-@node Extensible Streams
+@node Streams
@comment node-name, next, previous, up
-@chapter Extensible Streams
+@chapter Streams
-SBCL supports various extensions of ANSI Common Lisp streams.
+Streams which read or write Lisp character data from or to the outside
+world -- files, sockets or other external entities -- require the
+specification of a conversion between the external, binary data and the
+Lisp characters. In ANSI Common Lisp, this is done by specifying the
+@code{:external-format} argument when the stream is created. The major
+information required is an @emph{encoding}, specified by a keyword
+naming that encoding; however, it is also possible to specify
+refinements to that encoding as additional options to the external
+format designator.
+
+In addition, SBCL supports various extensions of ANSI Common Lisp
+streams:
@table @strong
@item Bivalent Streams
@end table
@menu
+* External Formats::
* Bivalent Streams::
* Gray Streams::
* Simple Streams::
@end menu
+@node External Formats
+@section External Formats
+@cindex External formats
+
+@findex @cl{stream-external-format}
+The encodings supported by SBCL as external formats are named by
+keyword. Each encoding has a canonical name, which will be encoding
+returned by @code{stream-external-format}, and a number of aliases for
+convenience, as shown in the table below:
+
+@include encodings.texi-temp
+
+@findex @cl{open}
+@findex @cl{with-open-file}
+In situations where an external file format designator is required, such
+as the @code{:external-format} argument in calls to @code{open} or
+@code{with-open-file}, users may supply the name of an encoding to
+denote the external format which is applying that encoding to Lisp
+characters.
+
+In addition to the basic encoding for an external format, options
+controlling various special cases may be passed, by using a list (whose
+first element must be an encoding name and whose rest is a plist) as an
+external file format designator. At present, the only supported key in
+the plist is @code{:replacement}, where the corresponding value is a
+string designator which is used as a replacement when an encoding or
+decoding error happens, handling those errors without user intervention;
+for example:
+@lisp
+(with-open-file (i pathname :external-format '(:utf-8 :replacement #\?))
+ (read-line i))
+@end lisp
+will read the first line of @var{pathname}, replacing any invalid utf-8
+sequences with question marks.
+
@node Bivalent Streams
@section Bivalent Streams
@quotation
Streams are @emph{not} created bivalent by default for performance
reasons. Bivalent streams are incompatible with
-@code{fast-read-char}, an internal optimization in sbcl's stream
+@code{fast-read-char}, an internal optimization in SBCL's stream
machinery that bulk-converts octets to characters and implements a
fast path through @code{read-char}.
@end quotation
@node Gray Streams
@section Gray Streams
+
+The Gray Streams interface is a widely supported extension that
+provides for definition of CLOS-extensible stream classes. Gray
+stream classes are implemented by adding methods to generic functions
+analogous to Common Lisp's standard I/O functions. Instances of Gray
+stream classes may be used with any I/O operation where a non-Gray
+stream can, provided that all required methods have been implemented
+suitably.
+
+@menu
+* Gray Streams classes::
+* Methods common to all streams::
+* Input stream methods::
+* Output stream methods::
+* Binary stream methods::
+* Character input stream methods::
+* Character output stream methods::
+* Gray Streams examples::
+@end menu
+
+@node Gray Streams classes
+@subsection Gray Streams classes
+
+The defined Gray Stream classes are these:
+
@include class-sb-gray-fundamental-stream.texinfo
-@include fun-sb-gray-stream-advance-to-column.texinfo
+@include class-sb-gray-fundamental-input-stream.texinfo
+
+@noindent
+The function input-stream-p will return true of any generalized
+instance of fundamental-input-stream.
+
+@include class-sb-gray-fundamental-output-stream.texinfo
+
+@noindent
+The function output-stream-p will return true of any generalized
+instance of fundamental-output-stream.
+
+@include class-sb-gray-fundamental-binary-stream.texinfo
+
+@noindent
+Note that instantiable subclasses of fundamental-binary-stream should
+provide (or inherit) an applicable method for the generic function
+stream-element-type.
+
+@include class-sb-gray-fundamental-character-stream.texinfo
+@include class-sb-gray-fundamental-binary-input-stream.texinfo
+@include class-sb-gray-fundamental-binary-output-stream.texinfo
+@include class-sb-gray-fundamental-character-input-stream.texinfo
+@include class-sb-gray-fundamental-character-output-stream.texinfo
+
+@node Methods common to all streams
+@subsection Methods common to all streams
+
+These generic functions can be specialized on any generalized instance
+of fundamental-stream.
+
+@include fun-common-lisp-stream-element-type.texinfo
+@include fun-common-lisp-close.texinfo
+@include fun-sb-gray-stream-file-position.texinfo
+
+
+
+@node Input stream methods
+@subsection Input stream methods
+
+These generic functions may be specialized on any generalized instance
+of fundamental-input-stream.
+
@include fun-sb-gray-stream-clear-input.texinfo
+@include fun-sb-gray-stream-read-sequence.texinfo
+
+@node Character input stream methods
+@subsection Character input stream methods
+
+These generic functions are used to implement subclasses of
+fundamental-input-stream:
+
+@include fun-sb-gray-stream-peek-char.texinfo
+@include fun-sb-gray-stream-read-char-no-hang.texinfo
+@include fun-sb-gray-stream-read-char.texinfo
+@include fun-sb-gray-stream-read-line.texinfo
+@include fun-sb-gray-stream-listen.texinfo
+@include fun-sb-gray-stream-unread-char.texinfo
+
+@node Output stream methods
+@subsection Output stream methods
+
+These generic functions are used to implement subclasses of
+fundamental-output-stream:
+
@include fun-sb-gray-stream-clear-output.texinfo
@include fun-sb-gray-stream-finish-output.texinfo
@include fun-sb-gray-stream-force-output.texinfo
+@include fun-sb-gray-stream-write-sequence.texinfo
+
+@node Binary stream methods
+@subsection Binary stream methods
+
+The following generic functions are available for subclasses of
+fundamental-binary-stream:
+
+@include fun-sb-gray-stream-read-byte.texinfo
+@include fun-sb-gray-stream-write-byte.texinfo
+
+@node Character output stream methods
+@subsection Character output stream methods
+
+These generic functions are used to implement subclasses of
+fundamental-character-output-stream:
+
+@include fun-sb-gray-stream-advance-to-column.texinfo
@include fun-sb-gray-stream-fresh-line.texinfo
@include fun-sb-gray-stream-line-column.texinfo
@include fun-sb-gray-stream-line-length.texinfo
-@include fun-sb-gray-stream-listen.texinfo
-@include fun-sb-gray-stream-peek-char.texinfo
-@include fun-sb-gray-stream-read-byte.texinfo
-@include fun-sb-gray-stream-read-char-no-hang.texinfo
-@include fun-sb-gray-stream-read-char.texinfo
-@include fun-sb-gray-stream-read-line.texinfo
-@include fun-sb-gray-stream-read-sequence.texinfo
@include fun-sb-gray-stream-start-line-p.texinfo
@include fun-sb-gray-stream-terpri.texinfo
-@include fun-sb-gray-stream-unread-char.texinfo
-@include fun-sb-gray-stream-write-byte.texinfo
@include fun-sb-gray-stream-write-char.texinfo
-@include fun-sb-gray-stream-write-sequence.texinfo
@include fun-sb-gray-stream-write-string.texinfo
+@include gray-streams-examples.texinfo
+
@node Simple Streams
@comment node-name, next, previous, up
@section Simple Streams
projects / sbcl.git / blobdiff