(12,UK Patent Application (,s,GB (11)2 350 213 (13)A
`
`(43) Date of A Publication 22.11.2000
`
`(21) Application No 9911739.2
`
`(22) Date of Filing 21.05.1999
`
`(71) Applicant(s)
`International Business Machines Corporation
`!Incorporated in USA - New York)
`Armonk, New York 10504, United States of America
`
`(72)
`
`lnventor(s)
`Gordon Douglas Hutchison
`Noel Rooney
`
`(74) Agent and/or Address for Service
`PWaldner
`IBM United Kingdom Limited, Intellectual Property
`Department, Hursley Park, WINCHESTER, Hampshire,
`SO21 2JN, United Kingdom
`
`(54) Abstract litle
`Web page downloading
`
`(51)
`
`INT CL7
`G06F 17/30
`
`(52) UK CL (Edition R )
`G4AAMU AUDB
`
`(56) Documents Cited
`WO 97 /46955 A 1
`http://libsun1.jr2.ox.ac.uk/training/ netscape.html
`HCLU,''Netscape Navigator", 1996
`
`(58) Field of Search
`UK CL (Edition R ) G4A AMU AUDB
`INT CL7 G06F 17 /30
`ONLINE: COMPUTER EPODOC JAPIO WPI INTERNET
`
`(57) A method of using a "markup language", such as HTML, browser, in which a page is loaded into display
`memory, the user selects multiple URLs from those displayed on the page, and the browser preloads pages
`corresponding to the URLs into a cache without necessarily displaying them, so the user may continue to view
`the original page. Before preloading a given page, it may update a navigation list with the corresponding URL,
`and a user may select an entry in this list, directly or via "forward" and "back" GUI buttons, to display
`immediately.
`
`Server
`12A
`
`Server
`128
`
`Platform 10
`Memory 16
`Browser20
`
`Browser Cache
`Code 22 memory
`24
`
`Cache
`Index
`26
`
`Preload Plugin 30
`I Register plug-in 40 I
`I Capture events 42 I
`I Download pages 44 l
`I Maintain list 46 I
`I Display page 48 I
`
`Webpage38 1
`
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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1024, p. i
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`

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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1024, p. ii
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`

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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1024, p. iii
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`page 110
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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1024, p. iv
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`Figure 3A
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`busy 112
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`
`Display 104
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`Update cached page table 122 I
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`I Update cache index 120 I
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`Update Icons 118
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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1024, p. v
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`Pager arrives 114
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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1024, p. vi
`Petitioners Microsoft Corporation and HP Inc. - Ex. 1024, p. vi
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`' .
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`1
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`WEB PAGE DOWNLOADING
`
`FIELD OF INVENTION
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`This invention relates to the Internet world wide web page
`downloading and in particular relates to browser prefetching of web
`pages.
`
`BACKGROUND OF INVENTION
`
`The Internet is a large number of computers connected in an ad hoc
`fashion forming a world wide network. It was originally conceived by the
`US government to allow a scaleable network of computers to talk to each
`other and share information and has the added effect of being resilient
`to malfunction of single computers in the network. This means a lower
`risk of loosing total communication between computers in the event of an
`intermediate computer failing because the network may be connected in
`other ways. The communication language of the Internet is the double
`layer Transmission Control Protocol/Internet Protocol (TCP/IP). TCP
`controls the way that data is broken down into small packets for
`transmission over the Internet and controls the way the packets are
`subsequently built up in the correct order. The Internet protocol
`controls the addressing of the packets so that they are transmitted to
`and received by the correct computer.
`
`The Internet's best known medium is the world wide web
`(WWW) which
`is very broadly a set of protocols allowing transfer of multimedia data
`between computers. One of these protocols is Hypertext Transfer Protocol
`(HTTP) which allows pages of data in hypertext mark up language (HTML) to
`be transferred. The application which sits on a computer to make this
`transfer possible is an Internet browser such as Microsoft Internet
`Explorer or Netscape Navigator.
`
`A very common mode of operation in web browsers is the following. A
`user enters criteria into a search engine prompt or goes to an
`index/contents page of link. The user is then presented with list of
`available web Uniform Resource Locators (URLs) a subset of which he/she
`wishes to browse and selects one location for download. The user then
`waits for the page to load from the Internet server to the proxy server
`and to his machine before viewing the page. After finding something of
`interest or not the user moves back to the index/list and makes a next
`selection, waits for download etc. This process repeats until the user
`has read or collected the relevant material.
`In this mode of operation
`it is necessary to repeatedly wait, sometimes for excessive periods, for
`the pages to download. One solution is to launch a ne_w browser t9 request
`a download from the selection and return to the original browser to
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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1024, p. 1
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`2
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`launch further browsers for each desired URL. This is a messy and
`irritating way to operate as one must keep track of where one is in the
`desired list and has no visual clue as to when the pages have been
`downloaded to the multiple windows and which to which window on the
`screen a particular page will appear at.
`
`Gotit from Ahead Software Inc., Redmond, WA
`( www.goahead.com)
`preloads web pages into proxy cache. Gotit is a www proxy gateway to the
`Internet for providing a portal and location for fire walls, security
`policy and web page caching as standard. For example most www proxies
`are likely to fetch www.yahoo.com many times each hour and the advantage
`of storing it and refreshing it say only every 10 minutes is clear. Gotit
`allows preloads of pages linked to the current page. The proxy server
`will download from the servers in the background all the pages that are
`linked to from a page currently being viewed it then stores these on the
`disk of the machine running the proxy.
`
`However in the Gotit solution the proxy has no interaction with the
`browser interface and visa versa during the background downloading
`process. This has two disadvantages: 1) The user's model is not improved
`since the process of moving to proxy pages remains inflexible. 2) The
`Gotit! proxy has no way of knowing which pages the user will actually hit
`so it downloads all of them that are linked to. It undoubtedly filters
`out these links for it's own use during the action of serving the linking
`page to the user. Depending on the performance of serving machine and the
`nature of the linking page, this could actually slow down performance if,
`for example, the user is only interested in the 3,4, 6 and 9th links as
`all 1 to 12 links will be fetched. Gotit's pre-fetch model blindly
`prefetches all links on a page. This would result in too many prefetched
`pages for the average browser set up and platform as sites now commonly
`have many navigation links at their top levels.
`
`SUMMARY OF INVENTION
`
`According to one aspect of the invention there is provided a method
`of browsing an H™L page on a TCP/IP network comprising: loading a first
`HTML page into browser memory from a network server; loading said memory
`into display memory for displaying said the page; providing means for
`selecting multiple URLs on the HTML page; and preloading pages
`corresponding to user selected URLs into browser memory without loading
`them into display memory or affecting the ability to select further URLs.
`The solution allows multiple requests by the user and res~lts in a much
`reduced start-to-finish time for a user who is using the net in a
`'query, list, browse' mode (as is commonly done). The_ .user need not· look
`at every page downloaded and available from cache memory. As most·of the
`pages wii."i be 'instant' from the cache, page providers may be~efit too by
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`3
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`receiving more 'hits' as users are much more likely to view a page if
`they can see that it will be displayed 'instantly' from the browser
`cache.
`
`Advantageously, this aspect of the invention further provides a
`step of on selection of a URL and before preloading the corresponding
`page, updating a navigation list with the URL. This allows a user, having
`finished making multiple selections from the first page, to instruct the
`browser to display pages from the navigation list even though the pages
`may not be fully loaded into memory. More advantageously the method
`further comprises updating the navigation list with information as to
`whether a URL on the list is fully loaded. In which case the user can
`maximise the time spent in viewing only fully loaded pages.
`
`Advantageously, on selection of a URL and before preloading the
`corresponding page into cache memory, there is provided a further step of
`updating a cache index file with the location of the page in cache. This
`allows a user, having finished making multiple selections from the first
`page, to instruct the browser to display pages from the navigation list
`even though the pages may not be fully loaded into memory.
`
`Advantageously pages corresponding to selected URLs are not
`displayed during preloading so that the user may view the original page
`until finished checking all the URLs. After the user is finished checking
`he may move on to one of the selected web pages.
`
`One beneficial method for navigating the selected URLs is to build
`a list of page references including that of the first page. A drop down
`list may be provided for selecting a page reference in the list so that
`the corresponding page can be displayed. Alternatively or as well as
`'forward' and 'back' GUI buttons may be provided for selecting the
`previous or next page reference in the list and displaying the
`corresponding page.
`
`The user is already used to using control-mouse-left-click (for
`copy-drag actions in Windows) and the above solves the problem in an
`intuitive way. As the model suggests, making use of the 'forward-arrow'
`for navigation through the pages downloaded in the background is a
`familiar navigation method for the user. The browser cache will end up
`in exactly the same state it would if he/she had interactively downloaded
`the pages one at a time and then used 'back-arrow' to return to the index
`page. Moreover the user is not faced with having to continually jump back
`to the top level and has much less 'waiting time' overall as the
`downloads occur in parallel. Furthermore the user has something active
`to do/read while downloads are going on the background the operation will
`be even more efficient/enjoyable.
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`4
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`Preferably a page reference is added to the list when its
`corresponding URL is selected from the first page so that the list is
`order sequentially in a logical order. Alternatively a page reference
`maybe added to the list when its corresponding page is substantially
`loaded into browser memory so that if a user moves forward in the list
`there is greater chance that the page will have loaded into the browser.
`This solution provides for a much more easily navigable model for doing
`parallel downloads over the current possible mechanisms. The solution is
`coherent with the current user model of path walking with marks for
`places visited. The solution is applicable to a
`'usage scenario'
`employed many times every day in a highly competitive area and is easily
`detectable.
`
`Browser memory comprises cache memory. When a preloaded page in
`proxy memory is required for display on a browser, the browser sends a
`TCP/IP request to the proxy for a page stored in proxy memory. The page
`is copied into both cache memory and display memory for display on the
`browser. It is advantageous to preload selected pages directly into cache
`memory from an TCP/IP network so that a quicker internal request from the
`browser to the cache memory renders the displayed page to the user in a
`shorter time as opposed to a slower TCP/IP request from the browser to
`the proxy.
`
`According to another aspect of the invention there is provided a
`system for browsing an HTML page on a TCP/IP network comprising: means
`for loading a first HTML page into browser memory from a network server;
`means for loading said memory into display memory for displaying said
`page; means for selecting multiple URLs on the HTML page; and means for
`preloading pages corresponding to selected URLs into browser memory
`without loading them into display memory.
`
`According to another aspect of the invention there is provided a
`method of processing a URL database comprising: loading the HTML result
`of a URL search into browser memory; loading the HTML results into
`display memory and displaying a list of located URLs; providing means for
`selecting multiple URLs from the list; and preloading web pages
`corresponding to selected URLs without displaying said web pages.
`
`According to a further aspect of the invention there is provided a
`computer program product comprising a computer usable medium having
`computer readable program code means embodied in the medium for
`processing work items in a data processing system, the program code means
`comprising: code means for causing the data processing system to load a
`first HTML page into browser memory from an network server; code means
`for causing the data processing system to load said first HTML page into
`display memory for displaying said page; code means for causing the data
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`5
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`processing system to provide means for selecting multiple URLs on the
`HTML page; and code means for causing the data processing system to
`preload pages corresponding to selected URLs into browser memory without
`loading them into display memory.
`
`According to a further aspect of the invention there is provided a
`computer program product comprising a computer usable medium having a
`computer readable code page embodied in the medium for processing work
`items in a data processing system, the code page comprising: code means
`for instructing a
`code page browser to display one or more links to
`other codes pages; and code means for, on selection of one or more of the
`displayed links, instructing a code page browser to load one or more of
`the code page into browser memory whilst instructing the code page
`browser to retain the current code page display of said one or more
`links.
`
`Once a user has completed the process of viewing all his/her
`desired pages by initiating each download interactively, all the
`previous pages are easily selectable for reviewing using the 'back' and
`'forward' features of the browser. As these work in conjunction with the
`browser cache one can quickly move backward through the list (and
`subsequently forward again). If it were possible to reverse this process
`how much easier say Yahoo or patent searches would be.
`
`Although the invention is described in terms of TCP/IP networks it
`could equally apply to other types of packet networks. Furthermore
`although the invention is described in terms of HTML pages it could
`equally apply to other types of mark up language data containing URLs.
`Although the invention is described in terms of URLs it could equally
`apply to other network data references.
`
`BRIEF DESCRIPTION OF DRAWINGS
`
`In order to promote a fuller understanding of this and other
`aspects of the present invention, an embodiment will now be described, by
`way of example only, with reference to the accompanying drawings in
`which:
`Figure 1 is a schematic representation of a computer system of the
`embodiment;
`Figure 2 is a screen dump of a cache memory;
`Figure 3A and 3B represent the procedures of the embodiment; and
`Figure 4 is a screen dump illustrating one of the advantages of the
`embodiment.
`
`DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1024, p. 5
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`6
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`Referring to Figure 1 there is represented an operational platform
`10 connected to a plurality of servers 12A, 12B, 12C, via a proxy server
`13 and an Internet network 14. Platform 10 is an Intel Pentium II 450Mhz
`processor based computer, having 128 MB 100 MHz SDRAM (reference number
`16 on Figure 1 ) , 17 GB ATA-33 hard drive (also represented as reference
`number 16 on Figure 1), 19" colour SVGA monitor, 16 MB video memory
`(reference number 18 on Figure 1), 17/40 x CD-ROM drive, 3 PCI, 1 ISA and
`1 AGP expansion slots and Microsoft Windows 98 operating system. The
`platform 10 has a TCP/IP browser 20 such as Netscape Navigator. The
`servers 12,13 have similar specifications to platform 10 but run under
`Microsoft Windows NT operating system. Although the example platform is
`described in detail, any processor and operating system combination
`capable of running a TCP/IP browser is suitable. The example browser need
`not be Netscape Navigator but any browser capable of receiving mark up
`code pages from a network, for instance Microsoft Internet Explorer.
`
`Browser 20 is the client application which is used to view pages of
`information sent by the servers. Five components of the browser are of
`interest in the present embodiment. The browser code 22; the cache memory
`24; the cache index 26; and the navigation list 28 are known components
`of browser 20. In this embodiment the invention is centred on a browser
`plug-in 30 so that no adaptation of the browser code is necessary and the
`invention may be incorporated into any present browser set up by adding
`the component to the browser.
`
`In another embodiment the browser code 22 may be modified with
`necessary functionality so that no plug-in to the shipped browser is
`necessary.
`
`In a further embodiment the methods of the invention may take the
`form of code (such as Javascript) within the web page data instructing
`the browser to carry out the steps of the invention.
`
`Proxy server 13 is the gateway to the Internet for the platform 10
`and potentially many other platforms. When web page information is
`downloaded from servers on the Internet to the browser it is stored in
`the proxy server 13 as well as being transferred to the cache memory 24
`of the browser 20.
`If any other browser using the proxy server 13 as a
`gateway requests the same page then the proxy server 13 can transfer it
`from its own memory without incurring the delay by transferring it again
`from the Internet. The proxy also has some security functionality for
`limiting what information is sent and received. Internal web pages can
`not be sent through 'fire wall' security measures in the proxy server.
`
`Browser code 22 contains the functionality of the browser including
`the TCP/IP interface code and the mark up language interpreter (both not
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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1024, p. 6
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`7
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`shown). Cache memory 24 stores several pages 32A and 32B including main
`pages and related files of information from the Internet servers. The
`proxy server 13 has a similar cache memory for Internet information but
`stores more information than a browser cache memory so that it may supply
`the other connected browsers. Cache index 26 contains the groups 34A,B,C
`of names and references of the files that make up web pages 32A and 32B.
`Navigation list 28 is a sequential list of web pages visited in the
`browser session with associated URLs. Both Netscape Navigator and
`Microsoft Internet Explorer have cache memories 24 where HTML, GIFs, MP3
`etc. files are cached in a hard disk directory with a cache index 26.
`With Internet Explorer these are held at
`C:\winnt\profiles\<user>\Temporary Internet Files\index.dat and in
`Netscape the equivalent file is, for example, C:\Program
`Files\Netscape\Users\<user>\Cache\fat.db. For Internet Explorer, these
`can be seen using Windows Explorer as shown in Figure 2.
`
`The navigation list contains the URLs 36A,B,C,D visited including
`the present web page 36B (indicated by the bold outline), those
`previously visited 36C,D (indicated by the dotted outlines) and the page
`36A to be visited in the future (indicated by the dotted line). The
`cache index 26 holds file references 34A for the present web page and
`perhaps those of the previous web page e.g. 34B and 34C but not the web
`page references of 36D which have been removed due to limited space for
`illustration only. The actual embodiment has extended cache memory 24 and
`holds from two to ten or more complete web pages. The cache memory 24
`holds the web page data 32A and 32B as referenced by the cache index 34A
`anbd 34B respectively and some or all of previous web pages, for example
`those referenced by pages 36C and 36D. The mark up code interpreter in
`the browser code 22 uses the mark up files 32A as indexed by cache index
`34A and pointed to by list item 36A to represent a web page 38 in
`graphical form in the display memory 18 which is displayed to the user on
`the monitor.
`
`Plug-in 30 uses a defined way of extending the functionality of the
`well-known browser described above without having to alter the underlying
`browser or requiring a recompilation of it. It works by a convention of
`entry points (or functions)
`that the browser can call within the plug-in
`and vice versa. The functions are called at significant points in the
`processing of a downloaded page and different page 'types' can be
`associated with different plugins.
`It is implemented as a dynamically
`loaded library and thus has access to the underlying computer's file
`system and other facilities (and so could manipulate the browser cache),
`it also has the ability to intercept mouse and keyboard actions from the
`user and have visibility of the browser's URL fetching via the defined
`browser to plug-in interface. Plugins conventionally deal with new file
`types (such as the well known VRML plug in that displays virtual reality
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`8
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`markup language and interacts with the user to control the display).
`However plug-in 30 deals with existing file types such as .HTML with
`slightly different processing than is conventionally used.
`
`To implement the embodiment we need to achieve the following
`functional units as identified in Figure 1: means 40 to register a
`plug-in that is called for 'standard' HTML and HTM web pages; means 42 to
`capture mouse or keyboard events to control the page downloads; means 44
`to request that pages are downloaded without being displayed and
`furthermore that these pages can be placed in the Netscape cache; means
`46 to maintain a list of pages that have been so placed in the cache to
`enable them to be displayed in response to the user selecting the
`'forward' and 'reverse' option in the user interface; and means 48 to
`trigger Netscape to display a particular page that is stored in the
`Netscape cache.
`
`Each of these five parts of the design is implemented using the
`Netscape plug-in interface and will be discussed in turn.
`
`1) Registering a plug-in that is called for 'standard' HTML and HTM web
`pages.
`
`When Communicator starts up, it checks for plug-in modules in the
`plugins directory for the platform:
`
`MS Windows: plugins subdirectory, in the same directory as the
`Communicator application.
`
`Mac OS: Plug-ins folder. A Mac OS plug-in can reside in a different
`directory if one installs a Macintosh alias that links to the plug-in in
`the Plug-ins folder.
`
`UNIX: usr/local/lib/Netscape/plugins or $HOME/.Netscape/plugins. If a
`different directory is wanted, the NPX_PLUG-IN_PATH environment variable
`is set to its filepath, for example, $HOME/yourplugins:/
`usr/local/lib/Netscape/plugins. Communicator searches any directory that
`this variable specifies. The local user location, if it exists, overrides
`the network location.
`
`On all platforms, the plugins default subdirectory or folder is in
`the same directory as the Communicator application. Users can install
`plugins in this directory manually, by using either an installation
`program or Communicator's JAR Manager facility. The plugins currently
`installed can be viewed under Netscape by selecting the 'help' menu
`option and
`the "About Plug-ins" menu item. This gives a list of
`installed· plugs ins currently registered with the Netscape Browser and
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`9
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`identifies the 'default' plug in that is run for all file types not
`registered with another plug in:
`
`Netscape Default Plug-in
`File name: C:\PROGRA-1\Netscape\COMMUN-1\Program\plugins\npnul32.DLL
`
`Default Plug-in
`Mime Type
`*
`
`Description
`Netscape Default Plug-in
`
`Suffixes
`*
`
`Enabled
`Yes
`
`There is usually no other plug in that is registered for the file
`type .HTM or .HTML as this type being handled by the default services of
`Netscape. The plug in architecture does not prevent this happening and
`allows a plug-in that is activated when a file of type .HTM or .HTML is
`loaded. A dynamic link library (DLL) file is developed that conforms to
`the plug-in conventions as documented in the "Netscape Communicator
`Plug-in Guide" with a number of known function entry points. The DLL file
`is placed in the appropriate directory on platform 10. When it starts
`up, Communicator checks for plug-in modules in the plug-in directory for
`the platform and registers them. It determines which plugins are
`installed and which types they support through a combination of user
`preferences that are private to Communicator and the contents of the
`plugins directory. When Netscape is initialising it sweeps this directory
`and for each plug-in DLL that it finds it calls the NPP_Initialise
`function entry point in the DLL file. It also examines the DLL's version
`information.
`
`On Windows, the plugin's directory is located in the same directory
`as the Communicator application and has a 8.3 filename beginning with NP
`and ending with .DLL. The Windows version information for the plug-in DLL
`determines the MIME types, file extensions, file open template, plug-in
`name, and description. In the MIME types and file extensions strings,
`multiple types and extensions are separated by the "I" character, for
`example: video/quicktimelaudio/aifflimage/jpeg
`
`The version stamp of the plug-in DLL contains the following lines
`so that Communicator recognises the plug-in,:
`
`File Extents: for file extensions
`
`MIME Type: for MIME types
`
`Language: for language in use
`
`In order to display an example of this use Windows Explorer to get
`to the C:\Program Files\Netscape\ Communicator\Program\Plugins> directory
`
`5
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`10
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`15
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`20
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`25
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`30
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`35
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`45
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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1024, p. 9
`
`

`

`10
`
`and right click on one of the np*.DLL files - use the pop-up menu to view
`the DLL's properties. Up will come a notebook, click on the Version Page
`Tab -> You will see fields called "File Extents" and "MIME Type" these
`fields are decoded by Netscape using the convention above.
`
`By creating a Netscape plug in using the instructions in the
`plug-in SDK and setting the values in the plug-in DLL's properties
`information to indicate that this plug is for file extensions of .HTM and
`.HTML we will cause Netscape to communicate with this plug in when files
`of this type are loaded.
`
`2) Capturing mouse or keyboard events to control mouse or keyboard events
`to control web page downloads.
`
`In order to capture mouse events that are driven from the HTML page
`the plug-in 30 operates as a
`'full page' plug-in. A full page plug-in is
`visible but not part of an HTML page. The server looks for the media
`(MIME) type registered by a plug-in, based on the file extension, and
`starts sending the file to the browser. Communicator looks up the MIME
`type and loads the plug-in if it finds a plug-in registered to that type.
`This type of plug-in completely fills the Communicator page and are
`commonly used for document viewers, such as Adobe Acrobat. Plug-in 30
`receives mouse events that take place while the mouse pointer is over
`it's own display window. The following events are visible to the plug-in
`
`WM_PAINT
`WM_LBUTTONDOWN
`WM_LBUTTONUP
`WM_LBUTTONDBLCLK
`WM_RBUTTONDOWN
`WM_RBUTTONUP
`WM_RBUTTONDBLCLK
`WM_MBUTTONDOWN
`WM_MBUTTONUP
`WM_MBUTTONDBLCLK
`WM_MOUSEMOVE
`WM_KEYUP
`WM_KEYDOWN
`WM_SETCURSOR
`WM_SETFOCUS
`WM_KILLFOCUS
`
`These events will be passed to the plug-in via the "int16
`NPP_HandleEvent(NPP instance, NPEvent *event);"
`function entry point
`defined in the plugin's DLL.
`In the embodiment the user holds down the
`control key to indicate that a background download of a URL. This causes
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`Petitioners Microsoft Corporation and HP Inc. - Ex. 1024, p. 10
`
`

`

`11
`
`a
`'WM_KEYDOWN event to take place for the control key. Plug-in 30
`maintains a flag that represents whether the control key is down or up.
`
`3) Requesting pages for download in cache memory without displaying
`
`When the download of a new page is requested and a plug-in is
`registered for that page type then browser 20 will create a new 'stream'
`that represents the stream of data in the web page. To tell the plug-in
`when a new stream is created, browser 20 calls a NPP_NewStream method.
`This method also determines which mode it should use to send data to the
`plug-in via a return parameter in the function call.
`
`The NPP_NewStream method has the following syntax:
`
`NPError NPP_NewStream(NPP instance, NPMIMEType type, NPStream *stream,
`NPBool seekable, uint16* stype);
`
`The instance parameter refers to the plug-in instance receiving the
`stream; the type parameter represents the stream's MIME type. The stream
`parameter is a pointer to the new stream, which is valid until the stream
`is destroyed. The seekable parameter specifies whether the stream is
`seekable (true) or not (false). Seekable streams support random access
`(for example, local files or HTTP servers that support byte-range
`requests). The plug-in can set the type output parameter type to various
`transmission modes and the embodiment chooses the mode based on whether
`the control key is down or not. If the control key is currently down
`(background download is requested) the type NP_ASFILEONLY is selected.
`The plug-in gets full random access to the data using platform-specific
`file operations. Browser 20 saves stream data to a local file in the
`cache, and, when the stream is complete and delivers the path of the file
`to the plug-in through a call to NPP_StrearnAsFile. The URL will not be
`launched in a browser window or replace the contents of the current
`window. This mode will fetch the page to the Netscape cache without
`causing it to be displayed on a window. If the control key is not held
`down then the type of the fetch will be NP_NORMAL which will allow for
`the default behaviour of the