From 6b2ec66ffafbad0aa1eef3a2c59d30dda033be2c Mon Sep 17 00:00:00 2001
From: Jean Pierre Cimalando <jp-dev@inbox.ru>
Date: Mon, 19 Oct 2020 16:53:55 +0200
Subject: [PATCH] Ref-count the global thread pool

---
 src/sfizz/FilePool.cpp | 28 +++++++++++++++++++++++++---
 src/sfizz/FilePool.h   |  3 +++
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/src/sfizz/FilePool.cpp b/src/sfizz/FilePool.cpp
index 115198cd..fbeca154 100644
--- a/src/sfizz/FilePool.cpp
+++ b/src/sfizz/FilePool.cpp
@@ -47,7 +47,29 @@
 #endif
 #include "threadpool/ThreadPool.h"
 using namespace std::placeholders;
-static ThreadPool threadPool { std::thread::hardware_concurrency() > 2 ? std::thread::hardware_concurrency() - 2 : 1 };
+
+static std::weak_ptr<ThreadPool> globalThreadPoolWeakPtr;
+static std::mutex globalThreadPoolMutex;
+
+static std::shared_ptr<ThreadPool> globalThreadPool()
+{
+    std::shared_ptr<ThreadPool> threadPool;
+
+    threadPool = globalThreadPoolWeakPtr.lock();
+    if (threadPool)
+        return threadPool;
+
+    std::lock_guard<std::mutex> lock(globalThreadPoolMutex);
+    threadPool = globalThreadPoolWeakPtr.lock();
+    if (threadPool)
+        return threadPool;
+
+    unsigned numThreads = std::thread::hardware_concurrency();
+    numThreads = (numThreads > 2) ? (numThreads - 2) : 1;
+    threadPool.reset(new ThreadPool(numThreads));
+    globalThreadPoolWeakPtr = threadPool;
+    return threadPool;
+}
 
 void readBaseFile(sfz::AudioReader& reader, sfz::FileAudioBuffer& output, uint32_t numFrames)
 {
@@ -96,7 +118,7 @@ void streamFromFile(sfz::AudioReader& reader, uint32_t numFrames, sfz::Oversampl
 }
 
 sfz::FilePool::FilePool(sfz::Logger& logger)
-    : logger(logger)
+    : logger(logger), threadPool(globalThreadPool())
 {
     loadingJobs.reserve(config::maxVoices);
     lastUsedFiles.reserve(config::maxVoices);
@@ -478,7 +500,7 @@ void sfz::FilePool::dispatchingJob() noexcept
 
         if (filesToLoad.try_pop(queuedData)) {
             loadingJobs.push_back(
-                threadPool.enqueue([this](const QueuedFileData& data) { loadingJob(data); }, queuedData));
+                threadPool->enqueue([this](const QueuedFileData& data) { loadingJob(data); }, queuedData));
         }
 
         // Clear finished jobs
diff --git a/src/sfizz/FilePool.h b/src/sfizz/FilePool.h
index a44ce948..a9f0ecff 100644
--- a/src/sfizz/FilePool.h
+++ b/src/sfizz/FilePool.h
@@ -44,6 +44,7 @@
 #include <thread>
 #include <future>
 #include "utility/SpinMutex.h"
+class ThreadPool;
 
 namespace sfz {
 using FileAudioBuffer = AudioBuffer<float, 2, config::defaultAlignment,
@@ -364,6 +365,8 @@ private:
     SpinMutex garbageMutex;
     std::vector<FileAudioBuffer> garbageToCollect;
 
+    std::shared_ptr<ThreadPool> threadPool;
+
     // Preloaded data
     absl::flat_hash_map<FileId, FileData> preloadedFiles;
     absl::flat_hash_map<FileId, FileData> loadedFiles;