Implement board mutation functions

board.c

@@ -0,0 +1,89 @@
+/**
+ * Sudoku board implementation
+ *
+ * Created by Gabriel Tofvesson
+ */
+
+#include <string.h>
+#include "board.h"
+
+/**
+ * Check if a given xy-pair is in bounds of a Sudoku board
+ */
+static inline bool
+is_in_bounds (board_pos x, board_pos y)
+{
+  return  x >= 0 &&
+          x <  9 &&
+          y >= 0 &&
+          y <  9 ;
+}
+
+/**
+ * Check if a given element value is within acceptable bounds
+ */
+static inline bool
+is_valid_value (element_value value)
+{
+  return  value >= 0 &&
+          value <  9 ;
+}
+
+
+void
+board_init (struct board *board)
+{
+  memset (board, 0, sizeof board->elements);
+  board->complexity = 0;
+}
+
+
+void
+board_set (
+  struct board *board,
+  board_pos x,
+  board_pos y,
+  element_value value
+)
+{
+  if (is_in_bounds (x, y) && is_valid_value (value))
+  {
+    struct board_element *elem = BOARD_ELEM (board, x, y);
+    elem->has_value = true;
+    elem->value = value;
+  }
+}
+
+
+void 
+board_mark (
+  struct board *board,
+  board_pos x,
+  board_pos y,
+  element_value value
+)
+{
+  if (is_in_bounds (x, y) && is_valid_value (value))
+  {
+    struct board_element *elem = BOARD_ELEM (board, x, y);
+    elem->potential |= 1 << value;
+  }
+}
+
+
+void 
+board_unmark (
+  struct board *board,
+  board_pos x,
+  board_pos y,
+  element_value value
+)
+{
+  if (is_in_bounds (x, y) && is_valid_value (value))
+  {
+    struct board_element *elem = BOARD_ELEM (board, x, y);
+
+    /* Shift bit to correct place and then invert first 9 bits */
+    elem->potential &= (1 << value) ^ 0x1FF;
+  }
+}

board.h

@@ -36,3 +36,50 @@ struct board {
   struct board_element elements[81];  /* Game board */
   unsigned char complexity;           /* Complexity of simplest element */
 };
+
+/**
+ * Initialize a board to a blank state with 0 complexity
+ */
+void
+board_init (struct board *board);
+
+
+/**
+ * Set the value of an element on the board
+ * 
+ * NOTE: This marks an element as having a decided value
+ */
+void
+board_set (
+  struct board *board,
+  board_pos x,
+  board_pos y,
+  element_value value
+);
+
+/**
+ * Mark a potential value of an element on the board
+ *
+ * NOTE: Marking an element with a decided value is undefined
+ */
+void
+board_mark (
+  struct board *board,
+  board_pos x,
+  board_pos y,
+  element_value value
+);
+
+
+/**
+ * Removes a marking of a potential value of an element on the board
+ *
+ * NOTE: Unmarking an element with a decied value is undefined
+ */
+void
+board_unmark (
+  struct board *board,
+  board_pos x,
+  board_pos y,
+  element_value value
+);