From 7bf3696a3bc50b0b36f28e8ce24ee9b763d57ee8 Mon Sep 17 00:00:00 2001
From: mumpf <git@porscha.eu>
Date: Fri, 21 Oct 2022 10:03:11 +0200
Subject: [PATCH] Feature175 binarysearch (#218)

* #175
added a binary search for address and assoc table
can be enabled by defining USE_BINSEARCH

* Corrected BIN_SEARCH

* AddressTableObject::contains minimal improve

* Review: changed ntohs to htons

* corrected byte order during access to sorted array

Co-authored-by: SirSydom <com@sirsydom.de>
Co-authored-by: Waldemar Porscha <wp@porscha.eu>
---
 src/knx/address_table_object.cpp     | 26 ++++++++++++++++++++------
 src/knx/association_table_object.cpp | 24 ++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 6 deletions(-)

diff --git a/src/knx/address_table_object.cpp b/src/knx/address_table_object.cpp
index c2e9154..7b18af4 100644
--- a/src/knx/address_table_object.cpp
+++ b/src/knx/address_table_object.cpp
@@ -37,9 +37,28 @@ uint16_t AddressTableObject::getGroupAddress(uint16_t tsap)
 uint16_t AddressTableObject::getTsap(uint16_t addr)
 {
     uint16_t size = entryCount();
+    #ifdef USE_BINSEARCH
+
+    uint16_t low,high,i;
+    low = 1;
+    high = size;
+
+    while(low <= high)
+    {
+        i = (low+high)/2;
+        uint16_t ga = ntohs(_groupAddresses[i]);
+        if (ga == addr)
+            return i;
+        if(addr < ga)
+            high = i - 1;
+        else
+            low = i + 1 ;
+    }
+    #else
     for (uint16_t i = 1; i <= size; i++)
         if (ntohs(_groupAddresses[i]) == addr)
             return i;
+    #endif
     return 0;
 }
 
@@ -58,12 +77,7 @@ const uint8_t* AddressTableObject::restore(const uint8_t* buffer)
 
 bool AddressTableObject::contains(uint16_t addr)
 {
-    uint16_t size = entryCount();
-    for (uint16_t i = 1; i <= size; i++)
-        if (ntohs(_groupAddresses[i]) == addr)
-            return true;
-
-    return false;
+    return (getTsap(addr) > 0);
 }
 
 void AddressTableObject::beforeStateChange(LoadState& newState)
diff --git a/src/knx/association_table_object.cpp b/src/knx/association_table_object.cpp
index 92cc839..2afbc7b 100644
--- a/src/knx/association_table_object.cpp
+++ b/src/knx/association_table_object.cpp
@@ -50,11 +50,35 @@ const uint8_t* AssociationTableObject::restore(const uint8_t* buffer)
 int32_t AssociationTableObject::translateAsap(uint16_t asap)
 {
     uint16_t entries = entryCount();
+    #ifdef USE_BINSEARCH
+    uint16_t low,high,i;
+    low = 0;
+    high = entries-1;
+
+    while(low <= high)
+    {
+        i = (low+high)/2;
+        uint16_t asap_i = getASAP(i);
+        if (asap_i == asap)
+        {
+             // as the binary search does not hit the first element in a list with identical items,
+             // search downwards to return the first occurence in the table
+            while(getASAP(--i) == asap)
+                ;
+            return getTSAP(i+1);
+        }
+        if(asap_i > asap)
+            high = i - 1;
+        else
+            low = i + 1 ;
+    }
+    #else
     for (uint16_t i = 0; i < entries; i++)
     {
         if (getASAP(i) == asap)
             return getTSAP(i);
     }
+    #endif
     return -1;
 }