spdlog implementation hiding (#498)

this change aims to hide logging internals from client code, in order to make it easier to extend and take more control over the logging process in the future. 

As a bonus side effect, the generated code is much tighter (net delta around 2.5% on the resulting executable which includes lots of thirdparty code) and should take less time to compile and link.

Client usage via macros is pretty much unchanged. The main exposure client code had to spdlog internals before was the use of custom loggers per subsystem, where it would be common to have `spdlog::logger` references to keep a reference to a logger within a class. This is now replaced by `zen::LoggerRef` which currently simply encapsulates an actual `spdlog::logger` instance, but this is intended to be an implementation detail which will change in the future.

The way the change works is that we now handle any formatting of log messages in the zencore logging subsystem instead of relying on `spdlog` to manage this. We use the `fmt` library to do the formatting which means the client usage is identical to using `spdlog`. The formatted message is then forwarded onto any sinks etc which are still implememted via `spdlog`.

1 files changed, 5 insertions, 9 deletions

diff --git a/src/zenstore/filecas.h b/src/zenstore/filecas.h
index c39a39bb7..cb1347580 100644
--- a/src/zenstore/filecas.h
+++ b/src/zenstore/filecas.h
@@ -16,10 +16,6 @@
 #include <atomic>
 #include <functional>
 
-namespace spdlog {
-class logger;
-}
-
 namespace zen {
 
 class BasicFile;
@@ -48,10 +44,10 @@ struct FileCasStrategy final : public GcStorage, public GcReferenceStore
 	virtual GcReferencePruner* CreateReferencePruner(GcCtx& Ctx, GcReferenceStoreStats& Stats) override;
 
 private:
-	void			MakeIndexSnapshot();
-	uint64_t		ReadIndexFile(const std::filesystem::path& IndexPath, uint32_t& OutVersion);
-	uint64_t		ReadLog(const std::filesystem::path& LogPath, uint64_t LogPosition);
-	spdlog::logger& Log() { return m_Log; }
+	void	  MakeIndexSnapshot();
+	uint64_t  ReadIndexFile(const std::filesystem::path& IndexPath, uint32_t& OutVersion);
+	uint64_t  ReadLog(const std::filesystem::path& LogPath, uint64_t LogPosition);
+	LoggerRef Log() { return m_Log; }
 
 	struct IndexEntry
 	{
@@ -61,7 +57,7 @@ private:
 
 	CasStore::InsertResult InsertChunkData(const void* ChunkData, size_t ChunkSize, const IoHash& ChunkHash);
 
-	spdlog::logger&		  m_Log;
+	LoggerRef			  m_Log;
 	GcManager&			  m_Gc;
 	std::filesystem::path m_RootDirectory;
 	RwLock				  m_Lock;