add gpu backend (not hooked up yet)
git-svn-id: http://skia.googlecode.com/svn/trunk@649 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gpu/include/GrRandom.h b/gpu/include/GrRandom.h
new file mode 100644
index 0000000..408f61d
--- /dev/null
+++ b/gpu/include/GrRandom.h
@@ -0,0 +1,62 @@
+/*
+ Copyright 2010 Google Inc.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+
+
+#ifndef GrRandom_DEFINED
+#define GrRandom_DEFINED
+
+class GrRandom {
+public:
+ GrRandom() : fSeed(0) {}
+ GrRandom(uint32_t seed) : fSeed(seed) {}
+
+ uint32_t seed() const { return fSeed; }
+
+ uint32_t nextU() {
+ fSeed = fSeed * kMUL + kADD;
+ return fSeed;
+ }
+
+ int32_t nextS() { return (int32_t)this->nextU(); }
+
+ /**
+ * Returns value [0...1) as a float
+ */
+ float nextF() {
+ // const is 1 / (2^32 - 1)
+ return (float)(this->nextU() * 2.32830644e-10);
+ }
+
+ /**
+ * Returns value [min...max) as a float
+ */
+ float nextF(float min, float max) {
+ return min + this->nextF() * (max - min);
+ }
+
+private:
+ /*
+ * These constants taken from "Numerical Recipes in C", reprinted 1999
+ */
+ enum {
+ kMUL = 1664525,
+ kADD = 1013904223
+ };
+ uint32_t fSeed;
+};
+
+#endif
+