Set file stream buffers to pre-allocated 1MB chunk on web builds

libs/io/include/psemek/io/file_stream.hpp

@@ -4,19 +4,40 @@
 
 #include <filesystem>
 #include <cstdio>
+#include <memory>
 
 namespace psemek::io
 {
 
+	namespace detail
+	{
+
+#ifdef __EMSCRIPTEN__
+		struct buffer_hook
+		{
+			static constexpr std::size_t buffer_size = 1 << 20; // 1 MB
+			std::unique_ptr<char[]> buffer{new char[buffer_size]};
+
+			void apply(FILE * file)
+			{
+				std::setvbuf(file, buffer.get(), _IOFBF, buffer_size);
+			}
+		};
+#else
+		struct buffer_hook
+		{
+			void apply(FILE *) {}
+		};
+#endif
+
+	}
+
 	struct file_istream
 		: istream
 	{
 		file_istream() = default;
 
-		file_istream(FILE * file)
-			: file_{file}
-		{}
-
+		file_istream(FILE * file);
 		file_istream(std::filesystem::path const & path);
 
 		file_istream(file_istream && s)
@@ -49,6 +70,7 @@ namespace psemek::io
 
 	private:
 		FILE * file_ = nullptr;
+		[[no_unique_address]] detail::buffer_hook buffer_hook_;
 	};
 
 	struct file_ostream
@@ -58,10 +80,7 @@ namespace psemek::io
 
 		file_ostream() = default;
 
-		file_ostream(FILE * file)
-			: file_{file}
-		{}
-
+		file_ostream(FILE * file);
 		file_ostream(std::filesystem::path const & path, unsigned flags = 0);
 
 		file_ostream(file_ostream && s)
@@ -94,6 +113,7 @@ namespace psemek::io
 
 	private:
 		FILE * file_ = nullptr;
+		[[no_unique_address]] detail::buffer_hook buffer_hook_;
 	};
 
 }

libs/io/source/file_stream.cpp

@@ -69,9 +69,17 @@ namespace psemek::io
 
 	}
 
+	file_istream::file_istream(FILE * file)
+		: file_{file}
+	{
+		buffer_hook_.apply(file_);
+	}
+
 	file_istream::file_istream(std::filesystem::path const & path)
 		: file_{safe_fopen(path, fopen_read_mode())}
-	{}
+	{
+		buffer_hook_.apply(file_);
+	}
 
 	void file_istream::reset()
 	{
@@ -92,9 +100,17 @@ namespace psemek::io
 		return std::feof(file_) != 0;
 	}
 
+	file_ostream::file_ostream(FILE * file)
+		: file_{file}
+	{
+		buffer_hook_.apply(file_);
+	}
+
 	file_ostream::file_ostream(std::filesystem::path const & path, unsigned flags)
 		: file_{safe_fopen(path, fopen_write_mode(flags))}
-	{}
+	{
+		buffer_hook_.apply(file_);
+	}
 
 	void file_ostream::reset()
 	{