[ostree/wip/error-handling: 2/2] Give more descriptive errors on some file operations

[Sam Thursfield <sthursfield src gnome org>]

commit 612061a1a1124b92f84ee3dad604a3266e9b6ba0
Author: Sam Thursfield <sam thursfield codethink co uk>
Date:   Fri Jul 13 17:22:15 2012 +0100

    Give more descriptive errors on some file operations

 src/libostree/ostree-core.c   |   12 ++++++------
 src/libotutil/ot-unix-utils.c |   28 ++++++++++++++++++++++++++++
 src/libotutil/ot-unix-utils.h |    2 ++
 3 files changed, 36 insertions(+), 6 deletions(-)
---
diff --git a/src/libostree/ostree-core.c b/src/libostree/ostree-core.c
index 2d61b18..a6736ed 100644
--- a/src/libostree/ostree-core.c
+++ b/src/libostree/ostree-core.c
@@ -1084,7 +1084,7 @@ ostree_create_file_from_input (GFile            *dest_file,
     {
       if (mkdir (ot_gfile_get_path_cached (dest_file), mode) < 0)
         {
-          ot_util_set_error_from_errno (error, errno);
+          ot_util_set_error_from_errno_full (error, errno, "Unable to make directory at %s: ", ot_gfile_get_path_cached (dest_file));
           goto out;
         }
     }
@@ -1109,7 +1109,7 @@ ostree_create_file_from_input (GFile            *dest_file,
       const char *target = g_file_info_get_attribute_byte_string (finfo, "standard::symlink-target");
       if (symlink (target, dest_path) < 0)
         {
-          ot_util_set_error_from_errno (error, errno);
+          ot_util_set_error_from_errno_full (error, errno, "Unable to create link %s to file %s: ", target, dest_path);
           goto out;
         }
     }
@@ -1118,7 +1118,7 @@ ostree_create_file_from_input (GFile            *dest_file,
       guint32 dev = g_file_info_get_attribute_uint32 (finfo, "unix::rdev");
       if (mknod (dest_path, mode, dev) < 0)
         {
-          ot_util_set_error_from_errno (error, errno);
+          ot_util_set_error_from_errno_full (error, errno, "Unable to make device node at %s: ", dest_path);
           goto out;
         }
     }
@@ -1126,7 +1126,7 @@ ostree_create_file_from_input (GFile            *dest_file,
     {
       if (mkfifo (dest_path, mode) < 0)
         {
-          ot_util_set_error_from_errno (error, errno);
+          ot_util_set_error_from_errno_full (error, errno, "Unable to make pipe at %s: ", dest_path);
           goto out;
         }
     }
@@ -1144,7 +1144,7 @@ ostree_create_file_from_input (GFile            *dest_file,
       
       if (lchown (dest_path, uid, gid) < 0)
         {
-          ot_util_set_error_from_errno (error, errno);
+          ot_util_set_error_from_errno_full (error, errno, "Unable to set owner of %s: ", dest_path);
           goto out;
         }
     }
@@ -1153,7 +1153,7 @@ ostree_create_file_from_input (GFile            *dest_file,
     {
       if (chmod (dest_path, mode) < 0)
         {
-          ot_util_set_error_from_errno (error, errno);
+          ot_util_set_error_from_errno_full (error, errno, "Unable to set mode of %s: ", dest_path);
           goto out;
         }
     }
diff --git a/src/libotutil/ot-unix-utils.c b/src/libotutil/ot-unix-utils.c
index ee8f039..fc6abc7 100644
--- a/src/libotutil/ot-unix-utils.c
+++ b/src/libotutil/ot-unix-utils.c
@@ -32,6 +32,7 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <dirent.h>
+#include <stdarg.h>
 
 gboolean
 ot_util_spawn_pager (GOutputStream  **out_stream,
@@ -172,6 +173,33 @@ ot_util_set_error_from_errno (GError **error,
 }
 
 void
+ot_util_set_error_from_errno_full (GError **error,
+                                   gint saved_errno,
+                                   const gchar *format,
+                                   ...)
+{
+  va_list args;
+  GString *message;
+
+  va_start (args, format);
+
+  message = g_string_new (NULL);
+  g_string_vprintf (message, format, args);
+  g_string_append (message, g_strerror (saved_errno));
+
+  g_set_error_literal (error,
+                       G_IO_ERROR,
+                       g_io_error_from_errno (saved_errno),
+                       message->str);
+
+  g_string_free (message, TRUE);
+
+  va_end (args);
+
+  errno = saved_errno;
+}
+
+void
 ot_util_fatal_literal (const char *msg)
 {
   g_printerr ("%s\n", msg);
diff --git a/src/libotutil/ot-unix-utils.h b/src/libotutil/ot-unix-utils.h
index 58dd59b..2ff99f5 100644
--- a/src/libotutil/ot-unix-utils.h
+++ b/src/libotutil/ot-unix-utils.h
@@ -49,6 +49,8 @@ gboolean ot_util_path_split_validate (const char *path, GPtrArray **out_componen
 
 void ot_util_set_error_from_errno (GError **error, gint saved_errno);
 
+void ot_util_set_error_from_errno_full (GError **error, gint saved_errno, const gchar *format, ...);
+
 G_END_DECLS
 
 #endif