http.n

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'\" Copyright (c) 1995-1997 Sun Microsystems, Inc.
'\" Copyright (c) 1998-2000 by Ajuba Solutions.
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'\" RCS: @(#) $Id: http.n,v 1.18 2002/07/23 18:17:12 jenglish Exp $
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.so man.macros
.TH "http" n 2.4 http "Tcl Bundled Packages"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
http \- Client-side implementation of the HTTP/1.0 protocol.
.SH SYNOPSIS
\fBpackage require http ?2.4?\fR
.sp
\fB::http::config \fI?options?\fR
.sp
\fB::http::geturl \fIurl ?options?\fR
.sp
\fB::http::formatQuery \fIlist\fR
.sp
\fB::http::reset \fItoken\fR
.sp
\fB::http::wait \fItoken\fR
.sp
\fB::http::status \fItoken\fR
.sp
\fB::http::size \fItoken\fR
.sp
\fB::http::code \fItoken\fR
.sp
\fB::http::ncode \fItoken\fR
.sp
\fB::http::data \fItoken\fR
.sp
\fB::http::error \fItoken\fR
.sp
\fB::http::cleanup \fItoken\fR
.sp
\fB::http::register \fIproto port command\fR
.sp
\fB::http::unregister \fIproto\fR
.BE

.SH DESCRIPTION
.PP
The \fBhttp\fR package provides the client side of the HTTP/1.0
protocol.  The package implements the GET, POST, and HEAD operations
of HTTP/1.0.  It allows configuration of a proxy host to get through
firewalls.  The package is compatible with the \fBSafesock\fR security
policy, so it can be used by untrusted applets to do URL fetching from
a restricted set of hosts. This package can be extended to support
additional HTTP transport protocols, such as HTTPS, by providing
a custom \fBsocket\fR command, via \fBhttp::register\fR.
.PP
The \fB::http::geturl\fR procedure does a HTTP transaction.
Its \fIoptions \fR determine whether a GET, POST, or HEAD transaction
is performed.  
The return value of \fB::http::geturl\fR is a token for the transaction.
The value is also the name of an array in the ::http namespace
that contains state information about the transaction.  The elements
of this array are described in the STATE ARRAY section.
.PP
If the \fB-command\fP option is specified, then
the HTTP operation is done in the background.
\fB::http::geturl\fR returns immediately after generating the
HTTP request and the callback is invoked
when the transaction completes.  For this to work, the Tcl event loop
must be active.  In Tk applications this is always true.  For pure-Tcl
applications, the caller can use \fB::http::wait\fR after calling
\fB::http::geturl\fR to start the event loop.
.SH COMMANDS
.TP
\fB::http::config\fP ?\fIoptions\fR?
The \fB::http::config\fR command is used to set and query the name of the
proxy server and port, and the User-Agent name used in the HTTP
requests.  If no options are specified, then the current configuration
is returned.  If a single argument is specified, then it should be one
of the flags described below.  In this case the current value of
that setting is returned.  Otherwise, the options should be a set of
flags and values that define the configuration:
.RS
.TP
\fB\-accept\fP \fImimetypes\fP
The Accept header of the request.  The default is */*, which means that
all types of documents are accepted.  Otherwise you can supply a 
comma separated list of mime type patterns that you are
willing to receive.  For example, "image/gif, image/jpeg, text/*".
.TP
\fB\-proxyhost\fP \fIhostname\fP
The name of the proxy host, if any.  If this value is the
empty string, the URL host is contacted directly.
.TP
\fB\-proxyport\fP \fInumber\fP
The proxy port number.
.TP
\fB\-proxyfilter\fP \fIcommand\fP
The command is a callback that is made during
\fB::http::geturl\fR
to determine if a proxy is required for a given host.  One argument, a
host name, is added to \fIcommand\fR when it is invoked.  If a proxy
is required, the callback should return a two element list containing
the proxy server and proxy port.  Otherwise the filter should return
an empty list.  The default filter returns the values of the
\fB\-proxyhost\fR and \fB\-proxyport\fR settings if they are
non-empty.
.TP
\fB\-useragent\fP \fIstring\fP
The value of the User-Agent header in the HTTP request.  The default
is \fB"Tcl http client package 2.4."\fR
.RE
.TP
\fB::http::geturl\fP \fIurl\fP ?\fIoptions\fP? 
The \fB::http::geturl\fR command is the main procedure in the package.
The \fB\-query\fR option causes a POST operation and
the \fB\-validate\fR option causes a HEAD operation;
otherwise, a GET operation is performed.  The \fB::http::geturl\fR command
returns a \fItoken\fR value that can be used to get
information about the transaction.  See the STATE ARRAY and ERRORS section for
details.  The \fB::http::geturl\fR command blocks until the operation
completes, unless the \fB\-command\fR option specifies a callback
that is invoked when the HTTP transaction completes.
\fB::http::geturl\fR takes several options:
.RS
.TP
\fB\-binary\fP \fIboolean\fP
Specifies whether to force interpreting the url data as binary.  Normally
this is auto-detected (anything not beginning with a \fBtext\fR content
type or whose content encoding is \fBgzip\fR or \fBcompress\fR is
considered binary data).
.TP
\fB\-blocksize\fP \fIsize\fP
The blocksize used when reading the URL.
At most \fIsize\fR bytes are read at once.  After each block, a call to the
\fB\-progress\fR callback is made (if that option is specified).
.TP
\fB\-channel\fP \fIname\fP
Copy the URL contents to channel \fIname\fR instead of saving it in
\fBstate(body)\fR.
.TP
\fB\-command\fP \fIcallback\fP
Invoke \fIcallback\fP after the HTTP transaction completes.
This option causes \fB::http::geturl\fP to return immediately.
The \fIcallback\fP gets an additional argument that is the \fItoken\fR returned
from \fB::http::geturl\fR. This token is the name of an array that is
described in the STATE ARRAY section.  Here is a template for the
callback:
.RS
.CS
proc httpCallback {token} {
    upvar #0 $token state
    # Access state as a Tcl array
}
.CE
.RE
.TP
\fB\-handler\fP \fIcallback\fP
Invoke \fIcallback\fP whenever HTTP data is available; if present, nothing
else will be done with the HTTP data.  This procedure gets two additional
arguments: the socket for the HTTP data and the \fItoken\fR returned from
\fB::http::geturl\fR.  The token is the name of a global array that is described
in the STATE ARRAY section.  The procedure is expected to return the number
of bytes read from the socket.  Here is a template for the callback:
.RS
.CS
proc httpHandlerCallback {socket token} {
    upvar #0 $token state
    # Access socket, and state as a Tcl array
    ...
    (example: set data [read $socket 1000];set nbytes [string length $data])
    ...
    return nbytes
}
.CE
.RE
.TP
\fB\-headers\fP \fIkeyvaluelist\fP
This option is used to add extra headers to the HTTP request.  The
\fIkeyvaluelist\fR argument must be a list with an even number of
elements that alternate between keys and values.  The keys become
header field names.  Newlines are stripped from the values so the
header cannot be corrupted.  For example, if \fIkeyvaluelist\fR is
\fBPragma no-cache\fR then the following header is included in the
HTTP request:
.CS
Pragma: no-cache
.CE
.TP
\fB\-progress\fP \fIcallback\fP
The \fIcallback\fR is made after each transfer of data from the URL.
The callback gets three additional arguments: the \fItoken\fR from
\fB::http::geturl\fR, the expected total size of the contents from the
\fBContent-Length\fR meta-data, and the current number of bytes
transferred so far.  The expected total size may be unknown, in which
case zero is passed to the callback.  Here is a template for the
progress callback:
.RS
.CS
proc httpProgress {token total current} {
    upvar #0 $token state
}
.CE
.RE
.TP
\fB\-query\fP \fIquery\fP
This flag causes \fB::http::geturl\fR to do a POST request that passes the
\fIquery\fR to the server. The \fIquery\fR must be a x-url-encoding
formatted query.  The \fB::http::formatQuery\fR procedure can be used to
do the formatting.
.TP
\fB\-queryblocksize\fP \fIsize\fP
The blocksize used when posting query data to the URL.
At most 
\fIsize\fR
bytes are written at once.  After each block, a call to the
\fB\-queryprogress\fR
callback is made (if that option is specified).
.TP
\fB\-querychannel\fP \fIchannelID\fP
This flag causes \fB::http::geturl\fR to do a POST request that passes the
data contained in \fIchannelID\fR to the server. The data contained in \fIchannelID\fR must be a x-url-encoding
formatted query unless the \fB\-type\fP option below is used.
If a Content-Length header is not specified via the \fB\-headers\fR options,
\fB::http::geturl\fR attempts to determine the size of the post data
in order to create that header.  If it is
unable to determine the size, it returns an error.
.TP
\fB\-queryprogress\fP \fIcallback\fP
The \fIcallback\fR is made after each transfer of data to the URL
(i.e. POST) and acts exactly like the \fB\-progress\fR option (the
callback format is the same).
.TP
\fB\-timeout\fP \fImilliseconds\fP
If \fImilliseconds\fR is non-zero, then \fB::http::geturl\fR sets up a timeout
to occur after the specified number of milliseconds.
A timeout results in a call to \fB::http::reset\fP and to
the \fB-command\fP callback, if specified.
The return value of \fB::http::status\fP is \fBtimeout\fP
after a timeout has occurred.
.TP
\fB\-type\fP \fImime-type\fP
Use \fImime-type\fR as the \fBContent-Type\fR value, instead of the
default value (\fBapplication/x-www-form-urlencoded\fR) during a
POST operation.
.TP
\fB\-validate\fP \fIboolean\fP
If \fIboolean\fR is non-zero, then \fB::http::geturl\fR does an HTTP HEAD
request.  This request returns meta information about the URL, but the
contents are not returned.  The meta information is available in the
\fBstate(meta) \fR variable after the transaction.  See the STATE
ARRAY section for details.
.RE
.TP
\fB::http::formatQuery\fP \fIkey value\fP ?\fIkey value\fP ...?
This procedure does x-url-encoding of query data.  It takes an even
number of arguments that are the keys and values of the query.  It
encodes the keys and values, and generates one string that has the
proper & and = separators.  The result is suitable for the
\fB\-query\fR value passed to \fB::http::geturl\fR.
.TP
\fB::http::reset\fP \fItoken\fP ?\fIwhy\fP?