156 lines
4.1 KiB
C#
156 lines
4.1 KiB
C#
//
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// ImapEncoding.cs
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//
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// Author: Jeffrey Stedfast <jestedfa@microsoft.com>
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//
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// Copyright (c) 2013-2020 .NET Foundation and Contributors
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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//
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using System.Text;
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namespace MailKit.Net.Imap {
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static class ImapEncoding
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{
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const string utf7_alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
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static readonly byte[] utf7_rank = {
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255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
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255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
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255,255,255,255,255,255,255,255,255,255,255, 62, 63,255,255,255,
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52, 53, 54, 55, 56, 57, 58, 59, 60, 61,255,255,255,255,255,255,
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255, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
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15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,255,255,255,255,255,
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255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
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41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,255,255,255,255,255,
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};
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public static string Decode (string text)
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{
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var decoded = new StringBuilder ();
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bool shifted = false;
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int bits = 0, v = 0;
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int index = 0;
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char c;
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while (index < text.Length) {
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c = text[index++];
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if (shifted) {
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if (c == '-') {
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// shifted back out of modified UTF-7
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shifted = false;
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bits = v = 0;
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} else if (c > 127) {
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// invalid UTF-7
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return text;
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} else {
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byte rank = utf7_rank[(byte) c];
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if (rank == 0xff) {
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// invalid UTF-7
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return text;
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}
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v = (v << 6) | rank;
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bits += 6;
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if (bits >= 16) {
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char u = (char) ((v >> (bits - 16)) & 0xffff);
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decoded.Append (u);
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bits -= 16;
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}
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}
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} else if (c == '&' && index < text.Length) {
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if (text[index] == '-') {
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decoded.Append ('&');
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index++;
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} else {
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// shifted into modified UTF-7
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shifted = true;
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}
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} else {
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decoded.Append (c);
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}
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}
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return decoded.ToString ();
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}
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static void Utf7ShiftOut (StringBuilder output, int u, int bits)
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{
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if (bits > 0) {
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int x = (u << (6 - bits)) & 0x3f;
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output.Append (utf7_alphabet[x]);
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}
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output.Append ('-');
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}
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public static string Encode (string text)
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{
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var encoded = new StringBuilder ();
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bool shifted = false;
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int bits = 0, u = 0;
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for (int index = 0; index < text.Length; index++) {
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char c = text[index];
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if (c >= 0x20 && c < 0x7f) {
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// characters with octet values 0x20-0x25 and 0x27-0x7e
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// represent themselves while 0x26 ("&") is represented
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// by the two-octet sequence "&-"
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if (shifted) {
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Utf7ShiftOut (encoded, u, bits);
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shifted = false;
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bits = 0;
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}
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if (c == 0x26)
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encoded.Append ("&-");
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else
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encoded.Append (c);
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} else {
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// base64 encode
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if (!shifted) {
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encoded.Append ('&');
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shifted = true;
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}
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u = (u << 16) | (c & 0xffff);
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bits += 16;
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while (bits >= 6) {
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int x = (u >> (bits - 6)) & 0x3f;
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encoded.Append (utf7_alphabet[x]);
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bits -= 6;
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}
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}
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}
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if (shifted)
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Utf7ShiftOut (encoded, u, bits);
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return encoded.ToString ();
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}
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}
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}
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