Annotation of libwww/Library/src/HTFormat.html, revision 2.83
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
2.83 ! frystyk 263: external program using a special "presenter stream" which for example can
! 264: use the local disk to transfer the data from libwww to the external program.
! 265: <P>
! 266: Libwww provides a default <A HREF="HTFWrite.html">HTSaveAndExecute</A>
! 267: stream which you may want to use for this purpose. However, any stream
! 268: that is of type <CODE>HTConverter</CODE> will do. You can manage the
! 269: special presenter stream using the following methods:
! 270: <PRE>
! 271: extern void HTPresentation_setConverter (HTConverter * pconv);
! 272: extern HTConverter * HTPresentation_converter (void);
! 273: </PRE>
! 274: Both presenters and converters are of the type
2.73 frystyk 275: <A HREF="#converter">HTConverter</A>.
2.31 frystyk 276: <PRE>
2.49 frystyk 277: extern void HTPresentation_add (HTList * conversions,
2.83 ! frystyk 278: const char * representation,
2.61 frystyk 279: const char * command,
280: const char * test_command,
2.49 frystyk 281: double quality,
282: double secs,
283: double secs_per_byte);
2.1 timbl 284:
2.50 frystyk 285: extern void HTPresentation_deleteAll (HTList * list);
286: </PRE>
2.67 frystyk 287: <H3>
2.73 frystyk 288: Basic Converters
2.67 frystyk 289: </H3>
290: <P>
2.73 frystyk 291: We have a small set of basic converters that can be hooked in anywhere. They
292: don't "convert" anything but are nice to have.
2.79 frystyk 293: <PRE>
294: extern HTConverter HTThroughLine;
2.73 frystyk 295: extern HTConverter HTBlackHoleConverter;
2.79 frystyk 296: extern HTConverter HTSaveConverter;
2.42 frystyk 297: </PRE>
2.67 frystyk 298: <H2>
299: <A NAME="encoding">Content and Transfer Encoders and Decoders</A>
300: </H2>
301: <P>
302: Content codins are transformations applied to an entity object after it was
303: created in its original form. The Library handles two types of codings:
2.64 frystyk 304: <DL>
2.67 frystyk 305: <DT>
306: <B>Content Codings</B>
307: <DD>
308: Content codings values indicate an encoding transformation that has been
309: applied to a resource. Content cosings are primarily used to allow a document
310: to be compressed or encrypted without loosing the identity of its underlying
311: media type.
312: <DT>
313: <B>Content Transfer Codings</B>
314: <DD>
315: Content transfer codings values are used to indicate an encoding transformation
316: that has been, can be, or may be need to be applied to an enity body in order
317: to ensure safe transport through the network. This differs from a content
318: coding in that the transfer coding is a property of the message, not the
319: original message.
2.64 frystyk 320: </DL>
2.67 frystyk 321: <P>
322: Both types of encodings use the same registration mechanism in the Library
323: which we describe below:
324: <H3>
325: Encoders and Decoders
326: </H3>
327: <P>
328: <EM>Encoders</EM> and <EM>decoders</EM> are subclassed from the
329: <A HREF="HTStream.html">generic stream class</A>. <EM>Encoders</EM> are capable
330: of adding a content coding to a data object and <EM>decoders</EM> can remove
331: a content coding.
2.50 frystyk 332: <PRE>
2.64 frystyk 333: typedef HTStream * HTCoder (HTRequest * request,
334: void * param,
335: HTEncoding coding,
336: HTStream * target);
2.50 frystyk 337: </PRE>
2.67 frystyk 338: <P>
339: The <EM>encoding</EM> is the name of the encoding mechanism reporesented
340: as an <A HREF="HTAtom.html">atom</A>, for example "zip", "chunked", etc.
341: Encodings are registered in lists and content encodings are separated from
342: transfer encodings by registering them in different lists.
343: <H3>
2.81 frystyk 344: Basic Encoders
345: </H3>
346: <P>
347: We have a small set of basic coders that can be hooked in anywhere.
348: <PRE>
349: extern HTCoder HTIdentityCoding;
350: </PRE>
351: <H3>
2.67 frystyk 352: The HTCoding Object
353: </H3>
354: <P>
355: The <EM>HTCoding</EM> object represents a registered encoding together with
356: a encoder and a decoder.
2.63 frystyk 357: <PRE>
2.64 frystyk 358: typedef struct _HTCoding HTCoding;
2.63 frystyk 359: </PRE>
2.67 frystyk 360: <P>
361: Predefined Coding Types We have a set of pre defined atoms for various types
362: of content encodings and transfer encodings. "chunked" is not exactly in
363: the same group as the other encodings such as "binary" but it really doesn't
364: make any difference as it is just a matter of how the words are chosen. The
365: first three transfer encodings are actually not encodings - they are just
366: left overs from brain dead mail systems.
2.42 frystyk 367: <PRE>
2.79 frystyk 368: #define WWW_CODING_7BIT HTAtom_for("7bit")
369: #define WWW_CODING_8BIT HTAtom_for("8bit")
370: #define WWW_CODING_BINARY HTAtom_for("binary")
371: #define WWW_CODING_IDENTITY HTAtom_for("identity")
2.64 frystyk 372:
2.79 frystyk 373: #define WWW_CODING_BASE64 HTAtom_for("base64")
374: #define WWW_CODING_MACBINHEX HTAtom_for("macbinhex")
375: #define WWW_CODING_CHUNKED HTAtom_for("chunked")
2.63 frystyk 376:
2.79 frystyk 377: #define WWW_CODING_COMPRESS HTAtom_for("compress")
378: #define WWW_CODING_GZIP HTAtom_for("gzip")
379: #define WWW_CODING_DEFLATE HTAtom_for("deflate")
2.42 frystyk 380: </PRE>
2.67 frystyk 381: <H3>
382: Register Content Coders
383: </H3>
384: <P>
2.73 frystyk 385: Some documents are not send in their original data obejct but is encoded
386: in some way. On the Web this is mostly some kind of compression but other
387: encodings for example base 64 can be encountered when talking to NNTP servers
388: etc. Just as for the other preferences, an application can register a supported
389: encoders or decodes as a list. Encoders and decoders are registered in the
390: same way with no differentiation whether it is a encoder or a decoder:
2.42 frystyk 391: <PRE>
2.64 frystyk 392: extern BOOL HTCoding_add (HTList * list,
393: const char * encoding,
394: HTCoder * encoder,
395: HTCoder * decoder,
396: double quality);
2.63 frystyk 397:
2.64 frystyk 398: extern void HTCoding_deleteAll (HTList * list);
2.42 frystyk 399:
2.64 frystyk 400: extern const char * HTCoding_name (HTCoding * me);
2.77 frystyk 401:
402: extern double HTCoding_quality (HTCoding * me);
2.42 frystyk 403: </PRE>
2.67 frystyk 404: <H2>
405: <A NAME="charset">Content Charsets</A>
406: </H2>
2.73 frystyk 407: <P>
408: As the Web reaches all parts of the Internet there are more and more documents
409: written in languages which contains characters not included in the ISO-8859-1
410: character set. A consequence of this the set of characters sets is often
411: tightly connected with the natural language. libwww does not directly support
412: other character sets but in case an application is capable of handling
413: alternative sets it can register these as preferred character sets along
414: with a quality factor just as all the other preferences in this section.
415: <PRE>extern void HTCharset_add (HTList * list, const char * charset, double quality);
2.42 frystyk 416: </PRE>
2.73 frystyk 417: <PRE>typedef struct _HTAcceptNode {
2.63 frystyk 418: HTAtom * atom;
419: double quality;
420: } HTAcceptNode;
421: </PRE>
422: <PRE>
2.50 frystyk 423: extern void HTCharset_deleteAll (HTList * list);
424: </PRE>
2.67 frystyk 425: <H2>
426: <A NAME="language">Content Languages</A>
427: </H2>
2.73 frystyk 428: <P>
429: The preferred natural language or languages is in almost all situations dependent
430: on the individual user and an application should therefore give the user
431: the opportunity to change the setup. When specifying a natural language
432: preference, libwww will send this preference along with all HTTP requests.
433: The remote server will then (it if supports this feature) look for a version
434: in the language or languages mentioned. If it finds a matching document then
435: it returns this one, otherwise it uses the best alternative. If no language
436: is specified the remote server may whatever version it finds.
437: <PRE>extern void HTLanguage_add (HTList * list, const char * lang, double quality);
2.51 frystyk 438: extern void HTLanguage_deleteAll (HTList * list);
2.50 frystyk 439: </PRE>
2.67 frystyk 440: <H2>
441: <A NAME="global">Global Preferences</A>
442: </H2>
443: <P>
2.50 frystyk 444: There are two places where these preferences can be registered: in a
2.67 frystyk 445: <EM>global</EM> list valid for <B>all</B> requests and a <EM>local</EM> list
446: valid for a particular request only. These are valid for <EM>all</EM> requests.
447: See the <A HREF="HTReq.html">Request Manager</A> fro local sets.
448: <H3>
2.73 frystyk 449: Global Converters and Presenters
2.67 frystyk 450: </H3>
451: <P>
452: The <EM>global</EM> list of specific conversions which the format manager
453: can do in order to fulfill the request. There is also a
454: <A HREF="HTReq.html"><EM>local</EM></A> list of conversions which contains
455: a generic set of possible conversions.
2.73 frystyk 456: <PRE>extern void HTFormat_setConversion (HTList * list);
2.50 frystyk 457: extern HTList * HTFormat_conversion (void);
2.69 frystyk 458:
459: extern void HTFormat_addConversion (const char * input_format,
460: const char * output_format,
461: HTConverter * converter,
462: double quality,
463: double secs,
464: double secs_per_byte);
2.31 frystyk 465: </PRE>
2.67 frystyk 466: <H3>
2.73 frystyk 467: Global Content Codings
2.67 frystyk 468: </H3>
2.73 frystyk 469: <PRE>extern void HTFormat_setContentCoding (HTList * list);
2.64 frystyk 470: extern HTList * HTFormat_contentCoding (void);
2.69 frystyk 471:
472: extern BOOL HTFormat_addCoding ( char * encoding,
473: HTCoder * encoder,
474: HTCoder * decoder,
475: double quality);
2.50 frystyk 476: </PRE>
2.74 frystyk 477: <P>
2.82 frystyk 478: We also define a macro to find out whether a content encoding is really an
479: encoding or whether it is a unity encoder.
2.74 frystyk 480: <PRE>
481: #define HTFormat_isUnityContent(me) \
2.79 frystyk 482: ((me)==NULL || \
483: (me)==WWW_CODING_BINARY || (me)==WWW_CODING_IDENTITY || \
484: (me)==WWW_CODING_7BIT || (me)==WWW_CODING_8BIT)
2.74 frystyk 485: </PRE>
2.67 frystyk 486: <H3>
2.77 frystyk 487: Global Transfer Codings
2.67 frystyk 488: </H3>
2.73 frystyk 489: <PRE>extern void HTFormat_setTransferCoding (HTList * list);
2.64 frystyk 490: extern HTList * HTFormat_transferCoding (void);
2.69 frystyk 491:
492: extern BOOL HTFormat_addTransferCoding ( char * encoding,
493: HTCoder * encoder,
494: HTCoder * decoder,
495: double quality);
2.64 frystyk 496: </PRE>
2.67 frystyk 497: <P>
498: We also define a macro to find out whether a transfer encoding is really
499: an encoding or whether it is just a "dummy" as for example 7bit, 8bit, and
500: binary.
2.64 frystyk 501: <PRE>
502: #define HTFormat_isUnityTransfer(me) \
2.79 frystyk 503: ((me)==NULL || \
504: (me)==WWW_CODING_BINARY || (me)==WWW_CODING_IDENTITY || \
505: (me)==WWW_CODING_7BIT || (me)==WWW_CODING_8BIT)
2.64 frystyk 506: </PRE>
2.67 frystyk 507: <H3>
2.73 frystyk 508: Global Content Languages
2.67 frystyk 509: </H3>
2.73 frystyk 510: <PRE>extern void HTFormat_setLanguage (HTList * list);
2.50 frystyk 511: extern HTList * HTFormat_language (void);
512: </PRE>
2.67 frystyk 513: <H3>
2.73 frystyk 514: Global Content Charsets
2.67 frystyk 515: </H3>
2.73 frystyk 516: <PRE>extern void HTFormat_setCharset (HTList * list);
2.50 frystyk 517: extern HTList * HTFormat_charset (void);
2.31 frystyk 518: </PRE>
2.67 frystyk 519: <H3>
520: Delete All Global Lists
521: </H3>
522: <P>
2.50 frystyk 523: This is a convenience function that might make life easier.
2.73 frystyk 524: <PRE>extern void HTFormat_deleteAll (void);
2.34 frystyk 525: </PRE>
2.67 frystyk 526: <H2>
527: <A NAME="CTStack">The Content Type Stream Stack</A>
528: </H2>
529: <P>
530: This is the routine which actually sets up the content type conversion. It
531: currently checks only for direct conversions, but multi-stage conversions
532: are forseen. It takes a stream into which the output should be sent in the
533: final format, builds the conversion stack, and returns a stream into which
534: the data in the input format should be fed. If <CODE>guess</CODE> is true
535: and input format is <CODE>www/unknown</CODE>, try to guess the format by
536: looking at the first few bytes of the stream.
2.31 frystyk 537: <PRE>
2.52 frystyk 538: extern HTStream * HTStreamStack (HTFormat rep_in,
539: HTFormat rep_out,
540: HTStream * output_stream,
541: HTRequest * request,
542: BOOL guess);
2.1 timbl 543: </PRE>
2.67 frystyk 544: <H3>
545: Cost of a Stream Stack
546: </H3>
547: <P>
548: Must return the cost of the same stack which HTStreamStack would set up.
2.31 frystyk 549: <PRE>
2.52 frystyk 550: extern double HTStackValue (HTList * conversions,
551: HTFormat format_in,
552: HTFormat format_out,
553: double initial_value,
554: long int length);
2.64 frystyk 555: </PRE>
2.67 frystyk 556: <H2>
557: <A NAME="CEStack">Content Encoding Stream Stack</A>
558: </H2>
559: <P>
560: When creating a coding stream stack, it is important that we keep the right
561: order of encoders and decoders. As an example, the HTTP spec specifies that
562: the list in the <EM>Content-Encoding</EM> header follows the order in which
563: the encodings have been applied to the object. Internally, we represent the
564: content encodings as <A HREF="HTAtom.html">atoms</A> in a linked
565: <A HREF="HTList.html">list object</A>.
566: <P>
567: The creation of the content coding stack is not based on quality factors
568: as we don't have the freedom as with content types. When using content codings
569: we <EM>must</EM> apply the codings specified or fail.
2.64 frystyk 570: <PRE>
571: extern HTStream * HTContentCodingStack (HTEncoding coding,
572: HTStream * target,
573: HTRequest * request,
574: void * param,
575: BOOL encoding);
576: </PRE>
2.67 frystyk 577: <P>
578: Here you can provide a complete list instead of a single token. The list
579: has to be filled up in the order the _encodings_ are to be applied
2.64 frystyk 580: <PRE>
581: extern HTStream * HTContentEncodingStack (HTList * encodings,
582: HTStream * target,
583: HTRequest * request,
584: void * param);
585: </PRE>
2.67 frystyk 586: <P>
587: Here you can provide a complete list instead of a single token. The list
588: has to be in the order the _encodings_ were applied - that is, the same way
589: that _encodings_ are to be applied. This is all consistent with the order
590: of the Content-Encoding header.
2.64 frystyk 591: <PRE>
592: extern HTStream * HTContentDecodingStack (HTList * encodings,
593: HTStream * target,
594: HTRequest * request,
595: void * param);
596: </PRE>
2.67 frystyk 597: <H2>
2.79 frystyk 598: <A NAME="TEStack">Transfer Encoding Stream Stack</A>
599: </H2>
600: <P>
601: When creating a coding stream stack, it is important that we keep the right
602: order of encoders and decoders. As an example, the HTTP spec specifies that
603: the list in the <EM>Transfer-Encoding</EM> header follows the order in which
604: the encodings have been applied to the object. Internally, we represent the
605: content encodings as <A HREF="HTAtom.html">atoms</A> in a linked
606: <A HREF="HTList.html">list object</A>.
607: <P>
608: The creation of the content coding stack is not based on quality factors
609: as we don't have the freedom as with content types. When using content codings
610: we <EM>must</EM> apply the codings specified or fail.
611: <PRE>
612: extern HTStream * HTTransferCodingStack (HTEncoding coding,
613: HTStream * target,
614: HTRequest * request,
615: void * param,
616: BOOL encoding);
617: </PRE>
618: <P>
619: Here you can provide a complete list instead of a single token. The list
620: has to be filled up in the order the _encodings_ are to be applied
621: <PRE>
622: extern HTStream * HTTransferEncodingStack (HTList * encodings,
623: HTStream * target,
624: HTRequest * request,
625: void * param);
626: </PRE>
627: <P>
628: Here you can provide a complete list instead of a single token. The list
629: has to be in the order the _encodings_ were applied - that is, the same way
630: that _encodings_ are to be applied. This is all consistent with the order
631: of the Transfer-Encoding header.
632: <PRE>
633: extern HTStream * HTTransferDecodingStack (HTList * encodings,
634: HTStream * target,
635: HTRequest * request,
636: void * param);
637: </PRE>
638: <H2>
2.77 frystyk 639: <A NAME="CTEStack">Transfer Encoding Stream Stack</A>
2.67 frystyk 640: </H2>
641: <P>
642: Creating the transfer content encoding stream stack is not based on quality
643: factors as we don't have the freedom as with content types. Specify whether
644: you you want encoding or decoding using the BOOL "encode" flag.
2.64 frystyk 645: <PRE>
2.79 frystyk 646: extern HTStream * HTContentTransferCodingStack (HTEncoding encoding,
647: HTStream * target,
648: HTRequest * request,
649: void * param,
650: BOOL encode);
2.64 frystyk 651: </PRE>
2.73 frystyk 652: <H3>
653: Presentation Object
654: </H3>
655: <P>
656: This object is not to be used - it should have been hidden
657: <PRE>typedef struct _HTPresentation {
658: HTFormat rep; /* representation name atomized */
659: HTFormat rep_out; /* resulting representation */
660: HTConverter *converter; /* The routine to gen the stream stack */
661: char * command; /* MIME-format string */
662: char * test_command; /* MIME-format string */
663: double quality; /* Between 0 (bad) and 1 (good) */
664: double secs;
665: double secs_per_byte;
666: } HTPresentation;
667: </PRE>
2.64 frystyk 668: <PRE>
2.42 frystyk 669: #endif /* HTFORMAT */
2.38 frystyk 670: </PRE>
2.67 frystyk 671: <P>
672: <HR>
2.63 frystyk 673: <ADDRESS>
2.83 ! frystyk 674: @(#) $Id: HTFormat.html,v 2.82 1999/01/27 13:55:25 frystyk Exp $
2.63 frystyk 675: </ADDRESS>
2.67 frystyk 676: </BODY></HTML>
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