To facilitate data exchange, the [e2rs] library re-uses and/or defines a number of standard file formats. These are designed to be both human-readable and machnie-readable, and to be editable in a text editor.
Tiles are indexed from 1, not 0. Where not otherwise specified, tile indexes refer to tiles in the tileset used in the Eternity 2 Puzzle.
Edges are indexed from 0, with 0 always referring to the "outside" edge type. When the edge set is not explicitly given, it defaults to the edges used in the Eternity 2 Puzzle.
Cells within boards are numbered as column,row or equivalently x,y, starting at the top-left corner. The coordinates index from 1. So cell 1,1 is the top-left cell of the puzzle board.
Rotations are indexed from 0, meaning no rotation to 3, meaning 270°. By default, rotations are anti-clockwise. Individual tools may provide switches to over-ride this.
Tiles have 4 sides, each of which is marked with an edge. These are numbered 0..3, going clockwise. North, East, South, West.
All formats accept comment lines.
These begin with #.
Comment lines are skipped from further parsing, and have no semantic import.
Blank lines are not comment lines, and will be treated by parsers as parsed.
Board shapes are given by one of two dimensions lines:
- <size>
- <columns> <rows>
If the single-value form is given, the board is taken to be square. If the two-value form is given, the board is taken to be rectangular. When dimension lines are optional, then the shape defaults to the Eternity 2 Puzzle dimensions of 16x16.
A clue is the placement of a tile at a particular position and orientation. Each clue line is a single clue in the following format:
<tile_number: u8> <column: u8> <row: u8> <rotation: {0,1,2,3}>
A clue can be validly placed on a board if the tile nubmer refers to a tile in the tileset for that board, and if the column and row are within range for the board's dimensions. Rotations are taken to be in the anti-clockwise direction by default, or unless explicitly marked as clockwise by import options.
A valid clue file is a series of lines, each one containing exactly one clue.
A tile is described by listing its 4 edges. Each tile line is a single tile in the following format:
<north: u8> <east: u8> <south: u8> <west: u8>
A tile is valid with respect to an edge set if each of the edges of a tile is a valid index into the set of edges.
A valid tiles file is a list of valid tile lines, each one containing exactly one tile.
A board specification file is an optional board shape line followed by any number of tile lines.
A solution file is an optional board shape line followed by any number of tile lines.