Started the scanner.

scanner.h

@@ -0,0 +1,55 @@
+#pragma once
+
+#include <ios>
+#include <string>
+#include <queue>
+#include <stack>
+
+namespace YAML
+{
+	class Token;
+
+	namespace Keys
+	{
+		const char Comment = '#';
+	}
+
+	class Scanner
+	{
+	public:
+		Scanner(std::istream& in);
+		~Scanner();
+
+		Token *ScanNextToken();
+		void ScanToNextToken();
+
+		void Scan();
+
+	private:
+		char GetChar();
+		void EatLineBreak();
+		void EatDocumentStart();
+		void EatDocumentEnd();
+
+		bool IsWhitespaceToBeEaten();
+		bool IsLineBreak();
+		bool IsBlank();
+		bool IsDocumentStart();
+		bool IsDocumentEnd();
+		template <typename T> T *ScanToken(T *pToken);
+
+	private:
+		// the stream
+		std::istream& INPUT;
+		int m_column;
+
+		// the output (tokens)
+		std::queue <Token *> m_tokens;
+
+		// state info
+		bool m_startedStream;
+		bool m_simpleKeyAllowed;
+		int m_flowLevel;                // number of unclosed '[' and '{' indicators
+		std::stack <int> m_indents;
+	};
+}