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nwg

nwg

Section: AFNIX Module (3) Updated: 2009-11-17
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NAME

nwg - standard network working group module  

STANDARD NETWORK WORKING GROUP OBJECT

This chapter covers the fundamental objects of the AFNIX standard network working group service module. This modules contain object that are generally defined by a RFC and used in networking application. All AFNIX network working group objects are located in the afnix-nwg module. This module must be loaded prior any operation. Multiple calls to the module initialization routine are harmless. The interpreter method module loads a specific module by name. When the module has been loaded, the object are available in the afnix:nwg nameset.

interp:library "afnix-nwg"

The uri class
The Uri class is a base class that parse a Uniform Resource Identifier or uri string and provides methods to access individual component of that uri. The implementation conforms to RFC 3986. The URI components are the scheme, the authority, the path, the query and the fragment. The class also takes care of the character escaping.

const uri (afnix:www:Uri "http://www.afnix.org")

An uri can be broken into several components called the scheme, the authority, the path, optionally the query and the fragment. The Uri class provide a method to retrieve each component of the parsed uri.

const uri (afnix:www:Uri "http://www.afnix.org/")
println (uri:get-scheme)    # http
println (uri:get-authority) # www.afnix.org
println (uri:get-path)      # /

Character conversion
The Uri class performs automatically the character conversion in the input uri. For example, the + character is replaced by a blank. The % character followed by two hexadecimal values is replaced by the corresponding ASCII character. Note that this conversion does now apply to the query string.

Query string
The get-query method returns the query string of the uri. The query string starts after the ? character. The query string is a series of key-pair values separated by the & character.

const uri (afnix:www:Uri 
  "http://www.afnix.org?name=hello&value=world")
println (uri:get-query) # name=hello&value=world

The module also provides the UriQuery class that parses the query string and store the result in the form of a property list. The query string parse is particularly useful when writing automated scripts.

# create a query string object
const qs (afnix:nwg:UriQuery (uri:get-query))
# get the name value
qs:get-value "name"

Managing a cgi request
Managing a cgi request involves primarily the parsing of the requesting uri. The uri generally contains the http referrer as well as parameter which are stored in the form of a query string. However, depending on the cgi method which can be of type GET or POST, the treatment is somewhat different.

Checking the protocol version
In the presence of a cgi protocol, it is always a good idea to check the protocol version, or at least to put an assertion. The protocol version is normally CGI/1.1 and is stored in the GATEWAY_INTERFACE environment variable.

# check the cgi protocol
assert "CGI/1.1" (afnix:sys:get-env "GATEWAY_INTERFACE")

Getting the query string
If the request method is GET, then the query string is available in the environment variable QUERY_STRING. If the request method is POST, the query string is available in the input stream. The length of the query string is given by the CONTENT_LENGTH environment variable. The following example illustrates the extraction of the query string.

# check the cgi protocol
assert "CGI/.1" (afnix:sys:get-env "GATEWAY_INTERFACE")
# initialize the query string
const query (afnix:sys:get-env "QUERY_STRING")
# get the request method
const rqm (afnix:sys:get-env "REQUEST_METHOD")
# check for a post request and update the query string
if (== rqm "POST") {
  # create a buffer from the content length
  const len (Integer (afnix:sys:get-env "CONTENT_LENGTH"))
  # get the standard input stream and read content
  const is  (interp:get-input-stream)
  const buf (is:read len)
  # set the query string
  query:= (buf:to-string)
}

Parsing the query string
The UriQuery class is designed to parse a cgi query string. Once the string has been parsed, it is possible to perform a query by key since the class operates with a property list.

const query  (afnix:www:UriQuery "name=hello&value=world")
query:length      # 2
query:get-value "name"  # hello
query:get-value "value" # world

The UriQuery class is the foundation to build cgi script. When the library is combined with the web application management (wam) service, powerful applications can be built easily.  

HTTP PROTOCOL OBJECT

This chapter covers the http objects of the AFNIX standard network working group service module.

HTTP transaction objects
The concept of http transactions is defined in RFC 2616. In the client/server approach, a client issues a request which is answered with a response. A special case arise when the server is asked to perform some extra works, such like executing a script. In this case, the answer is called a reply which is formatted into a response when the server does its job correctly. The nature of the http objects determines how the associated stream behaves. With a http request as well as the http reply, the client view is adopted which means that the object is designed to operate with an output stream. On the hand, the http response object is designed to operate as an input strem since its represents the represents the server response that can be read by a client. In other word, the object described here are designed for a client perspective and not a server, where the respective object should be reversed.

HTTP reply
The HttpReply class is a class designed to handle a HTTP reply transaction. Most of the time, this object is not needed since it is used by high level object. However, there is some situation where it might become handy. For example, a CGI script needs to reply with a text file that will be use for download. In this case, the HttpReply object provides a simple mechanism to perform this operation.

const reply (afnix:nwg:HttpReply)

The HttpReply class operates with a buffer which is used to accumulate characters. When the buffer is ready, this one is sent along with a header. The HTTP 1.1 protocol requires at least to inform the client of the content type of the data being transferred. The HttpReply has by default a text/plain content-type property set by default. This property can be changed at the object construction.

# create a reply object
const reply (afnix:nwg:HttpReply)
# add some data
reply:add-buffer "Hello world"
# write the reply to the output
reply:write

Cookie object
The Cookie object is a special object that can be used during a http session, to post data to the http client. The idea behind cookies is to be able to maintain some state, during the user session for some time. A cookie is a name/value pair and eventually an expiration time. By default, the AFNIX cookie object are defined for one http client session, but this behavior can be changed.

Managing cookies
A cookie is created with a name/value pair and eventually an expiration time. Such expiration time is called the maximum-age and is automatically formatted by the object. With two arguments a session cookie is created. With a third argument as an integer, the constructor set the maximum age in seconds.

# create a cookie with name/value
const cookie (afnix:nwg:Cookie "cartid" "123456789")

The cookie implementation follows the recommendation of the RFC-2965 for http state management. The most important point to remember is the interpretation of the maximum age that differs from one cookie version to another. With version 1, which is the default, the maximum age is defined relatively in seconds, while it is absolute with version 0.The maximum age is set either at construction or with the set-max-age method. The set-max-age method sets the cookie life time in seconds, in reference to the current time. A negative value is always reset to -1 and defined a session cookie. A 0 value tells the http client to remove the cookie. The set-path method defines the path for which this cookie apply.

Adding a cookie
Once the cookie is defined, the set-cookie method of the HttpReply object can be used to install the cookie. Combined with the write method, the cookie can be send to the http client.  

STANDARD NWG SERVICES REFERENCE

This appendix is a reference of the AFNIX standard nwg services module.
SymbolDescription
afnix-nwgmodule
afnix:nwgnameset

Uri
The Uri class is a base object used to parse or build a uniform resource identifier as defined by RFC 3986. The URI can be built by specifying each component or by parsing a string. When a string is given in the constructor, the class parses the string and extract all components. The uri components are the scheme, the authority, the path, the query and the fragment. The class also takes care of the character escaping.

Predicate

uri-p

Inheritance

Object

Constructors

Uri (none)
The Uri constructor creates an empty uri object.

Uri (String)
The Uri constructor create a uri object by value. The string argument is the uri to parse at the object construction.

Methods

parse -> none (String)
The parse method reset the uri object, parse the string argument and fill the uri object with the result.

get-scheme -> String (none)
The get-scheme method returns the scheme of the parsed uri object.

get-authority -> String (none)
The get-authority method returns the authority part of the parsed uri.

get-path -> String (none)
The get-path method returns the path of the parsed uri.

get-path-target -> String (none)
The get-path-target method returns the path target of the parsed uri. The path target is the last element of the uri path.

get-query -> String (none)
The get-query method returns the complete query string of the parsed uri. Note that characters are not escaped when getting the string.

get-fragment -> String (none)
The get-fragment method returns the complete query string of the parsed uri.

get-base -> String (none)
The get-base method returns the combined uri scheme and authority.

get-hname -> String (none)
The get-hname method returns the combined uri scheme, authority and path.

add-path -> Uri (String)
The add-path method adds a path to the calling uri and returns a new uri with the new path added to the old one.

get-href -> Uri (String)
The get-href method returns a new uri by eventually combining the string argument. If the strign argument correspond to an uri, the corresponding uri is built. Otherwise, the string argument is considered as a pth to be added to the current uri in order to build a new uri.

get-system-path -> String (none)
The get-system-path method returns the system path representation of the uri path. This function works only if the scheme if a file scheme.

get-path-encoded -> String (none)
The get-path-encoded method returns the uri in the encoded form. Normally the get-path removes the percent-encoded characters which might not be appropriate with some protocol such like the http protocol. The get-path-encoded returns the original path. Note that getting the path with getpath and doing a percent coding might result in a different result since the internal representation uses normalized string.

get-host -> String (none)
The get-host method returns the authority or path host name if any can be found with respect to the scheme. With a ftp, http or https scheme, the ost is extracted from the authority. With a mailto scheme, the host is extracted fromthe path.

get-port -> Integer (none)
The get-port method returns the authority port if any can be found with respect to the scheme.

UriQuery
The UriQuery class is a simple class that parses a uri query string and build property list. during the parsing process, a special transliteration process is done as specified by RFC 3986. This class is primarily used with cgi scripts. Note that the string to parse is exactly the one produced by the get-query method of the Uri class.

Predicate

uri-query-p

Inheritance

Plist

Constructors

UriQuery (none)
The UriQuery constructor creates an empty uri query object.

UriQuery (String)
The UriQuery constructor create a uri object by value. The string argument is the uri query string to parse at the object construction. The query string is the one obtained from the get-query method of the Uri class.

Methods

parse -> none (String)
The parse method reset the uri query object, parses the string argument and fill the property list object with the result.

get-query -> String (none)
The get-query method returns the original query string.

Functions

normalize-uri-name -> String (String)
The normalize-uri-name function normalizes the string argument by adding a uri scheme if missing in the original string. If the function detects that the name starts with a host name, the "http" scheme is added. If the function detects that the string starts with a path, the "file" scheme is added. otherwise, the name argument is left untouched.

system-uri-name -> String (String)
The system-uri-name function normalizes the string argument by prioritizing the system name. The function attempts to find a file that match the sring argument and eventually build a uri file scheme. If the file is not fond, the normalization process occurs with the normalize-uri-name function.
 

STANDARD NWG SERVICES REFERENCE

This appendix is a reference of the http protocol service, a sub-group of the AFNIX standard nwg services module.

HttpProto
The HttpProto class is a base class that ease the deployment of the http protocol. The base class is built with a property list which is used to define the message header. The class also defines the write methods which are used to write a message either on an output stream or into a buffer.

Inheritance

Object

Methods

set-header -> none (String Literal)
The set-header method adds a new property to the http header. The first argument is the property name. The second argument is a literal object which is internally converted to a string.

write -> none (none|Output|Buffer)
The write method formats and writes the http header to an output stream or a buffer. Without argument, the default output stream is used.

HttpRequest
The HttpRequest class class is a base class designed to format a http request. The class operates with the protocol version 1.1 as defined by RFC 2616. A request is formatted with a request command and a uri.

Predicate

http-request-p

Inheritance

HttpProto

Constructors

HttpRequest (String)
The HttpRequest constructor creates a http request object with a specific command. The string argument is the request command to use.

HttpRequest (Uri)
The HttpRequest constructor creates a http request object with a uri. The default request command is "GET".

HttpRequest (String String)
The HttpRequest constructor creates a http request object with a specific command and a uri name. The first string argument is the request command to use. The second string argument is the uri attached to the command. Note that the term uri should be understood as a request uri those scope applies to the whole server with certain commands such like the option command.

HttpRequest (String Uri)
The HttpRequest constructor creates a http request object with a specific command and a uri. The first string argument is the request command to use. The second argument is the uri attached to the command.

Methods

write -> none (none|Output|Buffer)
The write method formats and writes the request to an output stream or a buffer. Without argument, the default output stream is used.

set-command -> none (String)
The set-command method sets the command request. This method does not check that the command is a valid HTTP command; thus leaving plenty of room for server development. As a matter of fact, RFC 2616 does not prohibit the existence of such extension.

get-command -> String (none)
The get-command method returns the request command string.

set-uri -> none (String)
The set-uri method sets the request uri. The argument string does not have to be a valid uri string since some commands might accept special string such like "*" to indicate all applicable uri.

get-uri -> String (none)
The get-uri method returns the request uri string.

HttpResponse
The HttpResponse class class is a http protocol class that handle the response following a http request. The response from a request generally contains a status line followed by a header and the body. The class is bound to an input stream which is used to read characters. The object encoding mode is set automatically from the header if it is available.

Predicate

http-response-p

Inheritance

Input

Constructors

HttpResponse (none)
The HttpResponse constructor creates a default http response object. Without an input stream bound to it, the class operates like an input stream which operate on a character buffer.

HttpResponse (Input)
The HttpResponse constructor creates a http response object with a specific input stream. At construction, the local buffer is reset and the input stream is bound to the object. The input stream is subsequently read to determine the response nature.

Methods

reset -> none (none)
The reset method reset the http response stream by clearing the local input buffer and the response header. The bound input stream is not touched.

get-status-code -> Integer (none)
The get-status-code method returns the response status code. If the response was not succesfully read, the status code is 0.

ok-p -> Boolean (none)
The ok-p predicate returns true is the response status code is valid (aka status 200).

encoding-mode-p -> Boolean (none)
The encoding-mode-p predicate returns true is encoding mode is defined in the header. If not, it might be desirabe to set the stream encoding mode.

location-p -> Boolean (none)
The location-p predicate returns true is the response status code indicates that a request should be made at another location. The location can be found with the get-location method.

get-location -> String (none)
The get-location method returns the loction uri found in the response header. This method is equivalent to a header query.

get-media-type -> String (none)
The get-media-type method returns the media type found in the response header. This method is equivalent to a header query.

set-input-stream -> none (Input)
The set-input-stream method binds an input stream to the http response object. Once the stream is bound, the input stream is read to determine the nature of the response. In particular, the response header is parsed automatically and the stream is ready to operate like any other input stream. If the header contains a length attribute, the read method and the associated predicate will behave like a stream which has reached its end when the number of characters read reach the content length.

header-length -> Integer (none)
The header-length method returns the number of entries in the response header.

header-get -> Property (Integer)
The header-get method returns a header entry by index. The integer argument is the header index. The result is in the form of a property object.

header-find -> Property (String)
The header-find method returns a header entry by name. The string argument is the property name. The result is in the form of a property object. If the entry is not found, the nil object is returned.

header-lookup -> Property (String)
The header-lookup method returns a header entry by name. The string argument is the property name. The result is in the form of a property object. If the entry is not found, an exception is raised.

header-get-value -> String (String)
The header-get-value method returns a header value by name. The string argument is the header property name. If the entry is not found, an exception is raised.

HttpReply
The HttpReply class is a simple designed to format a http reply. The class holds a property list which is used to format the header and a buffer which is the reply content. When the write method is called, the header and the buffer is formatted to the output stream argument. The class creates initially the content-type property which is initialized to the text/plain mime value.

Predicate

http-reply-p

Inheritance

HttpProto

Constructors

HttpReply (none)
The HttpReply constructor creates an empty http reply object.

HttpReply (String)
The HttpReply constructor creates a http reply object with a specific content type. The string argument is the mime content type to set.

Methods

add-buffer -> none (Literal|Buffer)
The add-buffer method adds some content to the HTTP reply buffer. The argument can be either a literal r a buffer object.

write -> none (none|Output|Buffer)
The write method formats and writes the reply to an output stream or a buffer. Without argument, the default output stream is used.

set-cookie -> none (Cookie)
The set-cookie method sets a cookie object to the http header. The cookie version is properly handled by the method.

set-status -> none (Integer)
The set-status method sets a reply status code. The code must be a valid http status code. The method takes care to format properly the status message. Note that a reply body can be attached to describe the message status. Note also that RFC 2616 prohibits the presence of a message body with the status code 1xx (informational), 204 (no content) and 304 (not modified). This rule is enforced by the class.

redirect -> none (String)
The redirect method set the message status to indicate that the page should be redirected to the specified uri. The string argument is the target uri. The method operates by setting a status code 303 (see other) in the header. If a temporary redirection is preferable, the implementor is advised to set manually the appropriate status code.

Cookie
The Cookie class is a special class designed to handle cookie setting within a http transaction. A cookie is name/value pair that is set by the server and stored by the http client. Further connection with the client will result with the cookie value transmitted by the client to the server. A cookie has various parameters that controls its existence and behavior. The most important one is the cookie maximum age that is defined in seconds. A null value tells the client to discard the cookie. A cookie without maximum age is valid only during the http client session. A cookie can be added to the HttpReply object with the set-cookie method. A cookie can be constructed with a name/value pair. An optional third argument is the maximum age. The default cookie version is 1 as specified by RFC 2965. With a version 1, the maximum age is interpreted as the number of seconds before the cookie expires. With version 0, the maximum age is the absolute time.

Predicate

cookie-p

Inheritance

Object

Constructors

Cookie (String String)
The Cookie constructor creates a cookie with a name value pair. The first argument is the cookie name. The second argument is the cookie value.

Cookie (String String Integer)
The Cookie constructor creates a cookie with a name value pair and a maximum age. The first argument is the cookie name. The second argument is the cookie value. The third argument is the cookie maximum age.

Methods

get-version -> Integer (none)
The get-version method returns the cookie version.

set-version -> none (Integer)
The set-version method sets the cookie version. The version number can only be 0 or 1.

get-name -> String (none)
The get-name method returns the cookie name. This is the name store on the http client.

set-name -> none (String)
The set-name method sets the cookie name. This is the name store on the http client.

get-value -> String (none)
The get-value method returns the cookie value. This is the value stored on the http client bounded by the cookie name.

set-value -> none (String)
The set-value method sets the cookie value. This is the value store on the http client bounded by the cookie name.

get-maximum-age -> Integer (none)
The get-maximum-age method returns the cookie maximum age. The default value is -1, that is, no maximum age is set and the cookie is valid only for the http client session.

set-maximum-age -> none (Integer)
The set-maximum-age method sets the cookie maximum age. A negative value is reset to -1. A 0 value tells the http client to discard the cookie. A positive value tells the http client to store the cookie for the remaining seconds.

get-path -> String (none)
The get-path method returns the cookie path value. The path determines for which http request the cookie is valid.

set-path -> none (String)
The set-path method sets the cookie path value. The path determines for which http request the cookie is valid.

get-domain -> String (none)
The get-domain method returns the cookie domain value.

set-domain -> none (String)
The set-domain method sets the cookie domain value. It is string recommended to use the originator domain name since many http client can reject cookie those domain name does not match the originator name.

get-port -> Integer (none)
The get-port method returns the cookie port number.

set-port -> none (Integer)
The set-port method sets the cookie port number. This value is not used with a cookie version 0.

get-comment -> String (none)
The get-comment method returns the cookie comment value.

set-comment -> none (String)
The set-comment method sets the cookie comment value.

get-comment-url -> String (none)
The get-comment-url method returns the cookie comment url value.

set-comment-url -> none (String)
The set-comment-url method sets the cookie comment url value. This value is not used with cookie version 0.

get-discard -> Boolean (none)
The get-discard method returns the cookie discard flag.

set-discard -> none (Boolean)
The set-discard method sets the cookie discard flag. The discard flag the tells the user agent to destroy the cookie when it terminates. This value is not used with cookie version 0.

get-secure -> Boolean (none)
The get-secure method returns the cookie secure flag.

set-secure -> none (Boolean)
The set-secure method sets the cookie secure flag. When a cookie is secured, it is only returned by the http client if a connection has been secured (i.e use https).

to-string -> String (none)
The to-string method returns a string formatted for the http reply header. Normally this method should not be called since the set-cookie method of the httpReply takes care of such thing.

 

Index

NAME
STANDARD NETWORK WORKING GROUP OBJECT
HTTP PROTOCOL OBJECT
STANDARD NWG SERVICES REFERENCE
STANDARD NWG SERVICES REFERENCE

This document was created by man2html, using the manual pages.
Time: 21:41:42 GMT, April 16, 2011