EncodingTable.cs

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using System.Collections;
using System.Collections.Generic;
using System.Threading;
 
namespace System.Text;
 
internal static class EncodingTable
{
    private static readonly int[] s_encodingNameIndices = new int[43]
    {
        0, 14, 28, 33, 38, 43, 50, 61, 76, 82,
        88, 103, 113, 123, 131, 140, 149, 165, 175, 190,
        192, 198, 203, 210, 227, 244, 261, 278, 289, 291,
        299, 305, 313, 321, 327, 335, 343, 348, 353, 372,
        391, 410, 429
    };
 
    private static readonly ushort[] s_codePagesByName = new ushort[42]
    {
        20127, 20127, 20127, 20127, 28591, 20127, 28591, 65000, 20127, 28591,
        1200, 28591, 28591, 20127, 20127, 28591, 20127, 28591, 28591, 28591,
        28591, 1200, 1200, 65000, 65001, 65000, 65001, 1201, 20127, 20127,
        1200, 1201, 1200, 12000, 12001, 12000, 65000, 65001, 65000, 65001,
        65000, 65001
    };
 
    private static readonly ushort[] s_mappedCodePages = new ushort[8] { 1200, 1201, 12000, 12001, 20127, 28591, 65000, 65001 };
 
    private static readonly int[] s_uiFamilyCodePages = new int[8] { 1200, 1200, 1200, 1200, 1252, 1252, 1200, 1200 };
 
    private static readonly int[] s_webNameIndices = new int[9] { 0, 6, 14, 20, 28, 36, 46, 51, 56 };
 
    private static readonly int[] s_englishNameIndices = new int[9] { 0, 7, 27, 43, 70, 78, 100, 115, 130 };
 
    private static readonly uint[] s_flags = new uint[8] { 512u, 0u, 0u, 0u, 257u, 771u, 257u, 771u };
 
    private static readonly Hashtable s_nameToCodePage = Hashtable.Synchronized(new Hashtable(StringComparer.OrdinalIgnoreCase));
 
    private static CodePageDataItem[] s_codePageToCodePageData;
 
    internal static int GetCodePageFromName(string name)
    {
        if (name == null)
        {
            throw new ArgumentNullException("name");
        }
        object obj = s_nameToCodePage[name];
        if (obj != null)
        {
            return (int)obj;
        }
        int num = InternalGetCodePageFromName(name);
        s_nameToCodePage[name] = num;
        return num;
    }
 
    private static int InternalGetCodePageFromName(string name)
    {
        int i = 0;
        int num = s_encodingNameIndices.Length - 2;
        ReadOnlySpan<char> strA = name.ToLowerInvariant().AsSpan();
        while (num - i > 3)
        {
            int num2 = (num - i) / 2 + i;
            int num3 = string.CompareOrdinal(strA, "ansi_x3.4-1968ansi_x3.4-1986asciicp367cp819csasciicsisolatin1csunicode11utf7ibm367ibm819iso-10646-ucs-2iso-8859-1iso-ir-100iso-ir-6iso646-usiso8859-1iso_646.irv:1991iso_8859-1iso_8859-1:1987l1latin1ucs-2unicodeunicode-1-1-utf-7unicode-1-1-utf-8unicode-2-0-utf-7unicode-2-0-utf-8unicodefffeusus-asciiutf-16utf-16beutf-16leutf-32utf-32beutf-32leutf-7utf-8x-unicode-1-1-utf-7x-unicode-1-1-utf-8x-unicode-2-0-utf-7x-unicode-2-0-utf-8".AsSpan(s_encodingNameIndices[num2], s_encodingNameIndices[num2 + 1] - s_encodingNameIndices[num2]));
            if (num3 == 0)
            {
                return s_codePagesByName[num2];
            }
            if (num3 < 0)
            {
                num = num2;
            }
            else
            {
                i = num2;
            }
        }
        for (; i <= num; i++)
        {
            if (string.CompareOrdinal(strA, "ansi_x3.4-1968ansi_x3.4-1986asciicp367cp819csasciicsisolatin1csunicode11utf7ibm367ibm819iso-10646-ucs-2iso-8859-1iso-ir-100iso-ir-6iso646-usiso8859-1iso_646.irv:1991iso_8859-1iso_8859-1:1987l1latin1ucs-2unicodeunicode-1-1-utf-7unicode-1-1-utf-8unicode-2-0-utf-7unicode-2-0-utf-8unicodefffeusus-asciiutf-16utf-16beutf-16leutf-32utf-32beutf-32leutf-7utf-8x-unicode-1-1-utf-7x-unicode-1-1-utf-8x-unicode-2-0-utf-7x-unicode-2-0-utf-8".AsSpan(s_encodingNameIndices[i], s_encodingNameIndices[i + 1] - s_encodingNameIndices[i])) == 0)
            {
                return s_codePagesByName[i];
            }
        }
        throw new ArgumentException(SR.Format(SR.Argument_EncodingNotSupported, name), "name");
    }
 
    internal static EncodingInfo[] GetEncodings()
    {
        ushort[] array = s_mappedCodePages;
        EncodingInfo[] array2 = new EncodingInfo[LocalAppContextSwitches.EnableUnsafeUTF7Encoding ? array.Length : (array.Length - 1)];
        string text = "utf-16utf-16BEutf-32utf-32BEus-asciiiso-8859-1utf-7utf-8";
        int[] array3 = s_webNameIndices;
        int num = 0;
        for (int i = 0; i < array.Length; i++)
        {
            int num2 = array[i];
            if (num2 != 65000 || LocalAppContextSwitches.EnableUnsafeUTF7Encoding)
            {
                array2[num++] = new EncodingInfo(num2, text[array3[i]..array3[i + 1]], GetDisplayName(num2, i));
            }
        }
        return array2;
    }
 
    internal static EncodingInfo[] GetEncodings(Dictionary<int, EncodingInfo> encodingInfoList)
    {
        ushort[] array = s_mappedCodePages;
        string text = "utf-16utf-16BEutf-32utf-32BEus-asciiiso-8859-1utf-7utf-8";
        int[] array2 = s_webNameIndices;
        for (int i = 0; i < array.Length; i++)
        {
            int num = array[i];
            if (!encodingInfoList.ContainsKey(num) && (num != 65000 || LocalAppContextSwitches.EnableUnsafeUTF7Encoding))
            {
                encodingInfoList[num] = new EncodingInfo(num, text[array2[i]..array2[i + 1]], GetDisplayName(num, i));
            }
        }
        if (!LocalAppContextSwitches.EnableUnsafeUTF7Encoding)
        {
            encodingInfoList.Remove(65000);
        }
        EncodingInfo[] array3 = new EncodingInfo[encodingInfoList.Count];
        int num2 = 0;
        foreach (KeyValuePair<int, EncodingInfo> encodingInfo in encodingInfoList)
        {
            array3[num2++] = encodingInfo.Value;
        }
        return array3;
    }
 
    internal static CodePageDataItem GetCodePageDataItem(int codePage)
    {
        if (s_codePageToCodePageData == null)
        {
            Interlocked.CompareExchange(ref s_codePageToCodePageData, new CodePageDataItem[s_mappedCodePages.Length], null);
        }
        int num;
        switch (codePage)
        {
        case 1200:
            num = 0;
            break;
        case 1201:
            num = 1;
            break;
        case 12000:
            num = 2;
            break;
        case 12001:
            num = 3;
            break;
        case 20127:
            num = 4;
            break;
        case 28591:
            num = 5;
            break;
        case 65000:
            num = 6;
            break;
        case 65001:
            num = 7;
            break;
        default:
            return null;
        }
        CodePageDataItem codePageDataItem = s_codePageToCodePageData[num];
        if (codePageDataItem == null)
        {
            Interlocked.CompareExchange(ref s_codePageToCodePageData[num], InternalGetCodePageDataItem(codePage, num), null);
            codePageDataItem = s_codePageToCodePageData[num];
        }
        return codePageDataItem;
    }
 
    private static CodePageDataItem InternalGetCodePageDataItem(int codePage, int index)
    {
        int uiFamilyCodePage = s_uiFamilyCodePages[index];
        string text = "utf-16utf-16BEutf-32utf-32BEus-asciiiso-8859-1utf-7utf-8"[s_webNameIndices[index]..s_webNameIndices[index + 1]];
        string headerName = text;
        string bodyName = text;
        string displayName = GetDisplayName(codePage, index);
        uint flags = s_flags[index];
        return new CodePageDataItem(uiFamilyCodePage, text, headerName, bodyName, displayName, flags);
    }
 
    private static string GetDisplayName(int codePage, int englishNameIndex)
    {
        string text = SR.GetResourceString("Globalization_cp_" + codePage);
        if (string.IsNullOrEmpty(text))
        {
            text = "UnicodeUnicode (Big-Endian)Unicode (UTF-32)Unicode (UTF-32 Big-Endian)US-ASCIIWestern European (ISO)Unicode (UTF-7)Unicode (UTF-8)"[s_englishNameIndices[englishNameIndex]..s_englishNameIndices[englishNameIndex + 1]];
        }
        return text;
    }
}