Add support for dmdrvi eof API in _eof function

- Add bytes_read field to file_handle_t to track total bytes read
- Initialize bytes_read = 0 on file open (_fopen)
- Accumulate bytes_read after each _fread call
- Modify _eof to delegate to driver's eof API if implemented,
  otherwise fall back to comparing bytes_read against file size,
  and return 0 (not at EOF) if file size is unavailable

Co-authored-by: JohnAmadis <17320783+JohnAmadis@users.noreply.github.com>

Author: Copilot

src/dmdevfs.c

@@ -56,6 +56,7 @@ typedef struct
     const char* path;           // File path
     int mode;                   // File open mode
     int attr;                   // File attributes
+    size_t bytes_read;          // Total bytes read (used for EOF calculation when driver has no eof API)
 } file_handle_t;
 
 /**
@@ -253,6 +254,7 @@ dmod_dmfsi_dif_api_declaration( 1.0, dmdevfs, int, _fopen, (dmfsi_context_t ctx,
     handle->path = Dmod_StrDup(path);
     handle->mode = mode;
     handle->attr = attr;
+    handle->bytes_read = 0;
 
     *fp = handle;
     return DMFSI_OK;
@@ -326,6 +328,7 @@ dmod_dmfsi_dif_api_declaration( 1.0, dmdevfs, int, _fread, (dmfsi_context_t ctx,
     // dmdrvi_read returns size_t (bytes read), not error code
     size_t bytes_read = dmdrvi_read(handle->driver->driver_context, handle->driver_handle, buffer, size);
     if(read) *read = bytes_read;
+    handle->bytes_read += bytes_read;
 
     return DMFSI_OK;
 }
@@ -413,7 +416,9 @@ dmod_dmfsi_dif_api_declaration( 1.0, dmdevfs, long, _tell, (dmfsi_context_t ctx,
 
 /**
  * @brief Check if at end of file
- * @note Device drivers typically operate in streaming mode - always return 0 (not at EOF)
+ * @note If the driver implements the eof API, it is used directly.
+ *       Otherwise, EOF is determined by comparing bytes read against the file size.
+ *       If file size is unavailable, 0 (not at EOF) is returned as EOF cannot be determined.
  */
 dmod_dmfsi_dif_api_declaration( 1.0, dmdevfs, int, _eof, (dmfsi_context_t ctx, void* fp) )
 {
@@ -428,8 +433,24 @@ dmod_dmfsi_dif_api_declaration( 1.0, dmdevfs, int, _eof, (dmfsi_context_t ctx, v
         return 1;
     }
 
-    // Device drivers typically don't have EOF concept
-    // Return 0 (not at EOF) as devices can always potentially provide more data
+    file_handle_t* handle = (file_handle_t*)fp;
+    
+    // If the driver implements the eof API, delegate to it
+    dmod_dmdrvi_eof_t dmdrvi_eof = Dmod_GetDifFunction(handle->driver->driver, dmod_dmdrvi_eof_sig);
+    if(dmdrvi_eof != NULL)
+    {
+        return dmdrvi_eof(handle->driver->driver_context, handle->driver_handle);
+    }
+    
+    // Fallback: compare bytes read against file size reported by driver
+    dmdrvi_stat_t stat = {0};
+    int result = driver_stat(handle->driver, handle->path, &stat);
+    if(result == 0)
+    {
+        return (handle->bytes_read >= (size_t)stat.size) ? 1 : 0;
+    }
+    
+    // Size not available - cannot determine EOF
     return 0;
 }