From ec457551abfba3e39a8b7dfcf63d72d5e086496c Mon Sep 17 00:00:00 2001
From: Charles Kerr <charles@charleskerr.com>
Date: Sat, 20 Nov 2021 10:58:47 -0600
Subject: [PATCH] refactor: make Bandwidth.children a std::vector (#2197)

---
 libtransmission/bandwidth.cc | 21 ++++++++++++++++++---
 libtransmission/bandwidth.h  |  3 +--
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/libtransmission/bandwidth.cc b/libtransmission/bandwidth.cc
index e763517f7..da7a4a1fc 100644
--- a/libtransmission/bandwidth.cc
+++ b/libtransmission/bandwidth.cc
@@ -94,22 +94,37 @@ Bandwidth::Bandwidth(Bandwidth* new_parent)
 ****
 ***/
 
+static void remove_child(std::vector<Bandwidth*>& v, Bandwidth* remove_me)
+{
+    auto it = std::find(std::begin(v), std::end(v), remove_me);
+    if (it == std::end(v))
+    {
+        return;
+    }
+
+    // the list isn't sorted -- so instead of erase()ing `it`,
+    // do the cheaper option of overwriting it with the final item
+    *it = v.back();
+    v.resize(v.size() - 1);
+}
+
 void Bandwidth::setParent(Bandwidth* new_parent)
 {
     TR_ASSERT(this != new_parent);
 
     if (this->parent_ != nullptr)
     {
-        this->parent_->children_.erase(this);
+        remove_child(this->parent_->children_, this);
         this->parent_ = nullptr;
     }
 
     if (new_parent != nullptr)
     {
         TR_ASSERT(new_parent->parent_ != this);
-        TR_ASSERT(new_parent->children_.find(this) == new_parent->children_.end()); // does not exist
+        auto& children = new_parent->children_;
+        TR_ASSERT(std::find(std::begin(children), std::end(children), this) == std::end(children)); // not already there
 
-        new_parent->children_.insert(this);
+        new_parent->children_.push_back(this);
         this->parent_ = new_parent;
     }
 }
diff --git a/libtransmission/bandwidth.h b/libtransmission/bandwidth.h
index cc78b4676..e29cf5595 100644
--- a/libtransmission/bandwidth.h
+++ b/libtransmission/bandwidth.h
@@ -13,7 +13,6 @@
 #endif
 
 #include <array>
-#include <unordered_set>
 #include <vector>
 
 #include "transmission.h"
@@ -247,7 +246,7 @@ private:
 
     mutable std::array<Band, 2> band_ = {};
     Bandwidth* parent_ = nullptr;
-    std::unordered_set<Bandwidth*> children_;
+    std::vector<Bandwidth*> children_;
     tr_peerIo* peer_ = nullptr;
     tr_priority_t priority_ = 0;
 };