1 files changed, 62 insertions, 0 deletions
diff --git a/src/shaders/gradients/SkClampRange.h b/src/shaders/gradients/SkClampRange.h
new file mode 100644
index 0000000000..8a22e72d38
--- /dev/null
+++ b/src/shaders/gradients/SkClampRange.h
@@ -0,0 +1,62 @@
+/*
+ * Copyright 2011 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkClampRange_DEFINED
+#define SkClampRange_DEFINED
+
+#include "SkFixed.h"
+#include "SkScalar.h"
+
+#define SkGradFixed               SkFixed3232
+
+// We want the largest 32.32 value representable as a float. (float)0x7FFFFFFF
+// becomes too big, due to limited mantissa on the float and its rounding rules, so
+// we have to manually compute the next smaller value (aka nextafter).
+
+// #define SkGradFixedMaxScalar nextafterf(SkFixed3232ToFloat(SkFixed3232Max), 0)
+// #define SkGradFixedMinScalar nextafterf(SkFixed3232ToFloat(SkFixed3232Min), 0)
+#define SkGradFixedMaxScalar      ( 2147483520.0f)
+#define SkGradFixedMinScalar      (-2147483520.0f)
+#define SkScalarPinToGradFixed(x) SkScalarToFixed3232(SkTPin(x,                   \
+                                                             SkGradFixedMinScalar,\
+                                                             SkGradFixedMaxScalar))
+#define SkFixedToGradFixed(x)     SkFixedToFixed3232(x)
+#define SkGradFixedToFixed(x)     (SkFixed)((x) >> 16)
+#define kFracMax_SkGradFixed      0xFFFFFFFFLL
+
+/**
+ *  Iteration fixed fx by dx, clamping as you go to [0..kFracMax_SkGradFixed], this class
+ *  computes the (up to) 3 spans there are:
+ *
+ *  range0: use constant value V0
+ *  range1: iterate as usual fx += dx
+ *  range2: use constant value V1
+ */
+struct SkClampRange {
+    int fCount0;    // count for fV0
+    int fCount1;    // count for interpolating (fV0...fV1)
+    int fCount2;    // count for fV1
+    SkGradFixed fFx1;   // initial fx value for the fCount1 range.
+                    // only valid if fCount1 > 0
+    int fV0, fV1;
+
+    void init(SkGradFixed fx, SkGradFixed dx, int count, int v0, int v1);
+
+    void validate(int count) const {
+#ifdef SK_DEBUG
+        SkASSERT(fCount0 >= 0);
+        SkASSERT(fCount1 >= 0);
+        SkASSERT(fCount2 >= 0);
+        SkASSERT(fCount0 + fCount1 + fCount2 == count);
+#endif
+    }
+
+private:
+    void initFor1(SkGradFixed fx);
+};
+
+#endif