Add generatl bit replication function

Base/include/Bits.h

@@ -88,5 +88,28 @@ namespace FasTC {
     }
   };
 
+  // Replicates low numBits such that [(toBit - 1):(toBit - 1 - fromBit)]
+  // is the same as [(numBits - 1):0] and repeats all the way down.
+  template<typename IntType>
+  IntType Replicate(const IntType &val, uint32 numBits, uint32 toBit) {
+    if(numBits == 0) return 0;
+    if(toBit == 0) return 0;
+    IntType v = val & ((1 << numBits) - 1);
+    IntType res = v;
+    uint32 reslen = numBits;
+    while(reslen < toBit) {
+      uint32 comp = 0;
+      if(numBits > toBit - reslen) {
+        uint32 newshift = toBit - reslen;
+        comp = numBits - newshift;
+        numBits = newshift;
+      }
+      res <<= numBits;
+      res |= v >> comp;
+      reslen += numBits;
+    }
+    return res;
+  }
+
 }  // namespace FasTC
 #endif // __BASE_INCLUDE_BITS_H__

Base/src/Pixel.cpp

@@ -56,6 +56,8 @@
 #include <cassert>
 #include <algorithm>
 
+#include "Bits.h"
+
 template<typename T>
 static inline T Clamp(const T &v, const T &_min, const T &_max) {
   return std::max(_min, std::min(v, _max));
@@ -161,16 +163,7 @@ namespace FasTC {
     } else if(oldDepth == 0 && newDepth != 0) {
       return (1 << newDepth) - 1;
     } else if(newDepth > oldDepth) {
-      uint8 bitsLeft = newDepth;
-      uint8 ret = 0;
-      while(bitsLeft > oldDepth) {
-        ret |= val;
-        bitsLeft -= oldDepth;
-        ret <<= std::min(bitsLeft, oldDepth);
-      }
-
-      return ret | (val >> (oldDepth - bitsLeft));
-
+      return Replicate(val, oldDepth, newDepth);
     } else {
       // oldDepth > newDepth
       if(newDepth == 0) {

Base/test/CMakeLists.txt

@@ -55,7 +55,7 @@ INCLUDE_DIRECTORIES(${FasTC_BINARY_DIR}/Base/include )
 INCLUDE_DIRECTORIES(${FasTC_SOURCE_DIR}/GTest/include)
 
 SET(TESTS
-  Vector Matrix Pixel Image Color
+  Vector Matrix Pixel Image Color Bits
 )
 
 FOREACH(TEST ${TESTS})

Base/test/TestBits.cpp

@@ -0,0 +1,69 @@
+/* FasTC
+ * Copyright (c) 2014 University of North Carolina at Chapel Hill.
+ * All rights reserved.
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation for educational, research, and non-profit purposes, without
+ * fee, and without a written agreement is hereby granted, provided that the
+ * above copyright notice, this paragraph, and the following four paragraphs
+ * appear in all copies.
+ *
+ * Permission to incorporate this software into commercial products may be
+ * obtained by contacting the authors or the Office of Technology Development
+ * at the University of North Carolina at Chapel Hill <otd@unc.edu>.
+ *
+ * This software program and documentation are copyrighted by the University of
+ * North Carolina at Chapel Hill. The software program and documentation are
+ * supplied "as is," without any accompanying services from the University of
+ * North Carolina at Chapel Hill or the authors. The University of North
+ * Carolina at Chapel Hill and the authors do not warrant that the operation of
+ * the program will be uninterrupted or error-free. The end-user understands
+ * that the program was developed for research purposes and is advised not to
+ * rely exclusively on the program for any reason.
+ *
+ * IN NO EVENT SHALL THE UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL OR THE
+ * AUTHORS BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL,
+ * OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF
+ * THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF NORTH CAROLINA
+ * AT CHAPEL HILL OR THE AUTHORS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL AND THE AUTHORS SPECIFICALLY
+ * DISCLAIM ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE AND ANY 
+ * STATUTORY WARRANTY OF NON-INFRINGEMENT. THE SOFTWARE PROVIDED HEREUNDER IS ON
+ * AN "AS IS" BASIS, AND THE UNIVERSITY  OF NORTH CAROLINA AT CHAPEL HILL AND
+ * THE AUTHORS HAVE NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, 
+ * ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ * Please send all BUG REPORTS to <pavel@cs.unc.edu>.
+ *
+ * The authors may be contacted via:
+ *
+ * Pavel Krajcevski
+ * Dept of Computer Science
+ * 201 S Columbia St
+ * Frederick P. Brooks, Jr. Computer Science Bldg
+ * Chapel Hill, NC 27599-3175
+ * USA
+ * 
+ * <http://gamma.cs.unc.edu/FasTC/>
+ */
+
+#include "gtest/gtest.h"
+#include "Bits.h"
+
+TEST(Bits, Replicate) {
+  uint32 xv = 3;
+  EXPECT_EQ(FasTC::Replicate(xv, 2, 8), 0xFF);
+  EXPECT_EQ(FasTC::Replicate(xv, 0, 7), 0);
+  EXPECT_EQ(FasTC::Replicate(xv, 3, 4), 0x06);
+
+  xv = 0;
+  EXPECT_EQ(FasTC::Replicate(xv, 1, 0), 0);
+  EXPECT_EQ(FasTC::Replicate(xv, 0, 7), 0);
+
+  xv = 5;
+  EXPECT_EQ(FasTC::Replicate(xv, 2, 0), 0);
+  EXPECT_EQ(FasTC::Replicate(xv, 3, 6), 0x2D);
+}