Fix FAT driver file modes, update filewriter accordingly

ce/interp.c

@@ -426,12 +426,19 @@ static void execute_redir (struct ast_redir* redir, struct context* context) {
     return;
   }
 
+  uint32_t fw_flags = FW_CREATE_FILE | FW_TRUNCATE;
+
   struct filewriter fw;
-  if ((ret = filewriter_init (&fw, volume, path, FW_CREATE_FILE | FW_APPEND)) < 0) {
+  if ((ret = filewriter_init (&fw, volume, path, fw_flags)) < 0) {
     cprintf (context, "ERROR could not initialize filewriter for '%s:%s'\n", volume, path);
     return;
   }
 
+  if (context->strbuf.count == 0) {
+    filewriter_fini (&fw);
+    return;
+  }
+
   size_t chunk_size = 1024;
   size_t chunks = (context->strbuf.count - 1) / chunk_size;
   size_t rem = (context->strbuf.count - 1) % chunk_size;

include/write_file.h

@@ -1,6 +1,6 @@
 #ifndef _WRITE_FILE_H
 #define _WRITE_FILE_H
 
-#define WF_APPEND (1 << 0)
+#define WF_TRUNCATE (1 << 1)
 
 #endif // _WRITE_FILE_H

kernel/fs/fatfs.c

@@ -227,10 +227,11 @@ DEFINE_VFS_WRITE_FILE (fatfs_write_file) {
 
   FL_FILE* file;
 
-  if ((flags & WF_APPEND))
+  if ((flags & WF_TRUNCATE) && off == 0) {
+    file = fl_fopen (fatfs_ctx, path, "wb+");
+  } else {
     file = fl_fopen (fatfs_ctx, path, "rb+");
-  else
-    file = fl_fopen (fatfs_ctx, path, "wb");
+  }
 
   if (file == NULL)
     return -ST_NOT_FOUND;
@@ -276,7 +277,7 @@ DEFINE_VFS_CREATE_FILE (fatfs_create_file) {
   fatfs_ctx->proc = proc;
   fatfs_ctx->rctx = rctx;
 
-  FL_FILE* file = fl_fopen (fatfs_ctx, path, "wb+");
+  FL_FILE* file = fl_fopen (fatfs_ctx, path, "ab+");
 
   if (file == NULL)
     return -ST_NOT_FOUND;

libioutil/filewriter.c

@@ -38,8 +38,14 @@ int filewriter_init (struct filewriter* fw, const char* volume, const char* path
   fw->file_size = desc.size;
   fw->flags |= FW_OPEN;
 
-  if ((fw->flags & FW_APPEND))
+  if ((fw->flags & FW_APPEND)) {
     fw->write_cursor = desc.size;
+  } else if ((fw->flags & FW_TRUNCATE)) {
+    fw->write_cursor = 0;
+    fw->file_size = 0;
+  } else {
+    fw->write_cursor = 0;
+  }
 
   return FW_OK;
 }
@@ -57,26 +63,21 @@ int filewriter_write (struct filewriter* fw, uint8_t* buffer, size_t buffer_size
   if (!(fw->flags & FW_OPEN))
     return -FW_VOLUME_NOT_OPENED;
 
-  struct desc desc;
   int ret;
 
-  if ((fw->flags & FW_APPEND)) {
-    if ((ret = describe (fw->path, &desc)) < 0)
-      return -FW_DESC_ERROR;
-
-    fw->file_size = desc.size;
-    fw->write_cursor = fw->file_size;
-  }
-
   if (buffer_size > 0) {
-    if (!(fw->flags & FW_APPEND) && !(fw->write_cursor + buffer_size <= fw->file_size))
-      return -FW_CURSOR_OOB;
+    uint32_t wf_flags = 0;
 
-    uint32_t flags = (fw->flags & FW_APPEND) ? WF_APPEND : 0;
-    if ((ret = write_file (fw->path, fw->write_cursor, buffer, buffer_size, flags)) < 0)
+    if ((fw->flags & FW_TRUNCATE) && fw->write_cursor == 0) {
+      wf_flags |= WF_TRUNCATE;
+    }
+
+    if ((ret = write_file (fw->path, fw->write_cursor, buffer, buffer_size, wf_flags)) < 0)
       return -FW_WRITE_ERROR;
 
     fw->write_cursor += buffer_size;
+    if (fw->write_cursor > fw->file_size)
+      fw->file_size = fw->write_cursor;
   }
 
   return FW_OK;

libioutil/filewriter.h

@@ -17,6 +17,7 @@
 
 #define FW_CREATE_FILE (1 << 0)
 #define FW_APPEND      (1 << 1)
+#define FW_TRUNCATE    (1 << 2)
 #define FW_OPEN        (1 << 31)
 
 struct filewriter {