From 21b0c47700f1b570b6129384ce0b96a0c6b48ffd Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Mon, 7 Oct 2013 21:13:15 +0300
Subject: [PATCH] Implement automatic registration of image loaders

---
 source/graphics/devil/devilloader.cpp |  2 +
 source/graphics/devil/devilloader.h   |  3 ++
 source/graphics/imageloader.cpp       | 60 +++++++++++++++++----------
 source/graphics/imageloader.h         | 29 ++++++++++++-
 source/graphics/png/pngloader.cpp     |  2 +
 source/graphics/png/pngloader.h       |  3 ++
 6 files changed, 76 insertions(+), 23 deletions(-)

diff --git a/source/graphics/devil/devilloader.cpp b/source/graphics/devil/devilloader.cpp
index 392bde8..88beb04 100644
--- a/source/graphics/devil/devilloader.cpp
+++ b/source/graphics/devil/devilloader.cpp
@@ -59,6 +59,8 @@ int tell(void *handle)
 namespace Msp {
 namespace Graphics {
 
+ImageLoader::Register<DevilLoader> DevilLoader::reg;
+
 DevilLoader::DevilLoader(IO::Seekable &i):
 	io(i)
 {
diff --git a/source/graphics/devil/devilloader.h b/source/graphics/devil/devilloader.h
index 3b933ae..daab2a2 100644
--- a/source/graphics/devil/devilloader.h
+++ b/source/graphics/devil/devilloader.h
@@ -12,10 +12,13 @@ private:
 	IO::Base &io;
 	unsigned id;
 
+	static Register<DevilLoader> reg;
+
 public:
 	DevilLoader(IO::Seekable &);
 	virtual ~DevilLoader();
 
+	static unsigned get_signature_size() { return 128; }
 	static bool detect(const std::string &);
 
 	virtual void load(Image::Data &);
diff --git a/source/graphics/imageloader.cpp b/source/graphics/imageloader.cpp
index 6cdaef9..15f0e50 100644
--- a/source/graphics/imageloader.cpp
+++ b/source/graphics/imageloader.cpp
@@ -2,18 +2,14 @@
 #include <msp/io/file.h>
 #include <msp/strings/format.h>
 #include "imageloader.h"
-#ifdef WITH_LIBPNG
-#include "png/pngloader.h"
-#endif
-#ifdef WITH_DEVIL
-#include "devil/devilloader.h"
-#endif
 
 using namespace std;
 
 namespace Msp {
 namespace Graphics {
 
+bool ImageLoader::registered_loaders_changed = false;
+
 ImageLoader::ImageLoader():
 	source(0)
 { }
@@ -40,24 +36,25 @@ ImageLoader *ImageLoader::open_file(const string &fn)
 
 ImageLoader *ImageLoader::open_io(IO::Seekable &io)
 {
-	char sig_buf[8];
-	unsigned sig_len = io.read(sig_buf, sizeof(sig_buf));
-	string sig(sig_buf, sig_len);
-	io.seek(0, IO::S_BEG);
+	list<RegisterBase *> &loaders = get_registered_loaders();
+	if(registered_loaders_changed)
+	{
+		registered_loaders_changed = false;
+		loaders.sort(signature_size_compare);
+	}
+
+	vector<char> sig_buf(loaders.back()->get_signature_size());
+	unsigned sig_len = io.read(&sig_buf[0], sig_buf.size());
+	string signature(sig_buf.begin(), sig_buf.end());
 
-	// TODO register loader classes automatically
 	ImageLoader *loader = 0;
-	if(0)
-		;
-#ifdef WITH_LIBPNG
-	else if(PngLoader::detect(sig))
-		loader = new PngLoader(io);
-#endif
-#ifdef WITH_DEVIL
-	else if(DevilLoader::detect(sig))
-		loader = new DevilLoader(io);
-#endif
-	else
+	for(list<RegisterBase *>::const_iterator i=loaders.begin(); (!loader && i!=loaders.end()); ++i)
+		if((*i)->detect(signature))
+			loader = (*i)->create(io);
+
+	io.seek(0, IO::S_BEG);
+
+	if(!loader)
 	{
 		string sig_hex;
 		for(unsigned i=0; i<sig_len; ++i)
@@ -72,5 +69,24 @@ ImageLoader *ImageLoader::open_io(IO::Seekable &io)
 	return loader;
 }
 
+
+ImageLoader::RegisterBase::RegisterBase()
+{
+	get_registered_loaders().push_back(this);
+	registered_loaders_changed = true;
+}
+
+
+list<ImageLoader::RegisterBase *> &ImageLoader::get_registered_loaders()
+{
+	static list<RegisterBase *> regs;
+	return regs;
+}
+
+bool ImageLoader::signature_size_compare(RegisterBase *r1, RegisterBase *r2)
+{
+	return r1->get_signature_size()<r2->get_signature_size();
+}
+
 } // namespace Graphics
 } // namespace Msp
diff --git a/source/graphics/imageloader.h b/source/graphics/imageloader.h
index f953990..c06a759 100644
--- a/source/graphics/imageloader.h
+++ b/source/graphics/imageloader.h
@@ -24,9 +24,36 @@ public:
 class ImageLoader
 {
 private:
-	IO::Base *source;
+	class RegisterBase
+	{
+	protected:
+		RegisterBase();
+	public:
+		virtual ~RegisterBase() { }
+
+		virtual unsigned get_signature_size() const = 0;
+		virtual bool detect(const std::string &) const = 0;
+		virtual ImageLoader *create(IO::Seekable &) const = 0;
+	};
+
 protected:
+	template<typename T>
+	class Register: RegisterBase
+	{
+	public:
+		virtual unsigned get_signature_size() const { return T::get_signature_size(); }
+		virtual bool detect(const std::string &s) const { return T::detect(s); }
+		virtual T *create(IO::Seekable &io) const { return new T(io); }
+	};
+
+private:
+	IO::Base *source;
 
+	static std::list<RegisterBase *> &get_registered_loaders();
+	static bool registered_loaders_changed;
+	static bool signature_size_compare(RegisterBase *, RegisterBase *);
+
+protected:
 	ImageLoader();
 public:
 	virtual ~ImageLoader();
diff --git a/source/graphics/png/pngloader.cpp b/source/graphics/png/pngloader.cpp
index 3f2f959..15684b1 100644
--- a/source/graphics/png/pngloader.cpp
+++ b/source/graphics/png/pngloader.cpp
@@ -31,6 +31,8 @@ struct PngLoader::Private
 	png_info *info;
 };
 
+ImageLoader::Register<PngLoader> PngLoader::reg;
+
 PngLoader::PngLoader(IO::Base &io, unsigned sig_bytes):
 	priv(new Private)
 {
diff --git a/source/graphics/png/pngloader.h b/source/graphics/png/pngloader.h
index a81c34c..683f4d3 100644
--- a/source/graphics/png/pngloader.h
+++ b/source/graphics/png/pngloader.h
@@ -13,10 +13,13 @@ private:
 
 	Private *priv;
 
+	static Register<PngLoader> reg;
+
 public:
 	PngLoader(IO::Base &, unsigned = 0);
 	virtual ~PngLoader();
 
+	static unsigned get_signature_size() { return 8; }
 	static bool detect(const std::string &);
 
 	virtual void load(Image::Data &);
-- 
2.45.2