From 0b32fb36290a937a9013d7ddf4c1e3bc2a017f4a Mon Sep 17 00:00:00 2001
From: Gudmundur Adalsteinsson <ofpgummi@yahoo.com>
Date: Mon, 13 Apr 2020 20:30:45 +0000
Subject: [PATCH] Problem: poller item lookup can be simplified

Solution: Extract generic find function
---
 src/socket_poller.cpp | 76 ++++++++++++++++++-------------------------
 src/socket_poller.hpp | 31 +++++++++++-------
 2 files changed, 52 insertions(+), 55 deletions(-)

diff --git a/src/socket_poller.cpp b/src/socket_poller.cpp
index c761646e..4a41e5fc 100644
--- a/src/socket_poller.cpp
+++ b/src/socket_poller.cpp
@@ -41,6 +41,18 @@ static bool is_thread_safe (const zmq::socket_base_t &socket_)
     return socket_.is_thread_safe ();
 }
 
+// compare elements to value
+template <class It, class T, class Pred>
+static It find_if2 (It b_, It e_, const T &value, Pred pred)
+{
+    for (; b_ != e_; ++b_) {
+        if (pred (*b_, value)) {
+            break;
+        }
+    }
+    return b_;
+}
+
 zmq::socket_poller_t::socket_poller_t () :
     _tag (0xCAFEBABE),
     _signaler (NULL)
@@ -101,12 +113,10 @@ int zmq::socket_poller_t::add (socket_base_t *socket_,
                                void *user_data_,
                                short events_)
 {
-    for (items_t::iterator it = _items.begin (), end = _items.end (); it != end;
-         ++it) {
-        if (it->socket == socket_) {
-            errno = EINVAL;
-            return -1;
-        }
+    if (find_if2 (_items.begin (), _items.end (), socket_, &is_socket)
+        != _items.end ()) {
+        errno = EINVAL;
+        return -1;
     }
 
     if (is_thread_safe (*socket_)) {
@@ -151,12 +161,10 @@ int zmq::socket_poller_t::add (socket_base_t *socket_,
 
 int zmq::socket_poller_t::add_fd (fd_t fd_, void *user_data_, short events_)
 {
-    for (items_t::iterator it = _items.begin (), end = _items.end (); it != end;
-         ++it) {
-        if (!it->socket && it->fd == fd_) {
-            errno = EINVAL;
-            return -1;
-        }
+    if (find_if2 (_items.begin (), _items.end (), fd_, &is_fd)
+        != _items.end ()) {
+        errno = EINVAL;
+        return -1;
     }
 
     const item_t item = {
@@ -183,15 +191,10 @@ int zmq::socket_poller_t::add_fd (fd_t fd_, void *user_data_, short events_)
 
 int zmq::socket_poller_t::modify (const socket_base_t *socket_, short events_)
 {
-    const items_t::iterator end = _items.end ();
-    items_t::iterator it;
+    const items_t::iterator it =
+      find_if2 (_items.begin (), _items.end (), socket_, &is_socket);
 
-    for (it = _items.begin (); it != end; ++it) {
-        if (it->socket == socket_)
-            break;
-    }
-
-    if (it == end) {
+    if (it == _items.end ()) {
         errno = EINVAL;
         return -1;
     }
@@ -205,15 +208,10 @@ int zmq::socket_poller_t::modify (const socket_base_t *socket_, short events_)
 
 int zmq::socket_poller_t::modify_fd (fd_t fd_, short events_)
 {
-    const items_t::iterator end = _items.end ();
-    items_t::iterator it;
+    const items_t::iterator it =
+      find_if2 (_items.begin (), _items.end (), fd_, &is_fd);
 
-    for (it = _items.begin (); it != end; ++it) {
-        if (!it->socket && it->fd == fd_)
-            break;
-    }
-
-    if (it == end) {
+    if (it == _items.end ()) {
         errno = EINVAL;
         return -1;
     }
@@ -227,15 +225,10 @@ int zmq::socket_poller_t::modify_fd (fd_t fd_, short events_)
 
 int zmq::socket_poller_t::remove (socket_base_t *socket_)
 {
-    const items_t::iterator end = _items.end ();
-    items_t::iterator it;
+    const items_t::iterator it =
+      find_if2 (_items.begin (), _items.end (), socket_, &is_socket);
 
-    for (it = _items.begin (); it != end; ++it) {
-        if (it->socket == socket_)
-            break;
-    }
-
-    if (it == end) {
+    if (it == _items.end ()) {
         errno = EINVAL;
         return -1;
     }
@@ -252,15 +245,10 @@ int zmq::socket_poller_t::remove (socket_base_t *socket_)
 
 int zmq::socket_poller_t::remove_fd (fd_t fd_)
 {
-    const items_t::iterator end = _items.end ();
-    items_t::iterator it;
+    const items_t::iterator it =
+      find_if2 (_items.begin (), _items.end (), fd_, &is_fd);
 
-    for (it = _items.begin (); it != end; ++it) {
-        if (!it->socket && it->fd == fd_)
-            break;
-    }
-
-    if (it == end) {
+    if (it == _items.end ()) {
         errno = EINVAL;
         return -1;
     }
diff --git a/src/socket_poller.hpp b/src/socket_poller.hpp
index 204c1723..5917e018 100644
--- a/src/socket_poller.hpp
+++ b/src/socket_poller.hpp
@@ -86,6 +86,17 @@ class socket_poller_t
     bool check_tag () const;
 
   private:
+    typedef struct item_t
+    {
+        socket_base_t *socket;
+        fd_t fd;
+        void *user_data;
+        short events;
+#if defined ZMQ_POLL_BASED_ON_POLL
+        int pollfd_index;
+#endif
+    } item_t;
+
     static void zero_trail_events (zmq::socket_poller_t::event_t *events_,
                                    int n_events_,
                                    int found_);
@@ -103,6 +114,15 @@ class socket_poller_t
                                uint64_t &now_,
                                uint64_t &end_,
                                bool &first_pass_);
+    static bool is_socket (const item_t &item, const socket_base_t *socket_)
+    {
+        return item.socket == socket_;
+    }
+    static bool is_fd (const item_t &item, fd_t fd_)
+    {
+        return !item.socket && item.fd == fd_;
+    }
+
     int rebuild ();
 
     //  Used to check whether the object is a socket_poller.
@@ -111,17 +131,6 @@ class socket_poller_t
     //  Signaler used for thread safe sockets polling
     signaler_t *_signaler;
 
-    typedef struct item_t
-    {
-        socket_base_t *socket;
-        fd_t fd;
-        void *user_data;
-        short events;
-#if defined ZMQ_POLL_BASED_ON_POLL
-        int pollfd_index;
-#endif
-    } item_t;
-
     //  List of sockets
     typedef std::vector<item_t> items_t;
     items_t _items;