add block comment for using SkChecksum
git-svn-id: http://skia.googlecode.com/svn/trunk@8827 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/core/SkChecksum.h b/include/core/SkChecksum.h
index 9cb45c3..287109f 100644
--- a/include/core/SkChecksum.h
+++ b/include/core/SkChecksum.h
@@ -10,6 +10,15 @@
#include "SkTypes.h"
+/**
+ * Computes a 32bit checksum from a blob of 32bit aligned data. This is meant
+ * to be very very fast, as it is used internally by the font cache, in
+ * conjuction with the entire raw key. This algorithm does not generate
+ * unique values as well as others (e.g. MD5) but it performs much faster.
+ * Skia's use cases can survive non-unique values (since the entire key is
+ * always available). Clients should only be used in circumstances where speed
+ * over uniqueness is at a premium.
+ */
class SkChecksum : SkNoncopyable {
private:
/*