reader: add sp_capture_reader_copy()

This function allows copying a capture so that we can do
additional reads. This does, however, copy the buffers which
might be more memory than we want for large usage. We can
tweak things as we go to figure out the cursors.

lib/sp-capture-reader.c

@@ -812,3 +812,38 @@ sp_capture_reader_get_start_time (SpCaptureReader *self)
 
   return self->header.time;
 }
+
+/**
+ * sp_capture_reader_copy:
+ *
+ * This function makes a copy of the reader. Since readers use
+ * positioned reads with pread(), this allows you to have multiple
+ * readers with the shared file descriptor. This uses dup() to create
+ * another file descriptor.
+ *
+ * Returns: (transfer full): A copy of @self with a new file-descriptor.
+ */
+SpCaptureReader *
+sp_capture_reader_copy (SpCaptureReader *self)
+{
+  SpCaptureReader *copy;
+  int fd;
+
+  g_return_val_if_fail (self != NULL, NULL);
+
+  if (-1 == (fd = dup (self->fd)))
+    return NULL;
+
+  copy = g_new0 (SpCaptureReader, 1);
+
+  *copy = *self;
+
+  copy->ref_count = 1;
+  copy->filename = g_strdup (self->filename);
+  copy->fd = fd;
+
+  copy->buf = g_malloc (self->bufsz);
+  memcpy (copy->buf, self->buf, self->bufsz);
+
+  return copy;
+}

lib/sp-capture-reader.h

@@ -29,6 +29,7 @@ SpCaptureReader                   *sp_capture_reader_new                 (const
                                                                           GError             **error);
 SpCaptureReader                   *sp_capture_reader_new_from_fd         (int                  fd,
                                                                           GError             **error);
+SpCaptureReader                   *sp_capture_reader_copy                (SpCaptureReader     *self);
 SpCaptureReader                   *sp_capture_reader_ref                 (SpCaptureReader     *self);
 void                               sp_capture_reader_unref               (SpCaptureReader     *self);
 const gchar                       *sp_capture_reader_get_filename        (SpCaptureReader     *self);