StreamExtensions.cs

using System.Runtime.InteropServices;

namespace BytecodeApi.Extensions;

/// <summary>
/// Provides a set of <see langword="static" /> methods for interaction with <see cref="Stream" /> objects.
/// </summary>
public static class StreamExtensions
{
	extension(Stream stream)
	{
		/// <summary>
		/// Reads a structure of the specified type from the stream.
		/// </summary>
		/// <typeparam name="T">The type of the structure to read.</typeparam>
		/// <returns>
		/// A new structure of the specified type that was read from the stream.
		/// </returns>
		public T ReadStructure<T>() where T : struct
		{
			Check.ArgumentNull(stream);

			byte[] buffer = new byte[Marshal.SizeOf<T>()];
			stream.ReadExactly(buffer);
			return Convert.ToStructure<T>(buffer);
		}
		/// <summary>
		/// Writes a structure of the specified type to the stream.
		/// </summary>
		/// <typeparam name="T">The type of the structure to write.</typeparam>
		/// <param name="structure">The structure to write to this <see cref="Stream" />.</param>
		public void WriteStructure<T>(T structure) where T : struct
		{
			Check.ArgumentNull(stream);

			stream.Write(Convert.FromStructure(structure));
		}
		/// <summary>
		/// Searches this <see cref="Stream" /> for the first occurrence of <paramref name="sequence" />. If not found, returns -1.
		/// </summary>
		/// <param name="sequence">The <see cref="byte" />[] to search for.</param>
		/// <returns>
		/// The index of the first occurrence of <paramref name="sequence" /> and -1, if not found.
		/// </returns>
		public long FindSequence(byte[] sequence)
		{
			Check.ArgumentNull(stream);
			Check.ArgumentNull(sequence);
			Check.ArgumentEx.ArrayElementsRequired(sequence);

			long position = stream.Position;

			try
			{
				int readByte;
				int sequenceIndex = 0;

				for (long index = 0; (readByte = stream.ReadByte()) != -1; index++)
				{
					if (readByte == sequence[sequenceIndex])
					{
						sequenceIndex++;
						if (sequenceIndex == sequence.Length)
						{
							return index + 1 - sequence.Length;
						}
					}
					else
					{
						sequenceIndex = 0;
					}
				}
			}
			finally
			{
				stream.Seek(position, SeekOrigin.Begin);
			}

			return -1;
		}
	}
}