Annotation of libwww/Library/src/HTFormat.html, revision 2.82
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")
2.52 frystyk 163:
2.10 timbl 164: #define WWW_AUDIO HTAtom_for("audio/basic")
2.52 frystyk 165:
2.26 frystyk 166: #define WWW_VIDEO HTAtom_for("video/mpeg")
2.52 frystyk 167:
2.70 frystyk 168: #define WWW_GIF HTAtom_for("image/gif")
2.63 frystyk 169: #define WWW_JPEG HTAtom_for("image/jpeg")
170: #define WWW_TIFF HTAtom_for("image/tiff")
2.52 frystyk 171: #define WWW_PNG HTAtom_for("image/png")
172:
173: #define WWW_BINARY HTAtom_for("application/octet-stream")
174: #define WWW_POSTSCRIPT HTAtom_for("application/postscript")
175: #define WWW_RICHTEXT HTAtom_for("application/rtf")
2.48 frystyk 176: </PRE>
2.67 frystyk 177: <P>
178: We also have some MIME types that come from the various protocols when we
179: convert from ASCII to HTML.
2.48 frystyk 180: <PRE>
181: #define WWW_GOPHER_MENU HTAtom_for("text/x-gopher")
2.53 frystyk 182: #define WWW_CSO_SEARCH HTAtom_for("text/x-cso")
2.48 frystyk 183:
184: #define WWW_FTP_LNST HTAtom_for("text/x-ftp-lnst")
185: #define WWW_FTP_LIST HTAtom_for("text/x-ftp-list")
186:
187: #define WWW_NNTP_LIST HTAtom_for("text/x-nntp-list")
188: #define WWW_NNTP_OVER HTAtom_for("text/x-nntp-over")
189: #define WWW_NNTP_HEAD HTAtom_for("text/x-nntp-head")
2.59 frystyk 190:
191: #define WWW_HTTP HTAtom_for("text/x-http")
2.55 frystyk 192: </PRE>
2.67 frystyk 193: <P>
194: Finally we have defined a special format for our RULE files as they can be
195: handled by a special converter.
2.73 frystyk 196: <PRE>#define WWW_RULES HTAtom_for("application/x-www-rules")
197: </PRE>
198: <H3>
199: The Quality Factor
200: </H3>
201: <P>
202: Characteristic for all preferences is that there is a quality factor associated
203: with each member. The quality factor is a real number between 0 and 1 with
204: 0 meaning "very bad" and 1 means "perfect". By registering a natural language
205: or any or other preference in this group together with a quality factor you
206: can specify "how well the preference is handled" either by the application
207: or by the user. In the case of the user the quality factor of a natural language
208: is how well the user understands the language. In my case, the quality factors
209: for, for example Greek would be close to zero and 1 for Danish (nothing bad
210: said about Greek!).
211: <P>
212: It is a bit different for converters where it is often the application's
213: ability of handling the data format rather than the user's perception. As
214: an example it is often faster to use a converter than a presenter as it takes
215: time to launch the external application and libwww can not use progressive
216: display mechanisms which is often the case for converters. Therefore, as
217: an example, if we capable of handling an image in <EM>png</EM> format inline
218: but rely on an external viewer for presenting postscript, we might set up
219: the following list:
220: <P>
221: <SAMP>HTConversion_add (converters, "image", "www/present", GifPresenter,
222: <B>1.0</B>, 0.0, 0.0);<BR>
223: HTPresentation_add (presenters, "application/postscript", "ghostview %s",
224: NULL, <B>0.5</B>, 0.0, 0.0);></SAMP>
225: <P>
226: where the gif converter is registered with a quality factor of <B>1.0</B>
227: and the postscript presenter with a quality factor of <B>0.5</B>.Register
228: Presenters
229: <H3>
230: The Converter Class
231: </H3>
232: <P>
233: A <CODE>converter</CODE> is a stream with a special set of parameters and
234: which is registered as capable of converting from a MIME type to something
235: else (maybe another MIME-type). A converter is defined to be a function returning
236: a stream and accepting the following parameters. The content type elements
237: are atoms for which we have defined a prototype.
2.55 frystyk 238: <PRE>
2.73 frystyk 239: typedef HTStream * HTConverter (HTRequest * request,
240: void * param,
241: HTFormat input_format,
242: HTFormat output_format,
243: HTStream * output_stream);
244:
245: extern void HTConversion_add (HTList * conversions,
246: const char * rep_in,
247: const char * rep_out,
248: HTConverter * converter,
249: double quality,
250: double secs,
251: double secs_per_byte);
252:
253: extern void HTConversion_deleteAll (HTList * list);
2.28 frystyk 254: </PRE>
2.67 frystyk 255: <H3>
2.73 frystyk 256: The Presenter Class
2.67 frystyk 257: </H3>
258: <P>
2.73 frystyk 259: A <CODE>presenter</CODE> is a module (possibly an external program) which
260: can present a graphic object of a certain MIME type to the user. That is,
261: <CODE>presenters</CODE> are normally used to present objects that the
262: <CODE>converters</CODE> are not able to handle. Data is transferred to the
263: external program using for example the
264: <A HREF="HTFWrite.html">HTSaveAndExecute</A> stream which writes to a local
265: file. Both presenters and converters are of the type
266: <A HREF="#converter">HTConverter</A>.
2.31 frystyk 267: <PRE>
2.49 frystyk 268: extern void HTPresentation_add (HTList * conversions,
2.73 frystyk 269: </PRE>
270: <PRE> const char * representation,
2.61 frystyk 271: const char * command,
272: const char * test_command,
2.49 frystyk 273: double quality,
274: double secs,
275: double secs_per_byte);
2.1 timbl 276:
2.50 frystyk 277: extern void HTPresentation_deleteAll (HTList * list);
278: </PRE>
2.67 frystyk 279: <H3>
2.73 frystyk 280: Basic Converters
2.67 frystyk 281: </H3>
282: <P>
2.73 frystyk 283: We have a small set of basic converters that can be hooked in anywhere. They
284: don't "convert" anything but are nice to have.
2.79 frystyk 285: <PRE>
286: extern HTConverter HTThroughLine;
2.73 frystyk 287: extern HTConverter HTBlackHoleConverter;
2.79 frystyk 288: extern HTConverter HTSaveConverter;
2.42 frystyk 289: </PRE>
2.67 frystyk 290: <H2>
291: <A NAME="encoding">Content and Transfer Encoders and Decoders</A>
292: </H2>
293: <P>
294: Content codins are transformations applied to an entity object after it was
295: created in its original form. The Library handles two types of codings:
2.64 frystyk 296: <DL>
2.67 frystyk 297: <DT>
298: <B>Content Codings</B>
299: <DD>
300: Content codings values indicate an encoding transformation that has been
301: applied to a resource. Content cosings are primarily used to allow a document
302: to be compressed or encrypted without loosing the identity of its underlying
303: media type.
304: <DT>
305: <B>Content Transfer Codings</B>
306: <DD>
307: Content transfer codings values are used to indicate an encoding transformation
308: that has been, can be, or may be need to be applied to an enity body in order
309: to ensure safe transport through the network. This differs from a content
310: coding in that the transfer coding is a property of the message, not the
311: original message.
2.64 frystyk 312: </DL>
2.67 frystyk 313: <P>
314: Both types of encodings use the same registration mechanism in the Library
315: which we describe below:
316: <H3>
317: Encoders and Decoders
318: </H3>
319: <P>
320: <EM>Encoders</EM> and <EM>decoders</EM> are subclassed from the
321: <A HREF="HTStream.html">generic stream class</A>. <EM>Encoders</EM> are capable
322: of adding a content coding to a data object and <EM>decoders</EM> can remove
323: a content coding.
2.50 frystyk 324: <PRE>
2.64 frystyk 325: typedef HTStream * HTCoder (HTRequest * request,
326: void * param,
327: HTEncoding coding,
328: HTStream * target);
2.50 frystyk 329: </PRE>
2.67 frystyk 330: <P>
331: The <EM>encoding</EM> is the name of the encoding mechanism reporesented
332: as an <A HREF="HTAtom.html">atom</A>, for example "zip", "chunked", etc.
333: Encodings are registered in lists and content encodings are separated from
334: transfer encodings by registering them in different lists.
335: <H3>
2.81 frystyk 336: Basic Encoders
337: </H3>
338: <P>
339: We have a small set of basic coders that can be hooked in anywhere.
340: <PRE>
341: extern HTCoder HTIdentityCoding;
342: </PRE>
343: <H3>
2.67 frystyk 344: The HTCoding Object
345: </H3>
346: <P>
347: The <EM>HTCoding</EM> object represents a registered encoding together with
348: a encoder and a decoder.
2.63 frystyk 349: <PRE>
2.64 frystyk 350: typedef struct _HTCoding HTCoding;
2.63 frystyk 351: </PRE>
2.67 frystyk 352: <P>
353: Predefined Coding Types We have a set of pre defined atoms for various types
354: of content encodings and transfer encodings. "chunked" is not exactly in
355: the same group as the other encodings such as "binary" but it really doesn't
356: make any difference as it is just a matter of how the words are chosen. The
357: first three transfer encodings are actually not encodings - they are just
358: left overs from brain dead mail systems.
2.42 frystyk 359: <PRE>
2.79 frystyk 360: #define WWW_CODING_7BIT HTAtom_for("7bit")
361: #define WWW_CODING_8BIT HTAtom_for("8bit")
362: #define WWW_CODING_BINARY HTAtom_for("binary")
363: #define WWW_CODING_IDENTITY HTAtom_for("identity")
2.64 frystyk 364:
2.79 frystyk 365: #define WWW_CODING_BASE64 HTAtom_for("base64")
366: #define WWW_CODING_MACBINHEX HTAtom_for("macbinhex")
367: #define WWW_CODING_CHUNKED HTAtom_for("chunked")
2.63 frystyk 368:
2.79 frystyk 369: #define WWW_CODING_COMPRESS HTAtom_for("compress")
370: #define WWW_CODING_GZIP HTAtom_for("gzip")
371: #define WWW_CODING_DEFLATE HTAtom_for("deflate")
2.42 frystyk 372: </PRE>
2.67 frystyk 373: <H3>
374: Register Content Coders
375: </H3>
376: <P>
2.73 frystyk 377: Some documents are not send in their original data obejct but is encoded
378: in some way. On the Web this is mostly some kind of compression but other
379: encodings for example base 64 can be encountered when talking to NNTP servers
380: etc. Just as for the other preferences, an application can register a supported
381: encoders or decodes as a list. Encoders and decoders are registered in the
382: same way with no differentiation whether it is a encoder or a decoder:
2.42 frystyk 383: <PRE>
2.64 frystyk 384: extern BOOL HTCoding_add (HTList * list,
385: const char * encoding,
386: HTCoder * encoder,
387: HTCoder * decoder,
388: double quality);
2.63 frystyk 389:
2.64 frystyk 390: extern void HTCoding_deleteAll (HTList * list);
2.42 frystyk 391:
2.64 frystyk 392: extern const char * HTCoding_name (HTCoding * me);
2.77 frystyk 393:
394: extern double HTCoding_quality (HTCoding * me);
2.42 frystyk 395: </PRE>
2.67 frystyk 396: <H2>
397: <A NAME="charset">Content Charsets</A>
398: </H2>
2.73 frystyk 399: <P>
400: As the Web reaches all parts of the Internet there are more and more documents
401: written in languages which contains characters not included in the ISO-8859-1
402: character set. A consequence of this the set of characters sets is often
403: tightly connected with the natural language. libwww does not directly support
404: other character sets but in case an application is capable of handling
405: alternative sets it can register these as preferred character sets along
406: with a quality factor just as all the other preferences in this section.
407: <PRE>extern void HTCharset_add (HTList * list, const char * charset, double quality);
2.42 frystyk 408: </PRE>
2.73 frystyk 409: <PRE>typedef struct _HTAcceptNode {
2.63 frystyk 410: HTAtom * atom;
411: double quality;
412: } HTAcceptNode;
413: </PRE>
414: <PRE>
2.50 frystyk 415: extern void HTCharset_deleteAll (HTList * list);
416: </PRE>
2.67 frystyk 417: <H2>
418: <A NAME="language">Content Languages</A>
419: </H2>
2.73 frystyk 420: <P>
421: The preferred natural language or languages is in almost all situations dependent
422: on the individual user and an application should therefore give the user
423: the opportunity to change the setup. When specifying a natural language
424: preference, libwww will send this preference along with all HTTP requests.
425: The remote server will then (it if supports this feature) look for a version
426: in the language or languages mentioned. If it finds a matching document then
427: it returns this one, otherwise it uses the best alternative. If no language
428: is specified the remote server may whatever version it finds.
429: <PRE>extern void HTLanguage_add (HTList * list, const char * lang, double quality);
2.51 frystyk 430: extern void HTLanguage_deleteAll (HTList * list);
2.50 frystyk 431: </PRE>
2.67 frystyk 432: <H2>
433: <A NAME="global">Global Preferences</A>
434: </H2>
435: <P>
2.50 frystyk 436: There are two places where these preferences can be registered: in a
2.67 frystyk 437: <EM>global</EM> list valid for <B>all</B> requests and a <EM>local</EM> list
438: valid for a particular request only. These are valid for <EM>all</EM> requests.
439: See the <A HREF="HTReq.html">Request Manager</A> fro local sets.
440: <H3>
2.73 frystyk 441: Global Converters and Presenters
2.67 frystyk 442: </H3>
443: <P>
444: The <EM>global</EM> list of specific conversions which the format manager
445: can do in order to fulfill the request. There is also a
446: <A HREF="HTReq.html"><EM>local</EM></A> list of conversions which contains
447: a generic set of possible conversions.
2.73 frystyk 448: <PRE>extern void HTFormat_setConversion (HTList * list);
2.50 frystyk 449: extern HTList * HTFormat_conversion (void);
2.69 frystyk 450:
451: extern void HTFormat_addConversion (const char * input_format,
452: const char * output_format,
453: HTConverter * converter,
454: double quality,
455: double secs,
456: double secs_per_byte);
2.31 frystyk 457: </PRE>
2.67 frystyk 458: <H3>
2.73 frystyk 459: Global Content Codings
2.67 frystyk 460: </H3>
2.73 frystyk 461: <PRE>extern void HTFormat_setContentCoding (HTList * list);
2.64 frystyk 462: extern HTList * HTFormat_contentCoding (void);
2.69 frystyk 463:
464: extern BOOL HTFormat_addCoding ( char * encoding,
465: HTCoder * encoder,
466: HTCoder * decoder,
467: double quality);
2.50 frystyk 468: </PRE>
2.74 frystyk 469: <P>
2.82 ! frystyk 470: We also define a macro to find out whether a content encoding is really an
! 471: encoding or whether it is a unity encoder.
2.74 frystyk 472: <PRE>
473: #define HTFormat_isUnityContent(me) \
2.79 frystyk 474: ((me)==NULL || \
475: (me)==WWW_CODING_BINARY || (me)==WWW_CODING_IDENTITY || \
476: (me)==WWW_CODING_7BIT || (me)==WWW_CODING_8BIT)
2.74 frystyk 477: </PRE>
2.67 frystyk 478: <H3>
2.77 frystyk 479: Global Transfer Codings
2.67 frystyk 480: </H3>
2.73 frystyk 481: <PRE>extern void HTFormat_setTransferCoding (HTList * list);
2.64 frystyk 482: extern HTList * HTFormat_transferCoding (void);
2.69 frystyk 483:
484: extern BOOL HTFormat_addTransferCoding ( char * encoding,
485: HTCoder * encoder,
486: HTCoder * decoder,
487: double quality);
2.64 frystyk 488: </PRE>
2.67 frystyk 489: <P>
490: We also define a macro to find out whether a transfer encoding is really
491: an encoding or whether it is just a "dummy" as for example 7bit, 8bit, and
492: binary.
2.64 frystyk 493: <PRE>
494: #define HTFormat_isUnityTransfer(me) \
2.79 frystyk 495: ((me)==NULL || \
496: (me)==WWW_CODING_BINARY || (me)==WWW_CODING_IDENTITY || \
497: (me)==WWW_CODING_7BIT || (me)==WWW_CODING_8BIT)
2.64 frystyk 498: </PRE>
2.67 frystyk 499: <H3>
2.73 frystyk 500: Global Content Languages
2.67 frystyk 501: </H3>
2.73 frystyk 502: <PRE>extern void HTFormat_setLanguage (HTList * list);
2.50 frystyk 503: extern HTList * HTFormat_language (void);
504: </PRE>
2.67 frystyk 505: <H3>
2.73 frystyk 506: Global Content Charsets
2.67 frystyk 507: </H3>
2.73 frystyk 508: <PRE>extern void HTFormat_setCharset (HTList * list);
2.50 frystyk 509: extern HTList * HTFormat_charset (void);
2.31 frystyk 510: </PRE>
2.67 frystyk 511: <H3>
512: Delete All Global Lists
513: </H3>
514: <P>
2.50 frystyk 515: This is a convenience function that might make life easier.
2.73 frystyk 516: <PRE>extern void HTFormat_deleteAll (void);
2.34 frystyk 517: </PRE>
2.67 frystyk 518: <H2>
519: <A NAME="CTStack">The Content Type Stream Stack</A>
520: </H2>
521: <P>
522: This is the routine which actually sets up the content type conversion. It
523: currently checks only for direct conversions, but multi-stage conversions
524: are forseen. It takes a stream into which the output should be sent in the
525: final format, builds the conversion stack, and returns a stream into which
526: the data in the input format should be fed. If <CODE>guess</CODE> is true
527: and input format is <CODE>www/unknown</CODE>, try to guess the format by
528: looking at the first few bytes of the stream.
2.31 frystyk 529: <PRE>
2.52 frystyk 530: extern HTStream * HTStreamStack (HTFormat rep_in,
531: HTFormat rep_out,
532: HTStream * output_stream,
533: HTRequest * request,
534: BOOL guess);
2.1 timbl 535: </PRE>
2.67 frystyk 536: <H3>
537: Cost of a Stream Stack
538: </H3>
539: <P>
540: Must return the cost of the same stack which HTStreamStack would set up.
2.31 frystyk 541: <PRE>
2.52 frystyk 542: extern double HTStackValue (HTList * conversions,
543: HTFormat format_in,
544: HTFormat format_out,
545: double initial_value,
546: long int length);
2.64 frystyk 547: </PRE>
2.67 frystyk 548: <H2>
549: <A NAME="CEStack">Content Encoding Stream Stack</A>
550: </H2>
551: <P>
552: When creating a coding stream stack, it is important that we keep the right
553: order of encoders and decoders. As an example, the HTTP spec specifies that
554: the list in the <EM>Content-Encoding</EM> header follows the order in which
555: the encodings have been applied to the object. Internally, we represent the
556: content encodings as <A HREF="HTAtom.html">atoms</A> in a linked
557: <A HREF="HTList.html">list object</A>.
558: <P>
559: The creation of the content coding stack is not based on quality factors
560: as we don't have the freedom as with content types. When using content codings
561: we <EM>must</EM> apply the codings specified or fail.
2.64 frystyk 562: <PRE>
563: extern HTStream * HTContentCodingStack (HTEncoding coding,
564: HTStream * target,
565: HTRequest * request,
566: void * param,
567: BOOL encoding);
568: </PRE>
2.67 frystyk 569: <P>
570: Here you can provide a complete list instead of a single token. The list
571: has to be filled up in the order the _encodings_ are to be applied
2.64 frystyk 572: <PRE>
573: extern HTStream * HTContentEncodingStack (HTList * encodings,
574: HTStream * target,
575: HTRequest * request,
576: void * param);
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 in the order the _encodings_ were applied - that is, the same way
581: that _encodings_ are to be applied. This is all consistent with the order
582: of the Content-Encoding header.
2.64 frystyk 583: <PRE>
584: extern HTStream * HTContentDecodingStack (HTList * encodings,
585: HTStream * target,
586: HTRequest * request,
587: void * param);
588: </PRE>
2.67 frystyk 589: <H2>
2.79 frystyk 590: <A NAME="TEStack">Transfer Encoding Stream Stack</A>
591: </H2>
592: <P>
593: When creating a coding stream stack, it is important that we keep the right
594: order of encoders and decoders. As an example, the HTTP spec specifies that
595: the list in the <EM>Transfer-Encoding</EM> header follows the order in which
596: the encodings have been applied to the object. Internally, we represent the
597: content encodings as <A HREF="HTAtom.html">atoms</A> in a linked
598: <A HREF="HTList.html">list object</A>.
599: <P>
600: The creation of the content coding stack is not based on quality factors
601: as we don't have the freedom as with content types. When using content codings
602: we <EM>must</EM> apply the codings specified or fail.
603: <PRE>
604: extern HTStream * HTTransferCodingStack (HTEncoding coding,
605: HTStream * target,
606: HTRequest * request,
607: void * param,
608: BOOL encoding);
609: </PRE>
610: <P>
611: Here you can provide a complete list instead of a single token. The list
612: has to be filled up in the order the _encodings_ are to be applied
613: <PRE>
614: extern HTStream * HTTransferEncodingStack (HTList * encodings,
615: HTStream * target,
616: HTRequest * request,
617: void * param);
618: </PRE>
619: <P>
620: Here you can provide a complete list instead of a single token. The list
621: has to be in the order the _encodings_ were applied - that is, the same way
622: that _encodings_ are to be applied. This is all consistent with the order
623: of the Transfer-Encoding header.
624: <PRE>
625: extern HTStream * HTTransferDecodingStack (HTList * encodings,
626: HTStream * target,
627: HTRequest * request,
628: void * param);
629: </PRE>
630: <H2>
2.77 frystyk 631: <A NAME="CTEStack">Transfer Encoding Stream Stack</A>
2.67 frystyk 632: </H2>
633: <P>
634: Creating the transfer content encoding stream stack is not based on quality
635: factors as we don't have the freedom as with content types. Specify whether
636: you you want encoding or decoding using the BOOL "encode" flag.
2.64 frystyk 637: <PRE>
2.79 frystyk 638: extern HTStream * HTContentTransferCodingStack (HTEncoding encoding,
639: HTStream * target,
640: HTRequest * request,
641: void * param,
642: BOOL encode);
2.64 frystyk 643: </PRE>
2.73 frystyk 644: <H3>
645: Presentation Object
646: </H3>
647: <P>
648: This object is not to be used - it should have been hidden
649: <PRE>typedef struct _HTPresentation {
650: HTFormat rep; /* representation name atomized */
651: HTFormat rep_out; /* resulting representation */
652: HTConverter *converter; /* The routine to gen the stream stack */
653: char * command; /* MIME-format string */
654: char * test_command; /* MIME-format string */
655: double quality; /* Between 0 (bad) and 1 (good) */
656: double secs;
657: double secs_per_byte;
658: } HTPresentation;
659: </PRE>
2.64 frystyk 660: <PRE>
2.42 frystyk 661: #endif /* HTFORMAT */
2.38 frystyk 662: </PRE>
2.67 frystyk 663: <P>
664: <HR>
2.63 frystyk 665: <ADDRESS>
2.82 ! frystyk 666: @(#) $Id: HTFormat.html,v 2.81 1998/07/16 22:00:20 frystyk Exp $
2.63 frystyk 667: </ADDRESS>
2.67 frystyk 668: </BODY></HTML>
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