108 lines
3.9 KiB
C#
108 lines
3.9 KiB
C#
namespace FluidExplorer.Services.Search.Usn;
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/// <summary>
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/// 通配符匹配器：<c>?</c> 匹配任意单字符，<c>*</c> 匹配任意长度（含空），
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/// 大小写不敏感（用固定区域的大小写折叠，不产生任何分配、不受当前区域影响）。
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///
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/// 实现为经典的“双指针 + 最近星号回溯”，最坏 O(n*m)，但对文件名这种短串是纳秒级。
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/// </summary>
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public static class WildcardMatcher
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{
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public static bool IsMatch(ReadOnlySpan<char> text, ReadOnlySpan<char> pattern)
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{
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// ---- 快路径：绝大多数真实查询是 "*.json" / "log*" / "*tmp*" 这类“只有一个/两个通配符”的模式，
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// 直接退化成 EndsWith/StartsWith/IndexOf（走的是 BCL 的高度优化实现），比通用回溯快一个数量级。
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int stars = 0, questions = 0, firstStar = -1, lastStar = -1;
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for (int i = 0; i < pattern.Length; i++)
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{
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var c = pattern[i];
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if (c == '*')
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{
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stars++;
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if (firstStar < 0) firstStar = i;
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lastStar = i;
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}
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else if (c == '?')
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{
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questions++;
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}
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}
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if (questions == 0)
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{
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switch (stars)
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{
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case 0:
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return text.Equals(pattern, StringComparison.OrdinalIgnoreCase);
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case 1 when firstStar == 0:
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return text.EndsWith(pattern[1..], StringComparison.OrdinalIgnoreCase);
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case 1 when firstStar == pattern.Length - 1:
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return text.StartsWith(pattern[..^1], StringComparison.OrdinalIgnoreCase);
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case 2 when firstStar == 0 && lastStar == pattern.Length - 1:
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return text.IndexOf(pattern[1..^1], StringComparison.OrdinalIgnoreCase) >= 0;
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}
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}
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// ---- 通用路径：双指针 + 最近星号回溯 ----
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int t = 0, p = 0;
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int starPattern = -1;
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int starText = 0;
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while (t < text.Length)
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{
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if (p < pattern.Length && (pattern[p] == '?' || FoldEquals(pattern[p], text[t])))
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{
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t++;
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p++;
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}
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else if (p < pattern.Length && pattern[p] == '*')
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{
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// 记下最近的星号位置，先当它匹配空串继续往前走
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starPattern = p++;
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starText = t;
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}
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else if (starPattern >= 0)
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{
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// 回溯：让最近的星号多吃一个字符
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p = starPattern + 1;
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t = ++starText;
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}
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else
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{
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return false;
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}
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}
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while (p < pattern.Length && pattern[p] == '*') p++;
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return p == pattern.Length;
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}
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/// <summary>是否包含通配符。</summary>
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public static bool HasWildcard(ReadOnlySpan<char> pattern) =>
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pattern.IndexOfAny('*', '?') >= 0;
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/// <summary>
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/// 返回模式开头连续的字面量前缀（遇到 * 或 ? 为止），用于给通配符命中排优先级。
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/// </summary>
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public static ReadOnlySpan<char> LiteralPrefix(ReadOnlySpan<char> pattern)
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{
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int i = 0;
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while (i < pattern.Length && pattern[i] is not ('*' or '?')) i++;
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return pattern[..i];
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}
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/// <summary>区域无关的大小写折叠比较（只处理 ASCII 与 BMP 常见情形，足够文件名使用）。</summary>
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internal static bool FoldEquals(char a, char b) =>
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a == b || char.ToUpperInvariant(a) == char.ToUpperInvariant(b);
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/// <summary>模式里是否只剩星号（即 "*" 或 "**" 这类恒真模式）。</summary>
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internal static bool IsMatchAll(ReadOnlySpan<char> pattern)
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{
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foreach (var c in pattern)
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{
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if (c != '*') return false;
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}
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return true;
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}
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}
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