rsys

commit 1129cb29161e60fb1530afed29d06e8e1782ef31
parent b8d6272e6e4668e9dfa425eb6bf68f9cb2a018ba
Author: vaplv <vaplv@free.fr>
Date:   Sat,  3 May 2014 16:45:26 +0200

Add and test the log2i function

Diffstat:
M
cmake/CMakeLists.txt
 | 
2
+-
M
src/math.h
 | 
10
+++++++++-
M
src/test_math.c
 | 
8
++++++++

3 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/cmake/CMakeLists.txt b/cmake/CMakeLists.txt
@@ -116,7 +116,7 @@ new_test(test_library rsys)
 new_test(test_list rsys)
 new_test(test_mem_allocator rsys)
 new_test(test_binary_heap rsys)
-new_test(test_math)
+new_test(test_math m)
 new_test(test_ref)
 new_test(test_signal rsys)
 new_test(test_str rsys)
diff --git a/src/math.h b/src/math.h
@@ -12,7 +12,6 @@
 #define RCP_PI 0.31830988618379067154	/* 1/ pi */
 #define SQRT2 1.41421356237309504880 /* sqrt( 2 ) */
 
-
 static FINLINE size_t
 round_up_pow2(const size_t i)
 {
@@ -29,6 +28,15 @@ round_up_pow2(const size_t i)
   }
 }
 
+static FINLINE int
+log2i(const int i)
+{
+  union { float f; const int32_t i; } ucast;
+  ASSERT(i != 0);
+  ucast.f = (float)i;
+  return ((ucast.i>>23/*#bits mantissa*/) & ((1<<8/*#bits exponent*/)-1)) - 127;
+}
+
 static FINLINE float
 absf(const float flt)
 {
diff --git a/src/test_math.c b/src/test_math.c
@@ -36,6 +36,14 @@ main(int argc, char** argv)
   CHECK(IS_POW2(31), 0);
   CHECK(IS_POW2(64), 1);
   CHECK(IS_POW2(1 << 16), 1);
+  CHECK(log2i(3), 1);
+  CHECK(log2i(4), 2);
+  CHECK(log2i(5), 2);
+  CHECK(log2i(7), 2);
+  CHECK(log2i(8), 3);
+  CHECK(log2i(12), 3);
+  CHECK(log2i(511), 8);
+  CHECK(log2i(512), 9);
   CHECK(round_up_pow2(0), 1);
   CHECK(round_up_pow2(3), 4);
   CHECK(round_up_pow2(4), 4);