From d3b7b89493e025654d218fb77da095649b4f6ba2 Mon Sep 17 00:00:00 2001
From: michi_cc <michi_cc@openttd.org>
Date: Sat, 3 Dec 2011 23:40:46 +0000
Subject: (svn r23415) -Feature: Infrastructure maintenance costs.

---
 src/core/math_func.cpp | 30 ++++++++++++++++++++++++++++++
 src/core/math_func.hpp |  2 ++
 2 files changed, 32 insertions(+)

(limited to 'src/core')

diff --git a/src/core/math_func.cpp b/src/core/math_func.cpp
index 7f0630a97..2b8ca3309 100644
--- a/src/core/math_func.cpp
+++ b/src/core/math_func.cpp
@@ -46,3 +46,33 @@ int GreatestCommonDivisor(int a, int b)
 	return a;
 
 }
+
+/**
+ * Compute the integer square root.
+ * @param num Radicand.
+ * @return Rounded integer square root.
+ * @note Algorithm taken from http://en.wikipedia.org/wiki/Methods_of_computing_square_roots
+ */
+uint32 IntSqrt(uint32 num)
+{
+	uint32 res = 0;
+	uint32 bit = 1UL << 30; // Second to top bit number.
+
+	/* 'bit' starts at the highest power of four <= the argument. */
+	while (bit > num) bit >>= 2;
+
+	while (bit != 0) {
+		if (num >= res + bit) {
+			num -= res + bit;
+			res = (res >> 1) + bit;
+		} else {
+			res >>= 1;
+		}
+		bit >>= 2;
+	}
+
+	/* Arithmetic rounding to nearest integer. */
+	if (num > res) res++;
+
+	return res;
+}
diff --git a/src/core/math_func.hpp b/src/core/math_func.hpp
index 19f2f53d6..92893ed31 100644
--- a/src/core/math_func.hpp
+++ b/src/core/math_func.hpp
@@ -346,4 +346,6 @@ static FORCEINLINE int RoundDivSU(int a, uint b)
 	}
 }
 
+uint32 IntSqrt(uint32 num);
+
 #endif /* MATH_FUNC_HPP */
-- 
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