***** PREMLIMARY DRAFT *****


This is a preliminary draft for an alternate patching system to IPS.
If you have any comments on it, or would like to see some changes to 
this draft please email silo@blackbag.org before 31 July 1998.

Full source code to the patcher and creator will be made available
to any coder who wants it before the closure date and publically available
after.



        APS      : Advanced Patching System Version 1.2 
	
	Authors	 : Silo (silo@blackbag.org)
		   Fractal (fractal@blackbag.org)	

	
	
Introduction
~~~~~~~~~~~~
 APS has been designed with several features as standard.

	o No file limitations.
		With the ever expanding file sizes that are appearing ips files
                have problems with patching files that are greater than 16Mb.
		APS does not have this problem and should facilitate patching of
		files up to 2Gb.

	o Target file verification.
		APS will be capable of target verification. In the case of type 1
		(N64 patching) the patch will contain the CRC, Territory code and 
		Cart ID. This will allow the patching program to make sure that 
		the file about to be patched is the intended target.

	o Internal Descriptors.
		A small text field allowing APS authors to describe precisely 
		what the patch does.

	o Future expansion through different patch types and encoding methods.
	



Detailed File Structure
~~~~~~~~~~~~~~~~~~~~~~~

Standard Header
~~~~~~~~~~~~~~~
	BYTE 0-4        : Magic ("APS10")

	BYTE 5          : Patch Type : -
	                    0 for a Simple Patch
	                    1 for a N64 Specific Patch
                          This method allows future expansion for other definable patch types. 

	BYTE 6          : Encoding Method
                            0 for Simple Encoding (Similar to IPS & Defined Below)
                          (Again allowing for future expansion)
	
	BYTE 7-56       : Description
                          Space padded free text for patch information.

Type 0 : Simple Patching Header
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	BYTE 57-61	: Size of destination image.


Type 1 : N64 Header
~~~~~~~~~~~~~~~~~~~
Header specific information for a type 1 (N64 specific) patch.

	BYTE 57         : Original image file format
        	           0 = Doctor V64
                	   1 = CD64/Z64/Wc/SP

	BYTE 58-59      : CartID
        	           This is the two bytes of Cart ID taken directly from
                	   the original image. Stored in Motorola (human readable) 
			   endian.

	BYTE 60         : Country
	                   The original image's country code.Stored in Motorola
	                   (human readable) endian.

	BYTE 61-68      : CRC
        	           The original image's CRC taken directly out of the
        	           original image. Stored in Motorola (human readable) 
			   endian.
	
	BYTE 69-74      : Pad.
        	           For future expansion.

	BYTE 75-79 	: Size of destination image.




The Patch Itself
~~~~~~~~~~~~~~~~
Encoding Method #0. (offset 0x6 within the standard header)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Format : xxxx,y,zzzz
	
	xxxx 	= 4 byte file offset.
	
	y	= Number of bytes that will be changed.

	zzzz	= New data to be written ('y' number of bytes).

If paramter 'y' is set to zero (0) then paramter 'z' will be a two (2)
byte field. Byte zero (0) will be the data and byte one (1) will be the 
number of repetitions.


Examples
~~~~~~~~

Starting from File Offset 0x0015F9D0 replace 3 bytes with 01,02,03
D0 F9 15 00 03 01 02 03

Starting from File Offset 0x0015F9D0 replace 0x10 bytes with 0xFF
D0 F9 15 00 00 FF 10

*******************************************************************

Revision Log:

        13th July 1998.
                Initial Draft.                  Blackbag [Silo/Frac]