[Commit-gnuradio] [gnuradio] 04/04: blocks: delay block cannot be initialized with a negative number.

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trondeau pushed a commit to branch maint
in repository gnuradio.

commit 3897c850322eb51f72ec4e55e2c35c7429c90337
Author: Tom Rondeau <address@hidden>
Date:   Thu Aug 14 11:21:32 2014 -0400

    blocks: delay block cannot be initialized with a negative number.
    
    This commit puts in a check in the constructor and better
    documentation about the behavior.
---
 gr-blocks/include/gnuradio/blocks/delay.h | 14 ++++++++++++--
 gr-blocks/lib/delay_impl.cc               |  3 +++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/gr-blocks/include/gnuradio/blocks/delay.h 
b/gr-blocks/include/gnuradio/blocks/delay.h
index fc90e22..381669b 100644
--- a/gr-blocks/include/gnuradio/blocks/delay.h
+++ b/gr-blocks/include/gnuradio/blocks/delay.h
@@ -35,6 +35,11 @@ namespace gr {
      *
      * Positive delays insert zero items at the beginning of the stream.
      * Negative delays discard items from the stream.
+     *
+     * You cannot initialize this block with a negative delay,
+     * however. That leads to a causality issue with the buffers when
+     * they are initialized. If you need to negetively delay one path,
+     * then put the positive delay on the other path instead.
      */
     class BLOCKS_API delay : virtual public block
     {
@@ -45,11 +50,17 @@ namespace gr {
       /*!
        * \brief Make a delay block.
        * \param itemsize size of the data items.
-       * \param delay number of samples to delay stream.
+       * \param delay number of samples to delay stream (>= 0).
        */
       static sptr make(size_t itemsize, int delay);
 
       virtual int dly() const = 0;
+
+      /*!
+       * \brief Reset the delay.
+       * \param d change the delay value. This can be a positive or
+       * negative value.
+       */
       virtual void set_dly(int d) = 0;
     };
 
@@ -57,4 +68,3 @@ namespace gr {
 } /* namespace gr */
 
 #endif /* INCLUDED_BLOCKS_DELAY_H */
-
diff --git a/gr-blocks/lib/delay_impl.cc b/gr-blocks/lib/delay_impl.cc
index 7ae4037..0ebe124 100644
--- a/gr-blocks/lib/delay_impl.cc
+++ b/gr-blocks/lib/delay_impl.cc
@@ -44,6 +44,9 @@ namespace gr {
                  io_signature::make(1, -1, itemsize)),
         d_itemsize(itemsize)
     {
+      if(delay < 0) {
+        throw std::runtime_error("delay: Cannot initialize block with a delay 
< 0.");
+      }
       set_dly(delay);
       d_delta = 0;
     }