285 lines
11 KiB
C#
285 lines
11 KiB
C#
using System.Text;
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using System.Text.RegularExpressions;
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namespace Atomx.Utils.Files
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{
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/// <summary>
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/// 常用文件头识别工具（改进版：修复编译器警告、改善流读取安全性与类型判断）
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/// </summary>
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public static class FileTypes
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{
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// 保持原有 public 字段签名以兼容现有代码
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public static readonly Dictionary<string, byte[]> ImageHeader = new();
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public static readonly Dictionary<string, object> FilesHeader = new();
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public static readonly Dictionary<string, object> VideoHeader = new();
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static FileTypes()
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{
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ImageHeader.Add("gif", new byte[] { 71, 73, 70, 56, 57, 97 });
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ImageHeader.Add("bmp", new byte[] { 66, 77 });
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ImageHeader.Add("jpg", new byte[] { 255, 216, 255 });
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ImageHeader.Add("png", new byte[] { 137, 80, 78, 71, 13, 10, 26, 10, 0, 0, 0, 13, 73, 72, 68, 82 });
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FilesHeader.Add("pdf", new byte[] { 37, 80, 68, 70, 45, 49, 46, 53 });
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FilesHeader.Add("docx", new object[] { new byte[] { 80, 75, 3, 4, 20, 0, 6, 0, 8, 0, 0, 0, 33 }, new Regex(@"word/_rels/document\.xml\.rels", RegexOptions.IgnoreCase) });
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FilesHeader.Add("xlsx", new object[] { new byte[] { 80, 75, 3, 4, 20, 0, 6, 0, 8, 0, 0, 0, 33 }, new Regex(@"xl/_rels/workbook\.xml\.rels", RegexOptions.IgnoreCase) });
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FilesHeader.Add("pptx", new object[] { new byte[] { 80, 75, 3, 4, 20, 0, 6, 0, 8, 0, 0, 0, 33 }, new Regex(@"ppt/_rels/presentation\.xml\.rels", RegexOptions.IgnoreCase) });
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FilesHeader.Add("doc", new object[] { new byte[] { 208, 207, 17, 224, 161, 177, 26, 225 }, new Regex(@"microsoft( office)? word(?![\s\S]*?microsoft)", RegexOptions.IgnoreCase) });
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FilesHeader.Add("xls", new object[] { new byte[] { 208, 207, 17, 224, 161, 177, 26, 225 }, new Regex(@"microsoft( office)? excel(?![\s\S]*?microsoft)", RegexOptions.IgnoreCase) });
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FilesHeader.Add("ppt", new object[] { new byte[] { 208, 207, 17, 224, 161, 177, 26, 225 }, new Regex(@"c.u.r.r.e.n.t. .u.s.e.r(?![\s\S]*?[a-z])", RegexOptions.IgnoreCase) });
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FilesHeader.Add("avi", new byte[] { 65, 86, 73, 32 });
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FilesHeader.Add("mpg", new byte[] { 0, 0, 1, 0xBA });
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FilesHeader.Add("mpeg", new byte[] { 0, 0, 1, 0xB3 });
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FilesHeader.Add("rar", new byte[] { 82, 97, 114, 33, 26, 7 });
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FilesHeader.Add("zip", new byte[] { 80, 75, 3, 4 });
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VideoHeader.Add("avi", new byte[] { 65, 86, 73, 32 });
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VideoHeader.Add("mpg", new byte[] { 0, 0, 1, 0xBA });
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VideoHeader.Add("mpeg", new byte[] { 0, 0, 1, 0xB3 });
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}
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/// <summary>
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/// 检测视频类型扩展方法
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/// </summary>
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public static string VideoType(this Stream stream)
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{
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if (stream == null) throw new ArgumentNullException(nameof(stream));
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foreach (var kv in VideoHeader)
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{
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if (TryMatchHeader(stream, kv.Value, out var matched))
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{
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if (matched)
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return kv.Key;
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}
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}
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return string.Empty;
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}
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/// <summary>
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/// 检测常规文件类型扩展方法
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/// </summary>
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public static string FileType(this Stream stream)
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{
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if (stream == null) throw new ArgumentNullException(nameof(stream));
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foreach (var kv in FilesHeader)
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{
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if (TryMatchHeader(stream, kv.Value, out var matched))
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{
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if (matched)
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return kv.Key;
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}
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}
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return string.Empty;
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}
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/// <summary>
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/// 检测图片类型扩展方法
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/// </summary>
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public static string ImageType(this Stream stream)
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{
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if (stream == null) throw new ArgumentNullException(nameof(stream));
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foreach (var kv in ImageHeader)
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{
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var header = kv.Value;
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if (header == null || header.Length == 0) continue;
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if (ReadAndCompare(stream, header))
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return kv.Key;
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}
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// 额外尝试判断是否是纯文本（防止误判），若为纯文本则返回空
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// 只读取流内容进行检查，谨慎处理大流（可能会分配较大内存）
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try
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{
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var content = stream.ReadAllBytesAndRestorePosition();
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if (content.Length > 0)
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{
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var encodings = new[] { Encoding.ASCII, Encoding.UTF8 };
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foreach (var enc in encodings)
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{
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var text = enc.GetString(content);
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if (Regex.IsMatch(text, @"^[^\u0000-\u0008\u000B-\u000C\u000E-\u001F]*$"))
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{
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// 认为是文本，非图片
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return string.Empty;
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}
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}
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// Windows-936 编码仅在支持 CodePages 的情况下尝试使用
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try
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{
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var cp936 = Encoding.GetEncoding(936);
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var text936 = cp936.GetString(content);
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if (Regex.IsMatch(text936, @"^[^\u0000-\u0008\u000B-\u000C\u000E-\u001F]*$"))
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return string.Empty;
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}
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catch
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{
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// 在不支持 CodePages 的平台上忽略
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}
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}
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}
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catch
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{
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// 忽略检查错误，回退为无法识别
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}
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return string.Empty;
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}
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/// <summary>
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/// 将流完整读取为字节数组（更高效且保持原位置）
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/// </summary>
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public static byte[] StreamToBytes(this Stream stream)
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{
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if (stream == null) throw new ArgumentNullException(nameof(stream));
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return stream.ReadAllBytesAndRestorePosition();
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}
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// ---------- 辅助方法 ----------
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/// <summary>
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/// 根据字节头或复杂描述（object[]）进行匹配判断。
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/// object 类型支持：
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/// - byte[] : 仅比较头部字节
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/// - object[] : 第一个元素为 byte[] 头部；第二个元素可以为 Regex 或 int(表示尾部偏移)，后面可跟要比较的尾部 byte[] 列表
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/// </summary>
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private static bool TryMatchHeader(Stream stream, object value, out bool matched)
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{
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matched = false;
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if (value == null) return false;
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if (value is byte[] headerOnly)
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{
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matched = ReadAndCompare(stream, headerOnly);
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return true;
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}
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if (value is object[] arr && arr.Length > 0 && arr[0] is byte[] header)
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{
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// 先比较头部
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if (!ReadAndCompare(stream, header))
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return true; // header no match -> not this type
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// 若仅头部匹配，后续根据第二元素进一步校验
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if (arr.Length >= 2)
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{
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var second = arr[1];
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if (second is Regex regex)
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{
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var content = stream.ReadAllBytesAndRestorePosition();
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var text = Encoding.ASCII.GetString(content);
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matched = regex.IsMatch(text);
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return true;
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}
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else if (second is int tailOffset)
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{
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// arr[2..] 为若干尾部字节数组，比对任一相等则通过
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for (int i = 2; i < arr.Length; i++)
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{
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if (arr[i] is byte[] tailBytes)
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{
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if (ReadAndCompareTail(stream, tailOffset, tailBytes))
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{
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matched = true;
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return true;
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}
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}
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}
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matched = false;
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return true;
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}
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else
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{
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// 未知第二元素类型，视为仅头匹配
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matched = true;
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return true;
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}
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}
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matched = true;
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return true;
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}
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return false;
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}
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/// <summary>
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/// 从流头部读取与目标字节数组比较，比较完成后恢复流位置
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/// </summary>
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private static bool ReadAndCompare(Stream stream, byte[] target)
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{
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if (target == null || target.Length == 0) return false;
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var originalPos = stream.CanSeek ? stream.Position : (long?)null;
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try
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{
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var buffer = new byte[target.Length];
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if (!ReadFull(stream, buffer, 0, buffer.Length))
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return false;
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return buffer.SequenceEqual(target);
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}
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finally
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{
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if (originalPos.HasValue)
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stream.Position = originalPos.Value;
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}
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}
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/// <summary>
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/// 从流尾部根据偏移读取并比较
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/// </summary>
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private static bool ReadAndCompareTail(Stream stream, int offsetFromEnd, byte[] target)
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{
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if (target == null || target.Length == 0) return false;
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if (!stream.CanSeek) return false;
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var originalPos = stream.Position;
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try
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{
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if (stream.Length < offsetFromEnd + target.Length) return false;
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stream.Position = stream.Length - offsetFromEnd;
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var buffer = new byte[target.Length];
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if (!ReadFull(stream, buffer, 0, buffer.Length)) return false;
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return buffer.SequenceEqual(target);
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}
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finally
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{
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stream.Position = originalPos;
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}
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}
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/// <summary>
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/// 从流中读取指定长度的数据，直到读取到要求长度或 EOF（返回是否读取到完整长度）
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/// </summary>
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private static bool ReadFull(Stream stream, byte[] buffer, int offset, int count)
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{
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if (count <= 0) return true;
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int read;
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int total = 0;
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while (total < count && (read = stream.Read(buffer, offset + total, count - total)) > 0)
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{
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total += read;
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}
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return total == count;
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}
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/// <summary>
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/// 将流全部读取为字节数组并尝试恢复原始 Position（若支持）
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/// </summary>
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private static byte[] ReadAllBytesAndRestorePosition(this Stream stream)
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{
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var originalPos = stream.CanSeek ? stream.Position : (long?)null;
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try
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{
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using var ms = new MemoryStream();
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stream.CopyTo(ms);
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return ms.ToArray();
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}
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finally
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{
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if (originalPos.HasValue)
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stream.Position = originalPos.Value;
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}
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}
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}
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} |