completed ToH board ADT implementation

toh_board.c

@@ -14,7 +14,136 @@
 
 #include "config.h"
 #include "toh_disk.h"
+#include <stdlib.h>
+
+#ifdef NULL
+#undef NULL
+#define NULL ((void *)0)
+#endif
 
 /** Abstraction of a rod type */
 /* Hint: Define a type 'Rod' as a pointer to Disk 
    for usage in exchange with Disk array */
+
+struct TohBoardData {
+   Rod rods[3][MAX_DISKS];
+};
+
+static TohBoard static_board = NULL;
+
+/**
+ * Provides the instance of the 'Tower of Hanoi' board.
+ * Exactly one instance is supported.
+ * 
+ * @return TohBoard The board instance.
+ */
+TohBoard tb_get_board() {
+   if (tb_is_valid(static_board)) {
+      return static_board;
+   }
+
+   static_board = (TohBoard)calloc(sizeof(struct TohBoardData), 1);
+   for (int i = 0; i < 3; i++) {
+      for (int j = 0; j < MAX_DISKS; j++) {
+         static_board->rods[i][j] = NULL;
+      }
+   }
+   return static_board;
+}
+
+/**
+ * Removes all disks from any rod of the given board.
+ * 
+ * @param board The board instance in focus.
+ */
+void tb_clear_board(TohBoard board) {
+   for (int i = 0; i < 3; i++) {
+      for (int j = 0; j < MAX_DISKS; j++) {
+         board->rods[i][j] = NULL;
+      }
+   }
+}
+
+/**
+ * Determines whether or not the given board is valid.
+ * A board is NOT valid, if it is 0.
+ * 
+ * @param board The board to evaluate.
+ * @return If the given board is valid, false otherwise.
+ */
+bool tb_is_valid(TohBoard board) {
+   return board != NULL;
+}
+
+/**
+ * Provides the top-most disk of the given rod and removes it from this rod.
+ * 
+ * @param board The board instance in focus.
+ * @param rodName The rod from which the disk shall be taken and removed.
+ * @return The removed disk or 0, if no disk was on the rod.
+ */
+Disk tb_pop_disk(TohBoard board, RodName rodName) {
+   if (!tb_is_valid(board)) {
+      return NULL;
+   }
+
+   Disk disk = NULL;
+   for (int i = MAX_DISKS - 1; i >= 0; i--) {
+      if (board->rods[rodName][i] != NULL) {
+         disk = board->rods[rodName][i];
+         board->rods[rodName][i] = NULL;
+         break;
+      }
+   }
+
+   return disk;
+}
+
+/**
+ * Applies the given disk to the given rod, if this 
+ * is allowed according to the rules.
+ * 
+ * @param board The board instance in focus.
+ * @param rodName The rod on which the disk shall be placed.
+ * @param disk The disk to place on the rod.
+ * @return True if the disk could be legally placed on the rod 
+ * (move is allowed and disk is valid), false otherwise.
+ */
+bool tb_push_disk(TohBoard board, RodName rodName, Disk disk) {
+   if (!tb_is_valid(board) || !td_is_valid(disk)) {
+      return false;
+   }
+
+   for (int i = 0; i < MAX_DISKS; i++) {
+      if (board->rods[rodName][i] == NULL) {
+         // Check if it is at the bottom or if the it is smaller than the one below
+         if (i > 0 && !td_is_smaller(board->rods[rodName][i - 1], disk)) {
+            return false;
+         }
+
+         board->rods[rodName][i] = disk;
+         return true;
+      }
+   }
+
+   return false;
+}
+
+/**
+ * Provides the disk from the named rod at the given position.
+ * 
+ * @param board The board instance in focus.
+ * @param rodName The rod on which the disk shall be placed.
+ * @param idx The index of the desired disk on the named rod. 
+ *        Index 0 addresses the bottom-most disk.
+ * @return The addressed disk or 0, if not disk is located on the
+ *         index position of the named rod.
+ */
+Disk tb_get_disk(TohBoard board, RodName rodName, unsigned short idx) {
+   if (!tb_is_valid(board) || idx >= MAX_DISKS) {
+      return NULL;
+   }
+
+   // no need to check, as everything is going to be initalized with 0
+   return board->rods[rodName][idx];
+}

toh_board.h

@@ -26,7 +26,9 @@ typedef enum {
     LEFT,
     MIDDLE,
     RIGHT
-} Rod;
+} RodName;
+
+typedef Disk Rod;
 
 /** Declares type for the 'Tower of Hanoi' board */
 typedef struct TohBoardData* TohBoard;
@@ -62,7 +64,7 @@ bool tb_is_valid(TohBoard board);
  * @param rodName The rod from which the disk shall be taken and removed.
  * @return The removed disk or 0, if no disk was on the rod.
  */
-TohBoard tb_pop_disk(TohBoard board, Rod rodName);
+Disk tb_pop_disk(TohBoard board, RodName rodName);
 
 /**
  * Applies the given disk to the given rod, if this 
@@ -74,7 +76,7 @@ TohBoard tb_pop_disk(TohBoard board, Rod rodName);
  * @return True if the disk could be legally placed on the rod 
  * (move is allowed and disk is valid), false otherwise.
  */
-bool tb_push_disk(TohBoard board, Rod rodName, TohDisk disk);
+bool tb_push_disk(TohBoard board, RodName rodName, Disk disk);
 
 /**
  * Provides the disk from the named rod at the given position.
@@ -86,6 +88,6 @@ bool tb_push_disk(TohBoard board, Rod rodName, TohDisk disk);
  * @return The addressed disk or 0, if not disk is located on the
  *         index position of the named rod.
  */
-TohDisk tb_get_disk(TohBoard board, Rod rodName, unsigned short idx);
+Disk tb_get_disk(TohBoard board, RodName rodName, unsigned short idx);
 
 #endif