/***************************************************************************

	API doc for low level file management.  See chunk.txt for chunky file
	management.

***************************************************************************/


/****************************************
	Classes and types
****************************************/


	class FIL;
	typedef class FIL *PFIL;
		Low level file class.

	class FLO;
		File location class.  Has fields for a pfil, fp and cb.
		Legal as auto.

	typedef long FP;
		A file position (index into a file).


/****************************************
	Other hungarian
****************************************/

	short bo;
		Indicates byte order.

	short osk;
		Indicates an operating system.  Typically used to determine
		how to translate strings (from one character set to another).
		See TranslateStz and its cousins in utilstr.  These have the
		same value in either byte order.  Ie, their high and low bytes
		are the same.

	short el;
		Error level.  These, in order of severity, include elNil, kelWrite,
		kelRead, kelSeek, kelCritical.

	ushort grffil;
		A group of flags indicating file options.


/****************************************
	Constants
****************************************/

	short kboCur;		// byte order same as current machine
	short kboOther;		// byte order opposite from current machine

	short koskCur;		// current machine
	short koskMac;		// Mac OS
	short koskWin;		// Win OS

	ushort ffilNil;			// default options
	ushort ffilWriteEnable;	// open with write permissions
	ushort ffilTemp;		// make it a temp file
	ushort ffilMark;		// mark the file (see below)


/****************************************
	Concepts
****************************************/

Files have both a mark flag and an open count.  If you open a file that
is already open, the open count of the file is incremented.  Calling
pfil->Close() decrements the open count.  A pfil is only freed when
both the open count is zero and the mark flag is clear.  To set the
mark flag, specify ffilMark when opening or creating the file, or call
pfil->Mark().

To use Quill-style Mark-and-Free, open the file with ffilMark specified
and call pfil->Close().  At cleanup time, client code should call
FIL::ClearMarks() to clear all the mark flags, then enumerate files
still needed and call Mark() on them, then call FIL::CloseUnmarked().
Files that were marked or have non-zero open count will not be closed
by FIL::CloseUnmarked().

For a file used locally, open the file normally.  When you are done with
it, call close.  There is no need to monkey with the marking stuff if
you just need to do a quick file access.


Files have a delayed error handling mechanism.  If you have several
file accesses to make, you can generally do them all without checking
for errors.  If an error occurs, future file accesses will short circuit.
At the end of a section of several accesses, you should call ElError() to
check for an error.


/****************************************
	FIL static methods
****************************************/

	PFIL FIL::PfilFirst(void);
		The first pfil (they form a linked list).

	PFIL FIL::PfilFromFni(FNI *pfni);
		If the file indicated by *pfni is open, this returns a pointer
		to the FIL.  Otherwise it returns pNil.

	PFIL FIL::PfilOpen(FNI *pfni, ushort grffil);
		Opens the indicated file with the indicated options.  Read-only is
		the default.  To allow writing to a file, use ffilWriteEnable.
		If the file is already open, this ensures that the read/write
		permissions are high enough and increments the open count.  This
		call should be balanced with a call to pfil->Close().  Specifying
		ffilMark causes the file to be marked.  ffilTemp is illegal.

	PFIL FIL::PfilCreate(FNI *pfni, ushort grffil);
		Creates and opens the indicated file (asserts that it isn't
		already open) and sets the open count to 1.  Assumes
		ffilWriteEnable.  ffilMark is legal.  Use ffilTemp to create a temp
		file, which will be automatically deleted when it is closed.

	void FIL::ClearMarks(void);
		Clears the mark flag on all files.  See discussion under concepts.

	void FIL::CloseUnmarked(void);
		Closes all files that are not marked and have zero open count.
		See discussion under concepts.


/****************************************
	FIL methods
****************************************/

	PFIL FIL::Next(void);
		Returns the next file (in the linked list).

	void FIL::Open(void);
		Increment the open count, nothing more.

	void FIL::Close(void);
		Decrements the open count.  If the file is not marked and the
		open count becomes zero, the file is closed.

	void FIL::Mark(void);
		Sets the mark flag.

	short FIL::ElError(void);
		Returns the error level of the file.  elNil means no error.

	void FIL::SetTemp(bool f);
		Set or clear the temp flag.  Temp files are automatically deleted
		when closed.

	bool FIL::FTemp(void);
		Returns the temp flag.

	void FIL::GetFni(FNI *pfni);
		Gets the file name.

	void FIL::SetFpPos(FP fp);
		Sets the file position.

	FP FIL::FpPos(void);
		Returns the current file position.  If there has been a seek error
		(or higher level error), returns 0.

	bool FIL::FSetFpMac(FP fp);
		Sets the end of file.  Files can not be shrunk using this.  This
		asserts that the passed fp is greater than the current end of file.

	FP FIL::FpMac(void);
		Returns the length of the file.  If there has been a seek error
		(or higher level error), returns 0.

	bool FIL::FReadRgb(void *pv, long cb);
		Reads cb bytes from the current file position.  Advances the file
		position.  Asserts if you read past the end of file.

	bool FIL::FWriteRgb(void *pv, long cb);
		Writes cb bytes to the current file position.  Advances the file
		position (and eof if its reached).

	bool FIL::FSwapNames(PFIL pfil);
		Renames the files to swap names.  Typically used during a safe save.
		The files should live in the same directory.

	bool FIL::FRename(FNI *pfni);
		Renames the file.  The fni should be in the same directory as the
		file.


/****************************************
	FLO methods
****************************************/

FLO is an auto class: new is illegal; auto, member and global declarations
are legal.

	bool FLO::FRead(void *pv);
		Read data from the flo into pv.

	bool FLO::FWrite(void *pv);
		Write data from pv to the file.

	bool FLO::FReadRgb(void *pv, long cb, FP dfp);
		Read cb bytes of data from dfp into the flo into pv.  Asserts the
		range is totally contained within the flo.

	bool FLO::FWriteRgb(void *pv, long cb, FP dfp);
		Write cb bytes of data from pv to dfp into the flo.  Asserts the
		range is totally contained within the flo.

	bool FLO::FCopy(FLO *pfloDest);
		Copy data from one flo to the other.  Asserts the cb's are
		equal.