[glib] GFile: Support for splice(2) in copy_fallback

[Christian Kellner <gicmo src gnome org>]

commit bb4f63d6390fe5efd183f259e5bd891f89de9e24
Author: Christian Kellner <gicmo gnome org>
Date:   Sun Feb 7 17:23:38 2010 +0100

    GFile: Support for splice(2) in copy_fallback
    
    The (linux specific) system call splice can be
    used to transfer data between file descriptors
    whitout copying them into user space.
    See bug #604086 for additional details.

 configure.in |    1 +
 gio/gfile.c  |  187 ++++++++++++++++++++++++++++++++++++++++++++++++++++------
 2 files changed, 170 insertions(+), 18 deletions(-)
---
diff --git a/configure.in b/configure.in
index 37416b4..258f8f6 100644
--- a/configure.in
+++ b/configure.in
@@ -969,6 +969,7 @@ AC_CHECK_FUNCS(chown lchmod lchown fchmod fchown link statvfs statfs utimes getg
 AC_CHECK_FUNCS(getmntent_r setmntent endmntent hasmntopt getmntinfo)
 # Check for high-resolution sleep functions
 AC_CHECK_FUNCS(nanosleep nsleep)
+AC_CHECK_FUNCS(splice)
 
 AC_CHECK_HEADERS(crt_externs.h)
 AC_CHECK_FUNCS(_NSGetEnviron)
diff --git a/gio/gfile.c b/gio/gfile.c
index 5bd8915..9bad3f7 100644
--- a/gio/gfile.c
+++ b/gio/gfile.c
@@ -23,6 +23,13 @@
  */
 
 #include "config.h"
+#ifdef HAVE_SPLICE
+#define _GNU_SOURCE
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#endif
 #include <string.h>
 #include <sys/types.h>
 #ifdef HAVE_PWD_H
@@ -33,6 +40,7 @@
 #include "gioscheduler.h"
 #include "gsimpleasyncresult.h"
 #include "gfileattribute-priv.h"
+#include "gfiledescriptorbased.h"
 #include "gpollfilemonitor.h"
 #include "gappinfo.h"
 #include "gfileinputstream.h"
@@ -2120,7 +2128,7 @@ g_file_replace_finish (GFile         *file,
       if (g_simple_async_result_propagate_error (simple, error))
 	return NULL;
     }
-  
+
   iface = G_FILE_GET_IFACE (file);
   return (* iface->replace_finish) (file, res, error);
 }
@@ -2628,7 +2636,6 @@ g_file_copy_attributes (GFile           *source,
   return res;
 }
 
-/* Closes the streams */
 static gboolean
 copy_stream_with_progress (GInputStream           *in,
 			   GOutputStream          *out,
@@ -2714,25 +2721,133 @@ copy_stream_with_progress (GInputStream           *in,
 	progress_callback (current_size, total_size, progress_callback_data);
     }
 
-  if (!res)
-    error = NULL; /* Ignore further errors */
-
   /* Make sure we send full copied size */
   if (progress_callback)
     progress_callback (current_size, total_size, progress_callback_data);
-  
-  /* Don't care about errors in source here */
-  g_input_stream_close (in, cancellable, NULL);
 
-  /* But write errors on close are bad! */
-  if (!g_output_stream_close (out, cancellable, error))
-    res = FALSE;
+  return res;
+}
+
+#ifdef HAVE_SPLICE
+
+static gboolean
+do_splice (int     fd_in,
+	   loff_t *off_in,
+           int     fd_out,
+	   loff_t *off_out,
+           size_t  len,
+           long   *bytes_transferd,
+           GError **error)
+{
+  long result;
+
+retry:
+  result = splice (fd_in, off_in, fd_out, off_out, len, SPLICE_F_MORE);
+
+  if (result == -1)
+    {
+      int errsv = errno;
+
+      if (errsv == EINTR)
+        goto retry;
+      else if (errsv == ENOSYS || errsv == EINVAL)
+        g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
+                             "Splice not supported");
+      else
+        g_set_error (error, G_IO_ERROR,
+                     g_io_error_from_errno (errsv),
+                     _("Error splicing file: %s"),
+                     g_strerror (errsv));
+
+      return FALSE;
+    }
+
+  *bytes_transferd = result;
+  return TRUE;
+}
+
+static gboolean
+splice_stream_with_progress (GInputStream           *in,
+                             GOutputStream          *out,
+                             GCancellable           *cancellable,
+                             GFileProgressCallback   progress_callback,
+                             gpointer                progress_callback_data,
+                             GError                **error)
+{
+  int buffer[2];
+  gboolean res;
+  goffset total_size;
+  loff_t offset_in;
+  loff_t offset_out;
+  int fd_in, fd_out;
+
+  fd_in = g_file_descriptor_based_get_fd (G_FILE_DESCRIPTOR_BASED (in));
+  fd_out = g_file_descriptor_based_get_fd (G_FILE_DESCRIPTOR_BASED (out));
+
+  if (pipe (buffer) != 0)
+    {
+      g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
+                           "Pipe creation failed");
+      return FALSE;
+    }
+
+  total_size = -1;
+  /* avoid performance impact of querying total size when it's not needed */
+  if (progress_callback)
+    {
+      struct stat sbuf;
+
+      if (fstat (fd_in, &sbuf) == 0)
+        total_size = sbuf.st_size;
+    }
+
+  if (total_size == -1)
+    total_size = 0;
+
+  offset_in = offset_out = 0;
+  res = FALSE;
+  while (TRUE)
+    {
+      long n_read;
+      long n_written;
+
+      if (g_cancellable_set_error_if_cancelled (cancellable, error))
+        break;
+
+      if (!do_splice (fd_in, &offset_in, buffer[1], NULL, 1024*64, &n_read, error))
+        break;
+
+      if (n_read == 0)
+        {
+          res = TRUE;
+          break;
+        }
+
+      while (n_read > 0)
+        {
+          if (g_cancellable_set_error_if_cancelled (cancellable, error))
+            break;
+
+          if (!do_splice (buffer[0], NULL, fd_out, &offset_out, n_read, &n_written, error))
+            break;
+
+          n_read -= n_written;
+        }
+
+      if (progress_callback)
+        progress_callback (offset_in, total_size, progress_callback_data);
+    }
+
+  /* Make sure we send full copied size */
+  if (progress_callback)
+    progress_callback (offset_in, total_size, progress_callback_data);
+
+  close (buffer[0]);
+  close (buffer[1]);
 
-  g_object_unref (in);
-  g_object_unref (out);
-      
   return res;
 }
+#endif
 
 static gboolean
 file_copy_fallback (GFile                  *source,
@@ -2747,6 +2862,10 @@ file_copy_fallback (GFile                  *source,
   GOutputStream *out;
   GFileInfo *info;
   const char *target;
+  gboolean result;
+#ifdef HAVE_SPLICE
+  gboolean fallback = TRUE;
+#endif
 
   /* need to know the file type */
   info = g_file_query_info (source,
@@ -2814,13 +2933,45 @@ file_copy_fallback (GFile                  *source,
       return FALSE;
     }
 
-  if (!copy_stream_with_progress (in, out, source, cancellable,
-				  progress_callback, progress_callback_data,
-				  error))
+#ifdef HAVE_SPLICE
+  if (G_IS_FILE_DESCRIPTOR_BASED (in) && G_IS_FILE_DESCRIPTOR_BASED (out))
+    {
+      GError *splice_err = NULL;
+
+      result = splice_stream_with_progress (in, out, cancellable,
+                                            progress_callback, progress_callback_data,
+                                            &splice_err);
+
+      if (result || !g_error_matches (splice_err, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED))
+        {
+          fallback = FALSE;
+          if (!result)
+            g_propagate_error (error, splice_err);
+        }
+      else
+        g_clear_error (&splice_err);
+    }
+
+  if (fallback)
+#endif
+    result = copy_stream_with_progress (in, out, source, cancellable,
+		                        progress_callback, progress_callback_data,
+		                        error);
+
+  /* Don't care about errors in source here */
+  g_input_stream_close (in, cancellable, NULL);
+
+  /* But write errors on close are bad! */
+  if (!g_output_stream_close (out, cancellable, result ? error : NULL))
+    result = FALSE;
+
+  g_object_unref (in);
+  g_object_unref (out);
+
+  if (result == FALSE)
     return FALSE;
 
  copied_file:
-
   /* Ignore errors here. Failure to copy metadata is not a hard error */
   g_file_copy_attributes (source, destination,
 			  flags, cancellable, NULL);