From e1a5f4e292384046678edc5c1e360b3e13dc118c Mon Sep 17 00:00:00 2001
From: mtklein <mtklein@chromium.org>
Date: Mon, 26 Sep 2016 10:31:12 -0700
Subject: My take on SkAlign changes.

Like the other change, it makes SkAlignN(x) macros work for pointers, and makes the macros themselves just syntax sugar for SkAlign<N>(x).  We can still decide if we want to sed away the macros independently.

This just does it in a somewhat less repetitive way, and adds some tests.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2368293002

No public API changes.
TBR=reed@google.com

Review-Url: https://codereview.chromium.org/2368293002
---
 include/core/SkTypes.h | 45 +++++++++++++++++++++++++++++++++++----------
 1 file changed, 35 insertions(+), 10 deletions(-)

(limited to 'include/core/SkTypes.h')

diff --git a/include/core/SkTypes.h b/include/core/SkTypes.h
index 0cef8a1257..94650f01dc 100644
--- a/include/core/SkTypes.h
+++ b/include/core/SkTypes.h
@@ -332,20 +332,45 @@ template <typename T, size_t N> char (&SkArrayCountHelper(T (&array)[N]))[N];
     #define SK_END_REQUIRE_DENSE
 #endif
 
-#define SkAlign2(x)     (((x) + 1) >> 1 << 1)
-#define SkIsAlign2(x)   (0 == ((x) & 1))
+template <int N, typename T>
+struct SkAlign_traits {
+    static_assert (N > 0 && (N & (N-1)) == 0, "N must be a positive power of 2.");
+    constexpr static int Lg(int k) { return (k == 1) ? 0 : 1 + Lg(k/2); }
 
-#define SkAlign4(x)     (((x) + 3) >> 2 << 2)
-#define SkIsAlign4(x)   (0 == ((x) & 3))
+    constexpr static T Align(T x) { return (x + N-1) >> Lg(N) << Lg(N); }
+    constexpr static bool IsAligned(T x) { return 0 == (x & (N-1)); }
+};
+
+template <int N, typename P>
+struct SkAlign_traits<N, P*> {
+    constexpr static P* Align(P* p) {
+        return (P*)SkAlign_traits<N, uintptr_t>::Align((uintptr_t)p);
+    }
+    constexpr static bool IsAligned(P* p) {
+        return SkAlign_traits<N, uintptr_t>::IsAligned((uintptr_t)p);
+    }
+};
+
+template <int N, typename T>
+constexpr static inline T SkAlign(T x) { return SkAlign_traits<N,T>::Align(x); }
+
+template <int N, typename T>
+constexpr static bool SkIsAligned(T x) { return SkAlign_traits<N,T>::IsAligned(x); }
+
+#define SkAlign2(x)     SkAlign<2>(x)
+#define SkIsAlign2(x)   SkIsAligned<2>(x)
+
+#define SkAlign4(x)     SkAlign<4>(x)
+#define SkIsAlign4(x)   SkIsAligned<4>(x)
 
-#define SkAlign8(x)     (((x) + 7) >> 3 << 3)
-#define SkIsAlign8(x)   (0 == ((x) & 7))
+#define SkAlign8(x)     SkAlign<8>(x)
+#define SkIsAlign8(x)   SkIsAligned<8>(x)
 
-#define SkAlign16(x)     (((x) + 15) >> 4 << 4)
-#define SkIsAlign16(x)   (0 == ((x) & 15))
+#define SkAlign16(x)     SkAlign<16>(x)
+#define SkIsAlign16(x)   SkIsAligned<16>(x)
 
-#define SkAlignPtr(x)   (sizeof(void*) == 8 ?   SkAlign8(x) :   SkAlign4(x))
-#define SkIsAlignPtr(x) (sizeof(void*) == 8 ? SkIsAlign8(x) : SkIsAlign4(x))
+#define SkAlignPtr(x)   SkAlign<sizeof(void*)>(x)
+#define SkIsAlignPtr(x) SkIsAligned<sizeof(void*)>(x)
 
 typedef uint32_t SkFourByteTag;
 #define SkSetFourByteTag(a, b, c, d)    (((a) << 24) | ((b) << 16) | ((c) << 8) | (d))
-- 
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