Annotation of libwww/Library/src/HTFormat.html, revision 2.84
2.10 timbl 1: <HTML>
2: <HEAD>
2.71 frystyk 3: <!-- Changed by: Henrik Frystyk Nielsen, 15-Jul-1996 -->
2.75 frystyk 4: <TITLE>W3C Sample Code Library libwww Stream Pipe Manager</TITLE>
2.10 timbl 5: </HEAD>
2.1 timbl 6: <BODY>
2.67 frystyk 7: <H1>
2.68 frystyk 8: The Stream Pipe Manager
2.67 frystyk 9: </H1>
2.33 frystyk 10: <PRE>
11: /*
2.41 frystyk 12: ** (c) COPYRIGHT MIT 1995.
2.33 frystyk 13: ** Please first read the full copyright statement in the file COPYRIGH.
14: */
15: </PRE>
2.67 frystyk 16: <P>
2.68 frystyk 17: The Stream Pipe Manager is responsible for setting up the stream pipe from
18: the <A HREF="HTChannl.html">Channel Object</A> to the
19: <A HREF="HTReq.html">Request Object</A> when data is arriving, for example
20: as a response to s <A HREF="HTTP.html">HTTP</A> <B>Get</B> request. As data
21: arrives, we start to parse it and the more we know the more we can build
22: up our stream pipe. For example, in the case of HTTP, we first have a stream
23: that can parse the HTTP response line containing "<CODE>200 OK</CODE>". Then
24: we have a <A HREF="HTMIME.html">MIME parser</A> for handling the MIME headers.
25: When the MIME headers have been parsed, we know the content type and any
26: encoding of the MIME body. If we need to decode a chunked encoding then we
27: set up a chunked decoder, and if we have to parse a HTML object then we set
28: up a HTML parser.
2.67 frystyk 29: <P>
30: The Format Manager is also responsible for keeping track of the
31: "<I>preferences</I>" of the application and/or user. It is an integral part
32: of the Web and HTTP, that the client application can express its preferences
33: as a set of "accept" headers in a HTTP request. This task is highly related
34: to the task mentioned above as we there use the modules that are registered
35: and here tell the remote server what we are capable of doing and what we
36: would prefer.
37: <P>
38: <B>Note</B>: The library <B>core</B> does not define any default decoders
39: or parsers - they are all considered part of the application. The library
40: comes with a default set of parsers including the ones mentioned above which
41: can be initiated using the functions in <A HREF="HTInit.html">HTInit
42: module</A>. There are different initialization functions for content type
43: parsers and content encodings respectively.
44: <P>
45: <UL>
46: <LI>
47: <A HREF="#type">Content Type Converters and Presenters</A>
48: <LI>
49: <A HREF="#encoding">Content Encoders and Decoders</A>
50: <LI>
51: <A HREF="#charset">Content Charsets</A>
52: <LI>
53: <A HREF="#language">Natural Languages</A>
54: </UL>
55: <P>
56: The application can assign its preferences in two ways: either <I>locally</I>
57: to a single request or <I>globally</I> to all requests. The local assignment
58: can either <I>add to </I>or <I>override</I> the global settings depending
59: on how they are registered. All local registration is handled by the
60: <A HREF="HTReq.html">Request Object</A> and the global registration is handled
2.73 frystyk 61: by the Format Manager.
2.67 frystyk 62: <P>
63: This module is implemented by <A HREF="HTFormat.c">HTFormat.c</A>, and it
2.80 frystyk 64: is a part of the <A HREF="http://www.w3.org/Library/">W3C Sample Code
2.67 frystyk 65: Library</A>.
2.31 frystyk 66: <PRE>
67: #ifndef HTFORMAT_H
2.1 timbl 68: #define HTFORMAT_H
69:
2.63 frystyk 70: #include "<A HREF="HTUtils.html">HTUtils.h</A>"
71: #include "<A HREF="HTStream.html">HTStream.h</A>"
72: #include "<A HREF="HTAtom.html">HTAtom.h</A>"
73: #include "<A HREF="HTList.html">HTList.h</A>"
74: #include "<A HREF="HTAnchor.html">HTAnchor.h</A>"
75: #include "<A HREF="HTReq.html">HTReq.h</A>"
2.31 frystyk 76: </PRE>
2.67 frystyk 77: <H2>
2.73 frystyk 78: <A NAME="type">Converters and Presenters</A>
2.67 frystyk 79: </H2>
80: <P>
81: All content type converters are subclassed from the Generic stream objetc.
82: That way, we allow the application to do very fast progressive display of
83: incoming data. In other words, the stream model of the Library provides data
84: as soon as it arrives from the network, the application does not have to
85: wait until the whole document has been down loaded before it starts parsing
86: it.
87: <H3>
88: Predefined Content Types
89: </H3>
90: <P>
91: These macros (which used to be constants) define some basic internally referenced
92: representations. The <CODE>www/xxx</CODE> ones are of course not MIME standard.
93: They are internal representations used in the Library but they can't be exported
94: to other apps!
2.28 frystyk 95: <PRE>
2.82 frystyk 96: #define WWW_INTERNAL HTAtom_for("www/*") /* All internal formats */
97: </PRE>
98: <P>
99: <CODE>WWW_INTERNAL</CODE> represent all internal formats. This can for example
100: be used to match using the <A HREF="HTWWWStr.html">HTMIMEMatch(...)</A>.
101: <PRE>
2.57 frystyk 102: #define WWW_RAW HTAtom_for("www/void") /* Raw output from Protocol */
2.28 frystyk 103: </PRE>
2.67 frystyk 104: <P>
105: <CODE>WWW_RAW</CODE> is an output format which leaves the input untouched
106: <EM>exactly</EM> as it is received by the protocol module. For example, in
107: the case of FTP, this format returns raw ASCII objects for directory listings;
108: for HTTP, everything including the header is returned, for Gopher, a raw
109: ASCII object is returned for a menu etc.
110: <PRE>
111: #define WWW_SOURCE HTAtom_for("*/*")
112: </PRE>
113: <P>
114: <CODE>WWW_SOURCE</CODE> is an output format which leaves the input untouched
115: <EM>exactly</EM> as it is received by the protocol module <B>IF</B> not a
116: suitable converter has been registered with a quality factor higher than
117: 1 (for example 2). In this case the <EM>SUPER CONVERTER</EM> is preferred
118: for the raw output. This can be used as a filter effect that allows conversion
119: from, for example raw FTPdirectory listings into HTML but passes a MIME body
120: untouched.
121: <PRE>
122: #define WWW_PRESENT HTAtom_for("www/present")
123: </PRE>
124: <P>
125: <CODE>WWW_PRESENT</CODE> represents the user's perception of the document.
126: If you convert to <CODE>WWW_PRESENT</CODE>, you present the material to the
127: user.
2.58 frystyk 128: <PRE>
129: #define WWW_DEBUG HTAtom_for("www/debug")
130: </PRE>
2.67 frystyk 131: <P>
132: <CODE>WWW_DEBUG</CODE> represents the user's perception of debug information,
133: for example sent as a HTML document in a HTTP redirection message.
2.28 frystyk 134: <PRE>
2.52 frystyk 135: #define WWW_UNKNOWN HTAtom_for("www/unknown")
2.28 frystyk 136: </PRE>
2.67 frystyk 137: <P>
138: <CODE>WWW_UNKNOWN</CODE> is a really unknown type. It differs from the real
139: MIME type <EM>"application/octet-stream"</EM> in that we haven't even tried
140: to figure out the content type at this point.
2.71 frystyk 141: <PRE>
2.72 frystyk 142: #define WWW_CACHE HTAtom_for("www/cache")
143: #define WWW_CACHE_APPEND HTAtom_for("www/cache-append")
2.71 frystyk 144: </PRE>
145: <P>
146: <CODE>WWW_CACHE</CODE> is the internal content-type designated for a persistent
2.72 frystyk 147: cache module which can store the object to local storage. The cache append
148: format is special in that we append information to an already existing cache
149: entry. This can happen if we have issued a <CODE>If-Range </CODE>request
150: and got back a "206 Partial response".
2.67 frystyk 151: <P>
2.31 frystyk 152: These are regular MIME types defined. Others can be added!
2.28 frystyk 153: <PRE>
2.52 frystyk 154: #define WWW_HTML HTAtom_for("text/html")
2.28 frystyk 155: #define WWW_PLAINTEXT HTAtom_for("text/plain")
2.69 frystyk 156: #define WWW_FORM HTAtom_for("application/x-www-form-urlencoded")
2.52 frystyk 157:
158: #define WWW_MIME HTAtom_for("message/rfc822")
2.60 frystyk 159: #define WWW_MIME_HEAD HTAtom_for("message/x-rfc822-head")
2.65 frystyk 160: #define WWW_MIME_FOOT HTAtom_for("message/x-rfc822-foot")
2.72 frystyk 161: #define WWW_MIME_PART HTAtom_for("message/x-rfc822-partial")
2.76 frystyk 162: #define WWW_MIME_CONT HTAtom_for("message/x-rfc822-cont")
2.84 ! frystyk 163: #define WWW_MIME_UPGRADE HTAtom_for("message/x-rfc822-upgrade")
2.52 frystyk 164:
2.10 timbl 165: #define WWW_AUDIO HTAtom_for("audio/basic")
2.52 frystyk 166:
2.26 frystyk 167: #define WWW_VIDEO HTAtom_for("video/mpeg")
2.52 frystyk 168:
2.70 frystyk 169: #define WWW_GIF HTAtom_for("image/gif")
2.63 frystyk 170: #define WWW_JPEG HTAtom_for("image/jpeg")
171: #define WWW_TIFF HTAtom_for("image/tiff")
2.52 frystyk 172: #define WWW_PNG HTAtom_for("image/png")
173:
174: #define WWW_BINARY HTAtom_for("application/octet-stream")
175: #define WWW_POSTSCRIPT HTAtom_for("application/postscript")
176: #define WWW_RICHTEXT HTAtom_for("application/rtf")
2.48 frystyk 177: </PRE>
2.67 frystyk 178: <P>
179: We also have some MIME types that come from the various protocols when we
180: convert from ASCII to HTML.
2.48 frystyk 181: <PRE>
182: #define WWW_GOPHER_MENU HTAtom_for("text/x-gopher")
2.53 frystyk 183: #define WWW_CSO_SEARCH HTAtom_for("text/x-cso")
2.48 frystyk 184:
185: #define WWW_FTP_LNST HTAtom_for("text/x-ftp-lnst")
186: #define WWW_FTP_LIST HTAtom_for("text/x-ftp-list")
187:
188: #define WWW_NNTP_LIST HTAtom_for("text/x-nntp-list")
189: #define WWW_NNTP_OVER HTAtom_for("text/x-nntp-over")
190: #define WWW_NNTP_HEAD HTAtom_for("text/x-nntp-head")
2.59 frystyk 191:
192: #define WWW_HTTP HTAtom_for("text/x-http")
2.55 frystyk 193: </PRE>
2.67 frystyk 194: <P>
195: Finally we have defined a special format for our RULE files as they can be
196: handled by a special converter.
2.73 frystyk 197: <PRE>#define WWW_RULES HTAtom_for("application/x-www-rules")
198: </PRE>
199: <H3>
200: The Quality Factor
201: </H3>
202: <P>
203: Characteristic for all preferences is that there is a quality factor associated
204: with each member. The quality factor is a real number between 0 and 1 with
205: 0 meaning "very bad" and 1 means "perfect". By registering a natural language
206: or any or other preference in this group together with a quality factor you
207: can specify "how well the preference is handled" either by the application
208: or by the user. In the case of the user the quality factor of a natural language
209: is how well the user understands the language. In my case, the quality factors
210: for, for example Greek would be close to zero and 1 for Danish (nothing bad
211: said about Greek!).
212: <P>
213: It is a bit different for converters where it is often the application's
214: ability of handling the data format rather than the user's perception. As
215: an example it is often faster to use a converter than a presenter as it takes
216: time to launch the external application and libwww can not use progressive
217: display mechanisms which is often the case for converters. Therefore, as
218: an example, if we capable of handling an image in <EM>png</EM> format inline
219: but rely on an external viewer for presenting postscript, we might set up
220: the following list:
221: <P>
222: <SAMP>HTConversion_add (converters, "image", "www/present", GifPresenter,
223: <B>1.0</B>, 0.0, 0.0);<BR>
224: HTPresentation_add (presenters, "application/postscript", "ghostview %s",
225: NULL, <B>0.5</B>, 0.0, 0.0);></SAMP>
226: <P>
227: where the gif converter is registered with a quality factor of <B>1.0</B>
228: and the postscript presenter with a quality factor of <B>0.5</B>.Register
229: Presenters
230: <H3>
231: The Converter Class
232: </H3>
233: <P>
234: A <CODE>converter</CODE> is a stream with a special set of parameters and
235: which is registered as capable of converting from a MIME type to something
236: else (maybe another MIME-type). A converter is defined to be a function returning
237: a stream and accepting the following parameters. The content type elements
238: are atoms for which we have defined a prototype.
2.55 frystyk 239: <PRE>
2.73 frystyk 240: typedef HTStream * HTConverter (HTRequest * request,
241: void * param,
242: HTFormat input_format,
243: HTFormat output_format,
244: HTStream * output_stream);
245:
246: extern void HTConversion_add (HTList * conversions,
247: const char * rep_in,
248: const char * rep_out,
249: HTConverter * converter,
250: double quality,
251: double secs,
252: double secs_per_byte);
253:
254: extern void HTConversion_deleteAll (HTList * list);
2.28 frystyk 255: </PRE>
2.67 frystyk 256: <H3>
2.73 frystyk 257: The Presenter Class
2.67 frystyk 258: </H3>
259: <P>
2.73 frystyk 260: A <CODE>presenter</CODE> is a module (possibly an external program) which
261: can present a graphic object of a certain MIME type to the user. That is,
262: <CODE>presenters</CODE> are normally used to present objects that the
263: <CODE>converters</CODE> are not able to handle. Data is transferred to the
2.83 frystyk 264: external program using a special "presenter stream" which for example can
265: use the local disk to transfer the data from libwww to the external program.
266: <P>
267: Libwww provides a default <A HREF="HTFWrite.html">HTSaveAndExecute</A>
268: stream which you may want to use for this purpose. However, any stream
269: that is of type <CODE>HTConverter</CODE> will do. You can manage the
270: special presenter stream using the following methods:
271: <PRE>
272: extern void HTPresentation_setConverter (HTConverter * pconv);
273: extern HTConverter * HTPresentation_converter (void);
274: </PRE>
275: Both presenters and converters are of the type
2.73 frystyk 276: <A HREF="#converter">HTConverter</A>.
2.31 frystyk 277: <PRE>
2.49 frystyk 278: extern void HTPresentation_add (HTList * conversions,
2.83 frystyk 279: const char * representation,
2.61 frystyk 280: const char * command,
281: const char * test_command,
2.49 frystyk 282: double quality,
283: double secs,
284: double secs_per_byte);
2.1 timbl 285:
2.50 frystyk 286: extern void HTPresentation_deleteAll (HTList * list);
287: </PRE>
2.67 frystyk 288: <H3>
2.73 frystyk 289: Basic Converters
2.67 frystyk 290: </H3>
291: <P>
2.73 frystyk 292: We have a small set of basic converters that can be hooked in anywhere. They
293: don't "convert" anything but are nice to have.
2.79 frystyk 294: <PRE>
295: extern HTConverter HTThroughLine;
2.73 frystyk 296: extern HTConverter HTBlackHoleConverter;
2.79 frystyk 297: extern HTConverter HTSaveConverter;
2.42 frystyk 298: </PRE>
2.67 frystyk 299: <H2>
300: <A NAME="encoding">Content and Transfer Encoders and Decoders</A>
301: </H2>
302: <P>
303: Content codins are transformations applied to an entity object after it was
304: created in its original form. The Library handles two types of codings:
2.64 frystyk 305: <DL>
2.67 frystyk 306: <DT>
307: <B>Content Codings</B>
308: <DD>
309: Content codings values indicate an encoding transformation that has been
310: applied to a resource. Content cosings are primarily used to allow a document
311: to be compressed or encrypted without loosing the identity of its underlying
312: media type.
313: <DT>
314: <B>Content Transfer Codings</B>
315: <DD>
316: Content transfer codings values are used to indicate an encoding transformation
317: that has been, can be, or may be need to be applied to an enity body in order
318: to ensure safe transport through the network. This differs from a content
319: coding in that the transfer coding is a property of the message, not the
320: original message.
2.64 frystyk 321: </DL>
2.67 frystyk 322: <P>
323: Both types of encodings use the same registration mechanism in the Library
324: which we describe below:
325: <H3>
326: Encoders and Decoders
327: </H3>
328: <P>
329: <EM>Encoders</EM> and <EM>decoders</EM> are subclassed from the
330: <A HREF="HTStream.html">generic stream class</A>. <EM>Encoders</EM> are capable
331: of adding a content coding to a data object and <EM>decoders</EM> can remove
332: a content coding.
2.50 frystyk 333: <PRE>
2.64 frystyk 334: typedef HTStream * HTCoder (HTRequest * request,
335: void * param,
336: HTEncoding coding,
337: HTStream * target);
2.50 frystyk 338: </PRE>
2.67 frystyk 339: <P>
340: The <EM>encoding</EM> is the name of the encoding mechanism reporesented
341: as an <A HREF="HTAtom.html">atom</A>, for example "zip", "chunked", etc.
342: Encodings are registered in lists and content encodings are separated from
343: transfer encodings by registering them in different lists.
344: <H3>
2.81 frystyk 345: Basic Encoders
346: </H3>
347: <P>
348: We have a small set of basic coders that can be hooked in anywhere.
349: <PRE>
350: extern HTCoder HTIdentityCoding;
351: </PRE>
352: <H3>
2.67 frystyk 353: The HTCoding Object
354: </H3>
355: <P>
356: The <EM>HTCoding</EM> object represents a registered encoding together with
357: a encoder and a decoder.
2.63 frystyk 358: <PRE>
2.64 frystyk 359: typedef struct _HTCoding HTCoding;
2.63 frystyk 360: </PRE>
2.67 frystyk 361: <P>
362: Predefined Coding Types We have a set of pre defined atoms for various types
363: of content encodings and transfer encodings. "chunked" is not exactly in
364: the same group as the other encodings such as "binary" but it really doesn't
365: make any difference as it is just a matter of how the words are chosen. The
366: first three transfer encodings are actually not encodings - they are just
367: left overs from brain dead mail systems.
2.42 frystyk 368: <PRE>
2.79 frystyk 369: #define WWW_CODING_7BIT HTAtom_for("7bit")
370: #define WWW_CODING_8BIT HTAtom_for("8bit")
371: #define WWW_CODING_BINARY HTAtom_for("binary")
372: #define WWW_CODING_IDENTITY HTAtom_for("identity")
2.64 frystyk 373:
2.79 frystyk 374: #define WWW_CODING_BASE64 HTAtom_for("base64")
375: #define WWW_CODING_MACBINHEX HTAtom_for("macbinhex")
376: #define WWW_CODING_CHUNKED HTAtom_for("chunked")
2.63 frystyk 377:
2.79 frystyk 378: #define WWW_CODING_COMPRESS HTAtom_for("compress")
379: #define WWW_CODING_GZIP HTAtom_for("gzip")
380: #define WWW_CODING_DEFLATE HTAtom_for("deflate")
2.42 frystyk 381: </PRE>
2.67 frystyk 382: <H3>
383: Register Content Coders
384: </H3>
385: <P>
2.73 frystyk 386: Some documents are not send in their original data obejct but is encoded
387: in some way. On the Web this is mostly some kind of compression but other
388: encodings for example base 64 can be encountered when talking to NNTP servers
389: etc. Just as for the other preferences, an application can register a supported
390: encoders or decodes as a list. Encoders and decoders are registered in the
391: same way with no differentiation whether it is a encoder or a decoder:
2.42 frystyk 392: <PRE>
2.64 frystyk 393: extern BOOL HTCoding_add (HTList * list,
394: const char * encoding,
395: HTCoder * encoder,
396: HTCoder * decoder,
397: double quality);
2.63 frystyk 398:
2.64 frystyk 399: extern void HTCoding_deleteAll (HTList * list);
2.42 frystyk 400:
2.64 frystyk 401: extern const char * HTCoding_name (HTCoding * me);
2.77 frystyk 402:
403: extern double HTCoding_quality (HTCoding * me);
2.42 frystyk 404: </PRE>
2.67 frystyk 405: <H2>
406: <A NAME="charset">Content Charsets</A>
407: </H2>
2.73 frystyk 408: <P>
409: As the Web reaches all parts of the Internet there are more and more documents
410: written in languages which contains characters not included in the ISO-8859-1
411: character set. A consequence of this the set of characters sets is often
412: tightly connected with the natural language. libwww does not directly support
413: other character sets but in case an application is capable of handling
414: alternative sets it can register these as preferred character sets along
415: with a quality factor just as all the other preferences in this section.
416: <PRE>extern void HTCharset_add (HTList * list, const char * charset, double quality);
2.42 frystyk 417: </PRE>
2.73 frystyk 418: <PRE>typedef struct _HTAcceptNode {
2.63 frystyk 419: HTAtom * atom;
420: double quality;
421: } HTAcceptNode;
422: </PRE>
423: <PRE>
2.50 frystyk 424: extern void HTCharset_deleteAll (HTList * list);
425: </PRE>
2.67 frystyk 426: <H2>
427: <A NAME="language">Content Languages</A>
428: </H2>
2.73 frystyk 429: <P>
430: The preferred natural language or languages is in almost all situations dependent
431: on the individual user and an application should therefore give the user
432: the opportunity to change the setup. When specifying a natural language
433: preference, libwww will send this preference along with all HTTP requests.
434: The remote server will then (it if supports this feature) look for a version
435: in the language or languages mentioned. If it finds a matching document then
436: it returns this one, otherwise it uses the best alternative. If no language
437: is specified the remote server may whatever version it finds.
438: <PRE>extern void HTLanguage_add (HTList * list, const char * lang, double quality);
2.51 frystyk 439: extern void HTLanguage_deleteAll (HTList * list);
2.50 frystyk 440: </PRE>
2.67 frystyk 441: <H2>
442: <A NAME="global">Global Preferences</A>
443: </H2>
444: <P>
2.50 frystyk 445: There are two places where these preferences can be registered: in a
2.67 frystyk 446: <EM>global</EM> list valid for <B>all</B> requests and a <EM>local</EM> list
447: valid for a particular request only. These are valid for <EM>all</EM> requests.
448: See the <A HREF="HTReq.html">Request Manager</A> fro local sets.
449: <H3>
2.73 frystyk 450: Global Converters and Presenters
2.67 frystyk 451: </H3>
452: <P>
453: The <EM>global</EM> list of specific conversions which the format manager
454: can do in order to fulfill the request. There is also a
455: <A HREF="HTReq.html"><EM>local</EM></A> list of conversions which contains
456: a generic set of possible conversions.
2.73 frystyk 457: <PRE>extern void HTFormat_setConversion (HTList * list);
2.50 frystyk 458: extern HTList * HTFormat_conversion (void);
2.69 frystyk 459:
460: extern void HTFormat_addConversion (const char * input_format,
461: const char * output_format,
462: HTConverter * converter,
463: double quality,
464: double secs,
465: double secs_per_byte);
2.31 frystyk 466: </PRE>
2.67 frystyk 467: <H3>
2.73 frystyk 468: Global Content Codings
2.67 frystyk 469: </H3>
2.73 frystyk 470: <PRE>extern void HTFormat_setContentCoding (HTList * list);
2.64 frystyk 471: extern HTList * HTFormat_contentCoding (void);
2.69 frystyk 472:
473: extern BOOL HTFormat_addCoding ( char * encoding,
474: HTCoder * encoder,
475: HTCoder * decoder,
476: double quality);
2.50 frystyk 477: </PRE>
2.74 frystyk 478: <P>
2.82 frystyk 479: We also define a macro to find out whether a content encoding is really an
480: encoding or whether it is a unity encoder.
2.74 frystyk 481: <PRE>
482: #define HTFormat_isUnityContent(me) \
2.79 frystyk 483: ((me)==NULL || \
484: (me)==WWW_CODING_BINARY || (me)==WWW_CODING_IDENTITY || \
485: (me)==WWW_CODING_7BIT || (me)==WWW_CODING_8BIT)
2.74 frystyk 486: </PRE>
2.67 frystyk 487: <H3>
2.77 frystyk 488: Global Transfer Codings
2.67 frystyk 489: </H3>
2.73 frystyk 490: <PRE>extern void HTFormat_setTransferCoding (HTList * list);
2.64 frystyk 491: extern HTList * HTFormat_transferCoding (void);
2.69 frystyk 492:
493: extern BOOL HTFormat_addTransferCoding ( char * encoding,
494: HTCoder * encoder,
495: HTCoder * decoder,
496: double quality);
2.64 frystyk 497: </PRE>
2.67 frystyk 498: <P>
499: We also define a macro to find out whether a transfer encoding is really
500: an encoding or whether it is just a "dummy" as for example 7bit, 8bit, and
501: binary.
2.64 frystyk 502: <PRE>
503: #define HTFormat_isUnityTransfer(me) \
2.79 frystyk 504: ((me)==NULL || \
505: (me)==WWW_CODING_BINARY || (me)==WWW_CODING_IDENTITY || \
506: (me)==WWW_CODING_7BIT || (me)==WWW_CODING_8BIT)
2.64 frystyk 507: </PRE>
2.67 frystyk 508: <H3>
2.73 frystyk 509: Global Content Languages
2.67 frystyk 510: </H3>
2.73 frystyk 511: <PRE>extern void HTFormat_setLanguage (HTList * list);
2.50 frystyk 512: extern HTList * HTFormat_language (void);
513: </PRE>
2.67 frystyk 514: <H3>
2.73 frystyk 515: Global Content Charsets
2.67 frystyk 516: </H3>
2.73 frystyk 517: <PRE>extern void HTFormat_setCharset (HTList * list);
2.50 frystyk 518: extern HTList * HTFormat_charset (void);
2.31 frystyk 519: </PRE>
2.67 frystyk 520: <H3>
521: Delete All Global Lists
522: </H3>
523: <P>
2.50 frystyk 524: This is a convenience function that might make life easier.
2.73 frystyk 525: <PRE>extern void HTFormat_deleteAll (void);
2.34 frystyk 526: </PRE>
2.67 frystyk 527: <H2>
528: <A NAME="CTStack">The Content Type Stream Stack</A>
529: </H2>
530: <P>
531: This is the routine which actually sets up the content type conversion. It
532: currently checks only for direct conversions, but multi-stage conversions
533: are forseen. It takes a stream into which the output should be sent in the
534: final format, builds the conversion stack, and returns a stream into which
535: the data in the input format should be fed. If <CODE>guess</CODE> is true
536: and input format is <CODE>www/unknown</CODE>, try to guess the format by
537: looking at the first few bytes of the stream.
2.31 frystyk 538: <PRE>
2.52 frystyk 539: extern HTStream * HTStreamStack (HTFormat rep_in,
540: HTFormat rep_out,
541: HTStream * output_stream,
542: HTRequest * request,
543: BOOL guess);
2.1 timbl 544: </PRE>
2.67 frystyk 545: <H3>
546: Cost of a Stream Stack
547: </H3>
548: <P>
549: Must return the cost of the same stack which HTStreamStack would set up.
2.31 frystyk 550: <PRE>
2.52 frystyk 551: extern double HTStackValue (HTList * conversions,
552: HTFormat format_in,
553: HTFormat format_out,
554: double initial_value,
555: long int length);
2.64 frystyk 556: </PRE>
2.67 frystyk 557: <H2>
558: <A NAME="CEStack">Content Encoding Stream Stack</A>
559: </H2>
560: <P>
561: When creating a coding stream stack, it is important that we keep the right
562: order of encoders and decoders. As an example, the HTTP spec specifies that
563: the list in the <EM>Content-Encoding</EM> header follows the order in which
564: the encodings have been applied to the object. Internally, we represent the
565: content encodings as <A HREF="HTAtom.html">atoms</A> in a linked
566: <A HREF="HTList.html">list object</A>.
567: <P>
568: The creation of the content coding stack is not based on quality factors
569: as we don't have the freedom as with content types. When using content codings
570: we <EM>must</EM> apply the codings specified or fail.
2.64 frystyk 571: <PRE>
572: extern HTStream * HTContentCodingStack (HTEncoding coding,
573: HTStream * target,
574: HTRequest * request,
575: void * param,
576: BOOL encoding);
577: </PRE>
2.67 frystyk 578: <P>
579: Here you can provide a complete list instead of a single token. The list
580: has to be filled up in the order the _encodings_ are to be applied
2.64 frystyk 581: <PRE>
582: extern HTStream * HTContentEncodingStack (HTList * encodings,
583: HTStream * target,
584: HTRequest * request,
585: void * param);
586: </PRE>
2.67 frystyk 587: <P>
588: Here you can provide a complete list instead of a single token. The list
589: has to be in the order the _encodings_ were applied - that is, the same way
590: that _encodings_ are to be applied. This is all consistent with the order
591: of the Content-Encoding header.
2.64 frystyk 592: <PRE>
593: extern HTStream * HTContentDecodingStack (HTList * encodings,
594: HTStream * target,
595: HTRequest * request,
596: void * param);
597: </PRE>
2.67 frystyk 598: <H2>
2.79 frystyk 599: <A NAME="TEStack">Transfer Encoding Stream Stack</A>
600: </H2>
601: <P>
602: When creating a coding stream stack, it is important that we keep the right
603: order of encoders and decoders. As an example, the HTTP spec specifies that
604: the list in the <EM>Transfer-Encoding</EM> header follows the order in which
605: the encodings have been applied to the object. Internally, we represent the
606: content encodings as <A HREF="HTAtom.html">atoms</A> in a linked
607: <A HREF="HTList.html">list object</A>.
608: <P>
609: The creation of the content coding stack is not based on quality factors
610: as we don't have the freedom as with content types. When using content codings
611: we <EM>must</EM> apply the codings specified or fail.
612: <PRE>
613: extern HTStream * HTTransferCodingStack (HTEncoding coding,
614: HTStream * target,
615: HTRequest * request,
616: void * param,
617: BOOL encoding);
618: </PRE>
619: <P>
620: Here you can provide a complete list instead of a single token. The list
621: has to be filled up in the order the _encodings_ are to be applied
622: <PRE>
623: extern HTStream * HTTransferEncodingStack (HTList * encodings,
624: HTStream * target,
625: HTRequest * request,
626: void * param);
627: </PRE>
628: <P>
629: Here you can provide a complete list instead of a single token. The list
630: has to be in the order the _encodings_ were applied - that is, the same way
631: that _encodings_ are to be applied. This is all consistent with the order
632: of the Transfer-Encoding header.
633: <PRE>
634: extern HTStream * HTTransferDecodingStack (HTList * encodings,
635: HTStream * target,
636: HTRequest * request,
637: void * param);
638: </PRE>
639: <H2>
2.77 frystyk 640: <A NAME="CTEStack">Transfer Encoding Stream Stack</A>
2.67 frystyk 641: </H2>
642: <P>
643: Creating the transfer content encoding stream stack is not based on quality
644: factors as we don't have the freedom as with content types. Specify whether
645: you you want encoding or decoding using the BOOL "encode" flag.
2.64 frystyk 646: <PRE>
2.79 frystyk 647: extern HTStream * HTContentTransferCodingStack (HTEncoding encoding,
648: HTStream * target,
649: HTRequest * request,
650: void * param,
651: BOOL encode);
2.64 frystyk 652: </PRE>
2.73 frystyk 653: <H3>
654: Presentation Object
655: </H3>
656: <P>
657: This object is not to be used - it should have been hidden
658: <PRE>typedef struct _HTPresentation {
659: HTFormat rep; /* representation name atomized */
660: HTFormat rep_out; /* resulting representation */
661: HTConverter *converter; /* The routine to gen the stream stack */
662: char * command; /* MIME-format string */
663: char * test_command; /* MIME-format string */
664: double quality; /* Between 0 (bad) and 1 (good) */
665: double secs;
666: double secs_per_byte;
667: } HTPresentation;
668: </PRE>
2.64 frystyk 669: <PRE>
2.42 frystyk 670: #endif /* HTFORMAT */
2.38 frystyk 671: </PRE>
2.67 frystyk 672: <P>
673: <HR>
2.63 frystyk 674: <ADDRESS>
2.84 ! frystyk 675: @(#) $Id: HTFormat.html,v 2.83 1999/02/07 18:27:49 frystyk Exp $
2.63 frystyk 676: </ADDRESS>
2.67 frystyk 677: </BODY></HTML>
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