From baa73e1a3987bf5c8ac5410168684e37bea62194 Mon Sep 17 00:00:00 2001
From: Vincent Barrilliot <vincent.barrilliot@laposte.net>
Date: Fri, 12 Nov 2021 12:17:11 +0000
Subject: [PATCH] Add support for finding file position, or positionning from
 and of file, as this is available in other OSes

---
 src/dev/channel.h |  1 +
 src/dev/fsys.c    | 26 ++++++++++++++++----------
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/src/dev/channel.h b/src/dev/channel.h
index 781e935..8ed8cfd 100644
--- a/src/dev/channel.h
+++ b/src/dev/channel.h
@@ -38,6 +38,7 @@
 
 #define CDEV_SEEK_ABSOLUTE  0
 #define CDEV_SEEK_RELATIVE  1
+#define CDEV_SEEK_END       2
 
 /*
  * Structure defining a channel
diff --git a/src/dev/fsys.c b/src/dev/fsys.c
index c86103b..a6e1c24 100644
--- a/src/dev/fsys.c
+++ b/src/dev/fsys.c
@@ -544,23 +544,29 @@ short fchan_flush(t_channel * chan) {
 }
 
 /**
- * attempt to move the "cursor" position in the channel
+ * Attempt to move the "cursor" position in the channel
  */
 short fchan_seek(t_channel * chan, long position, short base) {
     FIL * file;
-    FRESULT result;
-    int total_written;
+    FSIZE_t new_position;
 
     file = fchan_to_file(chan);
     if (file) {
-        if (base == CDEV_SEEK_ABSOLUTE) {
-            result = f_lseek(file, position);
-            return fatfs_to_foenix(result);
-        } else if (base == CDEV_SEEK_RELATIVE) {
-            long current = f_tell(file);
-            result = f_lseek(file, current + position);
-            return fatfs_to_foenix(result);
+        switch (base) {
+        case CDEV_SEEK_ABSOLUTE:
+            new_position = position;    
+            break;
+        case CDEV_SEEK_RELATIVE:
+            new_position = f_tell(file) + position;
+            break;
+        case CDEV_SEEK_END:
+            new_position = f_size(file) - position;
+            break;
+        default:
+            return ERR_GENERAL; 
         }
+
+        return fatfs_to_foenix(f_lseek(file, position));
     }
 
     return ERR_BADCHANNEL;