[SLOF] [PATCH 1/4] fat-files: Fix access to FAT32 dir/files when cluster > 16-bits

[Benjamin Herrenschmidt]

On FAT32, the directory entry contains a new field providing the
top 16-bits of the cluster number. We didn't use it, thus reading
the wrong sectors when trying to access files or directories
beyond block 0x10000.

Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
---
 slof/fs/packages/fat-files.fs | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/slof/fs/packages/fat-files.fs b/slof/fs/packages/fat-files.fs
index d919452..9e389eb 100644
--- a/slof/fs/packages/fat-files.fs
+++ b/slof/fs/packages/fat-files.fs
@@ -73,6 +73,14 @@ INSTANCE VARIABLE next-cluster
     THEN
 ;
 
+\ Read cluster# from directory entry (handle FAT32 extension)
+: get-cluster ( direntry -- cluster# )
+  fat-type @ 20 = IF
+    dup 14 + 2c@ bwjoin 10 lshift
+  ELSE 0 THEN
+  swap 1a + 2c@ bwjoin +
+;
+
 : .time ( x -- )
   base @ >r decimal
   b #split 2 0.r [char] : emit  5 #split 2 0.r [char] : emit  2* 2 0.r
@@ -87,7 +95,7 @@ INSTANCE VARIABLE next-cluster
   dup 0b + c@ 8 and IF drop EXIT THEN \ volume label, not a file
   dup c@ e5 = IF drop EXIT THEN \ deleted file
   cr
-  dup 1a + 2c@ bwjoin [char] # emit 4 0.r space \ starting cluster
+  dup get-cluster [char] # emit 8 0.r space \ starting cluster
   dup 18 + 2c@ bwjoin .date space
   dup 16 + 2c@ bwjoin .time space
   dup 1c + 4c@ bljoin base @ decimal swap a .r base ! space \ size in bytes
@@ -114,8 +122,10 @@ CREATE dos-name b allot
 : (find-file) ( -- cluster file-len is-dir? true | false )
   data @ BEGIN dup data @ #data @ + < WHILE
   dup dos-name b comp WHILE 20 + REPEAT
-  dup 1a + 2c@ bwjoin swap dup 1c + 4c@ bljoin swap 0b + c@ 10 and 0<> true
+  dup get-cluster
+  swap dup 1c + 4c@ bljoin swap 0b + c@ 10 and 0<> true
   ELSE drop false THEN ;
+
 : find-file ( dir-cluster name len -- cluster file-len is-dir? true | false )
   make-dos-name read-dir BEGIN (find-file) 0= WHILE next-cluster @ WHILE
   next-cluster @ read-cluster REPEAT false ELSE true THEN ;
-- 
2.7.4