BufferBuilder.cs

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using System.Text;
 
namespace System.Net.Mail;
 
internal sealed class BufferBuilder
{
    private byte[] _buffer;
 
    private int _offset;
 
    internal int Length => _offset;
 
    internal BufferBuilder()
        : this(256)
    {
    }
 
    internal BufferBuilder(int initialSize)
    {
        _buffer = new byte[initialSize];
    }
 
    private void EnsureBuffer(int count)
    {
        if (count > _buffer.Length - _offset)
        {
            byte[] array = new byte[(_buffer.Length * 2 > _buffer.Length + count) ? (_buffer.Length * 2) : (_buffer.Length + count)];
            Buffer.BlockCopy(_buffer, 0, array, 0, _offset);
            _buffer = array;
        }
    }
 
    internal void Append(byte value)
    {
        EnsureBuffer(1);
        _buffer[_offset++] = value;
    }
 
    internal void Append(byte[] value)
    {
        Append(value, 0, value.Length);
    }
 
    internal void Append(byte[] value, int offset, int count)
    {
        EnsureBuffer(count);
        Buffer.BlockCopy(value, offset, _buffer, _offset, count);
        _offset += count;
    }
 
    internal void Append(string value)
    {
        Append(value, allowUnicode: false);
    }
 
    internal void Append(string value, bool allowUnicode)
    {
        if (!string.IsNullOrEmpty(value))
        {
            Append(value, 0, value.Length, allowUnicode);
        }
    }
 
    internal void Append(string value, int offset, int count, bool allowUnicode)
    {
        if (allowUnicode)
        {
            int byteCount = Encoding.UTF8.GetByteCount(value, offset, count);
            EnsureBuffer(byteCount);
            Encoding.UTF8.GetBytes(value, offset, count, _buffer, _offset);
            _offset += byteCount;
        }
        else
        {
            Append(value, offset, count);
        }
    }
 
    internal void Append(string value, int offset, int count)
    {
        EnsureBuffer(count);
        for (int i = 0; i < count; i++)
        {
            char c = value[offset + i];
            if (c > 'ÿ')
            {
                throw new FormatException(System.SR.Format(System.SR.MailHeaderFieldInvalidCharacter, c));
            }
            _buffer[_offset + i] = (byte)c;
        }
        _offset += count;
    }
 
    internal byte[] GetBuffer()
    {
        return _buffer;
    }
 
    internal void Reset()
    {
        _offset = 0;
    }
}