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1/*
2 * Copyright (c) 2011 Markus Olsson
3 * var mail = string.Join(".", new string[] {"j", "markus", "olsson"}) + string.Concat('@', "gmail.com");
4 * 
5 * Permission is hereby granted, free of charge, to any person obtaining a copy of this 
6 * software and associated documentation files (the "Software"), to deal in the Software without
7 * restriction, including without limitation the rights to use, copy, modify, merge, publish, 
8 * distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 * 
11 * The above copyright notice and this permission notice shall be
12 * included in all copies or substantial portions of the Software.
13 * 
14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING 
15 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
16 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
17 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
18 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
19 */
20
21
22using System;
23using System.Globalization;
24using System.Linq;
25using System.Text;
26using System.Net.Mime;
27
28namespace freakcode.Utilities
29{
30    public static class ContentDispositionUtils
31    {
32        // A bunch of characters most likely to be forbidden (or be troublesome to use) in a file system
33        private static char[] invalids = "<>:\"/\\|?*~".ToCharArray();
34
35        // We try to prevent theese characters from repeating in the resulting string.
36        private static char[] spacingCharacters = { ' ', '_', '-' };
37
38        /// <summary>
39        /// Normalizes the given file name removing diacritics and special characters so as to maximize
40        /// the compatibility with user agents regardless of system charsets. Note that this method does produce
41        /// a strictly compliant header since it will not quote the string if neccessary. Use the GetHeaderValue 
42        /// in order to produce a proper header value for use directly with an HttpResponse. The return value 
43        /// of this method can be used directly with the File* actionresults in ASP.NET MVC.
44        /// </summary>
45        /// <example>
46        /// Will convert "Ãœbername / document.pdf" to "Ubername document.pdf" and "c:\foobar.pdf" to "c_foobar.pdf"
47        /// </example>
48        /// <exception cref="ArgumentNullException">fileName was null</exception>
49        /// <exception cref="ArgumentException">fileName contained invalid Unicode characters.</exception>
50        public static string NormalizeFileName(string fileName)
51        {
52            if (fileName == null)
53                throw new ArgumentNullException("fileName");
54
55            if (fileName.Length == 0)
56                return string.Empty;
57
58            // Normalize string in order to remove diacritics. This will convert
59            // the string into a fully canonical form; ie Åäö will be converted to A°a¨o¨
60            char[] normalized = fileName.Normalize(NormalizationForm.FormD).ToCharArray();
61
62            // Set up a buffer for our return string that is at most (in case there's no diacritics and no forbidden characters)
63            // the same length as our normalized string.
64            char[] buf = new char[normalized.Length];
65            int p = 0;
66
67            for (int i = 0; i < normalized.Length; i++)
68            {
69                char c = normalized[i];
70
71                // Remove all non spacing marks (ie modifiers to base characters, umlauts and such);
72                if (CharUnicodeInfo.GetUnicodeCategory(c) == UnicodeCategory.NonSpacingMark)
73                    continue;
74
75                // Strip special characters and commonly forbidden file system characters
76                if (c < 32 || c > 126 || invalids.Contains(c))
77                    c = '_';
78
79                // Prevent repeating spacing characters
80                if (p != 0 && spacingCharacters.Contains(c) && spacingCharacters.Contains(buf[p - 1]))
81                    continue;
82
83                buf[p++] = c;
84            }
85
86            return new string(buf, 0, p);
87        }
88
89        /// <summary>
90        /// Returns a content-disposition attachment header value with a filename parameter containing
91        /// a normalized form of the provided filename (see NormalizeFileName for more information).
92        /// </summary>
93        /// <exception cref="ArgumentNullException">fileName was null</exception>
94        /// <exception cref="ArgumentException">fileName contained invalid Unicode characters.</exception>
95        public static string GetHeaderValue(string fileName)
96        {
97            if (fileName == null)
98                throw new ArgumentNullException("fileName");
99
100            var header = new ContentDisposition
101            {
102                FileName = NormalizeFileName(fileName)
103            };
104
105            return header.ToString();
106        }
107    }
108}