From 5b8d41afb70aaf79d2c3aac616de488f4c1de286 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20T=C5=AFma?= <tumic@cbox.cz>
Date: Sat, 29 Jul 2017 22:19:03 +0200
Subject: [PATCH] Detect OZF files by contents rather than by file extension

---
 src/offlinemap.cpp |  8 +-------
 src/ozf.cpp        | 16 ++++++++++++++++
 src/ozf.h          |  2 ++
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/src/offlinemap.cpp b/src/offlinemap.cpp
index c38ac6c5..a0d0e240 100644
--- a/src/offlinemap.cpp
+++ b/src/offlinemap.cpp
@@ -342,13 +342,7 @@ bool OfflineMap::getImageInfo(const QString &path)
 		return false;
 	}
 
-	QString suffix = ii.suffix().toLower();
-	if (suffix == "ozf4" || suffix == "ozfx4") {
-		_errorString = QString("%1: OZF4 image files not supported")
-		  .arg(QFileInfo(_imgPath).fileName());
-		return false;
-	} else if (suffix == "ozf2" || suffix == "ozfx2" || suffix == "ozf3"
-	  || suffix == "ozfx3") {
+	if (OZF::isOZF(_imgPath)) {
 		_ozf.load(_imgPath);
 		_size = _ozf.size();
 	} else {
diff --git a/src/ozf.cpp b/src/ozf.cpp
index 90adf8de..4dea0551 100644
--- a/src/ozf.cpp
+++ b/src/ozf.cpp
@@ -232,3 +232,19 @@ QPixmap OZF::tile(int x, int y)
 
 	return QPixmap::fromImage(img.mirrored());
 }
+
+bool OZF::isOZF(const QString &path)
+{
+	QFile file(path);
+	quint16 magic;
+
+	if (!file.open(QIODevice::ReadOnly))
+		return false;
+	if (file.read((char*)&magic, sizeof(magic)) < (qint64)sizeof(magic))
+		return false;
+
+	if (magic == OZF2_MAGIC || magic == OZF3_MAGIC)
+		return true;
+
+	return false;
+}
diff --git a/src/ozf.h b/src/ozf.h
index ccce0246..f995df4e 100644
--- a/src/ozf.h
+++ b/src/ozf.h
@@ -22,6 +22,8 @@ public:
 	QSize tileSize() const {return QSize(64, 64);}
 	QPixmap tile(int x, int y);
 
+	static bool isOZF(const QString &path);
+
 private:
 	template<class T> bool readValue(T &val);
 	bool read(void *data, size_t size);