56 lines
1.5 KiB
C#
56 lines
1.5 KiB
C#
using System;
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using System.Collections.Generic;
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namespace ProtoBuf.Reflection
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{
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internal sealed class Peekable<T> : IDisposable
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{
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public override string ToString()
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{
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T val;
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return Peek(out val) ? (val?.ToString() ?? "(null)") : "(EOF)";
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}
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private readonly IEnumerator<T> _iter;
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private T _peek, _prev;
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private bool _havePeek, _eof;
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public Peekable(IEnumerable<T> sequence)
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{
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_iter = sequence.GetEnumerator();
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}
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public T Previous => _prev;
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public bool Consume()
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{
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T val;
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bool haveData = _havePeek || Peek(out val);
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_prev = _peek;
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_havePeek = false;
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return haveData;
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}
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public bool Peek(out T next)
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{
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if (!_havePeek)
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{
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if (_iter.MoveNext())
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{
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_prev = _peek;
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_peek = _iter.Current;
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_havePeek = true;
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}
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else
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{
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_eof = true;
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_havePeek = false;
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}
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}
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if (_eof)
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{
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next = default(T);
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return false;
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}
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next = _peek;
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return true;
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}
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public void Dispose() => _iter?.Dispose();
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}
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}
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