From 97d7a9260e4f2f335b3632180877c25e0efdc8e3 Mon Sep 17 00:00:00 2001
From: Yang Tse <yangsita@gmail.com>
Date: Fri, 25 Nov 2011 13:51:55 +0100
Subject: [PATCH] tvdiff_secs(): sub-zero time difference adjustment

Skip a floating point addition operation when integral part of time difference
is zero. This avoids potential floating point addition rounding problems while
preserving decimal part value.
---
 lib/timeval.c            | 7 +++++--
 src/tool_util.c          | 7 +++++--
 tests/libtest/testutil.c | 7 +++++--
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/lib/timeval.c b/lib/timeval.c
index cb39308e0..2fd720144 100644
--- a/lib/timeval.c
+++ b/lib/timeval.c
@@ -120,8 +120,11 @@ long curlx_tvdiff(struct timeval newer, struct timeval older)
  */
 double curlx_tvdiff_secs(struct timeval newer, struct timeval older)
 {
-  return (double)(newer.tv_sec-older.tv_sec)+
-    (double)(newer.tv_usec-older.tv_usec)/1000000.0;
+  if(newer.tv_sec != older.tv_sec)
+    return (double)(newer.tv_sec-older.tv_sec)+
+      (double)(newer.tv_usec-older.tv_usec)/1000000.0;
+  else
+    return (double)(newer.tv_usec-older.tv_usec)/1000000.0;
 }
 
 /* return the number of seconds in the given input timeval struct */
diff --git a/src/tool_util.c b/src/tool_util.c
index 79c998295..93ab17fd4 100644
--- a/src/tool_util.c
+++ b/src/tool_util.c
@@ -123,8 +123,11 @@ long tool_tvdiff(struct timeval newer, struct timeval older)
  */
 double tool_tvdiff_secs(struct timeval newer, struct timeval older)
 {
-  return (double)(newer.tv_sec-older.tv_sec)+
-    (double)(newer.tv_usec-older.tv_usec)/1000000.0;
+  if(newer.tv_sec != older.tv_sec)
+    return (double)(newer.tv_sec-older.tv_sec)+
+      (double)(newer.tv_usec-older.tv_usec)/1000000.0;
+  else
+    return (double)(newer.tv_usec-older.tv_usec)/1000000.0;
 }
 
 /* return the number of seconds in the given input timeval struct */
diff --git a/tests/libtest/testutil.c b/tests/libtest/testutil.c
index 63393c589..4ee488e71 100644
--- a/tests/libtest/testutil.c
+++ b/tests/libtest/testutil.c
@@ -123,8 +123,11 @@ long tutil_tvdiff(struct timeval newer, struct timeval older)
  */
 double tutil_tvdiff_secs(struct timeval newer, struct timeval older)
 {
-  return (double)(newer.tv_sec-older.tv_sec)+
-    (double)(newer.tv_usec-older.tv_usec)/1000000.0;
+  if(newer.tv_sec != older.tv_sec)
+    return (double)(newer.tv_sec-older.tv_sec)+
+      (double)(newer.tv_usec-older.tv_usec)/1000000.0;
+  else
+    return (double)(newer.tv_usec-older.tv_usec)/1000000.0;
 }
 
 /* return the number of seconds in the given input timeval struct */