Re: Why is < illegal in an attribute value but the equivalent hex and decimal character entities are legal?

> 3. (Extra credit) Do you have C code that converts a hex or decimal
character entity to its character? E.g., &#x41 --> C code --> 'A'

Just cast to char:

(char)0x41

(char)65



[image: image.png]

Thanks,
Dimitre

On Wed, Mar 16, 2022 at 4:00 PM Roger L Costello <[email protected]> wrote:

> Hi Folks,
>
> For the parser that I am building I need to be sure that I know exactly
> what can (and can't) go within an attribute value. For example, can an
> attribute value contain &amp;? (Yes) Can an attribute value contain the
> greater-than symbol? (Yes)
>
> I created tests to see what characters are legal and what are illegal in
> an attribute value. See below.
>
> Questions:
> 1. Why is it that < is illegal but the equivalent hex and decimal
> character entities are legal?
> 2. Are there unusual things that are legal (or illegal) to put in an
> attribute value? For instance, you can't put a CDATA section or a PI in an
> attribute value, right?
> 3. (Extra credit) Do you have C code that converts a hex or decimal
> character entity to its character? E.g., &#x41 --> C code --> 'A'
>
> <Tests>
>     <Test foo="&amp;"/>         <!-- Okay -->
>     <Test foo="&lt;"/>                  <!-- Okay -->
>     <Test foo="&gt;"/>          <!-- Okay -->
>     <Test foo="&quot;"/>        <!-- Okay -->
>     <Test foo="&apos;"/>        <!-- Okay -->
>     <Test foo="'"/>                     <!-- Okay -->
>     <Test foo="""/>                      <!-- Error -->
>     <Test foo="<"/>                     <!-- Error -->
>     <Test foo="&#x3C;"/>        <!-- x3C = < ........... Why is this Okay?
> -->
>     <Test foo="&#60;"/>         <!-- 60  = < ........... Why is this Okay?
> -->
>     <Test foo=">"/>                     <!-- Okay -->
>     <Test foo="&#x0;"/>         <!-- x0 = NUL ........... Error -->
>     <Test foo="&#x1;"/>         <!-- x1 = SOH ........... Error -->
>     <Test foo="&#x2;"/>         <!-- x2 = STX ........... Error -->
>     <Test foo="&#x3;"/>         <!-- x3 = ETX ........... Error -->
>     <Test foo="&#x4;"/>         <!-- x4 = EOT ........... Error -->
>     <Test foo="&#x5;"/>         <!-- x5 = ENQ ........... Error -->
>     <Test foo="&#x6;"/>         <!-- x6 = ACK ........... Error -->
>     <Test foo="&#x7;"/>         <!-- x7 = BEL ........... Error -->
>     <Test foo="&#x8;"/>         <!-- x8 = BS ........... Error -->
>     <Test foo="&#x9;"/>         <!-- x9 = TAB ........... Okay -->
>     <Test foo="&#xA;"/>         <!-- xA = LF ........... Okay -->
>     <Test foo="&#xB;"/>         <!-- xB = VT ........... Error -->
>     <Test foo="&#xC;"/>         <!-- xC = FF ........... Error -->
>     <Test foo="&#xD;"/>         <!-- xD = CR ........... Okay -->
>     <Test foo="&#xE;"/>         <!-- xE = SO ........... Error -->
>     <Test foo="&#xF;"/>         <!-- xF = SI ........... Error -->
>     <Test foo="&#x10;"/>        <!-- x10 = DLE ........... Error -->
>     <Test foo="&#x11;"/>        <!-- x11 = DC1 ........... Error -->
>     <Test foo="&#x12;"/>        <!-- x12 = DC2 ........... Error -->
>     <Test foo="&#x13;"/>        <!-- x13 = DC3 ........... Error -->
>     <Test foo="&#x14;"/>        <!-- x14 = DC4 ........... Error -->
>     <Test foo="&#x15;"/>        <!-- x15 = NAK ........... Error -->
>     <Test foo="&#x16;"/>        <!-- x16 = SYN ........... Error -->
>     <Test foo="&#x17;"/>        <!-- x17 = ETB ........... Error -->
>     <Test foo="&#x18;"/>        <!-- x18 = CAN ........... Error -->
>     <Test foo="&#x19;"/>        <!-- x19 = EM ........... Error -->
>     <Test foo="&#x1A;"/>        <!-- x1A = SUB ........... Error -->
>     <Test foo="&#x1B;"/>        <!-- x1B = ESC ........... Error -->
>     <Test foo="&#x1C;"/>        <!-- x1C = FS ........... Error -->
>     <Test foo="&#x1D;"/>        <!-- x1D = GS ........... Error -->
>     <Test foo="&#x1E;"/>        <!-- x1E = RS ........... Error -->
>     <Test foo="&#x1F;"/>        <!-- x1F = US ........... Error -->
>     <Test foo="&#x20;"/>        <!-- x20 = Space ........... Okay -->
> </Tests>
>
> _______________________________________________________________________
>
> XML-DEV is a publicly archived, unmoderated list hosted by OASIS
> to support XML implementation and development. To minimize
> spam in the archives, you must subscribe before posting.
>
> [Un]Subscribe/change address: http://www.oasis-open.org/mlmanage/
> Or unsubscribe: [email protected]
> subscribe: [email protected]
> List archive: http://lists.xml.org/archives/xml-dev/
> List Guidelines: http://www.oasis-open.org/maillists/guidelines.php
>
>

-- 
Cheers,
Dimitre Novatchev
---------------------------------------
Truly great madness cannot be achieved without significant intelligence.
---------------------------------------
To invent, you need a good imagination and a pile of junk
-------------------------------------
Never fight an inanimate object
-------------------------------------
To avoid situations in which you might make mistakes may be the
biggest mistake of all
------------------------------------
Quality means doing it right when no one is looking.
-------------------------------------
You've achieved success in your field when you don't know whether what
you're doing is work or play
-------------------------------------
To achieve the impossible dream, try going to sleep.
-------------------------------------
Facts do not cease to exist because they are ignored.
-------------------------------------
Typing monkeys will write all Shakespeare's works in 200yrs.Will they write
all patents, too? :)
-------------------------------------
Sanity is madness put to good use.
-------------------------------------
I finally figured out the only reason to be alive is to enjoy it.