using System.IO;
using System.Text;
using System.Runtime.InteropServices;
namespace PriFileFormat
{
	internal static class Replenish
	{
		public static string ReadString (this BinaryReader reader, Encoding encoding, int length)
		{
			using (BinaryReader r = new BinaryReader (reader.BaseStream, encoding, true))
				return new string (r.ReadChars (length));
		}

		public static string ReadNullTerminatedString (this BinaryReader reader, Encoding encoding)
		{
			using (BinaryReader r = new BinaryReader (reader.BaseStream, encoding, true))
			{
				StringBuilder result = new StringBuilder ();
				char c;
				while ((c = r.ReadChar ()) != '\0')
					result.Append (c);
				return result.ToString ();
			}
		}

		public static void ExpectByte (this BinaryReader reader, byte expectedValue)
		{
			if (reader.ReadByte () != expectedValue)
				throw new InvalidDataException ("Unexpected value read.");
		}

		public static void ExpectUInt16 (this BinaryReader reader, ushort expectedValue)
		{
			if (reader.ReadUInt16 () != expectedValue)
				throw new InvalidDataException ("Unexpected value read.");
		}

		public static void ExpectUInt32 (this BinaryReader reader, uint expectedValue)
		{
			if (reader.ReadUInt32 () != expectedValue)
				throw new InvalidDataException ("Unexpected value read.");
		}

		public static void ExpectString (this BinaryReader reader, string s)
		{
			if (new string (reader.ReadChars (s.Length)) != s)
				throw new InvalidDataException ("Unexpected value read.");
		}
		public static string Limit (this string s, int length)
		{
			if (string.IsNullOrEmpty (s)) return s;
			return s.Length <= length ? s : s.Substring (0, length);
		}
	}
}