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finish up SRFI-98: docs and R6RS

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svn: r17302
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Matthew Flatt 2009-12-15 01:21:09 +00:00
parent 8996c49ee9
commit 9d9e586123
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12
collects/srfi/%3a98.ss Normal file
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#lang scheme/base
(require srfi/98
scheme/mpair)
(provide get-environment-variable
(rename-out (mpair:get-environment-variables
get-environment-variables)))
(define (mpair:get-environment-variables)
(list->mlist (map (lambda (pair)
(mcons (car pair) (cdr pair)))
(get-environment-variables))))

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collects/srfi/98.ss
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@ -1,76 +1,76 @@
;; Copyright (c) 2009 Derick Eddington. All rights reserved.
;; Permission is hereby granted, free of charge, to any person obtaining a
;; copy of this software and associated documentation files (the "Software"),
;; to deal in the Software without restriction, including without limitation
;; the rights to use, copy, modify, merge, publish, distribute, sublicense,
;; and/or sell copies of the Software, and to permit persons to whom the
;; Software is furnished to do so, subject to the following conditions:
;; The above copyright notice and this permission notice shall be included in
;; all copies or substantial portions of the Software.
;; Except as contained in this notice, the name(s) of the above copyright
;; holders shall not be used in advertising or otherwise to promote the sale,
;; use or other dealings in this Software without prior written authorization.
;; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
;; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
;; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
;; THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
;; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
;; FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
;; DEALINGS IN THE SOFTWARE.
;; Inspired by Danny Yoo's get-environment PLaneT package.
#lang scheme/base
(require scheme/foreign)
(provide (rename-out (getenv get-environment-variable))
get-environment-variables)
(unsafe!)
(define (get-environment-variables)
(define (split-strings l)
(for/list ([next (in-list l)])
(let loop ((i 0) (len (string-length next)))
(if (< i len)
(if (char=? #\= (string-ref next i))
(cons (substring next 0 i)
(substring next (+ 1 i) len))
(loop (+ 1 i) len))
(cons next #f)))))
(case (system-type)
[(windows)
(let ([get (get-ffi-obj "GetEnvironmentStringsW" #f (_fun #:abi 'stdcall -> _bytes))]
[free (get-ffi-obj "FreeEnvironmentStringsW" #f (_fun #:abi 'stdcall _pointer -> _void))])
(let* ([strs (get)]
[len (let loop ([i 0])
(if (and (= 0 (ptr-ref strs _byte i))
(= 0 (ptr-ref strs _byte (+ i 1)))
(= 0 (ptr-ref strs _byte (+ i 2)))
(= 0 (ptr-ref strs _byte (+ i 3))))
(+ i 4)
(loop (+ i 2))))]
[strs (cast strs _pointer (_bytes o len))])
(begin0
(split-strings
(let loop ([pos 0])
(let ([m (regexp-match-positions #rx"(?:..)*?\0\0" strs pos)])
(if m
(if (= (cdar m) (+ pos 2))
null
(cons (cast (ptr-add strs pos) _pointer _string/utf-16)
(loop (cdar m))))
null))))
(free strs))))]
[else
(let ([environ (get-ffi-obj "environ" (ffi-lib #f) _pointer)])
(split-strings
(let loop ([i 0])
(let ((next (ptr-ref environ _string/locale i)))
(if next
(cons next (loop (+ 1 i)))
null)))))]))
;; Copyright (c) 2009 Derick Eddington. All rights reserved.
;; Permission is hereby granted, free of charge, to any person obtaining a
;; copy of this software and associated documentation files (the "Software"),
;; to deal in the Software without restriction, including without limitation
;; the rights to use, copy, modify, merge, publish, distribute, sublicense,
;; and/or sell copies of the Software, and to permit persons to whom the
;; Software is furnished to do so, subject to the following conditions:
;; The above copyright notice and this permission notice shall be included in
;; all copies or substantial portions of the Software.
;; Except as contained in this notice, the name(s) of the above copyright
;; holders shall not be used in advertising or otherwise to promote the sale,
;; use or other dealings in this Software without prior written authorization.
;; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
;; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
;; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
;; THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
;; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
;; FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
;; DEALINGS IN THE SOFTWARE.
;; Inspired by Danny Yoo's get-environment PLaneT package.
#lang scheme/base
(require scheme/foreign)
(provide (rename-out (getenv get-environment-variable))
get-environment-variables)
(unsafe!)
(define (get-environment-variables)
(define (split-strings l)
(for/list ([next (in-list l)])
(let loop ((i 0) (len (string-length next)))
(if (< i len)
(if (char=? #\= (string-ref next i))
(cons (substring next 0 i)
(substring next (+ 1 i) len))
(loop (+ 1 i) len))
(cons next #f)))))
(case (system-type)
[(windows)
(let ([get (get-ffi-obj "GetEnvironmentStringsW" #f (_fun #:abi 'stdcall -> _bytes))]
[free (get-ffi-obj "FreeEnvironmentStringsW" #f (_fun #:abi 'stdcall _pointer -> _void))])
(let* ([strs (get)]
[len (let loop ([i 0])
(if (and (= 0 (ptr-ref strs _byte i))
(= 0 (ptr-ref strs _byte (+ i 1)))
(= 0 (ptr-ref strs _byte (+ i 2)))
(= 0 (ptr-ref strs _byte (+ i 3))))
(+ i 4)
(loop (+ i 2))))]
[strs (cast strs _pointer (_bytes o len))])
(begin0
(split-strings
(let loop ([pos 0])
(let ([m (regexp-match-positions #rx"(?:..)*?\0\0" strs pos)])
(if m
(if (= (cdar m) (+ pos 2))
null
(cons (cast (ptr-add strs pos) _pointer _string/utf-16)
(loop (cdar m))))
null))))
(free strs))))]
[else
(let ([environ (get-ffi-obj "environ" (ffi-lib #f) _pointer)])
(split-strings
(let loop ([i 0])
(let ((next (ptr-ref environ _string/locale i)))
(if next
(cons next (loop (+ 1 i)))
null)))))]))

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collects/srfi/srfi.scrbl
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@ -964,4 +964,11 @@ This SRFI's syntax is part of PLT Scheme's default reader (no
@; ----------------------------------------
@srfi[98]{An interface to access environment variables}
@redirect[98 '((get-environment-variable #f "get-environment-variable")
(get-environment-variables #f "get-environment-variables"))]
@; ----------------------------------------
@index-section[]

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html><head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8"><!-- DO NOT EDIT THIS FILE-->
<!-- Edit the .tex version instead-->
<title>SRFI 98: An interface to access environment variables.</title>
</head><body>
<h1>Title</h1>
An interface to access environment variables.
<h1>Author</h1>
Taro Minowa(Higepon)
<h1>Status</h1>
This SRFI is currently in ``final'' status. To see an explanation of
each status that a SRFI can hold, see <a href="http://srfi.schemers.org/srfi-process.html">here</a>.
To provide input on this SRFI, please send email to
<a href="mailto:srfi%20minus%2098%20at%20srfi%20dot%20schemers%20dot%20org">
<code>&lt;srfi minus 98 at srfi dot schemers dot org&gt;</code></a>. See
<a href="http://srfi.schemers.org/srfi-list-subscribe.html">instructions here</a> to subscribe to
the list. You can access the discusssion via
<a href="http://srfi.schemers.org/srfi-98/mail-archive/maillist.html">the archive of the mailing list</a>.
You can access
post-finalization messages via
<a href="http://srfi.schemers.org/srfi-98/post-mail-archive/maillist.html">
the archive of the mailing list</a>.
<p></p><ul>
<li>Received: <a href="http://srfi.schemers.org/cgi-bin/viewcvs.cgi/*checkout*/srfi/srfi-98/srfi-98.html?rev=1.2">2008/07/06</a></li>
<li>Draft: 2008/07/06 - 2008/09/06</li>
<li>Revised: <a href="http://srfi.schemers.org/cgi-bin/viewcvs.cgi/*checkout*/srfi/srfi-98/srfi-98.html?rev=1.3">2008/07/18</a></li>
<li>Revised: <a href="http://srfi.schemers.org/cgi-bin/viewcvs.cgi/*checkout*/srfi/srfi-98/srfi-98.html?rev=1.4">2008/07/18</a></li>
<li>Revised: <a href="http://srfi.schemers.org/cgi-bin/viewcvs.cgi/*checkout*/srfi/srfi-98/srfi-98.html?rev=1.5">2008/08/14</a></li>
<li>Final: <a href="http://srfi.schemers.org/cgi-bin/viewcvs.cgi/*checkout*/srfi/srfi-98/srfi-98.html?rev=1.7">2008/09/19</a></li>
<li>R6RS library name: <a href="http://srfi.schemers.org/cgi-bin/viewcvs.cgi/*checkout*/srfi/srfi-98/srfi-98.html?rev=1.8">2009/02/16</a></li>
</ul>
<h1>Abstract</h1>
This SRFI specifies the procedure get-environment-variable, which gets
the value of the specified environment variable, and the procedure
get-environment-variables, which gets an association list of all
environment variables.
<h1>Rationale</h1>
<p>Most operating systems provide a mechanism for passing auxiliary
parameters implicitly to child processes. Usually, this mechanism is
called "the environment", and is conceptually a map from string names
to string values. The string names are called enviornment
variables.</p>
<p>Some applications rely on environment variables to modify their
behavior according to local settings. Also, various established
protocols rely on environment variables as a form of interprocess
communication. For example, most implementations of the common
gateway interface (CGI) use environment variables to pass
Meta-Variables from the server to the script <a href="#0.1_cgi">[1]</a>.
Environment variables are also required
by <a href="http://srfi.schemers.org/srfi-96/srfi-96.html" title="SRFI
96: SLIB Prerequisites">SRFI 96: SLIB Prerequisites</a>.
Providing a means to access environment variables is therefore
indispensable for writing practical programs in Scheme.
</p>
<p>Most widely-used Scheme implementations provide a function for
getting the value of a specified environment variable. The name for
this function is usually getenv, but varies (<a href="#0.1_appendix">see
below</a>). Some implementations also provide a way to get all the
environment variables, but others do not.</p>
<p>This SRFI specifies a uniform interface for accessing environment
variables. That should make it easier to write portable programs
that need access to their environment.
For example, a CGI program may portably obtain the values of the
Meta-Variables "QUERY_STRING", "CONTENT_LENGTH" and
"REQUEST_METHOD" as in the following examples:</p>
<pre>(get-environment-variable "QUERY_STRING") =&gt; "foo=bar&amp;huga=hige"
(get-environment-variable "CONTENT_LENGTH") =&gt; "512"
(get-environment-variable "REQUEST_METHOD") =&gt; "post"
</pre>
<p><a name="0.1_cgi">[1]</a> The Common Gateway Interface (CGI) Version 1.1, RFC3875, <a href="http://www.ietf.org/rfc/rfc3875" target="_blank">http://www.ietf.org/rfc/rfc3875</a>.</p>
<h1>Specification</h1>
<pre>R6RS library name</pre>
The following two procedures belong to the R6RS library named (srfi :98 os-environment-variables).
<pre>Function: <a name="get-environment-variable">get-environment-variable</a> name</pre>Returns the value of
the named environment variable as a string, or #f if the named
environment variable is not found. The name argument is expected to be
a string.
get-environment-variable may use
locale-setting information to encode the name and decode the value of
the environment variable.
If get-environment-variable can't decode the value, get-environment-variable may raise an exception.
<pre>(get-environment-variable "PATH") =&gt; "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin"
</pre>
<pre>Function: <a name="get-environment-variables">get-environment-variables</a></pre>
Returns names and values of all the environment variables as an a-list.
The same decoding considerations as for get-environment-variable apply.
<pre>(get-environment-variables) =&gt; (("PATH" . "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin") ("USERNAME" . "taro"))
</pre>
<h1>Implementation</h1>
<h2>Gauche</h2>
<pre>(define get-environment-variable sys-getenv)
(define get-environment-variables sys-environ-&gt;alist)
</pre>
<h2>Scheme48</h2>
<pre>(define (get-environment-variable name)
(cond
((lookup-environment-variable name) =&gt; os-string-&gt;string)
(else #f)))
(define (get-environment-variables)
(map (lambda (p)
(cons (os-string-&gt;string (car p)) (os-string-&gt;string (cdr p))))
(environment-alist)))
</pre>
<h2>scsh</h2>
<pre>(define get-environment-variable getenv)
(define get-environment-variables env-&gt;alist)
</pre>
<h2>SCM</h2>
<pre>(define get-environment-variable getenv)
(define get-environment-variables getenv)
</pre>
<h1>Issues</h1>
<p>get-environment-variable is expected to return a "Scheme string".
Unfortunately, many current platforms, including POSIX-like ones, do
not require environment variables to be interpretable as sequences of
characters. In particular, environment variables can be used to name
files, and filenames on the system can amount to NULL-terminated byte
vectors, which, if the Scheme program were to collect uninterpreted
and pass to, say, the open call, would work just fine, but which might
not represent a string in the particular encoding the program expects.
While in principle it may be desirable to provide a mechanism for
accessing environment variables raw, this SRFI specifies a "string"
return type because that best represents the consensus of existing
implementations, and captures the semantically desirable behavior in
the common case that the byte sequence is interpretable as a string.</p>
<a name="0.1_appendix"></a>
<h1>Appendix: Existing implementations</h1>
<table border="1">
<tbody><tr><th>Scheme implementation</th><th>get environment variable</th><th>get all the environment variables as an a-list</th></tr>
<tr><td>Bigloo</td><td>(getenv name) =&gt; (or string? false) name:string?</td><td>&nbsp;</td></tr>
<tr><td>CHICKEN</td><td>(getenv name) =&gt; (or string? false) name:string?</td><td>&nbsp;</td></tr>
<tr><td>Gambit</td><td>(getenv name . &lt;default&gt;) =&gt;(or string? &lt;default&gt; &lt;Unbound OS environment variable error&gt;) name:string?</td><td>&nbsp;</td></tr>
<tr><td>Gauche</td><td>(sys-getenv name) =&gt; (or string? false) name:string?</td><td>(sys-environ)</td></tr>
<tr><td>Guile</td><td>(getenv name) =&gt; (or string? false) name:string?</td><td>&nbsp;</td></tr>
<tr><td>PLT</td><td>(getenv name) =&gt; (or string? false) name:string?</td><td>&nbsp;</td></tr>
<tr><td>MIT/GNU Scheme</td><td>(get-environment-variable name) =&gt; (or string? false) name:string?</td><td>&nbsp;</td></tr>
<tr><td>Scheme48</td><td>(lookup-environment-variable name) =&gt; (or string? false) name:string?</td><td>(environment-alist)</td></tr>
<tr><td>SLIB</td><td>(getenv name) =&gt; (or string? false) name:string?</td><td>&nbsp;</td></tr>
<tr><td>STk</td><td>(getenv name) =&gt; (or string? false) name:string?</td><td>&nbsp;</td></tr>
<tr><td>STklos</td><td>(getenv name) =&gt; (or string? false) name:string?</td><td>(getenv)</td></tr>
<tr><td>SCM</td><td>(getenv name) =&gt; (or string? false) name:string?</td><td>(getenv)</td></tr>
</tbody></table>
<h1>Acknowledgements</h1>
Thanks to Shiro Kawai, Alexey Radul, jmuk, Kokosabu, leque and all the members of the #Lisp_Scheme IRC channel on Freenode.
<h1>Copyright</h1>
Copyright (C) Taro Minowa(Higepon) (2008). All Rights Reserved.
<p>
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
</p>
<p>
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
</p>
<p>THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
</p>
<hr>
<address>Editor: <a href="mailto:srfi-editors%20at%20srfi%20dot%20schemers%20dot%20org">Mike Sperber</a></address>
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