clone saturating cast code for doubles

Bug: skia:
Change-Id: I4f35413995cf73c6f130476d6b36e530120aa7ed
Reviewed-on: https://skia-review.googlesource.com/57901
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Reed <reed@google.com>

include/private/SkFloatingPoint.h

@@ -90,6 +90,15 @@ static inline int sk_float_saturate2int(float x) {
     return (int)x;
 }
 
+/**
+ *  Return the closest int for the given double. Returns SK_MaxS32 for NaN.
+ */
+static inline int sk_double_saturate2int(double x) {
+    x = SkTMin<double>(x, SK_MaxS32);
+    x = SkTMax<double>(x, SK_MinS32);
+    return (int)x;
+}
+
 #define sk_float_floor2int(x)   sk_float_saturate2int(sk_float_floor(x))
 #define sk_float_round2int(x)   sk_float_saturate2int(sk_float_floor((x) + 0.5f))
 #define sk_float_ceil2int(x)    sk_float_saturate2int(sk_float_ceil(x))

src/core/SkScan_Path.cpp

@@ -573,7 +573,7 @@ static const double kRoundBias = 0.0;
 static inline int round_down_to_int(SkScalar x) {
     double xx = x;
     xx -= 0.5 + kRoundBias;
-    return (int)ceil(xx);
+    return sk_double_saturate2int(ceil(xx));
 }
 
 /**
@@ -583,7 +583,7 @@ static inline int round_down_to_int(SkScalar x) {
 static inline int round_up_to_int(SkScalar x) {
     double xx = x;
     xx += 0.5 + kRoundBias;
-    return (int)floor(xx);
+    return sk_double_saturate2int(floor(xx));
 }
 
 /**

tests/MathTest.cpp

@@ -693,3 +693,27 @@ DEF_TEST(FloatSaturate, reporter) {
         REPORTER_ASSERT(reporter, r.fExpectedInt == i);
     }
 }
+
+DEF_TEST(DoubleSaturate, reporter) {
+    const struct {
+        double  fDouble;
+        int     fExpectedInt;
+    } recs[] = {
+        { 0, 0 },
+        { 100.5, 100 },
+        { SK_MaxS32, SK_MaxS32 },
+        { SK_MinS32, SK_MinS32 },
+        { SK_MaxS32 - 1, SK_MaxS32 - 1 },
+        { SK_MinS32 + 1, SK_MinS32 + 1 },
+        { SK_MaxS32 * 100.0, SK_MaxS32 },
+        { SK_MinS32 * 100.0, SK_MinS32 },
+        { SK_ScalarInfinity, SK_MaxS32 },
+        { SK_ScalarNegativeInfinity, SK_MinS32 },
+        { SK_ScalarNaN, SK_MaxS32 },
+    };
+
+    for (auto r : recs) {
+        int i = sk_double_saturate2int(r.fDouble);
+        REPORTER_ASSERT(reporter, r.fExpectedInt == i);
+    }
+}