ref: a409cfe16978d8e98a3754c6053cd00b09d32b26
dir: /spectre-internal.h/
#include "spectre.h"
/*
* List macro of the names for hexagon types, which will be reused all
* over the place.
*
* (I have to call the parameter to this list macro something other
* than X, because here, X is also one of the macro arguments!)
*/
#define HEX_LETTERS(Z) Z(G) Z(D) Z(J) Z(L) Z(X) Z(P) Z(S) Z(F) Z(Y)
typedef enum Hex {
#define HEX_ENUM_DECL(x) HEX_##x,
HEX_LETTERS(HEX_ENUM_DECL)
#undef HEX_ENUM_DECL
} Hex;
static inline unsigned num_subhexes(Hex h)
{
return h == HEX_G ? 7 : 8;
}
static inline unsigned num_spectres(Hex h)
{
return h == HEX_G ? 2 : 1;
}
/*
* Data types used in the lookup tables.
*/
struct MapEntry {
bool internal;
unsigned char hi, lo;
};
struct MapEdge {
unsigned char startindex, len;
};
struct Possibility {
unsigned char hi, lo;
unsigned long prob;
};
/*
* Coordinate system for tracking Spectres and their hexagonal
* metatiles.
*
* SpectreCoords will store the index of a single Spectre within a
* smallest-size hexagon, plus an array of HexCoord each indexing a
* hexagon within the expansion of a larger hexagon.
*
* The last coordinate stored, sc->c[sc->nc-1], will have a hex type
* but no index (represented by index==-1). This means "we haven't
* decided yet what this level of metatile needs to be". If we need to
* refer to this level during the hatctx_step algorithm, we make it up
* at random, based on a table of what metatiles each type can
* possibly be part of, at what index.
*/
typedef struct HexCoord {
int index; /* index within that tile, or -1 if not yet known */
Hex type; /* type of this hexagon */
} HexCoord;
typedef struct SpectreCoords {
int index; /* index of Spectre within the order-0 hexagon */
HexCoord *c;
size_t nc, csize;
/* Used by spectre-test to four-colour output tilings, and
* maintained unconditionally because it's easier than making it
* conditional */
unsigned char hex_colour, prev_hex_colour, incoming_hex_edge;
} SpectreCoords;
SpectreCoords *spectre_coords_new(void);
void spectre_coords_free(SpectreCoords *hc);
void spectre_coords_make_space(SpectreCoords *hc, size_t size);
SpectreCoords *spectre_coords_copy(SpectreCoords *hc_in);
/*
* Coordinate system for locating Spectres in the plane.
*
* The 'Point' structure represents a single point by means of an
* integer linear combination of {1, d, d^2, d^3}, where d is the
* complex number exp(i pi/6) representing 1/12 of a turn about the
* origin.
*
* The 'Spectre' structure represents an entire Spectre in a tiling,
* giving both the locations of all of its vertices and its
* combinatorial coordinates. It also contains a linked-list pointer,
* used during breadth-first search to generate all the Spectres in an
* area.
*/
typedef struct Point {
int coeffs[4];
} Point;
typedef struct Spectre Spectre;
struct Spectre {
Point vertices[14];
SpectreCoords *sc;
Spectre *next; /* used in breadth-first search */
};
/* Fill in all the coordinates of a Spectre starting from any single edge */
void spectre_place(Spectre *spec, Point u, Point v, int index_of_u);
/* Free a Spectre and its contained coordinates */
void spectre_free(Spectre *spec);
/*
* A Point is really a complex number, so we can add, subtract and
* multiply them.
*/
static inline Point point_add(Point a, Point b)
{
Point r;
size_t i;
for (i = 0; i < 4; i++)
r.coeffs[i] = a.coeffs[i] + b.coeffs[i];
return r;
}
static inline Point point_sub(Point a, Point b)
{
Point r;
size_t i;
for (i = 0; i < 4; i++)
r.coeffs[i] = a.coeffs[i] - b.coeffs[i];
return r;
}
static inline Point point_mul_by_d(Point x)
{
Point r;
/* Multiply by d by using the identity d^4 - d^2 + 1 = 0, so d^4 = d^2+1 */
r.coeffs[0] = -x.coeffs[3];
r.coeffs[1] = x.coeffs[0];
r.coeffs[2] = x.coeffs[1] + x.coeffs[3];
r.coeffs[3] = x.coeffs[2];
return r;
}
static inline Point point_mul(Point a, Point b)
{
size_t i, j;
Point r;
/* Initialise r to be a, scaled by b's d^3 term */
for (j = 0; j < 4; j++)
r.coeffs[j] = a.coeffs[j] * b.coeffs[3];
/* Now iterate r = d*r + (next coefficient down), by Horner's rule */
for (i = 3; i-- > 0 ;) {
r = point_mul_by_d(r);
for (j = 0; j < 4; j++)
r.coeffs[j] += a.coeffs[j] * b.coeffs[i];
}
return r;
}
static inline bool point_equal(Point a, Point b)
{
size_t i;
for (i = 0; i < 4; i++)
if (a.coeffs[i] != b.coeffs[i])
return false;
return true;
}
/*
* Return the Point corresponding to a rotation of s steps around the
* origin, i.e. a rotation by 30*s degrees or s*pi/6 radians.
*/
static inline Point point_rot(int s)
{
Point r = {{ 1, 0, 0, 0 }};
Point dpower = {{ 0, 1, 0, 0 }};
/* Reduce to a sensible range */
s = s % 12;
if (s < 0)
s += 12;
while (true) {
if (s & 1)
r = point_mul(r, dpower);
s >>= 1;
if (!s)
break;
dpower = point_mul(dpower, dpower);
}
return r;
}
/*
* SpectreContext is the shared context of a whole run of the
* algorithm. Its 'prototype' SpectreCoords object represents the
* coordinates of the starting Spectre, and is extended as necessary;
* any other SpectreCoord that needs extending will copy the
* higher-order values from ctx->prototype as needed, so that once
* each choice has been made, it remains consistent.
*
* When we're inventing a random piece of tiling in the first place,
* we append to ctx->prototype by choosing a random (but legal)
* higher-level metatile for the current topmost one to turn out to be
* part of. When we're replaying a generation whose parameters are
* already stored, we don't have a random_state, and we make fixed
* decisions if not enough coordinates were provided, as in the
* corresponding hat.c system.
*
* For a normal (non-testing) caller, spectrectx_generate() is the
* main useful function. It breadth-first searches a whole area to
* generate all the Spectres in it, starting from a (typically
* central) one with the coordinates of ctx->prototype. The callback
* function processes each Spectre as it's generated, and returns true
* or false to indicate whether that Spectre is within the bounds of
* the target area (and therefore the search should continue exploring
* its neighbours).
*/
typedef struct SpectreContext {
random_state *rs;
bool must_free_rs;
Point start_vertices[2]; /* vertices 0,1 of the starting Spectre */
int orientation; /* orientation to put in SpectrePatchParams */
SpectreCoords *prototype;
} SpectreContext;
void spectrectx_init_random(SpectreContext *ctx, random_state *rs);
void spectrectx_init_from_params(
SpectreContext *ctx, const struct SpectrePatchParams *ps);
void spectrectx_cleanup(SpectreContext *ctx);
SpectreCoords *spectrectx_initial_coords(SpectreContext *ctx);
void spectrectx_extend_coords(SpectreContext *ctx, SpectreCoords *hc,
size_t n);
void spectrectx_step(SpectreContext *ctx, SpectreCoords *sc,
unsigned edge, unsigned *outedge);
void spectrectx_generate(SpectreContext *ctx,
bool (*callback)(void *cbctx, const Spectre *spec),
void *cbctx);
/* For spectre-test to directly generate a tiling of hexes */
void spectrectx_step_hex(SpectreContext *ctx, SpectreCoords *sc,
size_t depth, unsigned edge, unsigned *outedge);
/* Subroutines that step around the tiling specified by a SpectreCtx,
* delivering both plane and combinatorial coordinates as they go */
Spectre *spectre_initial(SpectreContext *ctx);
Spectre *spectre_adjacent(SpectreContext *ctx, const Spectre *src_spec,
unsigned src_edge, unsigned *dst_edge);
/* For extracting the point coordinates */
typedef struct Coord {
int c1, cr3; /* coefficients of 1 and sqrt(3) respectively */
} Coord;
static inline Coord point_x(Point p)
{
Coord x = { 2 * p.coeffs[0] + p.coeffs[2], p.coeffs[1] };
return x;
}
static inline Coord point_y(Point p)
{
Coord y = { 2 * p.coeffs[3] + p.coeffs[1], p.coeffs[2] };
return y;
}
static inline int coord_sign(Coord x)
{
if (x.c1 == 0 && x.cr3 == 0)
return 0;
if (x.c1 >= 0 && x.cr3 >= 0)
return +1;
if (x.c1 <= 0 && x.cr3 <= 0)
return -1;
if (x.c1 * x.c1 > 3 * x.cr3 * x.cr3)
return x.c1 < 0 ? -1 : +1;
else
return x.cr3 < 0 ? -1 : +1;
}
static inline Coord coord_construct(int c1, int cr3)
{
Coord c = { c1, cr3 };
return c;
}
static inline Coord coord_integer(int c1)
{
return coord_construct(c1, 0);
}
static inline Coord coord_add(Coord a, Coord b)
{
Coord sum;
sum.c1 = a.c1 + b.c1;
sum.cr3 = a.cr3 + b.cr3;
return sum;
}
static inline Coord coord_sub(Coord a, Coord b)
{
Coord diff;
diff.c1 = a.c1 - b.c1;
diff.cr3 = a.cr3 - b.cr3;
return diff;
}
static inline Coord coord_mul(Coord a, Coord b)
{
Coord prod;
prod.c1 = a.c1 * b.c1 + 3 * a.cr3 * b.cr3;
prod.cr3 = a.c1 * b.cr3 + a.cr3 * b.c1;
return prod;
}
static inline Coord coord_abs(Coord a)
{
int sign = coord_sign(a);
Coord abs;
abs.c1 = a.c1 * sign;
abs.cr3 = a.cr3 * sign;
return abs;
}
static inline int coord_cmp(Coord a, Coord b)
{
return coord_sign(coord_sub(a, b));
}