From a695142b33199de25327709d4983592d96e20414 Mon Sep 17 00:00:00 2001
From: Marcus Müller <mmueller@gnuradio.org>
Date: Sun, 20 Jun 2021 18:44:37 +0200
Subject: blocks: zero-output, zero-copy Head mode
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If you don't want to test a stream with an exact number of input, but
just want your flow graph to terminate after a given number of items,
having a head block without an output enables you to do that without
copying the data from Head's in- to its output.
Signed-off-by: Marcus Müller <mmueller@gnuradio.org>
---
gr-blocks/lib/head_impl.cc | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
(limited to 'gr-blocks/lib/head_impl.cc')
diff --git a/gr-blocks/lib/head_impl.cc b/gr-blocks/lib/head_impl.cc
index 0ee22682d0..567a12d1df 100644
--- a/gr-blocks/lib/head_impl.cc
+++ b/gr-blocks/lib/head_impl.cc
@@ -1,6 +1,7 @@
/* -*- c++ -*- */
/*
* Copyright 2004,2009,2013 Free Software Foundation, Inc.
+ * Copyright 2021 Marcus Müller
*
* This file is part of GNU Radio
*
@@ -27,7 +28,7 @@ head::sptr head::make(size_t sizeof_stream_item, uint64_t nitems)
head_impl::head_impl(size_t sizeof_stream_item, uint64_t nitems)
: sync_block("head",
io_signature::make(1, 1, sizeof_stream_item),
- io_signature::make(1, 1, sizeof_stream_item)),
+ io_signature::make(0, 1, sizeof_stream_item)),
d_nitems(nitems),
d_ncopied_items(0)
{
@@ -47,7 +48,12 @@ int head_impl::work(int noutput_items,
if (n == 0)
return 0;
- memcpy(output_items[0], input_items[0], n * input_signature()->sizeof_stream_item(0));
+ // can have zero or one output port, if zero, don't copy
+ if (!output_items.empty()) {
+ memcpy(output_items[0],
+ input_items[0],
+ n * input_signature()->sizeof_stream_item(0));
+ }
d_ncopied_items += n;
return n;
--
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