ByteEncoder.cs

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using System.Text;
 
namespace System.Net.Mime;
 
internal abstract class ByteEncoder : IByteEncoder
{
    internal abstract WriteStateInfoBase WriteState { get; }
 
    protected abstract bool HasSpecialEncodingForCRLF { get; }
 
    public string GetEncodedString()
    {
        return Encoding.ASCII.GetString(WriteState.Buffer, 0, WriteState.Length);
    }
 
    public int EncodeBytes(byte[] buffer, int offset, int count, bool dontDeferFinalBytes, bool shouldAppendSpaceToCRLF)
    {
        WriteState.AppendHeader();
        bool hasSpecialEncodingForCRLF = HasSpecialEncodingForCRLF;
        int i;
        for (i = offset; i < count + offset; i++)
        {
            if (LineBreakNeeded(buffer[i]))
            {
                AppendPadding();
                WriteState.AppendCRLF(shouldAppendSpaceToCRLF);
            }
            if (hasSpecialEncodingForCRLF && IsCRLF(buffer, i, count + offset))
            {
                AppendEncodedCRLF();
                i++;
            }
            else
            {
                ApppendEncodedByte(buffer[i]);
            }
        }
        if (dontDeferFinalBytes)
        {
            AppendPadding();
        }
        WriteState.AppendFooter();
        return i - offset;
    }
 
    public int EncodeString(string value, Encoding encoding)
    {
        if (encoding == Encoding.Latin1)
        {
            byte[] bytes = encoding.GetBytes(value);
            return EncodeBytes(bytes, 0, bytes.Length, dontDeferFinalBytes: true, shouldAppendSpaceToCRLF: true);
        }
        WriteState.AppendHeader();
        bool hasSpecialEncodingForCRLF = HasSpecialEncodingForCRLF;
        int num = 0;
        byte[] bytes2 = new byte[encoding.GetMaxByteCount(2)];
        for (int i = 0; i < value.Length; i++)
        {
            int codepointSize = GetCodepointSize(value, i);
            int bytes3 = encoding.GetBytes(value, i, codepointSize, bytes2, 0);
            if (codepointSize == 2)
            {
                i++;
            }
            if (LineBreakNeeded(bytes2, bytes3))
            {
                AppendPadding();
                WriteState.AppendCRLF(includeSpace: true);
            }
            if (hasSpecialEncodingForCRLF && IsCRLF(bytes2, bytes3))
            {
                AppendEncodedCRLF();
            }
            else
            {
                AppendEncodedCodepoint(bytes2, bytes3);
            }
            num += bytes3;
        }
        AppendPadding();
        WriteState.AppendFooter();
        return num;
    }
 
    protected abstract void AppendEncodedCRLF();
 
    protected abstract bool LineBreakNeeded(byte b);
 
    protected abstract bool LineBreakNeeded(byte[] bytes, int count);
 
    protected abstract int GetCodepointSize(string value, int i);
 
    public abstract void AppendPadding();
 
    protected abstract void ApppendEncodedByte(byte b);
 
    private void AppendEncodedCodepoint(byte[] bytes, int count)
    {
        for (int i = 0; i < count; i++)
        {
            ApppendEncodedByte(bytes[i]);
        }
    }
 
    protected bool IsSurrogatePair(string value, int i)
    {
        if (char.IsSurrogate(value[i]) && i + 1 < value.Length)
        {
            return char.IsSurrogatePair(value[i], value[i + 1]);
        }
        return false;
    }
 
    protected bool IsCRLF(byte[] bytes, int count)
    {
        if (count == 2)
        {
            return IsCRLF(bytes, 0, count);
        }
        return false;
    }
 
    private bool IsCRLF(byte[] buffer, int i, int bufferSize)
    {
        if (buffer[i] == 13 && i + 1 < bufferSize)
        {
            return buffer[i + 1] == 10;
        }
        return false;
    }
}