From 4a0a243530fe1701887b4b10036802743dffe472 Mon Sep 17 00:00:00 2001
From: Arjan Onwezen <arjan.onwezen@gmail.com>
Date: Sun, 12 Dec 2021 04:48:11 -0500
Subject: [PATCH] added binary search tree lookup to airlines.db

---
 firmware/application/apps/ui_adsb_rx.cpp | 43 +++++++++++++++++-------
 1 file changed, 31 insertions(+), 12 deletions(-)

diff --git a/firmware/application/apps/ui_adsb_rx.cpp b/firmware/application/apps/ui_adsb_rx.cpp
index d065163a..d192f58a 100644
--- a/firmware/application/apps/ui_adsb_rx.cpp
+++ b/firmware/application/apps/ui_adsb_rx.cpp
@@ -293,7 +293,7 @@ ADSBRxDetailsView::ADSBRxDetailsView(
 	bool found = false;
 	size_t number_of_airlines = 0;	
 	std::string airline_code;
-	size_t c;
+	//size_t c;
 	
 	add_children({
 		&labels,
@@ -320,18 +320,37 @@ ADSBRxDetailsView::ADSBRxDetailsView(
 		// Search for 3-letter code
 		number_of_airlines = (db_file.size() / 68); // determine number of airlines in file
 		airline_code = entry_copy.callsign.substr(0, 3);
-		c = 0;
-		do {
-			db_file.read(file_buffer, 4);
-			if (!file_buffer[0])
-				break;
-			if (!airline_code.compare(0, 4, file_buffer))
-				found = true;
-			else
-				c++;
-		} while (!found && (c < number_of_airlines));
+		//c = 0;
+		//do {
+		//	db_file.read(file_buffer, 4);
+		//	if (!file_buffer[0])
+		//		break;
+		//	if (!airline_code.compare(0, 4, file_buffer))
+		//		found = true;
+		//	else
+		//		c++;
+		//} while (!found && (c < number_of_airlines));
+
+  		// binary search
+    		int first = 0,         				// First search element       
+    		last = number_of_airlines - 1,        	 	// Last search element       
+    		middle,                				// Mid point of search       
+    		position = -1;         				// Position of search value   
+    		while (!found && first <= last) {  
+        		middle = (first + last) / 2;     	// Calculate mid point      
+        		db_file.seek(middle * 4); 
+			db_file.read(file_buffer, 3);
+			if (file_buffer == airline_code) {     	// If value is found at mid        
+                		found = true;         
+                		position = middle;      
+        		}      
+        		else if (file_buffer > airline_code)  	// If value is in lower half         
+            			last = middle - 1;      
+        		else         
+            			first = middle + 1;          	// If value is in upper half   
+    		}   
 		
-		if (found) {
+		if (position > -1) {
 			db_file.seek((number_of_airlines * 4) + (c << 6)); // seek starting after index
 			db_file.read(file_buffer, 32);
 			text_airline.set(file_buffer);