[libgsystem] fileutils: Add API to fstat() a stream

[Colin Walters <walters src gnome org>]

commit 4501b425953c3849112206c4a3f6f27cd3264936
Author: Colin Walters <walters verbum org>
Date:   Wed Aug 14 20:38:51 2013 -0400

    fileutils: Add API to fstat() a stream
    
    Will be used by ostree.  Since libgsystem will return raw
    GUnix{Input,Output}Stream, we need a way to fstat() them.  Maybe we
    should also have an API to synthesize a #GFileInfo, but that's hard
    without duplicating all the complex stuff in GIO.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=706031

 gsystem-file-utils.c |   39 +++++++++++++++++++++++++++++++++++++++
 gsystem-file-utils.h |    8 ++++++++
 2 files changed, 47 insertions(+), 0 deletions(-)
---
diff --git a/gsystem-file-utils.c b/gsystem-file-utils.c
index 28c55d9..c734d2d 100644
--- a/gsystem-file-utils.c
+++ b/gsystem-file-utils.c
@@ -32,6 +32,7 @@
 #include "gsystem-glib-compat.h"
 #include <glib/gstdio.h>
 #include <gio/gunixinputstream.h>
+#include <gio/gfiledescriptorbased.h>
 #include <gio/gunixoutputstream.h>
 #include <glib-unix.h>
 #include <limits.h>
@@ -130,6 +131,44 @@ gs_file_read_noatime (GFile         *file,
 }
 
 /**
+ * gs_stream_fstat:
+ * @stream: A stream containing a Unix file descriptor
+ * @stbuf: Memory location to write stat buffer
+ * @cancellable:
+ * @error:
+ *
+ * Some streams created via libgsystem are #GUnixInputStream; these do
+ * not support e.g. g_file_input_stream_query_info().  This function
+ * allows dropping to the raw unix fstat() call for these types of
+ * streams, while still conveniently wrapped with the normal GLib
+ * handling of @cancellable and @error.
+ */
+gboolean
+gs_stream_fstat (GFileDescriptorBased *stream,
+                 struct stat          *stbuf,
+                 GCancellable         *cancellable,
+                 GError              **error)
+{
+  gboolean ret = FALSE;
+  int fd;
+
+  if (g_cancellable_set_error_if_cancelled (cancellable, error))
+    goto out;
+
+  fd = g_file_descriptor_based_get_fd (stream);
+
+  if (fstat (fd, stbuf) == -1)
+    {
+      _set_error_from_errno (error);
+      goto out;
+    }
+
+  ret = TRUE;
+ out:
+  return ret;
+}
+
+/**
  * gs_file_map_noatime: (skip)
  * @file: a #GFile
  * @cancellable: a #GCancellable
diff --git a/gsystem-file-utils.h b/gsystem-file-utils.h
index 0d9994d..aae9944 100644
--- a/gsystem-file-utils.h
+++ b/gsystem-file-utils.h
@@ -22,6 +22,7 @@
 #define __GSYSTEM_FILE_UTILS_H__
 
 #include <gio/gio.h>
+#include <sys/stat.h>
 
 G_BEGIN_DECLS
 
@@ -42,6 +43,13 @@ GMappedFile *gs_file_map_noatime (GFile         *file,
                                   GCancellable  *cancellable,
                                   GError       **error);
 
+#ifndef __GI_SCANNER__
+gboolean gs_stream_fstat (GFileDescriptorBased *stream,
+                          struct stat          *out_stbuf,
+                          GCancellable         *cancellable,
+                          GError              **error);
+#endif
+
 #if GLIB_CHECK_VERSION(2,34,0)
 GBytes *gs_file_map_readonly (GFile         *file,
                               GCancellable  *cancellable,