Annotation of libwww/Library/src/HTFormat.html, revision 2.55
2.10 timbl 1: <HTML>
2: <HEAD>
2.45 frystyk 3: <TITLE>Format Negotiation Manager</TITLE>
2.55 ! frystyk 4: <!-- Changed by: Henrik Frystyk Nielsen, 15-Nov-1995 -->
2.15 timbl 5: <NEXTID N="z18">
2.10 timbl 6: </HEAD>
2.1 timbl 7: <BODY>
2.27 frystyk 8:
2.31 frystyk 9: <H1>The Format Manager</H1>
2.33 frystyk 10:
11: <PRE>
12: /*
2.41 frystyk 13: ** (c) COPYRIGHT MIT 1995.
2.33 frystyk 14: ** Please first read the full copyright statement in the file COPYRIGH.
15: */
16: </PRE>
2.31 frystyk 17:
18: Here we describe the functions of the HTFormat module which handles
19: conversion between different data representations. (In MIME parlance,
20: a representation is known as a content-type. In <A
2.46 frystyk 21: HREF="http://www.w3.org/pub/WWW/TheProject.html">WWW</A> the
2.31 frystyk 22: term <EM>format</EM> is often used as it is shorter). The content of
23: this module is:
24:
25: <UL>
2.42 frystyk 26: <LI><A HREF="#converter">Converters</A>
2.50 frystyk 27: <LI><A HREF="#user">Generic preferences (media type, language, charset etc.)</A>
28: <LI><A HREF="#global">Global Preferences</A>
2.42 frystyk 29: <LI><A HREF="#Rank">Content Negotiation</A>
2.31 frystyk 30: <LI><A HREF="#z3">The Stream Stack</A>
31: </UL>
32:
33: This module is implemented by <A HREF="HTFormat.c">HTFormat.c</A>, and
2.49 frystyk 34: it is a part of the <A HREF="http://www.w3.org/pub/WWW/Library/"> W3C
35: Reference Library</A>.
2.27 frystyk 36:
2.31 frystyk 37: <PRE>
38: #ifndef HTFORMAT_H
2.1 timbl 39: #define HTFORMAT_H
40:
2.31 frystyk 41: #include <A HREF="HTUtils.html">"HTUtils.h"</A>
42: #include <A HREF="HTStream.html">"HTStream.h"</A>
43: #include <A HREF="HTAtom.html">"HTAtom.h"</A>
44: #include <A HREF="HTList.html">"HTList.h"</A>
2.42 frystyk 45: #include <A HREF="HTAnchor.html">"HTAnchor.h"</A>
2.47 frystyk 46: #include <A HREF="HTReq.html">"HTReq.h"</A>
2.31 frystyk 47: </PRE>
2.1 timbl 48:
2.42 frystyk 49: <A NAME="converter"><H2>Stream Converters</H2></A>
2.18 luotonen 50:
2.42 frystyk 51: A <CODE><A NAME="z12">converter</A></CODE> is a stream with a special
52: set of parameters and which is registered as capable of converting
53: from a MIME type to something else (maybe another MIME-type). A
54: converter is defined to be a function returning a stream and accepting
55: the following parameters. The content type elements are atoms for
56: which we have defined a prototype.
2.18 luotonen 57:
2.31 frystyk 58: <PRE>
2.52 frystyk 59: typedef HTStream * HTConverter (HTRequest * request,
60: void * param,
61: HTFormat input_format,
62: HTFormat output_format,
63: HTStream * output_stream);
2.42 frystyk 64: </PRE>
2.18 luotonen 65:
2.50 frystyk 66: <A NAME="user"><H2>Generic Preferences</H2></A>
2.31 frystyk 67:
2.42 frystyk 68: The Library contains functionality for letting the application (or
69: user) express the preferences for the rendition of a given data object
70: when issuing a request. The categories supported are:
71:
72: <UL>
73: <LI>Content type (media type)
74: <LI>Encoding
75: <LI>Language
76: <LI>Charset
77: </UL>
2.17 luotonen 78:
2.42 frystyk 79: <A NAME="FormatTypes"><H3>Registration of Accepted Content Types</H3></A>
2.17 luotonen 80:
2.42 frystyk 81: A <CODE>presenter</CODE> is a module (possibly an external program)
82: which can present a graphic object of a certain MIME type to the
83: user. That is, <CODE>presenters</CODE> are normally used to present
84: objects that the <CODE>converters</CODE> are not able to handle. Data
85: is transferred to the external program using for example the <A
86: HREF="HTFWrite.html">HTSaveAndExecute</A> stream which writes to a
87: local file. Both presenters and converters are of the type <A
88: HREF="#converter">HTConverter</A>.
2.31 frystyk 89:
90: <PRE>
2.42 frystyk 91: typedef struct _HTPresentation {
92: HTFormat rep; /* representation name atomized */
93: HTFormat rep_out; /* resulting representation */
94: HTConverter *converter; /* The routine to gen the stream stack */
95: char * command; /* MIME-format string */
96: char * test_command; /* MIME-format string */
97: double quality; /* Between 0 (bad) and 1 (good) */
98: double secs;
99: double secs_per_byte;
100: } HTPresentation;
2.28 frystyk 101: </PRE>
102:
2.42 frystyk 103: <H4>Predefined Content Types</H4>
2.28 frystyk 104:
2.42 frystyk 105: These macros (which used to be constants) define some basic internally
106: referenced representations. The <CODE>www/xxx</CODE> ones are of
2.52 frystyk 107: course not MIME standard. They are internal representations used in
108: the Library but they can't be exported to other apps!
2.28 frystyk 109:
110: <PRE>
111: #define WWW_SOURCE HTAtom_for("*/*") /* Whatever it was originally */
112: </PRE>
113:
2.52 frystyk 114: <CODE>WWW_SOURCE</CODE> is an output format which leaves the input
2.54 frystyk 115: untouched <EM>exactly</EM> as it is received by the protocol
116: module. For example, in the case of FTP, this format returns raw ASCII
117: objects for directory listings; for HTTP, everything including the
118: header is returned, for Gopher, a raw ASCII object is returned for a
119: menu etc.
2.10 timbl 120:
2.28 frystyk 121: <PRE>
122: #define WWW_PRESENT HTAtom_for("www/present") /* The user's perception */
123: </PRE>
124:
2.52 frystyk 125: <CODE>WWW_PRESENT</CODE> represents the user's perception of the
126: document. If you convert to <CODE>WWW_PRESENT</CODE>, you present the
127: material to the user.
2.28 frystyk 128:
129: <PRE>
2.52 frystyk 130: #define WWW_UNKNOWN HTAtom_for("www/unknown")
2.28 frystyk 131: </PRE>
132:
2.52 frystyk 133: <CODE>WWW_UNKNOWN</CODE> is a really unknown type. It differs from the
134: real MIME type <EM>"application/octet-stream"</EM> in that we haven't
135: even tried to figure out the content type at this point.<P>
2.28 frystyk 136:
2.31 frystyk 137: These are regular MIME types defined. Others can be added!
2.28 frystyk 138:
139: <PRE>
2.52 frystyk 140: #define WWW_HTML HTAtom_for("text/html")
2.28 frystyk 141: #define WWW_PLAINTEXT HTAtom_for("text/plain")
2.52 frystyk 142:
143: #define WWW_MIME HTAtom_for("message/rfc822")
144:
2.10 timbl 145: #define WWW_AUDIO HTAtom_for("audio/basic")
2.52 frystyk 146:
2.26 frystyk 147: #define WWW_VIDEO HTAtom_for("video/mpeg")
2.52 frystyk 148:
2.38 frystyk 149: #define WWW_GIF HTAtom_for("image/gif")
2.52 frystyk 150: #define WWW_PNG HTAtom_for("image/png")
151:
152: #define WWW_BINARY HTAtom_for("application/octet-stream")
153: #define WWW_POSTSCRIPT HTAtom_for("application/postscript")
154: #define WWW_RICHTEXT HTAtom_for("application/rtf")
2.48 frystyk 155: </PRE>
156:
2.52 frystyk 157: We also have some MIME types that come from the various protocols when
158: we convert from ASCII to HTML.
2.48 frystyk 159:
160: <PRE>
161: #define WWW_GOPHER_MENU HTAtom_for("text/x-gopher")
2.53 frystyk 162: #define WWW_CSO_SEARCH HTAtom_for("text/x-cso")
2.48 frystyk 163:
164: #define WWW_FTP_LNST HTAtom_for("text/x-ftp-lnst")
165: #define WWW_FTP_LIST HTAtom_for("text/x-ftp-list")
166:
167: #define WWW_NNTP_LIST HTAtom_for("text/x-nntp-list")
168: #define WWW_NNTP_OVER HTAtom_for("text/x-nntp-over")
169: #define WWW_NNTP_HEAD HTAtom_for("text/x-nntp-head")
2.55 ! frystyk 170: </PRE>
! 171:
! 172: Finally we have defined a special format for our RULE files as they
! 173: can be handled by a special converter.
! 174:
! 175: <PRE>
! 176: #define WWW_RULES HTAtom_for("text/x-www-rules")
2.28 frystyk 177: </PRE>
178:
2.50 frystyk 179: <H4>Add a Presenter</H4>
180:
181: This function creates a presenter object and adds to the list of
182: conversions.
2.31 frystyk 183:
2.1 timbl 184: <DL>
2.31 frystyk 185: <DT>conversions
186: <DD>The list of <CODE>conveters</CODE> and <CODE>presenters</CODE>
2.50 frystyk 187: <DT>rep_in
2.42 frystyk 188: <DD>the MIME-style format name
2.50 frystyk 189: <DT>rep_out
190: <DD>is the resulting content-type after the conversion
191: <DT>converter
192: <DD>is the routine to call which actually does the conversion
2.1 timbl 193: <DT>quality
2.31 frystyk 194: <DD>A degradation faction [0..1]
2.1 timbl 195: <DT>maxbytes
2.31 frystyk 196: <DD>A limit on the length acceptable as input (0 infinite)
2.1 timbl 197: <DT>maxsecs
2.31 frystyk 198: <DD>A limit on the time user will wait (0 for infinity)
2.1 timbl 199: </DL>
200:
2.31 frystyk 201: <PRE>
2.49 frystyk 202: extern void HTPresentation_add (HTList * conversions,
203: CONST char * representation,
204: CONST char * command,
205: CONST char * test_command,
206: double quality,
207: double secs,
208: double secs_per_byte);
2.31 frystyk 209: </PRE>
2.1 timbl 210:
2.50 frystyk 211: <H4>Delete a list of Presenters</H4>
212:
213: <PRE>
214: extern void HTPresentation_deleteAll (HTList * list);
215: </PRE>
216:
217: <H4>Add a Converter</H4>
218:
219: This function creates a presenter object and adds to the list of
220: conversions.
2.1 timbl 221:
222: <DL>
2.31 frystyk 223: <DT>conversions
224: <DD>The list of <CODE>conveters</CODE> and <CODE>presenters</CODE>
2.1 timbl 225: <DT>rep_in
2.42 frystyk 226: <DD>the MIME-style format name
2.1 timbl 227: <DT>rep_out
2.31 frystyk 228: <DD>is the resulting content-type after the conversion
2.1 timbl 229: <DT>converter
2.31 frystyk 230: <DD>is the routine to call which actually does the conversion
231: <DT>quality
232: <DD>A degradation faction [0..1]
233: <DT>maxbytes
234: <DD>A limit on the length acceptable as input (0 infinite)
235: <DT>maxsecs
236: <DD>A limit on the time user will wait (0 for infinity)
2.1 timbl 237: </DL>
238:
239: <PRE>
2.49 frystyk 240: extern void HTConversion_add (HTList * conversions,
241: CONST char * rep_in,
242: CONST char * rep_out,
243: HTConverter * converter,
244: double quality,
245: double secs,
246: double secs_per_byte);
2.42 frystyk 247: </PRE>
248:
2.50 frystyk 249: <H4>Delete a list of Converters</H4>
250:
251: <PRE>
252: extern void HTConversion_deleteAll (HTList * list);
253: </PRE>
254:
2.42 frystyk 255: <A NAME="Encoding"><H3>Registration of Accepted Content Encodings</H3></A>
256:
257: Encodings are the HTTP extension of transfer encodings. Encodings
2.50 frystyk 258: include compress, gzip etc.
2.42 frystyk 259:
260: <PRE>
261: typedef struct _HTAcceptNode {
262: HTAtom * atom;
263: double quality;
264: } HTAcceptNode;
265: </PRE>
266:
267: <H4>Predefined Encoding Types</H4>
268:
269: <PRE>
270: #define WWW_ENC_7BIT HTAtom_for("7bit")
271: #define WWW_ENC_8BIT HTAtom_for("8bit")
272: #define WWW_ENC_BINARY HTAtom_for("binary")
273: #define WWW_ENC_BASE64 HTAtom_for("base64")
274: #define WWW_ENC_COMPRESS HTAtom_for("compress")
275: #define WWW_ENC_GZIP HTAtom_for("gzip")
276: </PRE>
277:
278: <H4>Register an Encoding</H4>
279:
280: <PRE>
2.50 frystyk 281: extern void HTEncoding_add (HTList * list,
282: CONST char * enc,
283: double quality);
2.42 frystyk 284: </PRE>
2.31 frystyk 285:
2.50 frystyk 286: <H4>Delete a list of Encoders</H4>
2.31 frystyk 287:
2.50 frystyk 288: <PRE>
2.51 frystyk 289: extern void HTEncoding_deleteAll (HTList * list);
2.50 frystyk 290: </PRE>
291:
292: <H3><A NAME="charset">Accepted Charsets</A></H3>
2.31 frystyk 293:
2.42 frystyk 294: <H4>Register a Charset</H4>
295:
296: <PRE>
2.50 frystyk 297: extern void HTCharset_add (HTList * list,
298: CONST char * charset,
299: double quality);
2.42 frystyk 300: </PRE>
301:
2.50 frystyk 302: <H4>Delete a list of Charsets</H4>
2.42 frystyk 303:
2.50 frystyk 304: <PRE>
305: extern void HTCharset_deleteAll (HTList * list);
306: </PRE>
307:
308: <A NAME="Language"><H3>Accepted Content Languages</H3></A>
2.31 frystyk 309:
2.42 frystyk 310: <H4>Register a Language</H4>
2.31 frystyk 311:
312: <PRE>
2.50 frystyk 313: extern void HTLanguage_add (HTList * list,
314: CONST char * lang,
315: double quality);
316: </PRE>
317:
318: <H4>Delete a list of Languages</H4>
319:
320: <PRE>
2.51 frystyk 321: extern void HTLanguage_deleteAll (HTList * list);
2.50 frystyk 322: </PRE>
323:
324: <A NAME="global"><H2>Global Registrations</H2></A>
325:
326: There are two places where these preferences can be registered: in a
327: <EM>global</EM> list valid for <B>all</B> requests and a
328: <EM>local</EM> list valid for a particular request only. These are
329: valid for <EM>all</EM> requests. See the <A HREF="HTReq.html">Request
330: Manager</A> fro local sets.
331:
2.51 frystyk 332: <H3>Converters and Presenters</H3>
2.50 frystyk 333:
334: The <EM>global</EM> list of specific conversions which the format
335: manager can do in order to fulfill the request. There is also a <A
336: HREF="HTReq.html"><EM>local</EM></A> list of conversions which
337: contains a generic set of possible conversions.
338:
339: <PRE>
340: extern void HTFormat_setConversion (HTList *list);
341: extern HTList * HTFormat_conversion (void);
2.31 frystyk 342: </PRE>
343:
2.50 frystyk 344: <H3>Content Encodings</H3>
2.42 frystyk 345:
2.50 frystyk 346: <PRE>
347: extern void HTFormat_setEncoding (HTList *list);
348: extern HTList * HTFormat_encoding (void);
349: </PRE>
2.1 timbl 350:
2.51 frystyk 351: <H3>Content Languages</H3>
2.50 frystyk 352:
353: <PRE>
354: extern void HTFormat_setLanguage (HTList *list);
355: extern HTList * HTFormat_language (void);
356: </PRE>
2.42 frystyk 357:
2.51 frystyk 358: <H3>Content Charsets</H3>
2.1 timbl 359:
2.31 frystyk 360: <PRE>
2.50 frystyk 361: extern void HTFormat_setCharset (HTList *list);
362: extern HTList * HTFormat_charset (void);
2.31 frystyk 363: </PRE>
364:
2.50 frystyk 365: <H3>Delete All Global Lists</H3>
2.42 frystyk 366:
2.50 frystyk 367: This is a convenience function that might make life easier.
2.34 frystyk 368:
369: <PRE>
2.50 frystyk 370: extern void HTFormat_deleteAll (void);
2.34 frystyk 371: </PRE>
2.31 frystyk 372:
373: <A NAME="Rank"><H2>Ranking of Accepted Formats</H2></A>
374:
2.36 frystyk 375: This function is used when the best match among several possible
376: documents is to be found as a function of the accept headers sent in
377: the client request.
2.31 frystyk 378:
379: <PRE>
2.42 frystyk 380: typedef struct _HTContentDescription {
381: char * filename;
382: HTAtom * content_type;
383: HTAtom * content_language;
384: HTAtom * content_encoding;
385: int content_length;
386: double quality;
387: } HTContentDescription;
388:
2.52 frystyk 389: extern BOOL HTRank (HTList * possibilities,
390: HTList * accepted_content_types,
391: HTList * accepted_content_languages,
392: HTList * accepted_content_encodings);
2.1 timbl 393: </PRE>
2.31 frystyk 394:
2.42 frystyk 395: <H2><A NAME="z3">The Stream Stack</A></H2>
2.31 frystyk 396:
397: This is the routine which actually sets up the conversion. It
398: currently checks only for direct conversions, but multi-stage
399: conversions are forseen. It takes a stream into which the output
400: should be sent in the final format, builds the conversion stack, and
401: returns a stream into which the data in the input format should be
2.42 frystyk 402: fed. If <CODE>guess</CODE> is true and input format is
2.31 frystyk 403: <CODE>www/unknown</CODE>, try to guess the format by looking at the
404: first few bytes of the stream. <P>
2.1 timbl 405:
2.31 frystyk 406: <PRE>
2.52 frystyk 407: extern HTStream * HTStreamStack (HTFormat rep_in,
408: HTFormat rep_out,
409: HTStream * output_stream,
410: HTRequest * request,
411: BOOL guess);
2.1 timbl 412: </PRE>
2.31 frystyk 413:
2.42 frystyk 414: <H2>Cost of a Stream Stack</H2>
2.31 frystyk 415:
416: Must return the cost of the same stack which HTStreamStack would set
2.1 timbl 417: up.
418:
2.31 frystyk 419: <PRE>
2.52 frystyk 420: extern double HTStackValue (HTList * conversions,
421: HTFormat format_in,
422: HTFormat format_out,
423: double initial_value,
424: long int length);
2.31 frystyk 425:
2.42 frystyk 426: #endif /* HTFORMAT */
2.38 frystyk 427: </PRE>
428:
2.42 frystyk 429: End of declaration module
2.31 frystyk 430:
431: </BODY>
2.10 timbl 432: </HTML>
Webmaster
![[BACK]](/cvsweb/icons/back.gif){kind=icon}
Return to HTFormat.html CVS log ![[TXT]](/cvsweb/icons/text.gif){kind=icon}
![[DIR]](/cvsweb/icons/dir.gif){kind=icon}
Up to [Public] / libwww / Library / src