System.Text.RegularExpressions.RegexFCD.FirstChars C# (CSharp) Method

        internal static RegexPrefix FirstChars(RegexTree t)
        {
            RegexFCD s = new RegexFCD();
            RegexFC fc = s.RegexFCFromRegexTree(t);

            if (fc == null || fc._nullable)
                return null;

            CultureInfo culture = ((t._options & RegexOptions.CultureInvariant) != 0) ? CultureInfo.InvariantCulture : CultureInfo.CurrentCulture;
            return new RegexPrefix(fc.GetFirstChars(culture), fc.IsCaseInsensitive());
        }

        internal RegexCode RegexCodeFromRegexTree(RegexTree tree)
        {
            int             length;
            RegexBoyerMoore moore;

            if ((tree._capnumlist == null) || (tree._captop == tree._capnumlist.Length))
            {
                length     = tree._captop;
                this._caps = null;
            }
            else
            {
                length     = tree._capnumlist.Length;
                this._caps = tree._caps;
                for (int i = 0; i < tree._capnumlist.Length; i++)
                {
                    this._caps[tree._capnumlist[i]] = i;
                }
            }
            this._counting = true;
Label_0076:
            if (!this._counting)
            {
                this._emitted = new int[this._count];
            }
            RegexNode node     = tree._root;
            int       curIndex = 0;

            this.Emit(0x17, 0);
Label_00A1:
            if (node._children == null)
            {
                this.EmitFragment(node._type, node, 0);
            }
            else if (curIndex < node._children.Count)
            {
                this.EmitFragment(node._type | 0x40, node, curIndex);
                node = (RegexNode)node._children[curIndex];
                this.PushInt(curIndex);
                curIndex = 0;
                goto Label_00A1;
            }
            if (!this.EmptyStack())
            {
                curIndex = this.PopInt();
                node     = node._next;
                this.EmitFragment(node._type | 0x80, node, curIndex);
                curIndex++;
                goto Label_00A1;
            }
            this.PatchJump(0, this.CurPos());
            this.Emit(40);
            if (this._counting)
            {
                this._counting = false;
                goto Label_0076;
            }
            RegexPrefix fcPrefix = RegexFCD.FirstChars(tree);

            if ((fcPrefix != null) && (RegexCharClass.SetSize(fcPrefix.Prefix) > 0))
            {
                fcPrefix = null;
            }
            RegexPrefix scPrefix    = null;
            RegexPrefix prefix3     = RegexFCD.Prefix(tree);
            bool        rightToLeft = (tree._options & RegexOptions.RightToLeft) != RegexOptions.None;
            CultureInfo culture     = ((tree._options & RegexOptions.CultureInvariant) != RegexOptions.None) ? CultureInfo.InvariantCulture : CultureInfo.CurrentCulture;

            if ((prefix3 != null) && (prefix3.Prefix.Length > 0))
            {
                moore = new RegexBoyerMoore(prefix3.Prefix, prefix3.CaseInsensitive, rightToLeft, culture);
            }
            else
            {
                moore = null;
            }
            return(new RegexCode(this._emitted, this._stringtable, this._trackcount, this._caps, length, moore, fcPrefix, scPrefix, RegexFCD.Anchors(tree), rightToLeft));
        }