capture: add sendfile() fallback

We want the capture format to be usable on systems other than Linux so that it can be used in places like GTK. To do this, we need a sendfile() fallback that can be portable/useful on those systems. FreeBSD has sendfile(), but the semantics differ slightly. This implementation will walk up to the nearest page size and then do page aligned pread()/write() which is likely good enough of an implementation anyway.
2025-12-31 20:36:25 +00:00 · 2019-05-06 16:20:14 -07:00
parent 36179e9ab4
commit 0580b4ef0d
1 changed files with 102 additions and 0 deletions
--- a/lib/capture/sp-capture-util-private.h
+++ b/lib/capture/sp-capture-util-private.h
@ -0,0 +1,102 @@
+/* sp-capture-util-private.h
+ *
+ * Copyright © 2019 Christian Hergert <chergert@redhat.com>
+ *
+ * This file is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This file is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef SP_CAPTURE_UTIL_PRIVATE_H
+#define SP_CAPTURE_UTIL_PRIVATE_H
+
+#include <glib.h>
+
+#ifdef __linux__
+# include <sys/sendfile.h>
+#endif
+#include <errno.h>
+#include <unistd.h>
+
+#ifdef __linux__
+# define _sp_sendfile sendfile
+#else
+static inline gssize
+_sp_sendfile (gint     out_fd,
+              gint     in_fd,
+              goffset *offset,
+              gsize    count)
+{
+  gssize total = 0;
+  goffset wpos = 0;
+  goffset rpos = 0;
+
+  errno = 0;
+
+  if (offset != NULL && *offset > 0)
+    wpos = rpos = *offset;
+
+  while (count > 0)
+    {
+      guint8 buf[4096*4];
+      gssize n_written = 0;
+      gssize n_read;
+      goffset off = 0;
+      gsize to_read;
+
+      /* Try to page align */
+      if ((rpos % 4096) != 0)
+        to_read = 4096 - rpos;
+      else
+        to_read = sizeof buf;
+
+      if (to_read > count)
+        to_read = count;
+
+      errno = 0;
+      n_read = pread (in_fd, buf, to_read, rpos);
+
+      if (n_read <= 0)
+        return -1;
+
+      g_assert (count >= n_read);
+
+      count -= n_read;
+      rpos += n_read;
+
+      while (wpos < rpos)
+        {
+          g_assert (off < sizeof buf);
+
+          errno = 0;
+          n_written = write (out_fd, &buf[off], rpos - wpos);
+
+          if (n_written <= 0)
+            return -1;
+
+          wpos += n_written;
+          off += n_written;
+          total += n_written;
+        }
+    }
+
+  g_assert (count == 0);
+
+  if (offset != NULL)
+    *offset = rpos;
+
+  errno = 0;
+  return total;
+}
+#endif
+
+#endif /* SP_CAPTURE_UTIL_PRIVATE_H */