[armedbear-cvs] r13254 - trunk/abcl/doc/design/streams

[Mark Evenson]

Author: mevenson
Date: Sun Mar 20 16:25:03 2011
New Revision: 13254

Log:
Reformat to 80 columns

Modified:
   trunk/abcl/doc/design/streams/design.rst

Modified: trunk/abcl/doc/design/streams/design.rst
==============================================================================
--- trunk/abcl/doc/design/streams/design.rst	(original)
+++ trunk/abcl/doc/design/streams/design.rst	Sun Mar 20 16:25:03 2011
@@ -5,40 +5,51 @@
 The previous design
 -------------------
 
-Previously, ABCL streams were built-in classes. This presented some problems for Gray streams,
-because ABCL CLOS can't use a built-in class as a base class, and Gray streams derive from
-a system-stream class. This was corrected by converting ABCL streams to be structure-objects
-instead of built-in classes, allowing CLOS to derive from the streams. There was, however, another
-problem that revealed a need to change the design in more drastic ways.
+Previously, ABCL streams were built-in classes. This presented some
+problems for Gray streams, because ABCL CLOS can't use a built-in
+class as a base class, and Gray streams derive from a system-stream
+class. This was corrected by converting ABCL streams to be
+structure-objects instead of built-in classes, allowing CLOS to derive
+from the streams. There was, however, another problem that revealed a
+need to change the design in more drastic ways.
 
 The problem with the previous design
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-While converting the streams from built-in classes to structure-objects allowed derivation,
-the pretty printer still didn't work with Gray streams. Gray streams replace the system stream
-functions, saving the old function symbols so that they can be later invoked. The pretty printer,
-however, just replaces the stream functions, and calls the low-level primitives directly, thus
-bypassing Gray streams completely. The attached image portrays the problem, where pprint will,
-for example, invoke %stream-write-char, thus bypassing any methods that there may be for 
-stream-write-char using Gray streams.
+While converting the streams from built-in classes to
+structure-objects allowed derivation, the pretty printer still didn't
+work with Gray streams. Gray streams replace the system stream
+functions, saving the old function symbols so that they can be later
+invoked. The pretty printer, however, just replaces the stream
+functions, and calls the low-level primitives directly, thus bypassing
+Gray streams completely. The attached image portrays the problem,
+where pprint will, for example, invoke %stream-write-char, thus
+bypassing any methods that there may be for stream-write-char using
+Gray streams.
 
 .. image:: pprint-problem.png
 
 The planned future design and solution to the problem
 -----------------------------------------------------
 
-The solution to the problem is quite similar to how SBCL does its streams. First of all, the pretty printer will
-no longer replace stream functions. The stream functionality will be based on closures in the slots of
-the structure-object representing the stream, and those closures will invoke low-level i/o functions that
-are stream-specific. 
-
-The pretty printer will just setup closures that will extract the underlying stream
-object from a pprint-wrapped stream, and invoke its low-level functions. If pprint wrapping isn't present,
-the slots will contain closures that directly invoke low-level functions of streams. Gray streams will
-still replace the stream functions, because it's capable of invoking the replaced functions.
-
-In addition to these changes, it is planned that the stream function primitives will be moved from the Stream
-java class to a streamfunctions library, allowing the stream functions to be written in lisp rather than java.
-There's an ongoing aspiration to increase the lisp/java code ratio of ABCL, and this new design allows for that.
+The solution to the problem is quite similar to how SBCL does its
+streams. First of all, the pretty printer will no longer replace
+stream functions. The stream functionality will be based on closures
+in the slots of the structure-object representing the stream, and
+those closures will invoke low-level i/o functions that are
+stream-specific.
+
+The pretty printer will just setup closures that will extract the
+underlying stream object from a pprint-wrapped stream, and invoke its
+low-level functions. If pprint wrapping isn't present, the slots will
+contain closures that directly invoke low-level functions of
+streams. Gray streams will still replace the stream functions, because
+it's capable of invoking the replaced functions.
+
+In addition to these changes, it is planned that the stream function
+primitives will be moved from the Stream java class to a
+streamfunctions library, allowing the stream functions to be written
+in lisp rather than java.  There's an ongoing aspiration to increase
+the lisp/java code ratio of ABCL, and this new design allows for that.
 
 .. image:: pprint-solution.png