Reduce memory usage of mtrie.

Signed-off-by: Staffan Gimåker <staffan@spotify.com>

src/mtrie.cpp

@@ -34,6 +34,7 @@
 #include "mtrie.hpp"
 
 zmq::mtrie_t::mtrie_t () :
+    pipes (0),
     min (0),
     count (0),
     live_nodes (0)
@@ -42,6 +43,11 @@ zmq::mtrie_t::mtrie_t () :
 
 zmq::mtrie_t::~mtrie_t ()
 {
+    if (pipes) {
+        delete pipes;
+        pipes = 0;
+    }
+
     if (count == 1) {
         zmq_assert (next.node);
         delete next.node;
@@ -65,8 +71,10 @@ bool zmq::mtrie_t::add_helper (unsigned char *prefix_, size_t size_,
 {
     //  We are at the node corresponding to the prefix. We are done.
     if (!size_) {
-        bool result = pipes.empty ();
-        pipes.insert (pipe_);
+        bool result = !pipes;
+        if (!pipes)
+            pipes = new pipes_t;
+        pipes->insert (pipe_);
         return result;
     }
 
@@ -154,8 +162,11 @@ void zmq::mtrie_t::rm_helper (pipe_t *pipe_, unsigned char **buff_,
     void *arg_)
 {
     //  Remove the subscription from this node.
-    if (pipes.erase (pipe_) && pipes.empty ())
+    if (pipes && pipes->erase (pipe_) && pipes->empty ()) {
         func_ (*buff_, buffsize_, arg_);
+        delete pipes;
+        pipes = 0;
+    }
 
     //  Adjust the buffer.
     if (buffsize_ >= maxbuffsize_) {
@@ -207,9 +218,15 @@ bool zmq::mtrie_t::rm_helper (unsigned char *prefix_, size_t size_,
     pipe_t *pipe_)
 {
     if (!size_) {
-        pipes_t::size_type erased = pipes.erase (pipe_);
-        zmq_assert (erased == 1);
-        return pipes.empty ();
+        if (pipes) {
+            pipes_t::size_type erased = pipes->erase (pipe_);
+            zmq_assert (erased == 1);
+            if (pipes->empty ()) {
+                delete pipes;
+                pipes = 0;
+            }
+        }
+        return !pipes;
     }
 
     unsigned char c = *prefix_;
@@ -245,9 +262,11 @@ void zmq::mtrie_t::match (unsigned char *data_, size_t size_,
     while (true) {
 
         //  Signal the pipes attached to this node.
-        for (pipes_t::iterator it = current->pipes.begin ();
-              it != current->pipes.end (); ++it)
-            func_ (*it, arg_);
+        if (current->pipes) {
+            for (pipes_t::iterator it = current->pipes->begin ();
+                  it != current->pipes->end (); ++it)
+                func_ (*it, arg_);
+        }
 
         //  If we are at the end of the message, there's nothing more to match.
         if (!size_)
@@ -281,5 +300,5 @@ void zmq::mtrie_t::match (unsigned char *data_, size_t size_,
 
 bool zmq::mtrie_t::is_redundant () const
 {
-    return pipes.empty () && live_nodes == 0;
+    return !pipes && live_nodes == 0;
 }

src/mtrie.hpp

@@ -73,7 +73,7 @@ namespace zmq
         bool is_redundant () const;
 
         typedef std::set <zmq::pipe_t*> pipes_t;
-        pipes_t pipes;
+        pipes_t *pipes;
 
         unsigned char min;
         unsigned short count;