4 files changed, 92 insertions, 7 deletions

diff --git a/TODO.md b/TODO.md
index 30803fb..4421b49 100644
--- a/TODO.md
+++ b/TODO.md
@@ -4,6 +4,12 @@ This is a list of things that I would like to add or change at some point.
 It's more of a personal reminder than anything else.
 
 ## After symcoord
+### fst_cube
+* slightly different from cube in v2.0.2: each "side" coordinate
+  is a transformation of the other, not an eorl or similar (changes
+  the permutation!)
+* inverse: for edges, just generate ep[12] and convert back
+* corners: big table (150Mb if 16bit integers are used)
 ### Solving standard coordinates
 * add Void * extradata to DfsArg and a custom move function
 * add optional custom pre-process for generating special table (nx)
@@ -12,13 +18,6 @@ It's more of a personal reminder than anything else.
 * implement nxopt with all tables and all tricks
   (maybe compile time variable for maximum memory to use?)
 * is_valid should also unniss / cleanup the alg
-### fst_cube
-* slightly different from cube in v2.0.2: each "side" coordinate
-  is a transformation of the other, not an eorl or similar (changes
-  the permutation!)
-* add fst_index for some coordinates?
-* inverse: for edges, just generate ep[12] and convert back
-* corners: big table (150Mb if 16bit integers are used)
 
 ## For version 2.1
 ### Changes to Step and Solve
diff --git a/src/cubetypes.h b/src/cubetypes.h
index f9b4011..bb1ad10 100644
--- a/src/cubetypes.h
+++ b/src/cubetypes.h
@@ -90,6 +90,7 @@ typedef struct commandargs        CommandArgs;
 typedef struct coordinate         Coordinate;
 typedef struct cube               Cube;
 typedef struct dfsarg             DfsArg;
+typedef struct fstcube            FstCube;
 typedef struct indexer            Indexer;
 typedef struct movable            Movable;
 typedef struct moveset            Moveset;
@@ -226,6 +227,21 @@ dfsarg
 };
 
 struct
+fstcube
+{
+        uint16_t                  uf_eofb;
+        uint16_t                  uf_eposepe;
+        uint16_t                  uf_coud;
+        uint16_t                  uf_cp;
+        uint16_t                  fr_eofb;
+        uint16_t                  fr_eposepe;
+        uint16_t                  fr_coud;
+        uint16_t                  rd_eofb;
+        uint16_t                  rd_eposepe;
+        uint16_t                  rd_coud;
+}
+
+struct
 indexer
 {
         int                       n;
diff --git a/src/fst.c b/src/fst.c
new file mode 100644
index 0000000..91c022a
--- /dev/null
+++ b/src/fst.c
@@ -0,0 +1,58 @@
+#define FST_C
+
+#include "fst.h"
+
+static void             fst_to_ep(FstCube fst, int *ep);
+
+FstCube
+cube_to_fst(Cube *cube)
+{
+        Cube c;
+        FstCube ret;
+
+        copy_cube(cube, &c);
+        ret.uf_eofb    = index_eofb(&c);
+        ret.uf_eposepe = index_eposepe(&c);
+        ret.uf_coud    = index_coud(&c);
+        ret.uf_cp      = index_cp(&c);
+        copy_cube(cube, &c);
+        transform_cube(fr, &c);
+        ret.fr_eofb    = index_eofb(&c);
+        ret.fr_eposepe = index_eposepe(&c);
+        ret.fr_coud    = index_coud(&c);
+        transform_cube(rd, &c);
+        ret.rd_eofb    = index_eofb(&c);
+        ret.rd_eposepe = index_eposepe(&c);
+        ret.rd_coud    = index_coud(&c);
+
+        return ret;
+}
+
+FstCube
+fst_inverse(FstCube fst)
+{
+        /* TODO */
+}
+
+FstCube
+fst_move(Move m, FstCube fst)
+{
+        /* TODO */
+}
+
+void
+fst_to_cube(FstCube fst, Cube *cube)
+{
+        invindex_eofb((uint64_t)fst.uf_eofb, cube);
+        fst_to_ep(fst, cube->ep);
+        invindex_coud((uint64_t)fst.uf_coud, cube);
+        invindex_cp((uint64_t)fst.uf_cp, cube);
+}
+
+static void
+fst_to_ep(FstCube fst, int *ep)
+{
+        /* TODO */
+}
+
+#endif
diff --git a/src/fst.h b/src/fst.h
new file mode 100644
index 0000000..94f6c30
--- /dev/null
+++ b/src/fst.h
@@ -0,0 +1,12 @@
+#ifndef FST_H
+#define FST_H
+
+#include "coord.h"
+
+FstCube     cube_to_fst(Cube *cube);
+FstCube     fst_inverse(FstCube fst);
+FstCube     fst_move(Move m, FstCube fst);
+void        fst_to_cube(FstCube fst, Cube *cube);
+
+#endif
+