Reflector error or optimisation?

Question

Long story short: I used reflector on the System.Security.Util.Tokenizer class, and there's loads of goto statements in there.

Here's a brief example snippet:

    Label_0026:
        if (this._inSavedCharacter != -1)
        {
            num = this._inSavedCharacter;
            this._inSavedCharacter = -1;
        }
        else
        {
            switch (this._inTokenSource)
            {
                case TokenSource.UnicodeByteArray:
                    if ((this._inIndex + 1) < this._inSize)
                    {
                        break;
                    }
                    stream.AddToken(-1);
                    return;

                case TokenSource.UTF8ByteArray:
                    if (this._inIndex < this._inSize)
                    {
                        goto Label_00CF;
                    }
                    stream.AddToken(-1);
                    return;

                case TokenSource.ASCIIByteArray:
                    if (this._inIndex < this._inSize)
                    {
                        goto Label_023C;
                    }
                    stream.AddToken(-1);
                    return;

                case TokenSource.CharArray:
                    if (this._inIndex < this._inSize)
                    {
                        goto Label_0272;
                    }
                    stream.AddToken(-1);
                    return;

                case TokenSource.String:
                    if (this._inIndex < this._inSize)
                    {
                        goto Label_02A8;
                    }
                    stream.AddToken(-1);
                    return;

                case TokenSource.NestedStrings:
                    if (this._inNestedSize == 0)
                    {
                        goto Label_030D;
                    }
                    if (this._inNestedIndex >= this._inNestedSize)
                    {
                        goto Label_0306;
                    }
                    num = this._inNestedString[this._inNestedIndex++];
                    goto Label_0402;

                default:
                    num = this._inTokenReader.Read();
                    if (num == -1)
                    {
                        stream.AddToken(-1);
                        return;
                    }
                    goto Label_0402;
            }
            num = (this._inBytes[this._inIndex + 1] << 8) + this._inBytes[this._inIndex];
            this._inIndex += 2;
        }
        goto Label_0402;
    Label_00CF:
        num = this._inBytes[this._inIndex++];
        if ((num & 0x80) != 0)
        {
            switch (((num & 240) >> 4))
            {
                case 8:
                case 9:
                case 10:
                case 11:
                    throw new XmlSyntaxException(this.LineNo);

                case 12:
                case 13:
                    num &= 0x1f;
                    num3 = 2;
                    break;

                case 14:
                    num &= 15;
                    num3 = 3;
                    break;

                case 15:
                    throw new XmlSyntaxException(this.LineNo);
            }
            if (this._inIndex >= this._inSize)
            {
                throw new XmlSyntaxException(this.LineNo, Environment.GetResourceString("XMLSyntax_UnexpectedEndOfFile"));
            }
            byte num2 = this._inBytes[this._inIndex++];
            if ((num2 & 0xc0) != 0x80)
            {
                throw new XmlSyntaxException(this.LineNo);
            }
            num = (num << 6) | (num2 & 0x3f);
            if (num3 != 2)
            {
                if (this._inIndex >= this._inSize)
                {
                    throw new XmlSyntaxException(this.LineNo, Environment.GetResourceString("XMLSyntax_UnexpectedEndOfFile"));
                }
                num2 = this._inBytes[this._inIndex++];
                if ((num2 & 0xc0) != 0x80)
                {
                    throw new XmlSyntaxException(this.LineNo);
                }
                num = (num << 6) | (num2 & 0x3f);
            }
        }
        goto Label_0402;
    Label_023C:
        num = this._inBytes[this._inIndex++];
        goto Label_0402;
    Label_0272:
        num = this._inChars[this._inIndex++];
        goto Label_0402;
    Label_02A8:
        num = this._inString[this._inIndex++];
        goto Label_0402;
    Label_0306:
        this._inNestedSize = 0;

I essentially wanted to know how the class worked, but the number of goto's makes it impossible. Arguably something like a Tokenizer class needs to be heavily optimised, so my question is: is Reflector getting it wrong, or is goto an optimisation for this class?

Answer 1

It looks like Reflector is unable to determine the original loop structure.

As a point of interest (and why this is sometimes the case) there aren't IL opcodes for things like while and for loops and break and continue. The equivalent IL is just if tests combined with jumps (i.e. gotos).