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<TITLE>Public Declaration of Request Manager</TITLE>
<!-- Changed by: Henrik Frystyk Nielsen, 28-Sep-1995 -->
<NEXTID N="z11">
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<H1>Public Declaration of Request Manager</H1>
<PRE>
/*
** (c) COPYRIGHT MIT 1995.
** Please first read the full copyright statement in the file COPYRIGH.
*/
</PRE>
The request manager consists of two parts: a public part and a private
part. The public part contains all the information needed to define a
request the parameters to be used when requesting a resource from the
network or local file system. When a request is handled, all kinds of
things about it need to be passed along together with a request.
<P>
This module is implemented by <A HREF="HTReqMan.c">HTReqMan.c</A>, and
it is a part of the <A HREF="http://www.w3.org/hypertext/WWW/Library/">
W3C Reference Library</A>. <P>
<PRE>
#ifndef HTREQ_H
#define HTREQ_H
typedef struct _HTRequest HTRequest;
#include "HTList.h"
#include "HTFormat.h"
#include "HTStream.h"
#include "HTEvntrg.h"
#include "HTNet.h"
</PRE>
<A NAME="flags"><H2>Global Flags</H2></A>
Flags and variables which may be set to control the Library
<H3>Allow Accss to Local File System</H3>
This flag can be used to deny an application to get access to the
local file system (through cache, file URLs etc.) It is a good way to
avoid accitendal access if an application provides telnet service etc.
<PRE>
extern BOOL HTSecure; /* Disable security holes? */
</PRE>
<H3>Name of Remote login Host</H3>
If an application is used for remote access (allowing telnet access,
like for example the Line Mode Browser), then set this variable to the
name of the remote host.
<PRE>
extern char * HTClientHost; /* Name or number of telnetting host */
</PRE>
<H3>Server Specific Flags</H3>
These two flags are set by a proxy and a server application
respectfully. They tell the Library to skip some of the client
application specific things.
<PRE>
extern char * HTImServer; /* If I'm cern_httpd */
extern BOOL HTImProxy; /* If I'm cern_httpd as a proxy */
</PRE>
<H2>Request a resource</H2>
This is an internal routine, which has an address AND a matching
anchor. (The public routines are called with one OR the other.)
<PRE>
extern BOOL HTLoad (HTRequest * request, HTPriority priority, BOOL recursive);
</PRE>
<H2>Request Terminate Call Back Function</H2>
This function is registered at startup time by HTLibInit() in order to
probably terminate a request to the Library. The application can
register addtional call back functions in the same manner:
<PRE>
extern HTNetCallBack HTLoad_terminate;
</PRE>
<H2>Creation and Deletion Methods</H2>
The request object is intended to live as long as the request is still
active, but can be deleted as soon as it has terminatedk, for example
in one of the request termination callback functions as described in
the <A HREF="HTNet.html">Net Manager</A>. Only the anchor object stays
around after the request itself is terminated.
<H3>Create new Object</H3>
Creates a new request object with a default set of options -- in most
cases it will need some information added which can be done using the
methods in this module, but it will work as is for a simple request.
<PRE>
extern HTRequest * HTRequest_new (void);
</PRE>
<H3>Delete Object</H3>
This function deletes the object and cleans up the memory.
<PRE>
extern void HTRequest_delete (HTRequest * request);
</PRE>
<H2>Bind an Anchor to a Request Object</H2>
Every request object has an anchor associated with it. The anchor
normally lives until the application terminates but a request object
only lives as long as the request is being serviced.
<PRE>
extern void HTRequest_setAnchor (HTRequest *request, HTAnchor *anchor);
extern HTParentAnchor * HTRequest_anchor (HTRequest *request);
</PRE>
<H2>Set the Method</H2>
The Method is the operation to be executed on the requested
object. The default set if the set of operations defined by the HTTP
protocol, that is "GET", "HEAD", "PUT", "POST", "LINK", "UNLINK", and
"DELETE" but many of these can be used in other protocols as well. The
important thing is to think of the requested element as an object on
which you want to perform an operation. Then it is for the specific
protocol implementation to try and carry this operation out. However,
not all operations can be implemented (or make sense) in all
protocols. <P>
Methods are handled by the <A HREF="HTMethod.html">Method Module</A>,
and the default value is "GET".
<PRE>
extern void HTRequest_setMethod (HTRequest *request, HTMethod method);
extern HTMethod HTRequest_method (HTRequest *request);
</PRE>
<H2>Update, Reload, or Refresh a Document</H2>
The Library has two concepts of caching: in memory and on file. When
loading a document, this flag can be set in order to define who can
give a response to the request. <EM>IMS</EM> means that a
"If-Modified-Since" Header is used in a HTTP request.
<PRE>
typedef enum _HTReload {
HT_ANY_VERSION = 0x0, /* Use any version available */
HT_MEM_REFRESH = 0x1, /* Reload from file cache or network */
HT_CACHE_REFRESH = 0x2, /* Update from network with IMS */
HT_FORCE_RELOAD = 0x4 /* Update from network with no-cache */
} HTReload;
extern void HTRequest_setReloadMode (HTRequest *request, HTReload mode);
extern HTReload HTRequest_reloadMode (HTRequest *request);
</PRE>
<H2>Max number of Retrys for a Down Load</H2>
Automatic reload can happen in two situations:
<UL>
<LI>The server sends a redirection response
<LI>The document has expired
</UL>
In order to avoid the Library going into an infinite loop, it is
necessary to keep track of the number of automatic reloads. Loops can
occur if the server has a reload to the same document or if the server
sends back a Expires header which has already expired. The default
maximum number of automatic reloads is 6.
<PRE>
extern BOOL HTRequest_setMaxRetry (int newmax);
extern int HTRequest_maxRetry (void);
extern BOOL HTRequest_retry (HTRequest *request);
</PRE>
<H2>Retry Request After</H2>
Some services, for example HTTP, can in case they are unavailable at
the time the request is issued send back a time and date stamp to the
client telling when they are expected to back online. In case a
request results in a HT_RETRY status, the application can use any time
indicated in this field to retry the request at a later time. The
Library does not initiate any request on its own - it's for the
application to do. The time returned by this function is in calendar
time or -1 if not available.
<PRE>
extern time_t HTRequest_retryTime (HTRequest * request);
</PRE>
<H2>Accept Headers</H2>
The Accept family of headers is an important part of HTTP handling the
format negotiation. The Library supports both a global set of accept
headers that are used in <EM>all</EM> HTTP requests and a local set of
accept headers that are used in specific requests only. The global
ones are defined in the <A HREF="HTFormat.html">Format
Manager</A>. <P>
Each request can have its local set of accept headers that either are
added to the global set or replaces the global set of accept
headers. Non of the headers <EM>have</EM> to be set. If the global set
is sufficient for all requests then this us perfectly fine. If the
parameter "override" is set then only local accept headers are used,
else <EM>both</EM> local and global headers are used.
<H3>Content Types</H3>
Th <EM>local</EM> list of specific conversions which the format
manager can do in order to fulfill the request. It typically points
to a list set up on initialisation time for example by <A
HREF="HTInit.html">HTInit()</A>. There is also a <A
HREF="HTFormat.html#z17"><EM>global</EM></A> list of conversions which
contains a generic set of possible conversions.
<PRE>
extern void HTRequest_setFormat (HTRequest *request, HTList *type, BOOL override);
extern HTList * HTRequest_format (HTRequest *request);
</PRE>
<H3>Content Encodings</H3>
The list of encodings acceptable in the output stream.
<PRE>
extern void HTRequest_setEncoding (HTRequest *request, HTList *enc, BOOL override);
extern HTList * HTRequest_encoding (HTRequest *request);
</PRE>
<H3>Content-Languages</H3>
The list of (human) language values acceptable in the response. The default
is all languages.
<PRE>
extern void HTRequest_setLanguage (HTRequest *request, HTList *lang, BOOL override);
extern HTList * HTRequest_language (HTRequest *request);
</PRE>
<H3>Charset</H3>
The list of charsets accepted by the application
<PRE>
extern void HTRequest_setCharset (HTRequest *request, HTList *charset, BOOL override);
extern HTList * HTRequest_charset (HTRequest *request);
</PRE>
<H2>Handling Metainformation (RFC822 Headers)</H2>
The Library supports a large set of headers that can be sent along
with a request (or a response for that matter). All headers can be
either disabled or enabled using bit flags that are defined in the
following.
<H3><A NAME="gnhd">General HTTP Header Mask</A></H3>
There are a few header fields which have general applicability for
both request and response mesages, but which do not apply to the
communication parties or theentity being transferred. This mask
enables and disables these headers. If the bit is not turned on they
are not sent. All headers are optional and the default value is <EM>NO
GENERAL HEADERS</EM>
<PRE>
typedef enum _HTGnHd {
HT_DATE = 0x1,
HT_FORWARDED = 0x2,
HT_MESSAGE_ID = 0x4,
HT_MIME = 0x8,
HT_CONNECTION = 0x10,
HT_NO_CACHE = 0x20 /* Pragma */
} HTGnHd;
#define DEFAULT_GENERAL_HEADERS HT_CONNECTION
extern void HTRequest_setGnHd (HTRequest *request, HTGnHd gnhd);
extern void HTRequest_addGnHd (HTRequest *request, HTGnHd gnhd);
extern HTGnHd HTRequest_gnHd (HTRequest *request);
</PRE>
<H3><A NAME="rqhd">Request Headers</A></H3>
The request header fields allow the client to pass additional
information about the request (and about the client itself) to the
server. All headers are optional but the default value is all request
headers if present <EM>except</EM> <CODE>From</CODE> and
<CODE>Pragma</CODE>.
<PRE>
typedef enum _HTRqHd {
HT_ACCEPT_TYPE = 0x1,
HT_ACCEPT_CHAR = 0x2,
HT_ACCEPT_ENC = 0x4,
HT_ACCEPT_LAN = 0x8,
HT_FROM = 0x10,
HT_IMS = 0x20,
HT_HOST = 0x40,
HT_REFERER = 0x80,
HT_USER_AGENT = 0x200
} HTRqHd;
#define DEFAULT_REQUEST_HEADERS \
HT_ACCEPT_TYPE+HT_ACCEPT_CHAR+HT_ACCEPT_ENC+HT_ACCEPT_LAN+HT_REFERER+HT_USER_AGENT
extern void HTRequest_setRqHd (HTRequest *request, HTRqHd rqhd);
extern void HTRequest_addRqHd (HTRequest *request, HTRqHd rqhd);
extern HTRqHd HTRequest_rqHd (HTRequest *request);
</PRE>
<H3><A NAME="enhd">Entity Header Mask</A></H3>
The entity headers contain information about the object sent in the
HTTP transaction. See the <A HREF="HTAnchor.html">Anchor module</A>,
for the storage of entity headers. This flag defines which headers are
to be sent in a request together with an entity body. All headers are
optional but the default value is <EM>ALL ENTITY HEADERS IF
PRESENT</EM>
<PRE>
typedef enum _HTEnHd {
HT_ALLOW = 0x1,
HT_CONTENT_ENCODING = 0x2,
HT_CONTENT_LANGUAGE = 0x4,
HT_CONTENT_LENGTH = 0x8,
HT_CTE = 0x10, /* Content-Transfer-Encoding */
HT_CONTENT_TYPE = 0x20,
HT_DERIVED_FROM = 0x40,
HT_EXPIRES = 0x80,
HT_LAST_MODIFIED = 0x200,
HT_LINK = 0x400,
HT_TITLE = 0x800,
HT_URI = 0x1000,
HT_VERSION = 0x2000
} HTEnHd;
#define DEFAULT_ENTITY_HEADERS 0xFFFF /* all */
extern void HTRequest_setEnHd (HTRequest *request, HTEnHd enhd);
extern void HTRequest_addEnHd (HTRequest *request, HTEnHd enhd);
extern HTEnHd HTRequest_enHd (HTRequest *request);
</PRE>
<H3>Referer Field</H3>
If this parameter is set then a `Referer: <parent address> can
be generated in the request to the server, see <A
HREF="http://www.w3.org/hypertext/WWW/Protocols/HTTP/HTRQ_Headers.html#z14">
Referer field in a HTTP Request</A>
<PRE>
extern void HTRequest_setParent (HTRequest *request, HTParentAnchor *parent);
extern HTParentAnchor * HTRequest_parent (HTRequest *request);
</PRE>
<H3>Extra Headers</H3>
Extra header information can be send along with a request using this
variable. The text is sent as is so it must be preformatted with
<CRLF> line terminators. This will get changed at some point so
that you can register a header together with a handler in the MIME
parser.
<PRE>
extern void HTRequest_setExtra (HTRequest *request, char *extra);
extern char *HTRequest_extra (HTRequest *request);
</PRE>
<H2>Streams From Network to Application</H2>
<H3>Default Output Stream</H3>
The output stream is to be used to put data down to as they come in
<B>from</B> the network and back to the application. The default value
is <CODE>NULL</CODE> which means that the stream goes to the user
(display).
<PRE>
extern void HTRequest_setOutputStream (HTRequest *request, HTStream *output);
extern HTStream *HTRequest_outputStream (HTRequest *request);
</PRE>
The desired format of the output stream. This can be used to get
unconverted data etc. from the library. If <CODE>NULL</CODE>, then <A
HREF="HTFormat.html#FormatTypes">WWW_PRESENT</A> is default value.
<PRE>
extern void HTRequest_setOutputFormat (HTRequest *request, HTFormat format);
extern HTFormat HTRequest_outputFormat (HTRequest *request);
</PRE>
<H3>Debug Stream</H3>
All object bodies sent from the server with status codes different
from <CODE>200 OK</CODE> will be put down this stream. This can be
used for redirecting body information in status codes different from
"200 OK" to for example a debug window. If the value is NULL (default)
then the stream is not set up.
<PRE>
extern void HTRequest_setDebugStream (HTRequest *request, HTStream *debug);
extern HTStream *HTRequest_debugStream (HTRequest *request);
</PRE>
The desired format of the error stream. This can be used to get
unconverted data etc. from the library. The default value if
<CODE>WWW_HTML</CODE> as a character based only has one WWW_PRESENT.
<PRE>
extern void HTRequest_setDebugFormat (HTRequest *request, HTFormat format);
extern HTFormat HTRequest_debugFormat (HTRequest *request);
</PRE>
<H2><A NAME="context">Context Swapping</A></H2>
In multi threaded applications it is often required to keep track of
the context of a request so that when the Library returns a result of
a request, it can be put into the context it was in before the request
was first passed to the Library. This call back function allows the
application to do this.
<PRE>
typedef int HTRequestCallback (HTRequest * request, void *param);
extern void HTRequest_setCallback (HTRequest *request, HTRequestCallback *cb);
extern HTRequestCallback *HTRequest_callback (HTRequest *request);
</PRE>
The callback function can be passed an arbitrary pointer (the void
part) which can describe the context of the current request
structure. If such context information is required then it can be set
using the following methods:
<PRE>
extern void HTRequest_setContext (HTRequest *request, void *context);
extern void *HTRequest_context (HTRequest *request);
</PRE>
<H2>Preemtive or Non-preemtive Access</H2>
A access scheme is defined with a default for using either preemtive
(blocking I/O) or non-premitve (non-blocking I/O). This is basically a
result of the implementation of the protocol module itself. However,
if non-blocking I/O is the default then some times it is nice to be
able to set the mode to blocking instead. For example when loading the
first document (the home page) then blocking can be used instead of
non-blocking.
<PRE>
extern void HTRequest_setPreemtive (HTRequest *request, BOOL mode);
extern BOOL HTRequest_preemtive (HTRequest *request);
</PRE>
<H2>Format Negotiation</H2>
When accessing the local file system, the Library is capable of
performing content negotioation as described by the HTTP
protocol. This is mainly for server applications, but some client
applications might also want to use content negotiation when accessing
the local file system. This method enables or disables content
negotiation - the default value is <EM>ON</EM>.
<PRE>
extern void HTRequest_setNegotiation (HTRequest *request, BOOL mode);
extern BOOL HTRequest_negotiation (HTRequest *request);
</PRE>
<H2>Error Manager Information</H2>
The error manager keeps a list (called an error stack) of all errors
and warnings occured during a request. The list of errors can be
accessed for generating an error message by the following function.
<PRE>
extern HTList *HTRequest_errorStack (HTRequest *request);
</PRE>
<H2>Bytes Read in Current Request</H2>
This function returns the bytes read in the current request. For a
deeper description of what the current request is, please read the
user's guide. This function can be used in for example the <A
HREF="HTAlert.html">HTAlert module</A> to give the number of bytes
read in a progress message.
<PRE>
extern long HTRequest_bytesRead(HTRequest * request);
</PRE>
<H2>Kill a Request</H2>
This function kills this particular request, see HTNet module for a
function that kills them all.
<PRE>
extern BOOL HTRequest_kill(HTRequest * request);
</PRE>
<PRE>
#endif /* HTREQ_H */
</PRE>
End of declaration
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