From b9caf8b6058de12bf028f907471561a6aa50f7e9 Mon Sep 17 00:00:00 2001
From: Pete Batard <pete@akeo.ie>
Date: Fri, 26 Feb 2016 13:26:34 +0000
Subject: [PATCH] [core] fix computation of FAT size for Large FAT32

* Ridgecropt's GetFATSizeSectors() computation was incorrect
  and resulted in data sectors being "wasted" (unaddressable)
* See: http://www.syslinux.org/archives/2016-February/024850.html
* Also revert the minfatsize check of Syslinux, since it no longer fails.
---
 src/format.c               | 25 +++++++------------------
 src/rufus.rc               | 10 +++++-----
 src/syslinux/libfat/open.c |  2 +-
 3 files changed, 13 insertions(+), 24 deletions(-)

diff --git a/src/format.c b/src/format.c
index 4adbce86..56c4d9d4 100644
--- a/src/format.c
+++ b/src/format.c
@@ -347,31 +347,20 @@ static DWORD GetVolumeID(void)
 }
 
 /*
- * This is the Microsoft calculation from FATGEN
- *
- * DWORD RootDirSectors = 0;
- * DWORD TmpVal1, TmpVal2, FATSz;
- *
- * TmpVal1 = DskSize - (ReservedSecCnt + RootDirSectors);
- * TmpVal2 = (256 * SecPerClus) + NumFATs;
- * TmpVal2 = TmpVal2 / 2;
- * FATSz = (TmpVal1 + (TmpVal2 - 1)) / TmpVal2;
- *
- * return( FatSz );
+ * Proper computation of FAT size
+ * See: http://www.syslinux.org/archives/2016-February/024850.html
+ * and subsequent replies.
  */
 static DWORD GetFATSizeSectors(DWORD DskSize, DWORD ReservedSecCnt, DWORD SecPerClus, DWORD NumFATs, DWORD BytesPerSect)
 {
 	ULONGLONG Numerator, Denominator;
 	ULONGLONG FatElementSize = 4;
+	ULONGLONG ReservedClusCnt = 2;
 	ULONGLONG FatSz;
 
-	// This is based on
-	// http://hjem.get2net.dk/rune_moeller_barnkob/filesystems/fat.html
-	Numerator = FatElementSize * (DskSize - ReservedSecCnt);
-	Denominator = (SecPerClus * BytesPerSect) + (FatElementSize * NumFATs);
-	FatSz = Numerator / Denominator;
-	// round up
-	FatSz += 1;
+	Numerator = DskSize - ReservedSecCnt + ReservedClusCnt * SecPerClus;
+	Denominator = SecPerClus * BytesPerSect / FatElementSize + NumFATs;
+	FatSz = Numerator / Denominator + 1;	// +1 to ensure we are rounded up
 
 	return (DWORD)FatSz;
 }
diff --git a/src/rufus.rc b/src/rufus.rc
index 34895c52..8921c761 100644
--- a/src/rufus.rc
+++ b/src/rufus.rc
@@ -33,7 +33,7 @@ LANGUAGE LANG_NEUTRAL, SUBLANG_NEUTRAL
 IDD_DIALOG DIALOGEX 12, 12, 242, 376
 STYLE DS_SETFONT | DS_MODALFRAME | DS_CENTER | WS_MINIMIZEBOX | WS_POPUP | WS_CAPTION | WS_SYSMENU
 EXSTYLE WS_EX_ACCEPTFILES
-CAPTION "Rufus 2.8.868"
+CAPTION "Rufus 2.8.869"
 FONT 8, "Segoe UI Symbol", 400, 0, 0x0
 BEGIN
     LTEXT           "Device",IDS_DEVICE_TXT,9,6,200,8
@@ -320,8 +320,8 @@ END
 //
 
 VS_VERSION_INFO VERSIONINFO
- FILEVERSION 2,8,868,0
- PRODUCTVERSION 2,8,868,0
+ FILEVERSION 2,8,869,0
+ PRODUCTVERSION 2,8,869,0
  FILEFLAGSMASK 0x3fL
 #ifdef _DEBUG
  FILEFLAGS 0x1L
@@ -338,13 +338,13 @@ BEGIN
         BEGIN
             VALUE "CompanyName", "Akeo Consulting (http://akeo.ie)"
             VALUE "FileDescription", "Rufus"
-            VALUE "FileVersion", "2.8.868"
+            VALUE "FileVersion", "2.8.869"
             VALUE "InternalName", "Rufus"
             VALUE "LegalCopyright", "© 2011-2016 Pete Batard (GPL v3)"
             VALUE "LegalTrademarks", "http://www.gnu.org/copyleft/gpl.html"
             VALUE "OriginalFilename", "rufus.exe"
             VALUE "ProductName", "Rufus"
-            VALUE "ProductVersion", "2.8.868"
+            VALUE "ProductVersion", "2.8.869"
         END
     END
     BLOCK "VarFileInfo"
diff --git a/src/syslinux/libfat/open.c b/src/syslinux/libfat/open.c
index dad372b3..4f0334d7 100644
--- a/src/syslinux/libfat/open.c
+++ b/src/syslinux/libfat/open.c
@@ -92,7 +92,7 @@ libfat_open(int (*readfunc) (intptr_t, void *, size_t, libfat_sector_t),
     } else
 	goto barf;		/* Impossibly many clusters */
 
-    minfatsize >>= LIBFAT_SECTOR_SHIFT;
+	minfatsize = (minfatsize + LIBFAT_SECTOR_SIZE - 1) >> LIBFAT_SECTOR_SHIFT;
 
     if (minfatsize > fatsize)
 	goto barf;		/* The FATs don't fit */