From 1d4acb8d95612384f603aa5c0c8d20060010fbc7 Mon Sep 17 00:00:00 2001
From: Ondrej Holy <oholy@redhat.com>
Date: Thu, 1 Aug 2024 12:35:43 +0200
Subject: [PATCH] daemon: Add support for edit mode

Currently, it is impossible to open the output stream without truncating
the file or appending it. This is a problem for many POSIX applications
relying on our FUSE daemon. Let's add an edit mode that could be used for
this purpose.

Related: https://gitlab.gnome.org/GNOME/gvfs/-/issues/249
---
 daemon/gvfsbackend.h         |  8 ++++++++
 daemon/gvfsjobopenforwrite.c | 23 +++++++++++++++++++++++
 daemon/gvfsjobopenforwrite.h |  3 ++-
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/daemon/gvfsbackend.h b/daemon/gvfsbackend.h
index 9c7476cf..0f97cff6 100644
--- a/daemon/gvfsbackend.h
+++ b/daemon/gvfsbackend.h
@@ -211,6 +211,14 @@ struct _GVfsBackendClass
 				 const char *etag,
 				 gboolean make_backup,
 				 GFileCreateFlags flags);
+  gboolean (*try_edit)          (GVfsBackend *backend,
+                                 GVfsJobOpenForWrite *job,
+                                 const char *filename,
+                                 GFileCreateFlags flags);
+  void     (*edit)              (GVfsBackend *backend,
+                                 GVfsJobOpenForWrite *job,
+                                 const char *filename,
+                                 GFileCreateFlags flags);
   void     (*close_write)       (GVfsBackend *backend,
 				 GVfsJobCloseWrite *job,
 				 GVfsBackendHandle handle);
diff --git a/daemon/gvfsjobopenforwrite.c b/daemon/gvfsjobopenforwrite.c
index 439b63c4..5b6e8033 100644
--- a/daemon/gvfsjobopenforwrite.c
+++ b/daemon/gvfsjobopenforwrite.c
@@ -220,6 +220,20 @@ run (GVfsJob *job)
 		      op_job->make_backup,
 		      op_job->flags);
     }
+  else if (op_job->mode == OPEN_FOR_WRITE_EDIT)
+    {
+      if (class->edit == NULL)
+        {
+          g_vfs_job_failed (job, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
+                            _("Operation not supported"));
+          return;
+        }
+
+      class->edit (op_job->backend,
+                   op_job,
+                   op_job->filename,
+                   op_job->flags);
+    }
   else
     g_assert_not_reached (); /* Handled in try */
 }
@@ -259,6 +273,15 @@ try (GVfsJob *job)
 				 op_job->make_backup,
 				 op_job->flags);
     }
+  else if (op_job->mode == OPEN_FOR_WRITE_EDIT)
+    {
+      if (class->try_edit == NULL)
+        return FALSE;
+      return class->try_edit (op_job->backend,
+                              op_job,
+                              op_job->filename,
+                              op_job->flags);
+    }
   else
     {
       GError *error = NULL;
diff --git a/daemon/gvfsjobopenforwrite.h b/daemon/gvfsjobopenforwrite.h
index 141189f3..e070d0ea 100644
--- a/daemon/gvfsjobopenforwrite.h
+++ b/daemon/gvfsjobopenforwrite.h
@@ -41,7 +41,8 @@ typedef struct _GVfsJobOpenForWriteClass   GVfsJobOpenForWriteClass;
 typedef enum {
   OPEN_FOR_WRITE_CREATE = 0,
   OPEN_FOR_WRITE_APPEND = 1,
-  OPEN_FOR_WRITE_REPLACE = 2
+  OPEN_FOR_WRITE_REPLACE = 2,
+  OPEN_FOR_WRITE_EDIT = 3
 } GVfsJobOpenForWriteMode;
 
 typedef enum {
-- 
2.46.2