From 37f6383c7c7383a5ee5402f2ad0d260db250bb7b Mon Sep 17 00:00:00 2001
From: Dimitri Stolnikov <horiz0n@gmx.net>
Date: Fri, 26 Apr 2013 21:50:50 +0200
Subject: [PATCH] hackf: implement start & stop methods

This allows a block to enable an associated driver to begin
transfering data just before we start to execute the scheduler.
The end result is that this reduces latency in the pipeline
when dealing with audio devices, usrps, etc.
---
 lib/hackrf/hackrf_source_c.cc | 39 ++++++++++++++++++++++++++++-------
 lib/hackrf/hackrf_source_c.h  |  3 +++
 2 files changed, 35 insertions(+), 7 deletions(-)

diff --git a/lib/hackrf/hackrf_source_c.cc b/lib/hackrf/hackrf_source_c.cc
index 51268c9..2b74afb 100644
--- a/lib/hackrf/hackrf_source_c.cc
+++ b/lib/hackrf/hackrf_source_c.cc
@@ -176,12 +176,6 @@ hackrf_source_c::hackrf_source_c (const std::string &args)
       _buf[i] = (unsigned short *) malloc(_buf_len);
   }
 
-  ret = hackrf_start_rx( _dev, _hackrf_rx_callback, (void *)this );
-  if (ret != HACKRF_SUCCESS)
-    std::cerr << "Failed to start streaming (" << ret << ")" << std::endl;
-
-  while ( ! hackrf_is_streaming( _dev ) );
-
 //  _thread = gruel::thread(_hackrf_wait, this);
 }
 
@@ -191,7 +185,6 @@ hackrf_source_c::hackrf_source_c (const std::string &args)
 hackrf_source_c::~hackrf_source_c ()
 {
   if (_dev) {
-    hackrf_stop_rx( _dev );
 //    _thread.join();
     hackrf_close( _dev );
     _dev = NULL;
@@ -253,6 +246,38 @@ void hackrf_source_c::hackrf_wait()
 {
 }
 
+bool hackrf_source_c::start()
+{
+  if ( ! _dev )
+    return false;
+
+  int ret = hackrf_start_rx( _dev, _hackrf_rx_callback, (void *)this );
+  if (ret != HACKRF_SUCCESS) {
+    std::cerr << "Failed to start RX streaming (" << ret << ")" << std::endl;
+    return false;
+  }
+
+  while ( ! hackrf_is_streaming( _dev ) );
+
+  return (bool) hackrf_is_streaming( _dev );
+}
+
+bool hackrf_source_c::stop()
+{
+  if ( ! _dev )
+    return false;
+
+  int ret = hackrf_stop_rx( _dev );
+  if (ret != HACKRF_SUCCESS) {
+    std::cerr << "Failed to stop RX streaming (" << ret << ")" << std::endl;
+    return false;
+  }
+
+  while ( hackrf_is_streaming( _dev ) );
+
+  return ! (bool) hackrf_is_streaming( _dev );
+}
+
 int hackrf_source_c::work( int noutput_items,
                         gr_vector_const_void_star &input_items,
                         gr_vector_void_star &output_items )
diff --git a/lib/hackrf/hackrf_source_c.h b/lib/hackrf/hackrf_source_c.h
index 67dd8c6..02ff2a5 100644
--- a/lib/hackrf/hackrf_source_c.h
+++ b/lib/hackrf/hackrf_source_c.h
@@ -78,6 +78,9 @@ private:
 public:
   ~hackrf_source_c (); 	// public destructor
 
+  bool start();
+  bool stop();
+
   int work( int noutput_items,
             gr_vector_const_void_star &input_items,
             gr_vector_void_star &output_items );