Binary Representation of Move Data
----------------------------------

Move and annotation data are stored as a sequence of bytes, terminated by 0xff.
The data is stored in the database column Game.GameText.

A halfmove is identified by 
- the moving piece (a-pawn to h-pawn, queen's knigth, king's knight etc.)
- an offset that indicates the direction of the move (see 2. Move Offsets)

Promotion moves and moves by promoted pieces are encoded by TWO bytes.

This encoding was chosen to encode most moves with one byte.
Note that the most straightforward encoding (source plus  destination square) 
would require at least 12 bits per move.


1. Byte Codes

0x00 .. 0x03	move of the a-pawn (see 2.1)
0x04 .. 0x07	move of the b-pawn (see 2.1)
0x08 .. 0x0b	move of the c-pawn (see 2.1)
0x0c .. 0x0f	move of the d-pawn (see 2.1)
0x10 .. 0x13	move of the e-pawn (see 2.1)
0x14 .. 0x17	move of the f-pawn (see 2.1)
0x18 .. 0x1b	move of the g-pawn (see 2.1)
0x1c .. 0x1f	move of the h-pawn (see 2.1)

0x20 .. 0x27	move of the queen's knight (see 2.2)
0x28 .. 0x2f	move of the king's knight (see 2.2)

0x30 .. 0x3f	move of the queen's bishop (see 2.3)
0x40 .. 0x4f	move of the king's bishop (see 2.3)

0x50 .. 0x5f	move of the queen's rook (see 2.4)
0x60 .. 0x6f	move of the king's rook (see 2.4)

0x70 .. 0x8f	move of the queen (see 2.5)
0x90 .. 0x97	move of the king (see 2.6)

0x98			kingside castling
0x99			queenside castling

0x9a            NULLMOVE (usually not stored in database)

0x9b .. 0x9f	reserved

0xa0 [+]		promotion move: a-pawn
				additional data is stored in second byte (see 2.7) 
0xa1 [+]		promotion move: b-pawn
0xa2 [+]		promotion move: c-pawn
0xa3 [+]		promotion move: d-pawn
0xa4 [+]		promotion move: e-pawn
0xa5 [+]		promotion move: f-pawn
0xa6 [+]		promotion move: g-pawn
0xa7 [+]		promotion move: h-pawn

0xa8 [+]		promoted piece move: "a" promotion piece
				additional data is stored in second byte  (see 2.8)
0xa9 [+]		promoted piece move: "b" promotion piece
0xaa [+]		promoted piece move: "c" promotion piece
0xab [+]		promoted piece move: "d" promotion piece
0xac [+]		promoted piece move: "e" promotion piece
0xad [+]		promoted piece move: "f" promotion piece
0xae [+]		promoted piece move: "g" promotion piece
0xaf [+]		promoted piece move: "h" promotion piece

0xb0 [+]		annotation 
				NAG code stored in second byte
				
0xb1 .. 0xcf	annotation (NAG codes 1 to 31)

0xd0			result: black wins
0xd1			result: draw
0xd2			result: white wins
0xd3			result unknown

0xd4 .. 0xdf	reserved 

0xe0 [+]		text comment
				followed by text data (see 3.)

0xe1 [+]		error: move not readable				followed by text data
0xe2 [+]		error: illegal move     				followed by text data
0xe3 [+]		error: ambiguous move					followed by text data
0xe4 [+]		error: unrecgonized input   			followed by text data

0xe5 .. 0xef	reserved

0xf0			start of variation: 
				following move data is a variation to the previous move
0xf1			end of variation

0xf2 .. 0xfe	reserved

0xff			end of data


2. Encoding of Moves


2.1 Offsets of Pawn Moves 

+---+---+---+
|   | 3 |   |
+---+---+---+
| 2 | 0 | 1 |
+---+---+---+
|   | x |   |
+---+---+---+


2.2 Offsets of Knight Moves

+---+---+---+---+---+
|   | 1 |   | 0 |   |
+---+---+---+---+---+
| 2 |   |   |   | 7 |
+---+---+---+---+---+
|   |   | x |   |   |
+---+---+---+---+---+
| 3 |   |   |   | 6 |
+---+---+---+---+---+
|   | 4 |   | 5 |   |
+---+---+---+---+---+


2.3 Offsets of Bishop Moves

+---+---+---+---+---+---+---+---+---+
|   | f |   |   |   |   |   | 7 |   |
+---+---+---+---+---+---+---+---+---+
|   |   | e |   |   |   | 6 |   |   |
+---+---+---+---+---+---+---+---+---+
|   |   |   | d |   | 5 |   |   |   |
+---+---+---+---+---+---+---+---+---+
|   |   |   |   | x |   |   |   |   |
+---+---+---+---+---+---+---+---+---+
|   |   |   | 3 |   | b |   |   |   |
+---+---+---+---+---+---+---+---+---+
|   |   | 2 |   |   |   | a |   |   |
+---+---+---+---+---+---+---+---+---+
|   | 1 |   |   |   |   |   | 9 |   |
+---+---+---+---+---+---+---+---+---+
| 0 |   |   |   |   |   |   |   | 8 |
+---+---+---+---+---+---+---+---+---+


2.4 Offsets of Rook Moves

+---+---+---+---+---+---+---+---+
|   |   |   |   | 7 |   |   |   |
+---+---+---+---+---+---+---+---+
|   |   |   |   | 6 |   |   |   |
+---+---+---+---+---+---+---+---+
|   |   |   |   | 5 |   |   |   |
+---+---+---+---+---+---+---+---+
| 8 | 9 | a | b | x | d | e | f |
+---+---+---+---+---+---+---+---+
|   |   |   |   | 3 |   |   |   |
+---+---+---+---+---+---+---+---+
|   |   |   |   | 2 |   |   |   |
+---+---+---+---+---+---+---+---+
|   |   |   |   | 1 |   |   |   |
+---+---+---+---+---+---+---+---+
|   |   |   |   | 0 |   |   |   |
+---+---+---+---+---+---+---+---+


2.5 Offsets of Queen Moves

+---+---+---+---+---+---+---+---+---+  
|   | f |   |   | 17|   |   | 7 |   |  
+---+---+---+---+---+---+---+---+---+  
|   |   | e |   | 16|   | 6 |   |   |  
+---+---+---+---+---+---+---+---+---+  
|   |   |   | d | 15| 5 |   |   |   |  
+---+---+---+---+---+---+---+---+---+  
| 18| 19| 1a| 1b| x | 1d| 1e| 1f|   |  
+---+---+---+---+---+---+---+---+---+  
|   |   |   | 3 | 13| b |   |   |   |  
+---+---+---+---+---+---+---+---+---+  
|   |   | 2 |   | 12|   | a |   |   |  
+---+---+---+---+---+---+---+---+---+  
|   | 1 |   |   | 11|   |   | 9 |   |  
+---+---+---+---+---+---+---+---+---+  
| 0 |   |   |   | 10|   |   |   | 8 |  
+---+---+---+---+---+---+---+---+---+  


2.6 Offsets of King Moves

+---+---+---+
| 1 | 4 | 0 |
+---+---+---+
| 6 | x | 7 |
+---+---+---+
| 2 | 5 | 3 |
+---+---+---+

Kingside Castling = 8
Queenside Castling = 9

2.7 Promotion info stored in second byte

| . . 1 0 |		uppermost 4 bits are reserved
| x x |			move offset (see 2.1)
| y y |			promotion piece (0=knight ..  3=queen)

this byte must never be 0.


2.8 Move info stored in second byte (promoted piece move)
				
| . . 1 |		uppermost 3 bits are reserved
| x x x x x |	move offset (see 2.2 to 2.5)

this byte must never be 0.


3. Encoding of text data

Comment text is stored as a sequence of UTF-8 encoded bytes, terminated by 0x00

| b1 | b2 | ... | 0x00 |