Annotation of libwww/Library/src/HTFormat.html, revision 2.81
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>
2.57 frystyk 96: #define WWW_RAW HTAtom_for("www/void") /* Raw output from Protocol */
2.28 frystyk 97: </PRE>
2.67 frystyk 98: <P>
99: <CODE>WWW_RAW</CODE> is an output format which leaves the input untouched
100: <EM>exactly</EM> as it is received by the protocol module. For example, in
101: the case of FTP, this format returns raw ASCII objects for directory listings;
102: for HTTP, everything including the header is returned, for Gopher, a raw
103: ASCII object is returned for a menu etc.
104: <PRE>
105: #define WWW_SOURCE HTAtom_for("*/*")
106: </PRE>
107: <P>
108: <CODE>WWW_SOURCE</CODE> is an output format which leaves the input untouched
109: <EM>exactly</EM> as it is received by the protocol module <B>IF</B> not a
110: suitable converter has been registered with a quality factor higher than
111: 1 (for example 2). In this case the <EM>SUPER CONVERTER</EM> is preferred
112: for the raw output. This can be used as a filter effect that allows conversion
113: from, for example raw FTPdirectory listings into HTML but passes a MIME body
114: untouched.
115: <PRE>
116: #define WWW_PRESENT HTAtom_for("www/present")
117: </PRE>
118: <P>
119: <CODE>WWW_PRESENT</CODE> represents the user's perception of the document.
120: If you convert to <CODE>WWW_PRESENT</CODE>, you present the material to the
121: user.
2.58 frystyk 122: <PRE>
123: #define WWW_DEBUG HTAtom_for("www/debug")
124: </PRE>
2.67 frystyk 125: <P>
126: <CODE>WWW_DEBUG</CODE> represents the user's perception of debug information,
127: for example sent as a HTML document in a HTTP redirection message.
2.28 frystyk 128: <PRE>
2.52 frystyk 129: #define WWW_UNKNOWN HTAtom_for("www/unknown")
2.28 frystyk 130: </PRE>
2.67 frystyk 131: <P>
132: <CODE>WWW_UNKNOWN</CODE> is a really unknown type. It differs from the real
133: MIME type <EM>"application/octet-stream"</EM> in that we haven't even tried
134: to figure out the content type at this point.
2.71 frystyk 135: <PRE>
2.72 frystyk 136: #define WWW_CACHE HTAtom_for("www/cache")
137: #define WWW_CACHE_APPEND HTAtom_for("www/cache-append")
2.71 frystyk 138: </PRE>
139: <P>
140: <CODE>WWW_CACHE</CODE> is the internal content-type designated for a persistent
2.72 frystyk 141: cache module which can store the object to local storage. The cache append
142: format is special in that we append information to an already existing cache
143: entry. This can happen if we have issued a <CODE>If-Range </CODE>request
144: and got back a "206 Partial response".
2.67 frystyk 145: <P>
2.31 frystyk 146: These are regular MIME types defined. Others can be added!
2.28 frystyk 147: <PRE>
2.52 frystyk 148: #define WWW_HTML HTAtom_for("text/html")
2.28 frystyk 149: #define WWW_PLAINTEXT HTAtom_for("text/plain")
2.69 frystyk 150: #define WWW_FORM HTAtom_for("application/x-www-form-urlencoded")
2.52 frystyk 151:
152: #define WWW_MIME HTAtom_for("message/rfc822")
2.60 frystyk 153: #define WWW_MIME_HEAD HTAtom_for("message/x-rfc822-head")
2.65 frystyk 154: #define WWW_MIME_FOOT HTAtom_for("message/x-rfc822-foot")
2.72 frystyk 155: #define WWW_MIME_PART HTAtom_for("message/x-rfc822-partial")
2.76 frystyk 156: #define WWW_MIME_CONT HTAtom_for("message/x-rfc822-cont")
2.52 frystyk 157:
2.10 timbl 158: #define WWW_AUDIO HTAtom_for("audio/basic")
2.52 frystyk 159:
2.26 frystyk 160: #define WWW_VIDEO HTAtom_for("video/mpeg")
2.52 frystyk 161:
2.70 frystyk 162: #define WWW_GIF HTAtom_for("image/gif")
2.63 frystyk 163: #define WWW_JPEG HTAtom_for("image/jpeg")
164: #define WWW_TIFF HTAtom_for("image/tiff")
2.52 frystyk 165: #define WWW_PNG HTAtom_for("image/png")
166:
167: #define WWW_BINARY HTAtom_for("application/octet-stream")
168: #define WWW_POSTSCRIPT HTAtom_for("application/postscript")
169: #define WWW_RICHTEXT HTAtom_for("application/rtf")
2.48 frystyk 170: </PRE>
2.67 frystyk 171: <P>
172: We also have some MIME types that come from the various protocols when we
173: convert from ASCII to HTML.
2.48 frystyk 174: <PRE>
175: #define WWW_GOPHER_MENU HTAtom_for("text/x-gopher")
2.53 frystyk 176: #define WWW_CSO_SEARCH HTAtom_for("text/x-cso")
2.48 frystyk 177:
178: #define WWW_FTP_LNST HTAtom_for("text/x-ftp-lnst")
179: #define WWW_FTP_LIST HTAtom_for("text/x-ftp-list")
180:
181: #define WWW_NNTP_LIST HTAtom_for("text/x-nntp-list")
182: #define WWW_NNTP_OVER HTAtom_for("text/x-nntp-over")
183: #define WWW_NNTP_HEAD HTAtom_for("text/x-nntp-head")
2.59 frystyk 184:
185: #define WWW_HTTP HTAtom_for("text/x-http")
2.55 frystyk 186: </PRE>
2.67 frystyk 187: <P>
188: Finally we have defined a special format for our RULE files as they can be
189: handled by a special converter.
2.73 frystyk 190: <PRE>#define WWW_RULES HTAtom_for("application/x-www-rules")
191: </PRE>
192: <H3>
193: The Quality Factor
194: </H3>
195: <P>
196: Characteristic for all preferences is that there is a quality factor associated
197: with each member. The quality factor is a real number between 0 and 1 with
198: 0 meaning "very bad" and 1 means "perfect". By registering a natural language
199: or any or other preference in this group together with a quality factor you
200: can specify "how well the preference is handled" either by the application
201: or by the user. In the case of the user the quality factor of a natural language
202: is how well the user understands the language. In my case, the quality factors
203: for, for example Greek would be close to zero and 1 for Danish (nothing bad
204: said about Greek!).
205: <P>
206: It is a bit different for converters where it is often the application's
207: ability of handling the data format rather than the user's perception. As
208: an example it is often faster to use a converter than a presenter as it takes
209: time to launch the external application and libwww can not use progressive
210: display mechanisms which is often the case for converters. Therefore, as
211: an example, if we capable of handling an image in <EM>png</EM> format inline
212: but rely on an external viewer for presenting postscript, we might set up
213: the following list:
214: <P>
215: <SAMP>HTConversion_add (converters, "image", "www/present", GifPresenter,
216: <B>1.0</B>, 0.0, 0.0);<BR>
217: HTPresentation_add (presenters, "application/postscript", "ghostview %s",
218: NULL, <B>0.5</B>, 0.0, 0.0);></SAMP>
219: <P>
220: where the gif converter is registered with a quality factor of <B>1.0</B>
221: and the postscript presenter with a quality factor of <B>0.5</B>.Register
222: Presenters
223: <H3>
224: The Converter Class
225: </H3>
226: <P>
227: A <CODE>converter</CODE> is a stream with a special set of parameters and
228: which is registered as capable of converting from a MIME type to something
229: else (maybe another MIME-type). A converter is defined to be a function returning
230: a stream and accepting the following parameters. The content type elements
231: are atoms for which we have defined a prototype.
2.55 frystyk 232: <PRE>
2.73 frystyk 233: typedef HTStream * HTConverter (HTRequest * request,
234: void * param,
235: HTFormat input_format,
236: HTFormat output_format,
237: HTStream * output_stream);
238:
239: extern void HTConversion_add (HTList * conversions,
240: const char * rep_in,
241: const char * rep_out,
242: HTConverter * converter,
243: double quality,
244: double secs,
245: double secs_per_byte);
246:
247: extern void HTConversion_deleteAll (HTList * list);
2.28 frystyk 248: </PRE>
2.67 frystyk 249: <H3>
2.73 frystyk 250: The Presenter Class
2.67 frystyk 251: </H3>
252: <P>
2.73 frystyk 253: A <CODE>presenter</CODE> is a module (possibly an external program) which
254: can present a graphic object of a certain MIME type to the user. That is,
255: <CODE>presenters</CODE> are normally used to present objects that the
256: <CODE>converters</CODE> are not able to handle. Data is transferred to the
257: external program using for example the
258: <A HREF="HTFWrite.html">HTSaveAndExecute</A> stream which writes to a local
259: file. Both presenters and converters are of the type
260: <A HREF="#converter">HTConverter</A>.
2.31 frystyk 261: <PRE>
2.49 frystyk 262: extern void HTPresentation_add (HTList * conversions,
2.73 frystyk 263: </PRE>
264: <PRE> const char * representation,
2.61 frystyk 265: const char * command,
266: const char * test_command,
2.49 frystyk 267: double quality,
268: double secs,
269: double secs_per_byte);
2.1 timbl 270:
2.50 frystyk 271: extern void HTPresentation_deleteAll (HTList * list);
272: </PRE>
2.67 frystyk 273: <H3>
2.73 frystyk 274: Basic Converters
2.67 frystyk 275: </H3>
276: <P>
2.73 frystyk 277: We have a small set of basic converters that can be hooked in anywhere. They
278: don't "convert" anything but are nice to have.
2.79 frystyk 279: <PRE>
280: extern HTConverter HTThroughLine;
2.73 frystyk 281: extern HTConverter HTBlackHoleConverter;
2.79 frystyk 282: extern HTConverter HTSaveConverter;
2.42 frystyk 283: </PRE>
2.67 frystyk 284: <H2>
285: <A NAME="encoding">Content and Transfer Encoders and Decoders</A>
286: </H2>
287: <P>
288: Content codins are transformations applied to an entity object after it was
289: created in its original form. The Library handles two types of codings:
2.64 frystyk 290: <DL>
2.67 frystyk 291: <DT>
292: <B>Content Codings</B>
293: <DD>
294: Content codings values indicate an encoding transformation that has been
295: applied to a resource. Content cosings are primarily used to allow a document
296: to be compressed or encrypted without loosing the identity of its underlying
297: media type.
298: <DT>
299: <B>Content Transfer Codings</B>
300: <DD>
301: Content transfer codings values are used to indicate an encoding transformation
302: that has been, can be, or may be need to be applied to an enity body in order
303: to ensure safe transport through the network. This differs from a content
304: coding in that the transfer coding is a property of the message, not the
305: original message.
2.64 frystyk 306: </DL>
2.67 frystyk 307: <P>
308: Both types of encodings use the same registration mechanism in the Library
309: which we describe below:
310: <H3>
311: Encoders and Decoders
312: </H3>
313: <P>
314: <EM>Encoders</EM> and <EM>decoders</EM> are subclassed from the
315: <A HREF="HTStream.html">generic stream class</A>. <EM>Encoders</EM> are capable
316: of adding a content coding to a data object and <EM>decoders</EM> can remove
317: a content coding.
2.50 frystyk 318: <PRE>
2.64 frystyk 319: typedef HTStream * HTCoder (HTRequest * request,
320: void * param,
321: HTEncoding coding,
322: HTStream * target);
2.50 frystyk 323: </PRE>
2.67 frystyk 324: <P>
325: The <EM>encoding</EM> is the name of the encoding mechanism reporesented
326: as an <A HREF="HTAtom.html">atom</A>, for example "zip", "chunked", etc.
327: Encodings are registered in lists and content encodings are separated from
328: transfer encodings by registering them in different lists.
329: <H3>
2.81 ! frystyk 330: Basic Encoders
! 331: </H3>
! 332: <P>
! 333: We have a small set of basic coders that can be hooked in anywhere.
! 334: <PRE>
! 335: extern HTCoder HTIdentityCoding;
! 336: </PRE>
! 337: <H3>
2.67 frystyk 338: The HTCoding Object
339: </H3>
340: <P>
341: The <EM>HTCoding</EM> object represents a registered encoding together with
342: a encoder and a decoder.
2.63 frystyk 343: <PRE>
2.64 frystyk 344: typedef struct _HTCoding HTCoding;
2.63 frystyk 345: </PRE>
2.67 frystyk 346: <P>
347: Predefined Coding Types We have a set of pre defined atoms for various types
348: of content encodings and transfer encodings. "chunked" is not exactly in
349: the same group as the other encodings such as "binary" but it really doesn't
350: make any difference as it is just a matter of how the words are chosen. The
351: first three transfer encodings are actually not encodings - they are just
352: left overs from brain dead mail systems.
2.42 frystyk 353: <PRE>
2.79 frystyk 354: #define WWW_CODING_7BIT HTAtom_for("7bit")
355: #define WWW_CODING_8BIT HTAtom_for("8bit")
356: #define WWW_CODING_BINARY HTAtom_for("binary")
357: #define WWW_CODING_IDENTITY HTAtom_for("identity")
2.64 frystyk 358:
2.79 frystyk 359: #define WWW_CODING_BASE64 HTAtom_for("base64")
360: #define WWW_CODING_MACBINHEX HTAtom_for("macbinhex")
361: #define WWW_CODING_CHUNKED HTAtom_for("chunked")
2.63 frystyk 362:
2.79 frystyk 363: #define WWW_CODING_COMPRESS HTAtom_for("compress")
364: #define WWW_CODING_GZIP HTAtom_for("gzip")
365: #define WWW_CODING_DEFLATE HTAtom_for("deflate")
2.42 frystyk 366: </PRE>
2.67 frystyk 367: <H3>
368: Register Content Coders
369: </H3>
370: <P>
2.73 frystyk 371: Some documents are not send in their original data obejct but is encoded
372: in some way. On the Web this is mostly some kind of compression but other
373: encodings for example base 64 can be encountered when talking to NNTP servers
374: etc. Just as for the other preferences, an application can register a supported
375: encoders or decodes as a list. Encoders and decoders are registered in the
376: same way with no differentiation whether it is a encoder or a decoder:
2.42 frystyk 377: <PRE>
2.64 frystyk 378: extern BOOL HTCoding_add (HTList * list,
379: const char * encoding,
380: HTCoder * encoder,
381: HTCoder * decoder,
382: double quality);
2.63 frystyk 383:
2.64 frystyk 384: extern void HTCoding_deleteAll (HTList * list);
2.42 frystyk 385:
2.64 frystyk 386: extern const char * HTCoding_name (HTCoding * me);
2.77 frystyk 387:
388: extern double HTCoding_quality (HTCoding * me);
2.42 frystyk 389: </PRE>
2.67 frystyk 390: <H2>
391: <A NAME="charset">Content Charsets</A>
392: </H2>
2.73 frystyk 393: <P>
394: As the Web reaches all parts of the Internet there are more and more documents
395: written in languages which contains characters not included in the ISO-8859-1
396: character set. A consequence of this the set of characters sets is often
397: tightly connected with the natural language. libwww does not directly support
398: other character sets but in case an application is capable of handling
399: alternative sets it can register these as preferred character sets along
400: with a quality factor just as all the other preferences in this section.
401: <PRE>extern void HTCharset_add (HTList * list, const char * charset, double quality);
2.42 frystyk 402: </PRE>
2.73 frystyk 403: <PRE>typedef struct _HTAcceptNode {
2.63 frystyk 404: HTAtom * atom;
405: double quality;
406: } HTAcceptNode;
407: </PRE>
408: <PRE>
2.50 frystyk 409: extern void HTCharset_deleteAll (HTList * list);
410: </PRE>
2.67 frystyk 411: <H2>
412: <A NAME="language">Content Languages</A>
413: </H2>
2.73 frystyk 414: <P>
415: The preferred natural language or languages is in almost all situations dependent
416: on the individual user and an application should therefore give the user
417: the opportunity to change the setup. When specifying a natural language
418: preference, libwww will send this preference along with all HTTP requests.
419: The remote server will then (it if supports this feature) look for a version
420: in the language or languages mentioned. If it finds a matching document then
421: it returns this one, otherwise it uses the best alternative. If no language
422: is specified the remote server may whatever version it finds.
423: <PRE>extern void HTLanguage_add (HTList * list, const char * lang, double quality);
2.51 frystyk 424: extern void HTLanguage_deleteAll (HTList * list);
2.50 frystyk 425: </PRE>
2.67 frystyk 426: <H2>
427: <A NAME="global">Global Preferences</A>
428: </H2>
429: <P>
2.50 frystyk 430: There are two places where these preferences can be registered: in a
2.67 frystyk 431: <EM>global</EM> list valid for <B>all</B> requests and a <EM>local</EM> list
432: valid for a particular request only. These are valid for <EM>all</EM> requests.
433: See the <A HREF="HTReq.html">Request Manager</A> fro local sets.
434: <H3>
2.73 frystyk 435: Global Converters and Presenters
2.67 frystyk 436: </H3>
437: <P>
438: The <EM>global</EM> list of specific conversions which the format manager
439: can do in order to fulfill the request. There is also a
440: <A HREF="HTReq.html"><EM>local</EM></A> list of conversions which contains
441: a generic set of possible conversions.
2.73 frystyk 442: <PRE>extern void HTFormat_setConversion (HTList * list);
2.50 frystyk 443: extern HTList * HTFormat_conversion (void);
2.69 frystyk 444:
445: extern void HTFormat_addConversion (const char * input_format,
446: const char * output_format,
447: HTConverter * converter,
448: double quality,
449: double secs,
450: double secs_per_byte);
2.31 frystyk 451: </PRE>
2.67 frystyk 452: <H3>
2.73 frystyk 453: Global Content Codings
2.67 frystyk 454: </H3>
2.73 frystyk 455: <PRE>extern void HTFormat_setContentCoding (HTList * list);
2.64 frystyk 456: extern HTList * HTFormat_contentCoding (void);
2.69 frystyk 457:
458: extern BOOL HTFormat_addCoding ( char * encoding,
459: HTCoder * encoder,
460: HTCoder * decoder,
461: double quality);
2.50 frystyk 462: </PRE>
2.74 frystyk 463: <P>
464: We also define a macro to find out whether a content encoding is really
465: an encoding or whether it is a unity encoder.
466: <PRE>
467: #define HTFormat_isUnityContent(me) \
2.79 frystyk 468: ((me)==NULL || \
469: (me)==WWW_CODING_BINARY || (me)==WWW_CODING_IDENTITY || \
470: (me)==WWW_CODING_7BIT || (me)==WWW_CODING_8BIT)
2.74 frystyk 471: </PRE>
2.67 frystyk 472: <H3>
2.77 frystyk 473: Global Transfer Codings
2.67 frystyk 474: </H3>
2.73 frystyk 475: <PRE>extern void HTFormat_setTransferCoding (HTList * list);
2.64 frystyk 476: extern HTList * HTFormat_transferCoding (void);
2.69 frystyk 477:
478: extern BOOL HTFormat_addTransferCoding ( char * encoding,
479: HTCoder * encoder,
480: HTCoder * decoder,
481: double quality);
2.64 frystyk 482: </PRE>
2.67 frystyk 483: <P>
484: We also define a macro to find out whether a transfer encoding is really
485: an encoding or whether it is just a "dummy" as for example 7bit, 8bit, and
486: binary.
2.64 frystyk 487: <PRE>
488: #define HTFormat_isUnityTransfer(me) \
2.79 frystyk 489: ((me)==NULL || \
490: (me)==WWW_CODING_BINARY || (me)==WWW_CODING_IDENTITY || \
491: (me)==WWW_CODING_7BIT || (me)==WWW_CODING_8BIT)
2.64 frystyk 492: </PRE>
2.67 frystyk 493: <H3>
2.73 frystyk 494: Global Content Languages
2.67 frystyk 495: </H3>
2.73 frystyk 496: <PRE>extern void HTFormat_setLanguage (HTList * list);
2.50 frystyk 497: extern HTList * HTFormat_language (void);
498: </PRE>
2.67 frystyk 499: <H3>
2.73 frystyk 500: Global Content Charsets
2.67 frystyk 501: </H3>
2.73 frystyk 502: <PRE>extern void HTFormat_setCharset (HTList * list);
2.50 frystyk 503: extern HTList * HTFormat_charset (void);
2.31 frystyk 504: </PRE>
2.67 frystyk 505: <H3>
506: Delete All Global Lists
507: </H3>
508: <P>
2.50 frystyk 509: This is a convenience function that might make life easier.
2.73 frystyk 510: <PRE>extern void HTFormat_deleteAll (void);
2.34 frystyk 511: </PRE>
2.67 frystyk 512: <H2>
513: <A NAME="CTStack">The Content Type Stream Stack</A>
514: </H2>
515: <P>
516: This is the routine which actually sets up the content type conversion. It
517: currently checks only for direct conversions, but multi-stage conversions
518: are forseen. It takes a stream into which the output should be sent in the
519: final format, builds the conversion stack, and returns a stream into which
520: the data in the input format should be fed. If <CODE>guess</CODE> is true
521: and input format is <CODE>www/unknown</CODE>, try to guess the format by
522: looking at the first few bytes of the stream.
2.31 frystyk 523: <PRE>
2.52 frystyk 524: extern HTStream * HTStreamStack (HTFormat rep_in,
525: HTFormat rep_out,
526: HTStream * output_stream,
527: HTRequest * request,
528: BOOL guess);
2.1 timbl 529: </PRE>
2.67 frystyk 530: <H3>
531: Cost of a Stream Stack
532: </H3>
533: <P>
534: Must return the cost of the same stack which HTStreamStack would set up.
2.31 frystyk 535: <PRE>
2.52 frystyk 536: extern double HTStackValue (HTList * conversions,
537: HTFormat format_in,
538: HTFormat format_out,
539: double initial_value,
540: long int length);
2.64 frystyk 541: </PRE>
2.67 frystyk 542: <H2>
543: <A NAME="CEStack">Content Encoding Stream Stack</A>
544: </H2>
545: <P>
546: When creating a coding stream stack, it is important that we keep the right
547: order of encoders and decoders. As an example, the HTTP spec specifies that
548: the list in the <EM>Content-Encoding</EM> header follows the order in which
549: the encodings have been applied to the object. Internally, we represent the
550: content encodings as <A HREF="HTAtom.html">atoms</A> in a linked
551: <A HREF="HTList.html">list object</A>.
552: <P>
553: The creation of the content coding stack is not based on quality factors
554: as we don't have the freedom as with content types. When using content codings
555: we <EM>must</EM> apply the codings specified or fail.
2.64 frystyk 556: <PRE>
557: extern HTStream * HTContentCodingStack (HTEncoding coding,
558: HTStream * target,
559: HTRequest * request,
560: void * param,
561: BOOL encoding);
562: </PRE>
2.67 frystyk 563: <P>
564: Here you can provide a complete list instead of a single token. The list
565: has to be filled up in the order the _encodings_ are to be applied
2.64 frystyk 566: <PRE>
567: extern HTStream * HTContentEncodingStack (HTList * encodings,
568: HTStream * target,
569: HTRequest * request,
570: void * param);
571: </PRE>
2.67 frystyk 572: <P>
573: Here you can provide a complete list instead of a single token. The list
574: has to be in the order the _encodings_ were applied - that is, the same way
575: that _encodings_ are to be applied. This is all consistent with the order
576: of the Content-Encoding header.
2.64 frystyk 577: <PRE>
578: extern HTStream * HTContentDecodingStack (HTList * encodings,
579: HTStream * target,
580: HTRequest * request,
581: void * param);
582: </PRE>
2.67 frystyk 583: <H2>
2.79 frystyk 584: <A NAME="TEStack">Transfer Encoding Stream Stack</A>
585: </H2>
586: <P>
587: When creating a coding stream stack, it is important that we keep the right
588: order of encoders and decoders. As an example, the HTTP spec specifies that
589: the list in the <EM>Transfer-Encoding</EM> header follows the order in which
590: the encodings have been applied to the object. Internally, we represent the
591: content encodings as <A HREF="HTAtom.html">atoms</A> in a linked
592: <A HREF="HTList.html">list object</A>.
593: <P>
594: The creation of the content coding stack is not based on quality factors
595: as we don't have the freedom as with content types. When using content codings
596: we <EM>must</EM> apply the codings specified or fail.
597: <PRE>
598: extern HTStream * HTTransferCodingStack (HTEncoding coding,
599: HTStream * target,
600: HTRequest * request,
601: void * param,
602: BOOL encoding);
603: </PRE>
604: <P>
605: Here you can provide a complete list instead of a single token. The list
606: has to be filled up in the order the _encodings_ are to be applied
607: <PRE>
608: extern HTStream * HTTransferEncodingStack (HTList * encodings,
609: HTStream * target,
610: HTRequest * request,
611: void * param);
612: </PRE>
613: <P>
614: Here you can provide a complete list instead of a single token. The list
615: has to be in the order the _encodings_ were applied - that is, the same way
616: that _encodings_ are to be applied. This is all consistent with the order
617: of the Transfer-Encoding header.
618: <PRE>
619: extern HTStream * HTTransferDecodingStack (HTList * encodings,
620: HTStream * target,
621: HTRequest * request,
622: void * param);
623: </PRE>
624: <H2>
2.77 frystyk 625: <A NAME="CTEStack">Transfer Encoding Stream Stack</A>
2.67 frystyk 626: </H2>
627: <P>
628: Creating the transfer content encoding stream stack is not based on quality
629: factors as we don't have the freedom as with content types. Specify whether
630: you you want encoding or decoding using the BOOL "encode" flag.
2.64 frystyk 631: <PRE>
2.79 frystyk 632: extern HTStream * HTContentTransferCodingStack (HTEncoding encoding,
633: HTStream * target,
634: HTRequest * request,
635: void * param,
636: BOOL encode);
2.64 frystyk 637: </PRE>
2.73 frystyk 638: <H3>
639: Presentation Object
640: </H3>
641: <P>
642: This object is not to be used - it should have been hidden
643: <PRE>typedef struct _HTPresentation {
644: HTFormat rep; /* representation name atomized */
645: HTFormat rep_out; /* resulting representation */
646: HTConverter *converter; /* The routine to gen the stream stack */
647: char * command; /* MIME-format string */
648: char * test_command; /* MIME-format string */
649: double quality; /* Between 0 (bad) and 1 (good) */
650: double secs;
651: double secs_per_byte;
652: } HTPresentation;
653: </PRE>
2.64 frystyk 654: <PRE>
2.42 frystyk 655: #endif /* HTFORMAT */
2.38 frystyk 656: </PRE>
2.67 frystyk 657: <P>
658: <HR>
2.63 frystyk 659: <ADDRESS>
2.81 ! frystyk 660: @(#) $Id: HTFormat.html,v 2.80 1998/05/14 02:10:30 frystyk Exp $
2.63 frystyk 661: </ADDRESS>
2.67 frystyk 662: </BODY></HTML>
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