AppContext.cs

using System.Diagnostics;
using System.IO.Hashing;
using System.Security.Cryptography;
using Humanizer.Bytes;
using Prism.Mvvm;

namespace F2Checker.Models;

public class AppContext : BindableBase
{
    private readonly int _bufferSize = 1024 * 1024 * 10;

    public AppContext()
    {
        Buffer = new byte[_bufferSize];
        FirstFilePath = string.Empty;
        Status = string.Empty;
    }

    /// <summary>
    ///     ハッシュ値計算の実行
    /// </summary>
    public async Task CheckSum(CancellationToken token)
    {
        // TODO: 仮実装で1つ目のファイルのみ計算。本来はパスの空チェックとかやる。
        FirstFileHash = await GetHashAsync(FirstFilePath, token).ConfigureAwait(false);
    }

    private async Task<string> GetHashAsync(string filename, CancellationToken token)
    {
        if (token.IsCancellationRequested)
            return string.Empty;
        using (var entryStream = File.OpenRead(filename))
        {
            var xxhash = new XxHash128();
            long totalBytesRead = 0;
            var bytesRead = await entryStream.ReadAsync(Buffer, 0, Buffer.Length, token)
                .ConfigureAwait(false);
            var startTime = DateTime.Now;
            var speed = new ByteSize();
            var hash = SHA256.Create();
            while (bytesRead > 0)
            {
                token.ThrowIfCancellationRequested();
                //hash.TransformBlock(Buffer, 0, bytesRead, null, 0);
                xxhash.Append(Buffer.AsSpan(0, bytesRead));
                totalBytesRead += bytesRead;
                speed = ByteSize.FromBytes(totalBytesRead / (DateTime.Now - startTime).TotalSeconds);
                Status = $"{speed.LargestWholeNumberValue:#.##}{speed.LargestWholeNumberSymbol}/s";
                bytesRead = await entryStream.ReadAsync(Buffer, 0, Buffer.Length, token)
                    .ConfigureAwait(false);
            }

            // hash.TransformFinalBlock(Buffer, 0, bytesRead);
            // return Convert.ToHexString(hash.Hash).ToLower();
            Array.Clear(Buffer, 0, Buffer.Length);
            return Convert.ToHexString(xxhash.GetHashAndReset()).ToLower();
        }
    }


    private byte[] Buffer { get; }

    private string _firstFilePath;

    /// <summary>
    ///     解析対象のファイルパス
    /// </summary>
    public string FirstFilePath

    {
        get => _firstFilePath;
        set => SetProperty(ref _firstFilePath, value);
    }

    private string _firstFileHash;

    public string FirstFileHash
    {
        get => _firstFileHash;
        set => SetProperty(ref _firstFileHash, value);
    }

    private string _status;

    /// <summary>
    ///     ステータス
    /// </summary>
    public string Status
    {
        get => _status;
        set => SetProperty(ref _status, value);
    }
}