From c9fb0982505291c6efab4abfc805fc907c575933 Mon Sep 17 00:00:00 2001
From: Björn Stenberg <bjorn@haxx.se>
Date: Mon, 4 Nov 2002 14:59:46 +0000
Subject: Bugfix: lseek() did not invalidate sector cache when seeking to start
 of file.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@2803 a1c6a512-1295-4272-9138-f99709370657
---
 firmware/common/file.c |  2 ++
 firmware/drivers/fat.c | 30 +++++++++++++++++-------------
 2 files changed, 19 insertions(+), 13 deletions(-)

(limited to 'firmware')

diff --git a/firmware/common/file.c b/firmware/common/file.c
index 7f0e0cd9bd..219858cff2 100644
--- a/firmware/common/file.c
+++ b/firmware/common/file.c
@@ -386,6 +386,8 @@ int lseek(int fd, int offset, int whence)
             }
             openfiles[fd].cacheoffset = sectoroffset;
         }
+        else
+            openfiles[fd].cacheoffset = -1;
     }
     else
         if ( openfiles[fd].cacheoffset != -1 )
diff --git a/firmware/drivers/fat.c b/firmware/drivers/fat.c
index f6d6c73e74..26149d4e4a 100644
--- a/firmware/drivers/fat.c
+++ b/firmware/drivers/fat.c
@@ -1202,25 +1202,29 @@ int fat_readwrite( struct fat_file *file, int sectorcount,
 
 int fat_seek(struct fat_file *file, int seeksector )
 {
-    int clusternum, sectornum, sector=0;
+    int clusternum=0, sectornum=0, sector=0;
     int cluster = file->firstcluster;
     int i;
 
-    seeksector--;
-    clusternum = seeksector / fat_bpb.bpb_secperclus;
-    sectornum = seeksector % fat_bpb.bpb_secperclus;
-
-    for (i=0; i<clusternum; i++) {
-        cluster = get_next_cluster(cluster);
-        if (!cluster) {
-            sector = -1;
-            break;
+    if (seeksector) {
+        /* we need to find the sector BEFORE the requested, since
+           the file struct stores the last accessed sector */
+        seeksector--;
+        clusternum = seeksector / fat_bpb.bpb_secperclus;
+        sectornum = seeksector % fat_bpb.bpb_secperclus;
+        
+        for (i=0; i<clusternum; i++) {
+            cluster = get_next_cluster(cluster);
+            if (!cluster) {
+                sector = -1;
+                break;
+            }
         }
+        
+        if ( sector > -1 )
+            sector = cluster2sec(cluster) + sectornum;
     }
 
-    if ( sector > -1 )
-        sector = cluster2sec(cluster) + sectornum;
-
     LDEBUGF("fat_seek(%x) == %x, %x, %x\n",
             seeksector, cluster, sector, sectornum);
 
-- 
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