| Allegro CL version 8.2 Unrevised from 8.1 to 8.2. 8.1 version |
Arguments: name arglist &body body
name should be a symbol.
arglist should be a macro lambda list with two
required arguments and two specified keyword arguments
:put-next-octet
, and
:external-format
. (You may choose your own names
for the required arguments, of course. The
arglist argument is present mostly to make this
macro similar in form to defmacro.) body should be
a list of forms.
This macro is just like defmacro except that name names an external-format, and the actual macro name (a gensym) for the macro being defined is stored in the external-format's chars-to-octets-macro slot. Also, if no external-format with name name exists, then a new external-format with name name is created.
The macro being defined must accept two required arguments, which we will call char, and state-loc (but you can, of course, call anything) and two keyword arguments which must be called put-next-octet and external-format. (The external-format argument is only used if name names an external-format that is a wrapper (ie, a composing external-format)).
When the macro actually being defined is called, the char will be a character to convert, and the state-loc will be a setf-able locative (similar to the first argument to setf) that can be used by the convertor to hold state information.
The put-next-octet argument to the macro being defined is a single-argument expression that is invoked in the macro's expansion at the point or points where the translation procedure requests that the next translated external-element (eg, octet) be output.
If the external-format named by name is a composing external-format, then the external-format argument to the macro being defined is the name of the external-format being wrapped.
;; Defines a chars -> octets procedure for latin1 characters. ;; (def-char-to-octets-macro :latin1-base (char state-loc &key put-next-octet external-format) (declare (ignore external-format state-loc)) (let ((code-var (gensym)) (char-var (gensym))) `(let ((,char-var ,char)) (let ((,code-var (char-int ,char-var))) (,put-next-octet ,code-var))))) ;; Defines a chars -> octets procedure for utf-8 characters. ;; (def-char-to-octets-macro :utf8-base (char state &key put-next-octet external-format) (declare (ignore external-format state)) (let ((code-var (gensym))) `(let ((,code-var (char-code ,char))) (if* (< ,code-var #x7f) thenret ;; ascii elseif (< ,code-var #x7ff) then (,put-next-octet (logior #xc0 (ash ,code-var -6))) (setq ,code-var (logior #x80 (logand ,code-var #x3f))) else (,put-next-octet (logior #xe0 (ash ,code-var -12))) (,put-next-octet (logior #x80 (logand (ash ,code-var -6) #x3f))) (setq ,code-var (logior #x80 (logand ,code-var #x3f)))) (,put-next-octet ,code-var)))) ;; Defines a composing external format that splits up #\newline into ;; #\return #\linefeed. ;; (def-char-to-octets-macro :crlf (char state &key put-next-octet external-format) (declare (ignorable state)) (let ((char-var (gensym))) `(let ((,char-var ,char)) (when (eq #\newline ,char-var) (char-to-octets ,external-format #\return ,state :put-next-octet ,put-next-octet) (setq ,char-var #\linefeed)) (char-to-octets ,external-format ,char-var ,state :put-next-octet ,put-next-octet)))) ;; The following uses the above defined wrapper external-format to ;; create a latin1 convertor with #\newline mapped to octets for ;; ASCII Carriage-Return and Linefeed. ;; ;; Note: Using (compose-external-formats :crlf :latin1-base) achieves as one ;; of its side-effects the same effect as evaluating the following: ;; (def-char-to-octets-macro :crlf-latin1-base (char state &key put-next-octet external-format) (declare (ignore external-format)) `(char-to-octets :crlf ,char ,state :put-next-octet ,put-next-octet :external-format :latin1-base))
See also char-to-octets.
See iacl.htm for more information on international character support in Allegro CL.
Copyright (c) 1998-2016, Franz Inc. Oakland, CA., USA. All rights reserved.
This page was not revised from the 8.1 page.
Created 2010.1.21.
| Allegro CL version 8.2 Unrevised from 8.1 to 8.2. 8.1 version |