling
+    SkFixedMul.
+*/
+bool SkPoint::setLength(SkFixed ox, SkFixed oy, SkFixed length) {
+    if (ox == 0) {
+        if (oy == 0) {
+            return false;
+        }
+        this->set(0, SkApplySign(length, SkExtractSign(oy)));
+        return true;
+    }
+    if (oy == 0) {
+        this->set(SkApplySign(length, SkExtractSign(ox)), 0);
+        return true;
+    }
+
+    unsigned x = SkAbs32(ox);
+    unsigned y = SkAbs32(oy);
+    int zeros = SkCLZ(x | y);
+
+    // make x,y 1.14 values so our fast sqr won't overflow
+    if (zeros > 17) {
+        x <<= zeros - 17;
+        y <<= zeros - 17; 
+    } else {
+        x >>= 17 - zeros;
+        y >>= 17 - zeros;
+    }
+    SkASSERT((x | y) <= 0x7FFF);
+
+    unsigned invrt = fast_invsqrt(x*x + y*y);
+
+    x = x * invrt >> 12;
+    y = y * invrt >> 12;
+
+    if (length != SK_Fixed1) {
+        x = SkFixedMul(x, length);
+        y = SkFixedMul(y, length);
+    }
+    this->set(SkApplySign(x, SkExtractSign(ox)),
+              SkApplySign(y, SkExtractSign(oy)));
+    return true;
+}
+#else
+/*
+    Normalize x,y, and then scale them by length.
+
+    The obvious way to do this would be the following:
+        S64 tmp1, tmp2;
+        tmp1.setMul(x,x);
+        tmp2.setMul(y,y);
+        tmp1.add(tmp2);
+        len = tmp1.getSqrt();
+        x' = SkFixedDiv(x, len);
+        y' = SkFixedDiv(y, len);
+    This is fine, but slower than what we do below.
+
+    The present technique does not compute the starting length, but
+    rather fiddles with x,y iteratively, all the while checking its
+    magnitude^2 (avoiding a sqrt).
+
+    We normalize by first shifting x,y so that at least one of them
+    has bit 31 set (after taking the abs of them).
+    Then we loop, refining x,y by squaring them and comparing
+    against a very large 1.0 (1 << 28), and then adding or subtracting
+    a delta (which itself is reduced by half each time through the loop).
+    For speed we want the squaring to be with a simple integer mul. To keep
+    that from overflowing we shift our coordinates down until we are dealing
+    with at most 15 bits (2^15-1)^2 * 2 says withing 32 bits)
+    When our square is close to 1.0, we shift x,y down into fixed range.
+*/
+bool SkPoint::setLength(SkFixed ox, SkFixed oy, SkFixed length) {
+    if (ox == 0) {
+        if (oy == 0)
+            return false;
+        this->set(0, SkApplySign(length, SkExtractSign(oy)));
+        return true;
+    }
+    if (oy == 0) {
+        this->set(SkApplySign(length, SkExtractSign(ox)), 0);
+        return true;
+    }
+
+    SkFixed x = SkAbs32(ox);
+    SkFixed y = SkAbs32(oy);
+
+    // shift x,y so that the greater of them is 15bits (1.14 fixed point)
+    {
+        int shift = SkCLZ(x | y);
+        // make them .30
+        x <<= shift - 1;
+        y <<= shift - 1;
+    }
+
+    SkFixed dx = x;
+    SkFixed dy = y;
+
+    for (int i = 0; i < 17; i++) {
+        dx >>= 1;
+        dy >>= 1;
+
+        U32 len2 = squarefixed(x) + squarefixed(y);
+        if (len2 >> 28) {
+            x -= dx;
+            y -= dy;
+        } else {
+            x += dx;
+            y += dy;
+        }
+    }
+    x >>= 14;
+    y >>= 14;
+
+#ifdef SK_DEBUGx    // measure how far we are from unit-length
+    {
+        static int gMaxError;
+        static int gMaxDiff;
+
+        SkFixed len = fixlen(x, y);
+        int err = len - SK_Fixed1;
+        err = SkAbs32(err);
+
+        if (err > gMaxError) {
+            gMaxError = err;
+            SkDebugf("gMaxError %d\n", err);
+        }
+
+        float fx = SkAbs32(ox)/65536.0f;
+        float fy = SkAbs32(oy)/65536.0f;
+        float mag = sqrtf(fx*fx + fy*fy);
+        fx /= mag;
+        fy /= mag;
+        SkFixed xx = (int)floorf(fx * 65536 + 0.5f);
+        SkFixed yy = (int)floorf(fy * 65536 + 0.5f);
+        err = SkMax32(SkAbs32(xx-x), SkAbs32(yy-y));
+        if (err > gMaxDiff) {
+            gMaxDiff = err;
+            SkDebugf("gMaxDiff %d\n", err);
+        }
+    }
+#endif
+
+    x = SkApplySign(x, SkExtractSign(ox));
+    y = SkApplySign(y, SkExtractSign(oy));
+    if (length != SK_Fixed1) {
+        x = SkFixedMul(x, length);
+        y = SkFixedMul(y, length);
+    }
+    
+    this->set(x, y);
+    return true;
+}
+#endif
+
+#endif
+