Marshall Extensions for System.IO.Stream

MarshallExtensions.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Diagnostics.Contracts;

namespace System.Runtime.InteropServices
{
    /// <summary>
    /// Marshall Extensions for <typeparamref name="System.IO.Stream"/>.
    /// </summary>
    public static class MarshallExtensions
    {
        /// <summary>
        /// Reads a struct of type <typeparamref name="T"/> from the input <paramref name="stream"/>. 
        /// </summary>
        /// <typeparam name="T">The element type of the struct to be read.</typeparam>
        /// <param name="stream">Input stream.</param>
        /// <returns>The stream marshalled into a struct of type <typeparamref name="T"/>.</returns>
        public static T Read<T>(this Stream stream) where T : struct
        {
            Contract.Requires(stream != null);

            if (stream == null)
            {
                throw new ArgumentNullException("stream");
            }

            byte[] buffer = new byte[Marshal.SizeOf(typeof(T))];
            stream.Read(buffer, 0, Marshal.SizeOf(typeof(T)));

            GCHandle handle = GCHandle.Alloc(buffer, GCHandleType.Pinned);

            T temp = default(T);

            try
            {
                temp = (T)Marshal.PtrToStructure(
                    handle.AddrOfPinnedObject(), typeof(T));
            }
            finally
            {
                handle.Free();
            }

            return temp;
        }

        /// <summary>
        /// Read a given amount of structs of type <typeparamref name="T"/> from the input <paramref name="stream"/>.
        /// </summary>
        /// <typeparam name="T">The element type of the struct to be read.</typeparam>
        /// <param name="stream">Input stream.</param>
        /// <param name="offset">Stream offset.</param>
        /// <param name="count">Amount of items to read.</param>
        /// <returns>A enumerator to the given amount of items of type <typeparamref name="T"/> read from the stream.</returns>
        public static IEnumerable<T> Read<T>(this Stream stream, long offset,
            int count) where T : struct
        {
            Contract.Requires(stream != null);
            Contract.Requires(offset >= 0);
            Contract.Requires(count > 0);

            if (stream == null)
                throw new ArgumentNullException("stream");

            if (offset < 0)
                throw new ArgumentException("Offset must be greater than or equal zero.");

            if (count <= 0)
                throw new ArgumentException("Count must be greater than zero.");

            stream.Position = offset;

            for (int i = 0; i < count; i++)
                yield return Read<T>(stream);

            stream.Position = 0;
        }

        /// <summary>
        /// Reads a string from a stream, give a offset and the length of the string, 
        /// using the system default encoding.
        /// </summary>
        /// <param name="stream">Stream to read from.</param>
        /// <param name="offset">Stream offset.</param>
        /// <param name="length">String length.</param>
        /// <returns>The string read from the stream.</returns>
        public static string ReadString(this Stream stream, long offset, int length)
        {
            Contract.Requires(stream != null);
            Contract.Requires(offset >= 0);
            Contract.Requires(length > 0);

            if (stream == null)
                throw new ArgumentNullException("stream");

            if (offset < 0)
                throw new ArgumentException("Offset must be greater than or equal zero.");

            if (length <= 0)
                throw new ArgumentException("Length must be greater than zero.");

            byte[] value = new byte[length];

            stream.Position = offset;
            stream.Read(value, 0, length);
            stream.Position = 0;

            return Encoding.Default.GetString(value.Take(value.Length - 1).ToArray());
        }
    }
}