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using System;
using System.Buffers;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
namespace Ryujinx.Common.Extensions
{
public static class SequenceReaderExtensions
{
/// <summary>
/// Dumps the entire <see cref="SequenceReader{byte}"/> to a file, restoring its previous location afterward.
/// Useful for debugging purposes.
/// </summary>
/// <param name="reader">The <see cref="SequenceReader{Byte}"/> to write to a file</param>
/// <param name="fileFullName">The path and name of the file to create and dump to</param>
public static void DumpToFile(this ref SequenceReader<byte> reader, string fileFullName)
{
var initialConsumed = reader.Consumed;
reader.Rewind(initialConsumed);
using (var fileStream = System.IO.File.Create(fileFullName, 4096, System.IO.FileOptions.None))
{
while (reader.End == false)
{
var span = reader.CurrentSpan;
fileStream.Write(span);
reader.Advance(span.Length);
}
}
reader.SetConsumed(initialConsumed);
}
/// <summary>
/// Returns a reference to the desired value. This ref should always be used. The argument passed in <paramref name="copyDestinationIfRequiredDoNotUse"/> should never be used, as this is only used for storage if the value
/// must be copied from multiple <see cref="ReadOnlyMemory{Byte}"/> segments held by the <see cref="SequenceReader{Byte}"/>.
/// </summary>
/// <typeparam name="T">Type to get</typeparam>
/// <param name="reader">The <see cref="SequenceReader{Byte}"/> to read from</param>
/// <param name="copyDestinationIfRequiredDoNotUse">A location used as storage if (and only if) the value to be read spans multiple <see cref="ReadOnlyMemory{Byte}"/> segments</param>
/// <returns>A reference to the desired value, either directly to memory in the <see cref="SequenceReader{Byte}"/>, or to <paramref name="copyDestinationIfRequiredDoNotUse"/> if it has been used for copying the value in to</returns>
/// <remarks>
/// DO NOT use <paramref name="copyDestinationIfRequiredDoNotUse"/> after calling this method, as it will only
/// contain a value if the value couldn't be referenced directly because it spans multiple <see cref="ReadOnlyMemory{Byte}"/> segments.
/// To discourage use, it is recommended to to call this method like the following:
/// <c>
/// ref readonly MyStruct value = ref sequenceReader.GetRefOrRefToCopy{MyStruct}(out _);
/// </c>
/// </remarks>
/// <exception cref="ArgumentOutOfRangeException">The <see cref="SequenceReader{Byte}"/> does not contain enough data to read a value of type <typeparamref name="T"/></exception>
public static ref readonly T GetRefOrRefToCopy<T>(this scoped ref SequenceReader<byte> reader, out T copyDestinationIfRequiredDoNotUse) where T : unmanaged
{
int lengthRequired = Unsafe.SizeOf<T>();
ReadOnlySpan<byte> span = reader.UnreadSpan;
if (lengthRequired <= span.Length)
{
reader.Advance(lengthRequired);
copyDestinationIfRequiredDoNotUse = default;
ReadOnlySpan<T> spanOfT = MemoryMarshal.Cast<byte, T>(span);
return ref spanOfT[0];
}
else
{
copyDestinationIfRequiredDoNotUse = default;
Span<T> valueSpan = MemoryMarshal.CreateSpan(ref copyDestinationIfRequiredDoNotUse, 1);
Span<byte> valueBytesSpan = MemoryMarshal.AsBytes(valueSpan);
if (!reader.TryCopyTo(valueBytesSpan))
{
throw new ArgumentOutOfRangeException(nameof(reader), "The sequence is not long enough to read the desired value.");
}
reader.Advance(lengthRequired);
return ref valueSpan[0];
}
}
/// <summary>
/// Reads an <see cref="int"/> as little endian.
/// </summary>
/// <param name="reader">The <see cref="SequenceReader{Byte}"/> to read from</param>
/// <param name="value">A location to receive the read value</param>
/// <exception cref="ArgumentOutOfRangeException">Thrown if there wasn't enough data for an <see cref="int"/></exception>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static void ReadLittleEndian(this ref SequenceReader<byte> reader, out int value)
{
if (!reader.TryReadLittleEndian(out value))
{
throw new ArgumentOutOfRangeException(nameof(value), "The sequence is not long enough to read the desired value.");
}
}
/// <summary>
/// Reads the desired unmanaged value by copying it to the specified <paramref name="value"/>.
/// </summary>
/// <typeparam name="T">Type to read</typeparam>
/// <param name="reader">The <see cref="SequenceReader{Byte}"/> to read from</param>
/// <param name="value">The target that will receive the read value</param>
/// <exception cref="ArgumentOutOfRangeException">The <see cref="SequenceReader{Byte}"/> does not contain enough data to read a value of type <typeparamref name="T"/></exception>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static void ReadUnmanaged<T>(this ref SequenceReader<byte> reader, out T value) where T : unmanaged
{
if (!reader.TryReadUnmanaged(out value))
{
throw new ArgumentOutOfRangeException(nameof(value), "The sequence is not long enough to read the desired value.");
}
}
/// <summary>
/// Sets the reader's position as bytes consumed.
/// </summary>
/// <param name="reader">The <see cref="SequenceReader{Byte}"/> to set the position</param>
/// <param name="consumed">The number of bytes consumed</param>
public static void SetConsumed(ref this SequenceReader<byte> reader, long consumed)
{
reader.Rewind(reader.Consumed);
reader.Advance(consumed);
}
/// <summary>
/// Try to read the given type out of the buffer if possible. Warning: this is dangerous to use with arbitrary
/// structs - see remarks for full details.
/// </summary>
/// <typeparam name="T">Type to read</typeparam>
/// <remarks>
/// IMPORTANT: The read is a straight copy of bits. If a struct depends on specific state of it's members to
/// behave correctly this can lead to exceptions, etc. If reading endian specific integers, use the explicit
/// overloads such as <see cref="SequenceReader{T}.TryReadLittleEndian"/>
/// </remarks>
/// <returns>
/// True if successful. <paramref name="value"/> will be default if failed (due to lack of space).
/// </returns>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static unsafe bool TryReadUnmanaged<T>(ref this SequenceReader<byte> reader, out T value) where T : unmanaged
{
ReadOnlySpan<byte> span = reader.UnreadSpan;
if (span.Length < sizeof(T))
{
return TryReadUnmanagedMultiSegment(ref reader, out value);
}
value = Unsafe.ReadUnaligned<T>(ref MemoryMarshal.GetReference(span));
reader.Advance(sizeof(T));
return true;
}
private static unsafe bool TryReadUnmanagedMultiSegment<T>(ref SequenceReader<byte> reader, out T value) where T : unmanaged
{
Debug.Assert(reader.UnreadSpan.Length < sizeof(T));
// Not enough data in the current segment, try to peek for the data we need.
T buffer = default;
Span<byte> tempSpan = new Span<byte>(&buffer, sizeof(T));
if (!reader.TryCopyTo(tempSpan))
{
value = default;
return false;
}
value = Unsafe.ReadUnaligned<T>(ref MemoryMarshal.GetReference(tempSpan));
reader.Advance(sizeof(T));
return true;
}
}
}
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