From 2ee5b08e94e76ad08f96f007474034e9fe5fdf17 Mon Sep 17 00:00:00 2001
From: Charles Kerr <charles@transmissionbt.com>
Date: Thu, 21 Oct 2010 23:47:23 +0000
Subject: [PATCH] (trunk libT) #3521 "rounding issue in tr_truncd()" -- try yet
 again to work out all the fringe cases :)

---
 libtransmission/utils-test.c | 11 +++++++++++
 libtransmission/utils.c      | 17 ++++++++++-------
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/libtransmission/utils-test.c b/libtransmission/utils-test.c
index d6363c690..c07d2fe64 100644
--- a/libtransmission/utils-test.c
+++ b/libtransmission/utils-test.c
@@ -1,3 +1,4 @@
+#include <math.h>
 #include <stdio.h> /* fprintf */
 #include <string.h> /* strcmp */
 
@@ -379,6 +380,7 @@ static int
 test_truncd( void )
 {
     char buf[32];
+    const double nan = sqrt( -1 );
 
     tr_snprintf( buf, sizeof( buf ), "%.2f%%", 99.999 );
     check( !strcmp( buf, "100.00%" ) );
@@ -395,6 +397,15 @@ test_truncd( void )
     tr_snprintf( buf, sizeof( buf ), "%.2f", tr_truncd( 2.05, 2 ) );
     check( !strcmp( buf, "2.05" ) );
 
+    tr_snprintf( buf, sizeof( buf ), "%.2f", tr_truncd( 3.3333, 2 ) );
+    check( !strcmp( buf, "3.33" ) );
+
+    tr_snprintf( buf, sizeof( buf ), "%.0f", tr_truncd( 3.3333, 0 ) );
+    check( !strcmp( buf, "3" ) );
+
+    tr_snprintf( buf, sizeof( buf ), "%.2f", tr_truncd( nan, 2 ) );
+    check( !strcmp( buf, "nan" ) );
+
     return 0;
 }
 
diff --git a/libtransmission/utils.c b/libtransmission/utils.c
index 1d621c3f3..77ff5e19d 100644
--- a/libtransmission/utils.c
+++ b/libtransmission/utils.c
@@ -24,6 +24,8 @@
 #include <assert.h>
 #include <ctype.h> /* isalpha(), tolower() */
 #include <errno.h>
+#include <float.h> /* DBL_EPSILON */
+#include <locale.h> /* localeconv() */
 #include <math.h> /* pow(), fabs(), floor() */
 #include <stdarg.h>
 #include <stdio.h>
@@ -1431,14 +1433,15 @@ tr_parseNumberRange( const char * str_in, int len, int * setmeCount )
 ***/
 
 double
-tr_truncd( double x, int decimal_places )
+tr_truncd( double x, int precision )
 {
-    /* sigh... surely there's a better way to do this */
-    char buf[1024];
-    const int i = (int) pow( 10, decimal_places );
-    snprintf( buf, sizeof( buf ), "%f", x*i );
-    *strchr(buf,'.') = '\0';
-    return atof(buf) / i;
+    char * pt;
+    char buf[128];
+    const int max_precision = (int) log10( 1.0 / DBL_EPSILON ) - 1; 
+    tr_snprintf( buf, sizeof( buf ), "%.*f", max_precision, x ); 
+    if(( pt = strstr( buf, localeconv()->decimal_point )))
+        pt[precision ? precision+1 : 0] = '\0';
+    return atof(buf);
 }
 
 char*