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><H1
><A
NAME="REF.LEGAL-VALUES"><SPAN
CLASS="PROPERTY"
>legal_values</SPAN
></H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN4615"
></A
><H2
>Name</H2
>Property <SPAN
CLASS="PROPERTY"
>legal_values</SPAN
> -- Impose constraints on the possible values for an option.</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN4619"><H2
>Synopsis</H2
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
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><TR
><TD
><PRE
CLASS="SYNOPSIS"
>cdl_option <name> {
legal_values <list expression>
…
}</PRE
></TD
></TR
></TABLE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN4621"
></A
><H2
>Description</H2
><P
>Options with the <TT
CLASS="LITERAL"
>data</TT
> or
<TT
CLASS="LITERAL"
>booldata</TT
> flavors can have an arbitrary sequence of
characters as their data. In nearly all cases some restrictions have
to be imposed, for example the data should correspond to a number
within a certain range, or it should be one of a small number of
constants. The <SPAN
CLASS="PROPERTY"
>legal_values</SPAN
> property can be used to impose such
constraints. The arguments to the property should be a <SPAN
CLASS="APPLICATION"
>CDL</SPAN
> list
expression, see <A
HREF="language.values.html#LANGUAGE.LIST-EXPRESSION"
>the Section called <I
>List Expressions</I
> in Chapter 3</A
> for the
syntactic details. Common examples include:</P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
> legal_values 0 to 0x7fff
legal_values 9600 19200 38400
legal_values { "RAM" "ROM" }</PRE
></TD
></TR
></TABLE
><P
>The <SPAN
CLASS="PROPERTY"
>legal_values</SPAN
> property can only be used for options with the
<TT
CLASS="LITERAL"
>data</TT
> or <TT
CLASS="LITERAL"
>booldata</TT
> flavors, since
it makes little sense to further constrain the legal values of a
boolean option. An option can have at most one <SPAN
CLASS="PROPERTY"
>legal_values</SPAN
>
property.</P
><DIV
CLASS="TIP"
><BLOCKQUOTE
CLASS="TIP"
><P
><B
>Tip: </B
>If the first entry in a <SPAN
CLASS="PROPERTY"
>legal_values</SPAN
> list expression is a negative
number, for example
<TT
CLASS="LITERAL"
>legal_values -1 to 1</TT
> then this can
be misinterpreted as an option instead of as part of the expression.
Currently the <SPAN
CLASS="PROPERTY"
>legal_values</SPAN
> property does not take any options, but
this may change in future. Option processing halts at the sequence
<TT
CLASS="LITERAL"
>--</TT
>, so the desired range can be expressed safely
using <TT
CLASS="LITERAL"
>legal_values -- -1 to 1</TT
></P
></BLOCKQUOTE
></DIV
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>Architectural HAL packages should provide constants which can be used
in <SPAN
CLASS="PROPERTY"
>legal_values</SPAN
> list expressions. For example it should be possible
to specify a numeric range such as
<TT
CLASS="LITERAL"
>0 to CYGARC_MAXINT</TT
>, rather than
hard-wiring numbers such as <TT
CLASS="LITERAL"
>0x7fffffff</TT
> which may
not be valid on all targets. Current HAL packages do not define such
constants. </P
></BLOCKQUOTE
></DIV
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>The <SPAN
CLASS="PROPERTY"
>legal_values</SPAN
> property is restricted mainly to numerical ranges
and simple enumerations, and cannot cope with more complicated data
items. Future versions of the configuration system will provide
additional data validation facilities, for example a
<TT
CLASS="LITERAL"
>check_proc</TT
> property which specifies a Tcl script
that can be used to perform the validation.</P
></BLOCKQUOTE
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN4651"
></A
><H2
>Example</H2
><TABLE
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WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>cdl_option CYGNUM_LIBC_TIME_STD_DEFAULT_OFFSET {
display "Default Standard Time offset"
flavor data
legal_values -- -90000 to 90000
default_value -- 0
description "
This option controls the offset from UTC in
seconds when in local Standard Time. This
value can be positive or negative. It
can also be set at run time using the
cyg_libc_time_setzoneoffsets() function."
}</PRE
></TD
></TR
></TABLE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN4654"
></A
><H2
>See Also</H2
><P
>Properties <A
HREF="ref.calculated.html"
><SPAN
CLASS="PROPERTY"
>calculated</SPAN
></A
>,
<A
HREF="ref.default-value.html"
><SPAN
CLASS="PROPERTY"
>default_value</SPAN
></A
>, and
<A
HREF="ref.flavor.html"
><SPAN
CLASS="PROPERTY"
>flavor</SPAN
></A
>.</P
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