Annotation of libwww/Library/src/HTFormat.html, revision 2.29
2.10 timbl 1: <HTML>
2: <HEAD>
2.1 timbl 3: <TITLE>HTFormat: The format manager in the WWW Library</TITLE>
2.29 ! howcome 4: <!-- Changed by: , 12-Oct-1994 -->
2.15 timbl 5: <NEXTID N="z18">
2.10 timbl 6: </HEAD>
2.1 timbl 7: <BODY>
8: <H1>Manage different document formats</H1>Here we describe the functions of
2.27 frystyk 9: the HTFormat module which handles conversion between different data
10: representations. (In MIME parlance, a representation is known as a content-
11: type. In WWW the term "format" is often used as it is shorter).<P>
12: This module is implemented by <A NAME="z0" HREF="HTFormat.c">HTFormat.c</A>.
13:
14: The module is a part of the <A NAME="z10" HREF="Overview.html">WWW library</A>.
15:
2.1 timbl 16: <H2>Preamble</H2>
17: <PRE>#ifndef HTFORMAT_H
18: #define HTFORMAT_H
19:
20: #include "HTUtils.h"
21: #include <A
2.10 timbl 22: NAME="z7" HREF="HTStream.html">"HTStream.h"</A>
2.1 timbl 23: #include "HTAtom.h"
2.2 timbl 24: #include "HTList.h"
2.1 timbl 25:
26: #ifdef SHORT_NAMES
27: #define HTOutputSource HTOuSour
28: #define HTOutputBinary HTOuBina
29: #endif
30:
2.18 luotonen 31:
32: typedef struct _HTContentDescription {
33: char * filename;
34: HTAtom * content_type;
35: HTAtom * content_language;
36: HTAtom * content_encoding;
37: int content_length;
38: float quality;
39: } HTContentDescription;
40:
41: PUBLIC void HTAcceptEncoding PARAMS((HTList * list,
42: char * enc,
43: float quality));
44:
45: PUBLIC void HTAcceptLanguage PARAMS((HTList * list,
46: char * lang,
47: float quality));
48:
49: PUBLIC BOOL HTRank PARAMS((HTList * possibilities,
50: HTList * accepted_content_types,
51: HTList * accepted_content_languages,
52: HTList * accepted_content_encodings));
53:
54:
2.1 timbl 55: </PRE>
2.17 luotonen 56: <H2>HT<A
57: NAME="z15"> Input Socket: Buffering for network
58: in</A></H2>This routines provide simple character
59: input from sockets. These are used
60: for parsing input in arbitrary IP
61: protocols (Gopher, NNTP, FTP).
62: <PRE>#define INPUT_BUFFER_SIZE 4096 /* Tradeoff spped vs memory*/
63: typedef struct _socket_buffer {
2.25 luotonen 64: char input_buffer[INPUT_BUFFER_SIZE];
2.17 luotonen 65: char * input_pointer;
66: char * input_limit;
67: int input_file_number;
2.25 luotonen 68: BOOL s_do_buffering;
69: char * s_buffer;
70: int s_buffer_size;
71: char * s_buffer_cur;
2.17 luotonen 72: } HTInputSocket;
73:
74: </PRE>
75: <H3>Create input buffer and set file
76: number</H3>
77: <PRE>extern HTInputSocket* HTInputSocket_new PARAMS((int file_number));
78:
79: </PRE>
80: <H3>Get next character from buffer</H3>
2.24 frystyk 81: <PRE>extern int HTInputSocket_getCharacter PARAMS((HTInputSocket* isoc));
2.17 luotonen 82:
83: </PRE>
2.22 timbl 84: <H3>Read block from input socket</H3>Read *len characters and return a
85: buffer (don't free) containing *len
86: characters ( *len may have changed).
87: Buffer is not NULL-terminated.
2.17 luotonen 88: <PRE>extern char * HTInputSocket_getBlock PARAMS((HTInputSocket * isoc,
89: int * len));
90:
91: </PRE>
92: <H3>Free input socket buffer</H3>
93: <PRE>extern void HTInputSocket_free PARAMS((HTInputSocket * isoc));
94:
2.22 timbl 95:
2.17 luotonen 96: PUBLIC char * HTInputSocket_getLine PARAMS((HTInputSocket * isoc));
97: PUBLIC char * HTInputSocket_getUnfoldedLine PARAMS((HTInputSocket * isoc));
98: PUBLIC char * HTInputSocket_getStatusLine PARAMS((HTInputSocket * isoc));
99: PUBLIC BOOL HTInputSocket_seemsBinary PARAMS((HTInputSocket * isoc));
100:
101: </PRE>
2.25 luotonen 102:
103:
104: <H3>Security Buffering</H3>
105:
106: When it's necessary to get e.g. the header section, or part of it,
107: exactly as it came from the client to calculate the message digest,
108: these functions turn buffering on and off. All the material returned
109: by <CODE>HTInputSocket_getStatusLine()</CODE>,
110: <CODE>HTInputSocket_getUnfoldedLine()</CODE> and
111: <CODE>HTInputSocket_getLine()</CODE> gets buffered after a call to
112: <CODE>HTInputSocket_startBuffering()</CODE> until either
113: <CODE>HTInputSocket_stopBuffering()</CODE> is called, or an empty line is
114: returned by any of these functions (end of body section).
115: <CODE>HTInputSocket_getBuffer()</CODE> returns the number of
116: characters buffered, and sets the given buffer pointer to point to
117: internal buffer. This buffer exists until <CODE>HTInputSocket</CODE>
118: object is freed.
119: <PRE>
120:
121: PUBLIC void HTInputSocket_startBuffering PARAMS((HTInputSocket * isoc));
122: PUBLIC void HTInputSocket_stopBuffering PARAMS((HTInputSocket * isoc));
123: PUBLIC int HTInputSocket_getBuffer PARAMS((HTInputSocket * isoc,
124: char ** buffer_ptr));
125: </PRE>
126:
2.1 timbl 127: <H2>The HTFormat type</H2>We use the HTAtom object for holding
128: representations. This allows faster
129: manipulation (comparison and copying)
2.14 timbl 130: that if we stayed with strings.<P>
131: The following have to be defined
132: in advance of the other include files
133: because of circular references.
2.1 timbl 134: <PRE>typedef HTAtom * HTFormat;
2.13 timbl 135:
2.14 timbl 136: #include <A
137: NAME="z14" HREF="HTAccess.html">"HTAccess.h"</A> /* Required for HTRequest definition */
138:
2.28 frystyk 139: </PRE>
140:
141: These macros (which used to be constants) define some basic internally
142: referenced representations.
143:
144: <H3>Internal ones</H3>
145:
146: The www/xxx ones are of course not MIME standard.<P>
147:
148: star/star is an output format which leaves the input untouched. It is
149: useful for diagnostics, and for users who want to see the original,
150: whatever it is.
151:
152: <PRE>
153: #define WWW_SOURCE HTAtom_for("*/*") /* Whatever it was originally */
154: </PRE>
155:
156: www/present represents the user's perception of the document. If you
157: convert to www/present, you present the material to the user.
2.10 timbl 158:
2.28 frystyk 159: <PRE>
160: #define WWW_PRESENT HTAtom_for("www/present") /* The user's perception */
161: </PRE>
162:
163: The message/rfc822 format means a MIME message or a plain text message
164: with no MIME header. This is what is returned by an HTTP server.
165:
166: <PRE>
167: #define WWW_MIME HTAtom_for("www/mime") /* A MIME message */
168: </PRE>
169:
170: www/print is like www/present except it represents a printed copy.
171:
172: <PRE>
173: #define WWW_PRINT HTAtom_for("www/print") /* A printed copy */
174: </PRE>
2.13 timbl 175:
2.28 frystyk 176: www/unknown is a really unknown type. Some default action is
177: appropriate.
2.13 timbl 178:
2.28 frystyk 179: <PRE>
180: #define WWW_UNKNOWN HTAtom_for("www/unknown")
2.13 timbl 181: </PRE>
2.28 frystyk 182:
183:
184: <H3>MIME ones (a few)</H3>
185:
186: These are regular MIME types. HTML is assumed to be added by the W3
187: code. application/octet-stream was mistakenly application/binary in
2.11 timbl 188: earlier libwww versions (pre 2.11).
2.28 frystyk 189:
190: <PRE>
191: #define WWW_PLAINTEXT HTAtom_for("text/plain")
2.1 timbl 192: #define WWW_POSTSCRIPT HTAtom_for("application/postscript")
193: #define WWW_RICHTEXT HTAtom_for("application/rtf")
2.10 timbl 194: #define WWW_AUDIO HTAtom_for("audio/basic")
2.1 timbl 195: #define WWW_HTML HTAtom_for("text/html")
2.11 timbl 196: #define WWW_BINARY HTAtom_for("application/octet-stream")
2.26 frystyk 197: #define WWW_VIDEO HTAtom_for("video/mpeg")
2.28 frystyk 198: </PRE>
199:
200: Extra types used in the library
201:
202: <PRE>
203: #define WWW_NEWSLIST HTAtom_for("text/newslist")
204: </PRE>
2.7 timbl 205:
2.28 frystyk 206: We must include the following file after defining HTFormat, to which
2.10 timbl 207: it makes reference.
2.28 frystyk 208:
2.10 timbl 209: <H2>The HTEncoding type</H2>
210: <PRE>typedef HTAtom* HTEncoding;
211:
212: </PRE>The following are values for the
213: MIME types:
214: <PRE>#define WWW_ENC_7BIT HTAtom_for("7bit")
215: #define WWW_ENC_8BIT HTAtom_for("8bit")
216: #define WWW_ENC_BINARY HTAtom_for("binary")
217:
218: </PRE>We also add
219: <PRE>#define WWW_ENC_COMPRESS HTAtom_for("compress")
220:
221: #include "HTAnchor.h"
2.1 timbl 222:
223: </PRE>
224:
2.28 frystyk 225: <H2>The HTPresentation and HTConverter types</H2>
226:
227: This HTPresentation structure represents a possible conversion
228: algorithm from one format to annother. It includes a pointer to a
229: conversion routine. The conversion routine returns a stream to which
230: data should be fed. See also <A NAME="z5"
231: HREF="#z3">HTStreamStack</A> which scans the list of registered
232: converters and calls one. See the <A NAME="z6"
233: HREF="HTInit.html">initialisation module</A> for a list of conversion
234: routines.
235:
236: <PRE>
237: typedef struct _HTPresentation HTPresentation;
238:
239: typedef HTStream * <A NAME="z12">HTConverter</A> PARAMS((
2.13 timbl 240: HTRequest * request,
241: void * param,
242: HTFormat input_format,
243: HTFormat output_format,
244: HTStream * output_stream));
2.1 timbl 245:
246: struct _HTPresentation {
2.13 timbl 247: HTAtom* rep; /* representation name atomized */
2.1 timbl 248: HTAtom* rep_out; /* resulting representation */
2.2 timbl 249: HTConverter *converter; /* The routine to gen the stream stack */
2.1 timbl 250: char * command; /* MIME-format string */
2.29 ! howcome 251: char * test_command; /* MIME-format string */
2.1 timbl 252: float quality; /* Between 0 (bad) and 1 (good) */
253: float secs;
254: float secs_per_byte;
255: };
2.28 frystyk 256: </PRE>
257:
258: A global list of converters is kept by this module. It is also
259: scanned by modules which want to know the set of formats supported.
260: for example. Note there is also an additional list associated with
261: each <A NAME="z16" HREF="HTAccess.html#z5">request</A>.
2.1 timbl 262:
2.15 timbl 263: <PRE>extern HTList * <A
264: NAME="z17">HTConversions</A> ;
2.1 timbl 265:
2.12 timbl 266:
2.1 timbl 267: </PRE>
268: <H2>HTSetPresentation: Register a system
269: command to present a format</H2>
2.8 timbl 270: <H3>On entry,</H3>
2.1 timbl 271: <DL>
272: <DT>rep
273: <DD> is the MIME - style format name
274: <DT>command
275: <DD> is the MAILCAP - style command
276: template
277: <DT>quality
278: <DD> A degradation faction 0..1
279: <DT>maxbytes
280: <DD> A limit on the length acceptable
281: as input (0 infinite)
282: <DT>maxsecs
283: <DD> A limit on the time user
284: will wait (0 for infinity)
285: </DL>
286:
287: <PRE>extern void HTSetPresentation PARAMS((
2.13 timbl 288: HTList * conversions,
289: CONST char * representation,
290: CONST char * command,
291: float quality,
292: float secs,
293: float secs_per_byte
2.1 timbl 294: ));
295:
296:
297: </PRE>
298: <H2>HTSetConversion: Register a converstion
299: routine</H2>
2.8 timbl 300: <H3>On entry,</H3>
2.1 timbl 301: <DL>
302: <DT>rep_in
303: <DD> is the content-type input
304: <DT>rep_out
305: <DD> is the resulting content-type
306: <DT>converter
307: <DD> is the routine to make
308: the stream to do it
309: </DL>
310:
311: <PRE>
312: extern void HTSetConversion PARAMS((
2.13 timbl 313: HTList * conversions,
2.1 timbl 314: CONST char * rep_in,
315: CONST char * rep_out,
2.2 timbl 316: HTConverter * converter,
2.1 timbl 317: float quality,
318: float secs,
319: float secs_per_byte
320: ));
321:
322:
323: </PRE>
324: <H2><A
2.10 timbl 325: NAME="z3">HTStreamStack: Create a stack of
2.1 timbl 326: streams</A></H2>This is the routine which actually
327: sets up the conversion. It currently
328: checks only for direct conversions,
2.8 timbl 329: but multi-stage conversions are forseen.
2.2 timbl 330: It takes a stream into which the
2.1 timbl 331: output should be sent in the final
332: format, builds the conversion stack,
333: and returns a stream into which the
334: data in the input format should be
335: fed. The anchor is passed because
336: hypertxet objects load information
337: into the anchor object which represents
2.23 luotonen 338: them. <P>
339: If <CODE>guess</CODE> is true and input format is
340: <CODE>www/unknown</CODE>, try to guess the format
341: by looking at the first few butes of the stream. <P>
2.1 timbl 342: <PRE>extern HTStream * HTStreamStack PARAMS((
343: HTFormat format_in,
2.23 luotonen 344: HTRequest * request,
345: BOOL guess));
2.1 timbl 346:
347: </PRE>
348: <H2>HTStackValue: Find the cost of a
349: filter stack</H2>Must return the cost of the same
350: stack which HTStreamStack would set
351: up.
2.8 timbl 352: <H3>On entry,</H3>
2.1 timbl 353: <DL>
354: <DT>format_in
355: <DD> The fomat of the data to
356: be converted
357: <DT>format_out
358: <DD> The format required
359: <DT>initial_value
360: <DD> The intrinsic "value"
361: of the data before conversion on
362: a scale from 0 to 1
363: <DT>length
364: <DD> The number of bytes expected
365: in the input format
366: </DL>
367:
368: <PRE>extern float HTStackValue PARAMS((
2.13 timbl 369: HTList * conversions,
2.1 timbl 370: HTFormat format_in,
2.13 timbl 371: HTFormat format_out,
2.1 timbl 372: float initial_value,
373: long int length));
374:
375: #define NO_VALUE_FOUND -1e20 /* returned if none found */
376:
377: </PRE>
378: <H2><A
2.10 timbl 379: NAME="z1">HTCopy: Copy a socket to a stream</A></H2>This is used by the protocol engines
2.6 secret 380: to send data down a stream, typically
2.22 timbl 381: one which has been generated by HTStreamStack.
382: Returns the number of bytes transferred.
2.19 luotonen 383: <PRE>extern int HTCopy PARAMS((
2.1 timbl 384: int file_number,
385: HTStream* sink));
386:
387:
2.6 secret 388: </PRE>
389: <H2><A
2.10 timbl 390: NAME="c6">HTFileCopy: Copy a file to a stream</A></H2>This is used by the protocol engines
2.6 secret 391: to send data down a stream, typically
2.7 timbl 392: one which has been generated by HTStreamStack.
393: It is currently called by <A
2.12 timbl 394: NAME="z9" HREF="#c7">HTParseFile</A>
2.6 secret 395: <PRE>extern void HTFileCopy PARAMS((
396: FILE* fp,
397: HTStream* sink));
398:
399:
2.7 timbl 400: </PRE>
401: <H2><A
2.10 timbl 402: NAME="c2">HTCopyNoCR: Copy a socket to a stream,
2.7 timbl 403: stripping CR characters.</A></H2>It is slower than <A
2.12 timbl 404: NAME="z2" HREF="#z1">HTCopy</A> .
2.1 timbl 405: <PRE>
406: extern void HTCopyNoCR PARAMS((
407: int file_number,
408: HTStream* sink));
409:
2.16 luotonen 410:
411: </PRE>
2.1 timbl 412: <H2>HTParseSocket: Parse a socket given
413: its format</H2>This routine is called by protocol
414: modules to load an object. uses<A
2.12 timbl 415: NAME="z4" HREF="#z3">
2.1 timbl 416: HTStreamStack</A> and the copy routines
417: above. Returns HT_LOADED if succesful,
418: <0 if not.
419: <PRE>extern int HTParseSocket PARAMS((
420: HTFormat format_in,
421: int file_number,
2.13 timbl 422: HTRequest * request));
2.6 secret 423:
424: </PRE>
425: <H2><A
2.10 timbl 426: NAME="c1">HTParseFile: Parse a File through
2.7 timbl 427: a file pointer</A></H2>This routine is called by protocols
428: modules to load an object. uses<A
2.12 timbl 429: NAME="z4" HREF="#z3"> HTStreamStack</A>
2.7 timbl 430: and <A
2.12 timbl 431: NAME="c7" HREF="#c6">HTFileCopy</A> . Returns HT_LOADED
2.7 timbl 432: if succesful, <0 if not.
2.6 secret 433: <PRE>extern int HTParseFile PARAMS((
434: HTFormat format_in,
435: FILE *fp,
2.13 timbl 436: HTRequest * request));
2.8 timbl 437:
438: </PRE>
2.11 timbl 439: <H2><A
440: NAME="z11">HTNetToText: Convert Net ASCII to
441: local representation</A></H2>This is a filter stream suitable
442: for taking text from a socket and
443: passing it into a stream which expects
444: text in the local C representation.
445: It does ASCII and newline conversion.
446: As usual, pass its output stream
447: to it when creating it.
448: <PRE>extern HTStream * HTNetToText PARAMS ((HTStream * sink));
449:
450: </PRE>
2.8 timbl 451: <H2>HTFormatInit: Set up default presentations
452: and conversions</H2>These are defined in HTInit.c or
453: HTSInit.c if these have been replaced.
454: If you don't call this routine, and
455: you don't define any presentations,
456: then this routine will automatically
457: be called the first time a conversion
458: is needed. However, if you explicitly
459: add some conversions (eg using HTLoadRules)
460: then you may want also to explicitly
461: call this to get the defaults as
462: well.
2.20 frystyk 463: <PRE>
464: extern void HTFormatInit PARAMS((HTList * conversions));
2.22 timbl 465:
2.21 frystyk 466: </PRE>
2.22 timbl 467: <H2>HTFormatInitNIM: Set up default presentations
468: and conversions</H2>This is a slightly different version
469: of HTFormatInit, but without any
470: conversions that might use third
471: party programs. This is intended
472: for Non Interactive Mode.
473: <PRE>extern void HTFormatInitNIM PARAMS((HTList * conversions));
2.21 frystyk 474:
2.1 timbl 475: </PRE>
2.22 timbl 476: <H2>HTFormatDelete: Remove presentations
477: and conversions</H2>Deletes the list from HTFormatInit
478: or HTFormatInitNIM
479: <PRE>extern void HTFormatDelete PARAMS((HTList * conversions));
2.21 frystyk 480:
481: </PRE>
482:
2.1 timbl 483: <H2>Epilogue</H2>
484: <PRE>extern BOOL HTOutputSource; /* Flag: shortcut parser */
485: #endif
486:
2.22 timbl 487: </PRE>end</BODY>
2.10 timbl 488: </HTML>
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