From 9b7150266974cb29db8482ada315622a3a5fdf92 Mon Sep 17 00:00:00 2001
From: James Zern <jzern@google.com>
Date: Mon, 4 Jun 2012 18:36:38 -0700
Subject: [PATCH] histogram: add log2 wrapper

Change-Id: I5e68efaf5f763a42ace1af83f4b7887e0ddfd099
---
 src/enc/histogram.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/enc/histogram.c b/src/enc/histogram.c
index f9dfbdc8..6bb92e01 100644
--- a/src/enc/histogram.c
+++ b/src/enc/histogram.c
@@ -7,6 +7,9 @@
 //
 // Author: Jyrki Alakuijala (jyrki@google.com)
 //
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
 
 #ifdef USE_LOSSLESS_ENCODER
 
@@ -17,6 +20,17 @@
 #include "./histogram.h"
 #include "../dsp/lossless.h"
 
+#if defined(_MSC_VER) && !defined(NOT_HAVE_LOG2)
+# define NOT_HAVE_LOG2 1
+#endif
+
+#ifdef NOT_HAVE_LOG2
+static WEBP_INLINE double log2(double d) {
+  const double kLog2Reciprocal = 1.442695040888963;
+  return log(d) * kLog2Reciprocal;
+}
+#endif
+
 static void HistogramClear(VP8LHistogram* const p) {
   memset(p->literal_, 0, sizeof(p->literal_));
   memset(p->red_, 0, sizeof(p->red_));