149 lines
3.9 KiB
C#
149 lines
3.9 KiB
C#
using System;
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namespace UnityEngine.InputSystem.Utilities
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{
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// this parser uses Span<T> so it's only available from later unity versions
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#if UNITY_2021_2_OR_NEWER
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internal struct PredictiveParser
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{
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public void ExpectSingleChar(ReadOnlySpan<char> str, char c)
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{
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if (str[m_Position] != c)
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throw new InvalidOperationException($"Expected a '{c}' character at position {m_Position} in : {str.ToString()}");
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++m_Position;
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}
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public int ExpectInt(ReadOnlySpan<char> str)
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{
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int pos = m_Position;
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int sign = 1;
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if (str[pos] == '-')
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{
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sign = -1;
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++pos;
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}
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int value = 0;
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for (;;)
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{
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var n = str[pos];
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if (n >= '0' && n <= '9')
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{
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value *= 10;
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value += n - '0';
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++pos;
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}
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else
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break;
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}
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if (m_Position == pos)
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throw new InvalidOperationException($"Expected an int at position {m_Position} in {str.ToString()}");
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m_Position = pos;
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return value * sign;
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}
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public ReadOnlySpan<char> ExpectString(ReadOnlySpan<char> str)
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{
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var startPos = m_Position;
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if (str[startPos] != '\"')
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throw new InvalidOperationException($"Expected a '\"' character at position {m_Position} in {str.ToString()}");
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++m_Position;
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for (;;)
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{
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var c = str[m_Position];
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c |= ' ';
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if (c >= 'a' && c <= 'z')
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{
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++m_Position;
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continue;
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}
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break;
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}
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// if the first non-alpha character is not a quote, throw
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if (str[m_Position] != '\"')
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throw new InvalidOperationException($"Expected a closing '\"' character at position {m_Position} in string: {str.ToString()}");
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if (m_Position - startPos == 1)
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return ReadOnlySpan<char>.Empty;
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var output = str.Slice(startPos + 1, m_Position - startPos - 1);
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++m_Position;
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return output;
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}
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public bool AcceptSingleChar(ReadOnlySpan<char> str, char c)
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{
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if (str[m_Position] != c)
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return false;
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m_Position++;
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return true;
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}
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public bool AcceptString(ReadOnlySpan<char> input, out ReadOnlySpan<char> output)
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{
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output = default;
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var startPos = m_Position;
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var endPos = startPos;
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if (input[endPos] != '\"')
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return false;
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++endPos;
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for (;;)
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{
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var c = input[endPos];
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c |= ' ';
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if (c >= 'a' && c <= 'z')
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{
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++endPos;
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continue;
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}
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break;
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}
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// if the first non-alpha character is not a quote, throw
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if (input[endPos] != '\"')
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return false;
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// empty string?
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if (m_Position - startPos == 1)
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output = ReadOnlySpan<char>.Empty;
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else
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output = input.Slice(startPos + 1, endPos - startPos - 1);
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m_Position = endPos + 1;
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return true;
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}
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public void AcceptInt(ReadOnlySpan<char> str)
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{
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// skip negative sign
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if (str[m_Position] == '-')
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++m_Position;
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for (;;)
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{
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var n = str[m_Position];
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if (n >= '0' && n <= '9')
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++m_Position;
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else
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break;
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}
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}
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private int m_Position;
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}
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#endif
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}
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