From b41f6bde71bf32a2faf11830d302d3eb53cb68e6 Mon Sep 17 00:00:00 2001
From: arch1t3cht <arch1t3cht@gmail.com>
Date: Thu, 1 Jun 2023 23:35:20 +0200
Subject: [PATCH] Don't immediately delete unused extradata entries

Instead, count how many consecutive times the entry has been found to be
unused and delete it once that count exceeds a limit. This will prevent
excessive reallocating of extradata ID's in applications like folding.
---
 src/ass_file.cpp   | 10 ++++++++--
 src/ass_file.h     |  1 +
 src/ass_parser.cpp |  2 +-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/ass_file.cpp b/src/ass_file.cpp
index 6d36d37a5..e39e9fc1a 100644
--- a/src/ass_file.cpp
+++ b/src/ass_file.cpp
@@ -236,7 +236,7 @@ uint32_t AssFile::AddExtradata(std::string const& key, std::string const& value)
 			return data.id;
 		}
 	}
-	Extradata.push_back(ExtradataEntry{next_extradata_id, key, value});
+	Extradata.push_back(ExtradataEntry{next_extradata_id, 0, key, value});
 	return next_extradata_id++; // return old value, then post-increment
 }
 
@@ -334,10 +334,16 @@ void AssFile::CleanExtradata() {
 		}
 	}
 
+	for (ExtradataEntry &e : Extradata) {
+		if (ids_used.count(e.id))
+			e.expiration_counter = 0;
+		else
+			e.expiration_counter++;
+	}
 	if (ids_used.size() != Extradata.size()) {
 		// Erase all no-longer-used extradata entries
 		Extradata.erase(std::remove_if(begin(Extradata), end(Extradata), [&](ExtradataEntry const& e) {
-			return !ids_used.count(e.id);
+			return e.expiration_counter >= 10;
 		}), end(Extradata));
 	}
 }
diff --git a/src/ass_file.h b/src/ass_file.h
index 1ccbf627b..de0165148 100644
--- a/src/ass_file.h
+++ b/src/ass_file.h
@@ -50,6 +50,7 @@ using EntryList = typename boost::intrusive::make_list<T, boost::intrusive::cons
 
 struct ExtradataEntry {
 	uint32_t id;
+	int expiration_counter;
 	std::string key;
 	std::string value;
 };
diff --git a/src/ass_parser.cpp b/src/ass_parser.cpp
index f55fc3567..52c70ebd5 100644
--- a/src/ass_parser.cpp
+++ b/src/ass_parser.cpp
@@ -219,7 +219,7 @@ void AssParser::ParseExtradataLine(std::string const &data) {
 
 		// ensure next_extradata_id is always at least 1 more than the largest existing id
 		target->next_extradata_id = std::max(id+1, target->next_extradata_id);
-		target->Extradata.push_back(ExtradataEntry{id, std::move(key), std::move(value)});
+		target->Extradata.push_back(ExtradataEntry{id, 0, std::move(key), std::move(value)});
 	}
 }