From fba94b3c371983c2b84d34db100e46d21055f3b6 Mon Sep 17 00:00:00 2001
From: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Date: Sun, 3 Dec 2006 14:53:27 -0200
Subject: [PATCH] --- yaml --- r: 42061 b: refs/heads/master c:
 2bbf29acd8f7adcf161de7e5d891b4095687a59f h: refs/heads/master i:   42059:
 1085d3abefd8105e9d57f9636922da11b0e9aa2b v: v3

---
 [refs]                                   |  2 +-
 trunk/net/dccp/ccids/lib/tfrc_equation.c | 38 +++++++++++++++---------
 2 files changed, 25 insertions(+), 15 deletions(-)

diff --git a/[refs] b/[refs]
index c08629384bc6..502d4be1e54f 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 44158306d756c88272c8faf243ca68897498e219
+refs/heads/master: 2bbf29acd8f7adcf161de7e5d891b4095687a59f
diff --git a/trunk/net/dccp/ccids/lib/tfrc_equation.c b/trunk/net/dccp/ccids/lib/tfrc_equation.c
index 0a4a3d2feba5..ddac2c511e2f 100644
--- a/trunk/net/dccp/ccids/lib/tfrc_equation.c
+++ b/trunk/net/dccp/ccids/lib/tfrc_equation.c
@@ -594,6 +594,21 @@ static const u32 tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE][2] = {
 	{ 243315981, 271305 }
 };
 
+/* return largest index i such that fval <= lookup[i][small] */
+static inline u32 tfrc_binsearch(u32 fval, u8 small)
+{
+	u32 try, low = 0, high = TFRC_CALC_X_ARRSIZE - 1;
+
+	while (low < high) {
+		try = (low + high) / 2;
+		if (fval <= tfrc_calc_x_lookup[try][small])
+			high = try;
+		else
+			low  = try + 1;
+	}
+	return high;
+}
+
 /**
  * tfrc_calc_x - Calculate the send rate as per section 3.1 of RFC3448
  *
@@ -656,8 +671,7 @@ EXPORT_SYMBOL_GPL(tfrc_calc_x);
  */
 u32 tfrc_calc_x_reverse_lookup(u32 fvalue)
 {
-	int ctr = 0;
-	int small;
+	int index;
 
 	if (fvalue == 0)	/* f(p) = 0  whenever  p = 0 */
 		return 0;
@@ -672,18 +686,14 @@ u32 tfrc_calc_x_reverse_lookup(u32 fvalue)
 		return 1000000;
 	}
 
-	if (fvalue <= tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE - 1][1])
-		small = 1;
-	else
-		small = 0;
-
-	while (fvalue > tfrc_calc_x_lookup[ctr][small])
-		ctr++;
-
-	if (small)
-		return (ctr + 1) * TFRC_CALC_X_SPLIT / TFRC_CALC_X_ARRSIZE;
-	else
-		return (ctr + 1) * 1000000 / TFRC_CALC_X_ARRSIZE;
+	if (fvalue <= tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE - 1][1]) {
+		index = tfrc_binsearch(fvalue, 1);
+		return (index + 1) * TFRC_CALC_X_SPLIT / TFRC_CALC_X_ARRSIZE;
+ 	}
+ 
+	/* else ... it must be in the coarse-grained column */
+	index = tfrc_binsearch(fvalue, 0);
+	return (index + 1) * 1000000 / TFRC_CALC_X_ARRSIZE;
 }
 
 EXPORT_SYMBOL_GPL(tfrc_calc_x_reverse_lookup);