TextElementEnumerator.cs

using System.Collections;
using System.Runtime.InteropServices;
using System.Runtime.Serialization;

namespace System.Globalization
{
    [Serializable]
    [ComVisible(true)]
    [__DynamicallyInvokable]
    public class TextElementEnumerator : IEnumerator
    {
        private string str;

        private int index;

        private int startIndex;

        [NonSerialized]
        private int strLen;

        [NonSerialized]
        private int currTextElementLen;

        [OptionalField(VersionAdded = 2)]
        private UnicodeCategory uc;

        [OptionalField(VersionAdded = 2)]
        private int charLen;

        private int endIndex;

        private int nextTextElementLen;

        [__DynamicallyInvokable]
        public object Current
        {
            [__DynamicallyInvokable]
            get
            {
                return GetTextElement();
            }
        }

        [__DynamicallyInvokable]
        public int ElementIndex
        {
            [__DynamicallyInvokable]
            get
            {
                if (index == startIndex)
                {
                    throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EnumNotStarted"));
                }
                return index - currTextElementLen;
            }
        }

        internal TextElementEnumerator(string str, int startIndex, int strLen)
        {
            this.str = str;
            this.startIndex = startIndex;
            this.strLen = strLen;
            Reset();
        }

        [OnDeserializing]
        private void OnDeserializing(StreamingContext ctx)
        {
            charLen = -1;
        }

        [OnDeserialized]
        private void OnDeserialized(StreamingContext ctx)
        {
            strLen = endIndex + 1;
            currTextElementLen = nextTextElementLen;
            if (charLen == -1)
            {
                uc = CharUnicodeInfo.InternalGetUnicodeCategory(str, index, out charLen);
            }
        }

        [OnSerializing]
        private void OnSerializing(StreamingContext ctx)
        {
            endIndex = strLen - 1;
            nextTextElementLen = currTextElementLen;
        }

        [__DynamicallyInvokable]
        public bool MoveNext()
        {
            if (index >= strLen)
            {
                index = strLen + 1;
                return false;
            }
            currTextElementLen = StringInfo.GetCurrentTextElementLen(str, index, strLen, ref uc, ref charLen);
            index += currTextElementLen;
            return true;
        }

        [__DynamicallyInvokable]
        public string GetTextElement()
        {
            if (index == startIndex)
            {
                throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EnumNotStarted"));
            }
            if (index > strLen)
            {
                throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EnumEnded"));
            }
            return str.Substring(index - currTextElementLen, currTextElementLen);
        }

        [__DynamicallyInvokable]
        public void Reset()
        {
            index = startIndex;
            if (index < strLen)
            {
                uc = CharUnicodeInfo.InternalGetUnicodeCategory(str, index, out charLen);
            }
        }
    }
}