From: Scott Worley <scottworley@scottworley.com>
Date: Thu, 31 Dec 2015 08:22:27 +0000 (-0800)
Subject: Input validation
X-Git-Url: http://git.scottworley.com/slidingtile/commitdiff_plain/b18667f24728cb960b0c60fa55824062582278bf?hp=19bd29f9b2a3e4721943496debfc55e2a7d71da5

Input validation
---

diff --git a/sliding_tile_lib.cc b/sliding_tile_lib.cc
index 24642f1..3b7806b 100644
--- a/sliding_tile_lib.cc
+++ b/sliding_tile_lib.cc
@@ -21,6 +21,29 @@ signed char adjacent[BOARD_SIZE][5] = {
   11,  14,  -1,  -1,  -1,
 };
 
+bool Board::is_valid() {
+  bool seen[BOARD_SIZE];
+  for (int i = 0; i < BOARD_SIZE; i++) {
+    seen[i] = false;
+  }
+
+  for (int i = 0; i < BOARD_SIZE; i++) {
+    if (board[i] < 0 || board[i] >= BOARD_SIZE || seen[board[i]]) {
+      return false;
+    }
+    seen[board[i]] = true;
+  }
+
+  // Redundant because pigeon-hole-principle, but check anyway
+  for (int i = 0; i < BOARD_SIZE; i++) {
+    if (!seen[i]) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
 std::istream& operator>>(std::istream& is, Board& board) {
   for (int i = 0; i < BOARD_SIZE; i++) {
     if (!is.good()) {
@@ -35,5 +58,8 @@ std::istream& operator>>(std::istream& is, Board& board) {
     is >> numeric;
     board.board[i] = numeric;
   }
+  if (!board.is_valid()) {
+    is.setstate(std::istream::failbit);
+  }
   return is;
 }
diff --git a/sliding_tile_lib.h b/sliding_tile_lib.h
index 1ffe6fa..89c65c1 100644
--- a/sliding_tile_lib.h
+++ b/sliding_tile_lib.h
@@ -8,6 +8,7 @@ const int BOARD_SIZE = BOARD_DIM * BOARD_DIM;
 
 struct Board {
   signed char board[BOARD_SIZE];
+  bool is_valid();
 };
 std::istream& operator>>(std::istream& is, Board& board);
 
diff --git a/sliding_tile_lib_test.cc b/sliding_tile_lib_test.cc
index a0a6b52..7f032a4 100644
--- a/sliding_tile_lib_test.cc
+++ b/sliding_tile_lib_test.cc
@@ -55,3 +55,24 @@ TEST(Board, NonNumericInput) {
   is >> b;
   EXPECT_TRUE(is.fail());
 }
+
+TEST(Board, RepeatedTileInput) {
+  std::istringstream is{"15,15,9,13,3,1,12,8,0,11,6,4,7,5,2,10"};
+  Board b;
+  is >> b;
+  EXPECT_TRUE(is.fail());
+}
+
+TEST(Board, LowTileInput) {
+  std::istringstream is{"-1,14,9,13,3,1,12,8,0,11,6,4,7,5,2,10"};
+  Board b;
+  is >> b;
+  EXPECT_TRUE(is.fail());
+}
+
+TEST(Board, HighTileInput) {
+  std::istringstream is{"16,14,9,13,3,1,12,8,0,11,6,4,7,5,2,10"};
+  Board b;
+  is >> b;
+  EXPECT_TRUE(is.fail());
+}