159 lines
4.4 KiB
C#
159 lines
4.4 KiB
C#
/*
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* Copyright 2016 The Cartographer Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System.IO.Compression;
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using System.Text;
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using System.Text.Json;
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namespace CartographerSharp.IO;
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/// <summary>
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/// A reader of the format produced by ProtoStreamWriter.
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/// </summary>
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public class ProtoStreamReader : IProtoStreamReader, IDisposable
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{
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// First eight bytes to identify our proto stream format.
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private const ulong Magic = 0x7b1d1f7b5bf501db;
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private static readonly JsonSerializerOptions JsonOptions = new()
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{
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PropertyNameCaseInsensitive = true
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};
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private readonly FileStream _fileStream;
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private bool _disposed;
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private bool _magicRead;
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public ProtoStreamReader(string filename)
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{
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if (string.IsNullOrEmpty(filename))
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throw new ArgumentException("Filename cannot be null or empty", nameof(filename));
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if (!File.Exists(filename))
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throw new FileNotFoundException($"File not found: {filename}", filename);
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_fileStream = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read);
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ReadMagic();
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}
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private void ReadMagic()
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{
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ulong magic = ReadSizeAsLittleEndian();
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if (magic != Magic)
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{
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throw new InvalidDataException($"Invalid proto stream format. Expected magic: 0x{Magic:X16}, got: 0x{magic:X16}");
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}
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_magicRead = true;
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}
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private ulong ReadSizeAsLittleEndian()
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{
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ulong size = 0;
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for (int i = 0; i < 8; i++)
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{
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int byteValue = _fileStream.ReadByte();
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if (byteValue == -1)
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throw new EndOfStreamException("Unexpected end of stream while reading size");
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size >>= 8;
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size += (ulong)byteValue << 56;
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}
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return size;
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}
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private bool Read(out string decompressedData)
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{
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decompressedData = string.Empty;
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if (!_magicRead)
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{
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ReadMagic();
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}
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if (_fileStream.Position >= _fileStream.Length)
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{
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return false; // EOF
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}
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// Read compressed size
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ulong compressedSize = ReadSizeAsLittleEndian();
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if (compressedSize == 0 || compressedSize > int.MaxValue)
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{
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return false;
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}
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// Read compressed data
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byte[] compressedBytes = new byte[compressedSize];
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int bytesRead = _fileStream.Read(compressedBytes, 0, (int)compressedSize);
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if (bytesRead != (int)compressedSize)
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{
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return false;
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}
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// Decompress using GZip
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using var memoryStream = new MemoryStream(compressedBytes);
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using var gzipStream = new GZipStream(memoryStream, CompressionMode.Decompress);
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using var reader = new StreamReader(gzipStream, Encoding.UTF8);
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decompressedData = reader.ReadToEnd();
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return true;
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}
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/// <summary>
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/// Deserializes compressed proto from the pb stream.
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/// </summary>
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public bool ReadProto<T>(out T? proto)
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{
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proto = default;
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if (!Read(out string decompressedData))
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{
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return false;
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}
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try
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{
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proto = JsonSerializer.Deserialize<T>(decompressedData, JsonOptions);
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return proto != null && !EqualityComparer<T>.Default.Equals(proto, default);
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}
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catch (JsonException)
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{
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proto = default;
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return false;
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}
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}
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/// <summary>
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/// 'End-of-file' marker for the pb stream.
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/// </summary>
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public bool Eof => _fileStream.Position >= _fileStream.Length;
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public void Dispose()
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{
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if (!_disposed)
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{
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_fileStream?.Dispose();
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_disposed = true;
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}
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GC.SuppressFinalize(this);
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}
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}
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