Add xdg_app_overlay_symlink_tree helper

This will be used during exports

xdg-app-utils.c

@@ -7,6 +7,11 @@
 #include "libgsystem.h"
 
 #include <stdlib.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
 #include <sys/utsname.h>
 
 const char *
@@ -83,3 +88,157 @@ xdg_app_find_deploy_dir_for_ref (const char *ref,
   return deploy;
 
 }
+
+
+static void
+set_error_from_errno (GError **error,
+                      gint     saved_errno)
+{
+  g_set_error_literal (error,
+                       G_IO_ERROR,
+                       g_io_error_from_errno (saved_errno),
+                       g_strerror (saved_errno));
+  errno = saved_errno;
+}
+
+static gboolean
+overlay_symlink_tree_dir (int            source_parent_fd,
+                          const char    *source_name,
+                          const char    *source_symlink_prefix,
+                          int            destination_parent_fd,
+                          const char    *destination_name,
+                          GCancellable  *cancellable,
+                          GError       **error)
+{
+  gboolean ret = FALSE;
+  int res;
+  int source_dfd = -1;
+  int destination_dfd = -1;
+  DIR *srcd = NULL;
+  struct dirent *dent;
+
+  if (source_name == NULL)
+    source_dfd = source_parent_fd; /* We take ownership of the passed fd and close it */
+  else
+    {
+      if (!gs_file_open_dir_fd_at (source_parent_fd, source_name,
+                                   &source_dfd,
+                                   cancellable, error))
+        goto out;
+    }
+
+  if (destination_name == NULL)
+    destination_dfd = destination_parent_fd; /* We take ownership of the passed fd and close it */
+  else
+    {
+      do
+        res = mkdirat (destination_parent_fd, destination_name, 0777);
+      while (G_UNLIKELY (res == -1 && errno == EINTR));
+      if (res == -1)
+        {
+          if (errno != EEXIST)
+            {
+              set_error_from_errno (error, errno);
+              goto out;
+            }
+        }
+
+      if (!gs_file_open_dir_fd_at (destination_parent_fd, destination_name,
+                                   &destination_dfd,
+                                   cancellable, error))
+        goto out;
+    }
+
+  srcd = fdopendir (source_dfd);
+  if (!srcd)
+    {
+      set_error_from_errno (error, errno);
+      goto out;
+    }
+
+  while ((dent = readdir (srcd)) != NULL)
+    {
+      const char *name = dent->d_name;
+      struct stat child_stbuf;
+
+      if (strcmp (name, ".") == 0 ||
+          strcmp (name, "..") == 0)
+        continue;
+
+      if (fstatat (source_dfd, name, &child_stbuf,
+                   AT_SYMLINK_NOFOLLOW) != 0)
+        {
+          set_error_from_errno (error, errno);
+          goto out;
+        }
+
+      if (S_ISDIR (child_stbuf.st_mode))
+        {
+          gs_free gchar *target = g_build_filename ("..", source_symlink_prefix, name, NULL);
+          if (!overlay_symlink_tree_dir (source_dfd, name, target, destination_dfd, name,
+                                         cancellable, error))
+            goto out;
+        }
+      else
+        {
+          gs_free gchar *target = g_build_filename (source_symlink_prefix, name, NULL);
+
+          if (unlinkat (destination_dfd, name, 0) != 0 && errno != ENOENT)
+            {
+              set_error_from_errno (error, errno);
+              goto out;
+            }
+
+          if (symlinkat (target, destination_dfd, name) != 0)
+            {
+              set_error_from_errno (error, errno);
+              goto out;
+            }
+        }
+    }
+
+  ret = TRUE;
+ out:
+  if (srcd != NULL)
+    closedir (srcd); /* This closes source_dfd */
+  else if (source_dfd != -1)
+    close (source_dfd);
+  if (destination_dfd != -1)
+    close (destination_dfd);
+
+  return ret;
+}
+
+gboolean
+xdg_app_overlay_symlink_tree (GFile    *source,
+                              GFile    *destination,
+                              const char *symlink_prefix,
+                              GCancellable  *cancellable,
+                              GError       **error)
+{
+  gboolean ret = FALSE;
+  int source_dfd = -1;
+  int destination_dfd = -1;
+
+  if (!gs_file_open_dir_fd (source, &source_dfd, cancellable, error))
+    goto out;
+
+  if (!gs_file_ensure_directory (destination, TRUE, cancellable, error) ||
+      !gs_file_open_dir_fd (destination, &destination_dfd, cancellable, error))
+    {
+      close (source_dfd);
+      goto out;
+    }
+
+  /* The fds are closed by this call */
+  if (!overlay_symlink_tree_dir (source_dfd, NULL,
+                                 symlink_prefix,
+                                 destination_dfd, NULL,
+                                 cancellable, error))
+    goto out;
+
+  ret = TRUE;
+
+ out:
+  return ret;
+}

xdg-app-utils.h

@@ -18,4 +18,10 @@ GFile * xdg_app_find_deploy_dir_for_ref (const char *ref,
                                          GCancellable *cancellable,
                                          GError **error);
 
+gboolean xdg_app_overlay_symlink_tree (GFile    *source,
+                                       GFile    *destination,
+                                       const char *symlink_prefix,
+                                       GCancellable  *cancellable,
+                                       GError       **error);
+
 #endif /* __XDG_APP_UTILS_H__ */