+++ /dev/null
-<!-- Copyright (C) 2003 Red Hat, Inc. -->
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-<HTML
-><HEAD
-><TITLE
->The CDL Language</TITLE
-><meta name="MSSmartTagsPreventParsing" content="TRUE">
-<META
-NAME="GENERATOR"
-CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
-"><LINK
-REL="HOME"
-TITLE="The eCos Component Writer's Guide"
-HREF="cdl-guide.html"><LINK
-REL="PREVIOUS"
-TITLE="Making a Package Distribution"
-HREF="package.distrib.html"><LINK
-REL="NEXT"
-TITLE="CDL Commands"
-HREF="language.commands.html"></HEAD
-><BODY
-CLASS="CHAPTER"
-BGCOLOR="#FFFFFF"
-TEXT="#000000"
-LINK="#0000FF"
-VLINK="#840084"
-ALINK="#0000FF"
-><DIV
-CLASS="NAVHEADER"
-><TABLE
-SUMMARY="Header navigation table"
-WIDTH="100%"
-BORDER="0"
-CELLPADDING="0"
-CELLSPACING="0"
-><TR
-><TH
-COLSPAN="3"
-ALIGN="center"
->The <SPAN
-CLASS="APPLICATION"
->eCos</SPAN
-> Component Writer's Guide</TH
-></TR
-><TR
-><TD
-WIDTH="10%"
-ALIGN="left"
-VALIGN="bottom"
-><A
-HREF="package.distrib.html"
-ACCESSKEY="P"
->Prev</A
-></TD
-><TD
-WIDTH="80%"
-ALIGN="center"
-VALIGN="bottom"
-></TD
-><TD
-WIDTH="10%"
-ALIGN="right"
-VALIGN="bottom"
-><A
-HREF="language.commands.html"
-ACCESSKEY="N"
->Next</A
-></TD
-></TR
-></TABLE
-><HR
-ALIGN="LEFT"
-WIDTH="100%"></DIV
-><DIV
-CLASS="CHAPTER"
-><H1
-><A
-NAME="LANGUAGE">Chapter 3. The CDL Language</H1
-><DIV
-CLASS="TOC"
-><DL
-><DT
-><B
->Table of Contents</B
-></DT
-><DT
-><A
-HREF="language.html#LANGUAGE.OVERVIEW"
->Language Overview</A
-></DT
-><DT
-><A
-HREF="language.commands.html"
->CDL Commands</A
-></DT
-><DT
-><A
-HREF="language.properties.html"
->CDL Properties</A
-></DT
-><DT
-><A
-HREF="language.naming.html"
->Option Naming Convention</A
-></DT
-><DT
-><A
-HREF="language.tcl.html"
->An Introduction to Tcl</A
-></DT
-><DT
-><A
-HREF="language.values.html"
->Values and Expressions</A
-></DT
-><DT
-><A
-HREF="language.interface.html"
->Interfaces</A
-></DT
-><DT
-><A
-HREF="language.database.html"
->Updating the <SPAN
-CLASS="DATABASE"
->ecos.db</SPAN
-> database</A
-></DT
-></DL
-></DIV
-><P
->The <SPAN
-CLASS="APPLICATION"
->CDL</SPAN
-> language is a key part of the <SPAN
-CLASS="APPLICATION"
->eCos</SPAN
-> component framework.
-All packages must come with at least one <SPAN
-CLASS="APPLICATION"
->CDL</SPAN
-> script, to describe
-that package to the framework. The information in that script includes
-details of all the configuration options and how to build the package.
-Implementing a new component or turning some existing code into an
-<SPAN
-CLASS="APPLICATION"
->eCos</SPAN
-> component always involves writing corresponding <SPAN
-CLASS="APPLICATION"
->CDL</SPAN
->. This
-chapter provides a description of the <SPAN
-CLASS="APPLICATION"
->CDL</SPAN
-> language. Detailed
-information on specific parts of the language can be found in <A
-HREF="reference.html"
->Chapter 5</A
->.</P
-><DIV
-CLASS="SECT1"
-><H1
-CLASS="SECT1"
-><A
-NAME="LANGUAGE.OVERVIEW">Language Overview</H1
-><P
->A very simple <SPAN
-CLASS="APPLICATION"
->CDL</SPAN
-> script would look like this:</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->cdl_package CYGPKG_ERROR {
- display "Common error code support"
- compile strerror.cxx
- include_dir cyg/error
- description "
- This package contains the common list of error and
- status codes. It is held centrally to allow
- packages to interchange error codes and status
- codes in a common way, rather than each package
- having its own conventions for error/status
- reporting. The error codes are modelled on the
- POSIX style naming e.g. EINVAL etc. This package
- also provides the standard strerror() function to
- convert error codes to textual representation."
-}</PRE
-></TD
-></TR
-></TABLE
-><P
->This describes a single package, the error code package, which does
-not have any sub-components or configuration options. The package has
-an internal name, <TT
-CLASS="VARNAME"
->CYGPKG_ERROR</TT
->, which can be
-referenced in other <SPAN
-CLASS="APPLICATION"
->CDL</SPAN
-> scripts using e.g.
-<TT
-CLASS="LITERAL"
->requires CYGPKG_ERROR</TT
->. There will also be a
-<TT
-CLASS="LITERAL"
->#define</TT
-> for this symbol in a configuration header
-file. In addition to the package name, this script provides a number
-of properties for the package as a whole. The <SPAN
-CLASS="PROPERTY"
->display</SPAN
-> property
-provides a short description. The <SPAN
-CLASS="PROPERTY"
->description</SPAN
-> property involves a
-rather longer one, for when users need a bit more information. The
-<SPAN
-CLASS="PROPERTY"
->compile</SPAN
-> and <SPAN
-CLASS="PROPERTY"
->include_dir</SPAN
-> properties list the consequences of this
-package at build-time. The package appears to lack any on-line
-documentation. </P
-><P
->Packages could be even simpler than this. If the package only provides
-an interface and there are no files to be compiled then there is no
-need for a <SPAN
-CLASS="PROPERTY"
->compile</SPAN
-> property. Alternatively if there are no exported
-header files, or if the exported header files should go to the
-top-level of the <TT
-CLASS="FILENAME"
->install/include</TT
-> directory, then there is
-no need for an <SPAN
-CLASS="PROPERTY"
->include_dir</SPAN
-> property. Strictly speaking the
-<SPAN
-CLASS="PROPERTY"
->description</SPAN
-> and <SPAN
-CLASS="PROPERTY"
->display</SPAN
-> properties are optional as well, although
-application developers would not appreciate the resulting lack of
-information about what the package is supposed to do.</P
-><P
->However many packages tend to be a bit more complicated than the error
-package, containing various sub-components and configuration options.
-These are also defined in the <SPAN
-CLASS="APPLICATION"
->CDL</SPAN
-> scripts and in much the same way
-as the package. For example, the following excerpt comes from the
-infrastructure package:</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->cdl_component CYGDBG_INFRA_DEBUG_TRACE_ASSERT_BUFFER {
- display "Buffered tracing"
- default_value 1
- active_if CYGDBG_USE_TRACING
- description "
- An output module which buffers output from tracing and
- assertion events. The stored messages are output when an
- assert fires, or CYG_TRACE_PRINT() (defined in
- <cyg/infra/cyg_trac.h>) is called. Of course, there will
- only be stored messages if tracing per se (CYGDBG_USE_TRACING)
- is enabled above."
-
- cdl_option CYGDBG_INFRA_DEBUG_TRACE_BUFFER_SIZE {
- display "Trace buffer size"
- flavor data
- default_value 32
- legal_values 5 to 65535
- description "
- The size of the trace buffer. This counts the number of
- trace records stored. When the buffer fills it either
- wraps, stops recording, or generates output."
- }
-
- …
-}</PRE
-></TD
-></TR
-></TABLE
-><P
->Like a <TT
-CLASS="LITERAL"
->cdl_package</TT
->, a <TT
-CLASS="LITERAL"
->cdl_component</TT
-> has a name and a body. The
-body contains various properties for that component, and may also
-contain sub-components or options. Similarly a <TT
-CLASS="LITERAL"
->cdl_option</TT
-> has a
-name and a body of properties. This example lists a number of
-new properties: <SPAN
-CLASS="PROPERTY"
->default_value</SPAN
->, <SPAN
-CLASS="PROPERTY"
->active_if</SPAN
->, <SPAN
-CLASS="PROPERTY"
->flavor</SPAN
-> and
-<SPAN
-CLASS="PROPERTY"
->legal_values</SPAN
->. The meaning of most of these should be fairly obvious.
-The next sections describe the various <SPAN
-CLASS="APPLICATION"
->CDL</SPAN
-> commands and properties. </P
-><P
->There is one additional and very important point: <SPAN
-CLASS="APPLICATION"
->CDL</SPAN
-> is not a
-completely new language; instead it is implemented as an extension of
-the existing <SPAN
-CLASS="APPLICATION"
->Tcl</SPAN
-> scripting language. The syntax of a <SPAN
-CLASS="APPLICATION"
->CDL</SPAN
-> script is
-<SPAN
-CLASS="APPLICATION"
->Tcl</SPAN
-> syntax, which is described below. In addition some of the more
-advanced facilities of <SPAN
-CLASS="APPLICATION"
->CDL</SPAN
-> involve embedded fragments of <SPAN
-CLASS="APPLICATION"
->Tcl</SPAN
-> code,
-for example there is a <SPAN
-CLASS="PROPERTY"
->define_proc</SPAN
-> property which specifies some
-code that needs to be executed when the component framework generates
-the configuration header files.</P
-></DIV
-></DIV
-><DIV
-CLASS="NAVFOOTER"
-><HR
-ALIGN="LEFT"
-WIDTH="100%"><TABLE
-SUMMARY="Footer navigation table"
-WIDTH="100%"
-BORDER="0"
-CELLPADDING="0"
-CELLSPACING="0"
-><TR
-><TD
-WIDTH="33%"
-ALIGN="left"
-VALIGN="top"
-><A
-HREF="package.distrib.html"
-ACCESSKEY="P"
->Prev</A
-></TD
-><TD
-WIDTH="34%"
-ALIGN="center"
-VALIGN="top"
-><A
-HREF="cdl-guide.html"
-ACCESSKEY="H"
->Home</A
-></TD
-><TD
-WIDTH="33%"
-ALIGN="right"
-VALIGN="top"
-><A
-HREF="language.commands.html"
-ACCESSKEY="N"
->Next</A
-></TD
-></TR
-><TR
-><TD
-WIDTH="33%"
-ALIGN="left"
-VALIGN="top"
->Making a Package Distribution</TD
-><TD
-WIDTH="34%"
-ALIGN="center"
-VALIGN="top"
-> </TD
-><TD
-WIDTH="33%"
-ALIGN="right"
-VALIGN="top"
->CDL Commands</TD
-></TR
-></TABLE
-></DIV
-></BODY
-></HTML
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