SynchronousIOManager.cs

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using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Threading;
 
using Microsoft.Extensions.Logging;
 
namespace Tgstation.Server.Host.IO
{
    sealed class SynchronousIOManager : ISynchronousIOManager
    {
        readonly ILogger<SynchronousIOManager> logger;
 
        public SynchronousIOManager(ILogger<SynchronousIOManager> logger)
        {
            this.logger = logger ?? throw new ArgumentNullException(nameof(logger));
        }
 
        public bool CreateDirectory(string path, CancellationToken cancellationToken)
        {
            if (IsDirectory(path))
                return true;
            cancellationToken.ThrowIfCancellationRequested();
            Directory.CreateDirectory(path);
            return false;
        }
 
        public bool DeleteDirectory(string path)
        {
            if (File.Exists(path))
                return false;
 
            if (!Directory.Exists(path))
                return true;
 
            if (Directory.EnumerateFileSystemEntries(path).Any())
                return false;
 
            Directory.Delete(path);
            return true;
        }
 
        public IEnumerable<string> GetDirectories(string path, CancellationToken cancellationToken)
        {
            foreach (var directoryName in Directory.EnumerateDirectories(path))
            {
                yield return Path.GetFileName(directoryName);
                cancellationToken.ThrowIfCancellationRequested();
            }
        }
 
        public IEnumerable<string> GetFiles(string path, CancellationToken cancellationToken)
        {
            foreach (var fileName in Directory.EnumerateFiles(path))
            {
                yield return Path.GetFileName(fileName);
                cancellationToken.ThrowIfCancellationRequested();
            }
        }
 
        public bool IsDirectory(string path)
        {
            ArgumentNullException.ThrowIfNull(path);
            return Directory.Exists(path);
        }
 
        public byte[] ReadFile(string path)
        {
            ArgumentNullException.ThrowIfNull(path);
            return File.ReadAllBytes(path);
        }
 
        public bool WriteFileChecked(string path, Stream data, ref string? sha1InOut, CancellationToken cancellationToken)
        {
            ArgumentNullException.ThrowIfNull(path);
            ArgumentNullException.ThrowIfNull(data);
 
            cancellationToken.ThrowIfCancellationRequested();
            var directory = Path.GetDirectoryName(path) ?? throw new ArgumentException("path cannot be rooted!", nameof(path));
            Directory.CreateDirectory(directory);
 
            var newFile = !File.Exists(path);
 
            cancellationToken.ThrowIfCancellationRequested();
 
            logger.LogTrace("Starting checked write to {path} ({fileType} file)", path, newFile ? "New" : "Pre-existing");
 
            using (var file = File.Open(path, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None))
            {
                cancellationToken.ThrowIfCancellationRequested();
 
                // no sha1? no write
                if (file.Length != 0 && sha1InOut == null)
                {
                    logger.LogDebug("Aborting checked write due to missing SHA!");
                    return false;
                }
 
                // suppressed due to only using for consistency checks
                using (var sha1 = SHA1.Create())
                {
                    string? GetSha1(Stream dataToHash)
                    {
                        if (dataToHash == null)
                            return null;
 
                        byte[] sha1Computed = dataToHash.Length != 0
                            ? sha1.ComputeHash(dataToHash)
                            : sha1.ComputeHash(Array.Empty<byte>());
 
                        return String.Join(String.Empty, sha1Computed.Select(b => b.ToString("x2", CultureInfo.InvariantCulture)));
                    }
 
                    var originalSha1 = GetSha1(file);
 
                    if (!newFile)
                        logger.LogTrace("Existing SHA calculated to be {sha}", originalSha1);
 
                    if (originalSha1 != sha1InOut && !(newFile && sha1InOut == null))
                    {
                        sha1InOut = originalSha1;
                        return false;
                    }
 
                    sha1InOut = GetSha1(data);
                }
 
                cancellationToken.ThrowIfCancellationRequested();
 
                if (data.Length != 0)
                {
                    logger.LogDebug("Writing file of length {size}", data.Length);
                    file.Seek(0, SeekOrigin.Begin);
                    data.Seek(0, SeekOrigin.Begin);
 
                    cancellationToken.ThrowIfCancellationRequested();
                    file.SetLength(data.Length);
                    data.CopyTo(file);
                }
            }
 
            if (data.Length == 0)
            {
                logger.LogDebug("Stream is empty, deleting file");
                File.Delete(path);
            }
 
            return true;
        }
    }
}