using System.IO;

namespace BSO.Net
{
    /// <summary>
    /// BinaryReader fuer Daten aus dem Netz (wie bei MSCO): jede Laengenangabe wird gegen die tatsaechlich vorhandenen
    /// Bytes geprueft - eine gefaelschte Laenge darf nicht zu einer riesigen Speicheranforderung fuehren.
    /// </summary>
    public sealed class PacketReader : BinaryReader
    {
        public PacketReader(byte[] data) : base(new MemoryStream(data ?? new byte[0], false)) { }

        long Remaining => BaseStream.Length - BaseStream.Position;

        public override byte[] ReadBytes(int count)
        {
            if (count < 0 || count > Remaining) throw new EndOfStreamException("Invalid length " + count);
            return base.ReadBytes(count);
        }

        public override char[] ReadChars(int count)
        {
            if (count < 0 || count > Remaining) throw new EndOfStreamException("Invalid length " + count);
            return base.ReadChars(count);
        }

        public override string ReadString()
        {
            long start = BaseStream.Position;
            int length = Read7BitEncodedInt();
            if (length < 0 || length > Remaining) throw new EndOfStreamException("Invalid string length " + length);
            BaseStream.Position = start;
            return base.ReadString();
        }
    }
}