1 files changed, 165 insertions, 0 deletions
diff --git a/effects/gradients/SkClampRange.cpp b/effects/gradients/SkClampRange.cpp
new file mode 100644
index 00000000..3e2ca8e9
--- /dev/null
+++ b/effects/gradients/SkClampRange.cpp
@@ -0,0 +1,165 @@
+
+/*
+ * Copyright 2011 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+
+#include "SkClampRange.h"
+
+/*
+ *  returns [0..count] for the number of steps (<= count) for which x0 <= edge
+ *  given each step is followed by x0 += dx
+ */
+static int chop(int64_t x0, SkFixed edge, int64_t x1, int64_t dx, int count) {
+    SkASSERT(dx > 0);
+    SkASSERT(count >= 0);
+
+    if (x0 >= edge) {
+        return 0;
+    }
+    if (x1 <= edge) {
+        return count;
+    }
+    int64_t n = (edge - x0 + dx - 1) / dx;
+    SkASSERT(n >= 0);
+    SkASSERT(n <= count);
+    return (int)n;
+}
+
+static bool overflows_fixed(int64_t x) {
+    return x < -SK_FixedMax || x > SK_FixedMax;
+}
+
+void SkClampRange::initFor1(SkFixed fx) {
+    fCount0 = fCount1 = fCount2 = 0;
+    if (fx <= 0) {
+        fCount0 = 1;
+    } else if (fx < 0xFFFF) {
+        fCount1 = 1;
+        fFx1 = fx;
+    } else {
+        fCount2 = 1;
+    }
+}
+
+void SkClampRange::init(SkFixed fx0, SkFixed dx0, int count, int v0, int v1) {
+    SkASSERT(count > 0);
+
+    fV0 = v0;
+    fV1 = v1;
+    fOverflowed = false;
+
+    // special case 1 == count, as it is slightly common for skia
+    // and avoids us ever calling divide or 64bit multiply
+    if (1 == count) {
+        this->initFor1(fx0);
+        return;
+    }
+
+    int64_t fx = fx0;
+    int64_t dx = dx0;
+    // start with ex equal to the last computed value
+    int64_t ex = fx + (count - 1) * dx;
+    fOverflowed = overflows_fixed(ex);
+
+    if ((uint64_t)(fx | ex) <= 0xFFFF) {
+        fCount0 = fCount2 = 0;
+        fCount1 = count;
+        fFx1 = fx0;
+        return;
+    }
+    if (fx <= 0 && ex <= 0) {
+        fCount1 = fCount2 = 0;
+        fCount0 = count;
+        return;
+    }
+    if (fx >= 0xFFFF && ex >= 0xFFFF) {
+        fCount0 = fCount1 = 0;
+        fCount2 = count;
+        return;
+    }
+
+    int extraCount = 0;
+
+    // now make ex be 1 past the last computed value
+    ex += dx;
+    fOverflowed = overflows_fixed(ex);
+    // now check for over/under flow
+    if (fOverflowed) {
+        int originalCount = count;
+        int64_t ccount;
+        bool swap = dx < 0;
+        if (swap) {
+            dx = -dx;
+            fx = -fx;
+        }
+        ccount = (SK_FixedMax - fx + dx - 1) / dx;
+        if (swap) {
+            dx = -dx;
+            fx = -fx;
+        }
+        SkASSERT(ccount > 0 && ccount <= SK_FixedMax);
+
+        count = (int)ccount;
+        if (0 == count) {
+            this->initFor1(fx0);
+            if (dx > 0) {
+                fCount2 += originalCount - 1;
+            } else {
+                fCount0 += originalCount - 1;
+            }
+            return;
+        }
+        extraCount = originalCount - count;
+        ex = fx + dx * count;
+    }
+
+    bool doSwap = dx < 0;
+
+    if (doSwap) {
+        ex -= dx;
+        fx -= dx;
+        SkTSwap(fx, ex);
+        dx = -dx;
+    }
+
+
+    fCount0 = chop(fx, 0, ex, dx, count);
+    count -= fCount0;
+    fx += fCount0 * dx;
+    SkASSERT(fx >= 0);
+    SkASSERT(fCount0 == 0 || (fx - dx) < 0);
+    fCount1 = chop(fx, 0xFFFF, ex, dx, count);
+    count -= fCount1;
+    fCount2 = count;
+
+#ifdef SK_DEBUG
+    fx += fCount1 * dx;
+    SkASSERT(fx <= ex);
+    if (fCount2 > 0) {
+        SkASSERT(fx >= 0xFFFF);
+        if (fCount1 > 0) {
+            SkASSERT(fx - dx < 0xFFFF);
+        }
+    }
+#endif
+
+    if (doSwap) {
+        SkTSwap(fCount0, fCount2);
+        SkTSwap(fV0, fV1);
+        dx = -dx;
+    }
+
+    if (fCount1 > 0) {
+        fFx1 = fx0 + fCount0 * (int)dx;
+    }
+
+    if (dx > 0) {
+        fCount2 += extraCount;
+    } else {
+        fCount0 += extraCount;
+    }
+}