Ucs4Decoder.cs

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using System.Text;
 
namespace System.Xml;
 
internal abstract class Ucs4Decoder : Decoder
{
    internal byte[] lastBytes = new byte[4];
 
    internal int lastBytesCount;
 
    public override int GetCharCount(byte[] bytes, int index, int count)
    {
        return (count + lastBytesCount) / 4;
    }
 
    internal abstract int GetFullChars(byte[] bytes, int byteIndex, int byteCount, char[] chars, int charIndex);
 
    public override int GetChars(byte[] bytes, int byteIndex, int byteCount, char[] chars, int charIndex)
    {
        int num = lastBytesCount;
        if (lastBytesCount > 0)
        {
            while (lastBytesCount < 4 && byteCount > 0)
            {
                lastBytes[lastBytesCount] = bytes[byteIndex];
                byteIndex++;
                byteCount--;
                lastBytesCount++;
            }
            if (lastBytesCount < 4)
            {
                return 0;
            }
            num = GetFullChars(lastBytes, 0, 4, chars, charIndex);
            charIndex += num;
            lastBytesCount = 0;
        }
        else
        {
            num = 0;
        }
        num = GetFullChars(bytes, byteIndex, byteCount, chars, charIndex) + num;
        int num2 = byteCount & 3;
        if (num2 >= 0)
        {
            for (int i = 0; i < num2; i++)
            {
                lastBytes[i] = bytes[byteIndex + byteCount - num2 + i];
            }
            lastBytesCount = num2;
        }
        return num;
    }
 
    public override void Convert(byte[] bytes, int byteIndex, int byteCount, char[] chars, int charIndex, int charCount, bool flush, out int bytesUsed, out int charsUsed, out bool completed)
    {
        bytesUsed = 0;
        charsUsed = 0;
        int num = 0;
        int i = lastBytesCount;
        if (i > 0)
        {
            for (; i < 4; i++)
            {
                if (byteCount <= 0)
                {
                    break;
                }
                lastBytes[i] = bytes[byteIndex];
                byteIndex++;
                byteCount--;
                bytesUsed++;
            }
            if (i < 4)
            {
                lastBytesCount = i;
                completed = true;
                return;
            }
            num = GetFullChars(lastBytes, 0, 4, chars, charIndex);
            charIndex += num;
            charCount -= num;
            charsUsed = num;
            lastBytesCount = 0;
        }
        else
        {
            num = 0;
        }
        if (charCount * 4 < byteCount)
        {
            byteCount = charCount * 4;
            completed = false;
        }
        else
        {
            completed = true;
        }
        bytesUsed += byteCount;
        charsUsed = GetFullChars(bytes, byteIndex, byteCount, chars, charIndex) + num;
        int num2 = byteCount & 3;
        if (num2 >= 0)
        {
            for (int j = 0; j < num2; j++)
            {
                lastBytes[j] = bytes[byteIndex + byteCount - num2 + j];
            }
            lastBytesCount = num2;
        }
    }
 
    internal void Ucs4ToUTF16(uint code, char[] chars, int charIndex)
    {
        chars[charIndex] = (char)(55296 + (ushort)((code >> 16) - 1) + (ushort)((code >> 10) & 0x3F));
        chars[charIndex + 1] = (char)(56320 + (ushort)(code & 0x3FF));
    }
}