Revert ftell checks from r5532. Add documentation.

I suppose not checking gives a chance for ftell to go wrong in which case we can get an error (size -1). 
Arguably which solution is better - I reverted it simply because not changing old behavior is probably better than changing it.
Also added documentation about getSize to IReadFile, IWriteFile and IFileReadCallBack that those functions can return -1L on error
(thanks @dixx for mentioning that in http://irrlicht.sourceforge.net/forum/viewtopic.php?f=4&t=52086).


git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@5538 dfc29bdd-3216-0410-991c-e03cc46cb475

include/IReadFile.h

@@ -36,7 +36,7 @@ namespace io
 		virtual long getSize() const = 0;
 
 		//! Get the current position in the file.
-		/** \return Current position in the file in bytes. */
+		/** \return Current position in the file in bytes on success or -1L on failure. */
 		virtual long getPos() const = 0;
 
 		//! Get name of file.

include/IWriteFile.h

@@ -32,7 +32,7 @@ namespace io
 		virtual bool seek(long finalPos, bool relativeMovement = false) = 0;
 
 		//! Get the current position in the file.
-		/** \return Current position in the file in bytes. */
+		/** \return Current position in the file in bytes on success or -1L on failure */
 		virtual long getPos() const = 0;
 
 		//! Get name of file.

include/irrXML.h

@@ -224,7 +224,7 @@ namespace io
 		\return Returns how much bytes were read. */
 		virtual int read(void* buffer, int sizeToRead) = 0;
 
-		//! Returns size of file in bytes
+		//! Returns size of file in bytes on success or -1L on failure.
 		virtual long getSize() const = 0;
 	};
 

source/Irrlicht/CReadFile.cpp

@@ -83,11 +83,9 @@ void CReadFile::openFile()
 	{
 		// get FileSize
 
-		if ( fseek(File, 0, SEEK_END) == 0 )
-		{
-			FileSize = getPos();
-			fseek(File, 0, SEEK_SET);
-		}
+		fseek(File, 0, SEEK_END);
+		FileSize = getPos();
+		fseek(File, 0, SEEK_SET);
 	}
 }
 

source/Irrlicht/CWriteFile.cpp

@@ -91,12 +91,9 @@ void CWriteFile::openFile(bool append)
 	{
 		// get FileSize
 
-		if ( fseek(File, 0, SEEK_END) == 0 )
-		{
-			FileSize = ftell(File);
-			fseek(File, 0, SEEK_SET);
-
-		}
+		fseek(File, 0, SEEK_END);
+		FileSize = ftell(File);
+		fseek(File, 0, SEEK_SET);
 	}
 }
 

source/Irrlicht/irrXML.cpp

@@ -67,11 +67,9 @@ private:
 	//! retrieves the file size of the open file
 	void getFileSize()
 	{
-		if ( fseek(File, 0, SEEK_END) == 0 )
-		{
-			Size = ftell(File);
-			fseek(File, 0, SEEK_SET);
-		}
+		fseek(File, 0, SEEK_END);
+		Size = ftell(File);
+		fseek(File, 0, SEEK_SET);
 	}
 
 	FILE* File;