100 lines
3.4 KiB
C#
100 lines
3.4 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using System.Threading.Tasks;
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namespace Spine.Utils
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{
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/// <summary>
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/// UTF8 格式检测工具类
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/// </summary>
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public static class Utf8Validator
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{
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/// <summary>
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/// 判断某段数据是否是 UTF8 格式, 会忽略尾部不完整数据
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/// </summary>
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public static bool IsUtf8(byte[] data, int maxLength = 1024)
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{
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int length = Math.Min(data.Length, maxLength);
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int start = 0;
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if (length >= 3 && data[0] == 0xEF && data[1] == 0xBB && data[2] == 0xBF)
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{
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start = 3;
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}
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int expectedContinuationBytes = 0;
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for (int i = start; i < length; i++)
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{
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byte currentByte = data[i];
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if (expectedContinuationBytes == 0)
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{
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if ((currentByte & 0x80) == 0x00)
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{
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// 0xxxxxxx，ASCII 字符
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continue;
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}
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// 计算需要的续字节数
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int needed;
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if ((currentByte & 0xE0) == 0xC0)
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{
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// 110xxxxx，1 个续字节
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if (currentByte == 0xC0 || currentByte == 0xC1)
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return false; // 避免过长编码
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needed = 1;
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}
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else if ((currentByte & 0xF0) == 0xE0)
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{
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// 1110xxxx，2 个续字节
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needed = 2;
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}
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else if ((currentByte & 0xF8) == 0xF0)
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{
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// 11110xxx，3 个续字节
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if (currentByte > 0xF4)
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return false; // 超出 Unicode 范围
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needed = 3;
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}
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else
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{
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// 非法的起始字节
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return false;
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}
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// 如果剩余字节不足以完成这个字符，就当作“尾部不完整”，跳出主循环
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if (i + needed >= length)
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break;
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// 否则进入续字节检查
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expectedContinuationBytes = needed;
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}
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else
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{
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// 检查续字节（10xxxxxx）
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if ((currentByte & 0xC0) != 0x80)
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return false;
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expectedContinuationBytes--;
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}
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}
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// 如果在跳出时，expectedContinuationBytes>0，说明我们跳过了一些尾部续字节，
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// 本着“忽略尾部不完整字符”的原则，仍然返回 true
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return expectedContinuationBytes == 0;
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}
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/// <summary>
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/// 判断某个文件是否是 UTF8 格式, 会忽略尾部不完整数据
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/// </summary>
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public static bool IsUtf8(string path, int maxLength = 1024)
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{
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using var stream = File.OpenRead(path);
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byte[] data = new byte[maxLength];
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var actualLength = stream.Read(data, 0, data.Length);
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return IsUtf8(data, actualLength);
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}
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}
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}
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