147 lines
4.4 KiB
C#
147 lines
4.4 KiB
C#
using NewLife.Data;
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namespace NewLife.Caching.Buffers;
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/// <summary>缓存的读取器</summary>
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public ref struct BufferedReader
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{
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#region 属性
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private ReadOnlySpan<Byte> _span;
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/// <summary>数据片段</summary>
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public ReadOnlySpan<Byte> Span => _span;
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private Int32 _index;
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/// <summary>已读取字节数</summary>
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public Int32 Position { get => _index; set => _index = value; }
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/// <summary>总容量</summary>
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public Int32 Capacity => _span.Length;
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/// <summary>空闲容量</summary>
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public Int32 FreeCapacity => _span.Length - _index;
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private readonly Stream _stream;
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private readonly Int32 _bufferSize;
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private IPacket _data;
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#endregion
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#region 构造
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/// <summary>实例化Span读取器</summary>
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/// <param name="stream"></param>
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/// <param name="data"></param>
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/// <param name="bufferSize"></param>
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public BufferedReader(Stream stream, IPacket data, Int32 bufferSize = 8192)
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{
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_stream = stream;
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_bufferSize = bufferSize;
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_data = data;
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_span = data.GetSpan();
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}
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#endregion
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#region 基础方法
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/// <summary>告知有多少数据已从缓冲区读取</summary>
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/// <param name="count"></param>
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public void Advance(Int32 count)
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{
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if (count < 0) throw new ArgumentOutOfRangeException(nameof(count));
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if (_index + count > _span.Length) throw new ArgumentOutOfRangeException(nameof(count));
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_index += count;
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}
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/// <summary>返回要写入到的Span，其大小按 sizeHint 参数指定至少为所请求的大小</summary>
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/// <param name="sizeHint"></param>
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/// <returns></returns>
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/// <exception cref="ArgumentOutOfRangeException"></exception>
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public ReadOnlySpan<Byte> GetSpan(Int32 sizeHint = 0)
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{
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if (sizeHint > FreeCapacity) throw new ArgumentOutOfRangeException(nameof(sizeHint));
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return _span[_index..];
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}
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#endregion
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#region 读取方法
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/// <summary>确保缓冲区中有足够的空间。</summary>
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/// <param name="size">需要的字节数。</param>
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/// <exception cref="InvalidOperationException"></exception>
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public void EnsureSpace(Int32 size)
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{
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// 检查剩余空间大小，不足时，再从数据流中读取。此时需要注意，创建新的OwnerPacket后，需要先把之前剩余的一点数据拷贝过去，然后再读取Stream
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var remain = FreeCapacity;
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if (remain < size)
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{
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var idx = 0;
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var pk = new OwnerPacket(_bufferSize);
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if (_data != null && remain > 0)
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{
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if (!_data.TryGetArray(out var arr)) throw new NotSupportedException();
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arr.AsSpan(_index, remain).CopyTo(pk.Buffer);
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idx += remain;
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}
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_data.TryDispose();
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_data = pk;
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_index = 0;
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// 多次读取，直到满足需求
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//var n = _stream.ReadExactly(pk.Buffer, pk.Offset + idx, pk.Length - idx);
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while (idx < size)
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{
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var n = _stream.Read(pk.Buffer, pk.Offset + idx, pk.Length - idx);
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if (n < 0) break;
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idx += n;
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}
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if (idx < size)
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throw new InvalidOperationException("Not enough data to read.");
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pk.Resize(idx);
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_span = pk.GetSpan();
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}
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if (_index + size > _span.Length)
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throw new InvalidOperationException("Not enough data to read.");
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}
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/// <summary>读取单个字节</summary>
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/// <returns></returns>
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public Byte ReadByte()
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{
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var size = sizeof(Byte);
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EnsureSpace(size);
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var result = _span[_index];
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_index += size;
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return result;
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}
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/// <summary>读取字节数组</summary>
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/// <param name="length"></param>
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/// <returns></returns>
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/// <exception cref="InvalidOperationException"></exception>
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public ReadOnlySpan<Byte> ReadBytes(Int32 length)
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{
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EnsureSpace(length);
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var result = _span.Slice(_index, length);
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_index += length;
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return result;
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}
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/// <summary>读取数据包</summary>
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/// <param name="length"></param>
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/// <returns></returns>
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public IPacket ReadPacket(Int32 length)
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{
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EnsureSpace(length);
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var result = _data.Slice(_index, length);
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_index += length;
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return result;
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}
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#endregion
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}
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