Annotation of libwww/Library/src/HTFormat.html, revision 2.26
2.10 timbl 1: <HTML>
2: <HEAD>
2.1 timbl 3: <TITLE>HTFormat: The format manager in the WWW Library</TITLE>
2.15 timbl 4: <NEXTID N="z18">
2.10 timbl 5: </HEAD>
2.1 timbl 6: <BODY>
7: <H1>Manage different document formats</H1>Here we describe the functions of
8: the HTFormat module which handles
9: conversion between different data
10: representations. (In MIME parlance,
11: a representation is known as a content-type.
2.2 timbl 12: In WWW the term "format" is often
2.1 timbl 13: used as it is shorter).<P>
14: This module is implemented by <A
2.10 timbl 15: NAME="z0" HREF="HTFormat.c">HTFormat.c</A>
2.7 timbl 16: . This hypertext document is used
17: to generate the <A
2.11 timbl 18: NAME="z8" HREF="HTFormat.h">HTFormat.h</A> include
2.9 timbl 19: file. Part of the <A
2.10 timbl 20: NAME="z10" HREF="Overview.html">WWW library</A> .
2.1 timbl 21: <H2>Preamble</H2>
22: <PRE>#ifndef HTFORMAT_H
23: #define HTFORMAT_H
24:
25: #include "HTUtils.h"
26: #include <A
2.10 timbl 27: NAME="z7" HREF="HTStream.html">"HTStream.h"</A>
2.1 timbl 28: #include "HTAtom.h"
2.2 timbl 29: #include "HTList.h"
2.1 timbl 30:
31: #ifdef SHORT_NAMES
32: #define HTOutputSource HTOuSour
33: #define HTOutputBinary HTOuBina
34: #endif
35:
2.18 luotonen 36:
37: typedef struct _HTContentDescription {
38: char * filename;
39: HTAtom * content_type;
40: HTAtom * content_language;
41: HTAtom * content_encoding;
42: int content_length;
43: float quality;
44: } HTContentDescription;
45:
46: PUBLIC void HTAcceptEncoding PARAMS((HTList * list,
47: char * enc,
48: float quality));
49:
50: PUBLIC void HTAcceptLanguage PARAMS((HTList * list,
51: char * lang,
52: float quality));
53:
54: PUBLIC BOOL HTRank PARAMS((HTList * possibilities,
55: HTList * accepted_content_types,
56: HTList * accepted_content_languages,
57: HTList * accepted_content_encodings));
58:
59:
2.1 timbl 60: </PRE>
2.17 luotonen 61: <H2>HT<A
62: NAME="z15"> Input Socket: Buffering for network
63: in</A></H2>This routines provide simple character
64: input from sockets. These are used
65: for parsing input in arbitrary IP
66: protocols (Gopher, NNTP, FTP).
67: <PRE>#define INPUT_BUFFER_SIZE 4096 /* Tradeoff spped vs memory*/
68: typedef struct _socket_buffer {
2.25 luotonen 69: char input_buffer[INPUT_BUFFER_SIZE];
2.17 luotonen 70: char * input_pointer;
71: char * input_limit;
72: int input_file_number;
2.25 luotonen 73: BOOL s_do_buffering;
74: char * s_buffer;
75: int s_buffer_size;
76: char * s_buffer_cur;
2.17 luotonen 77: } HTInputSocket;
78:
79: </PRE>
80: <H3>Create input buffer and set file
81: number</H3>
82: <PRE>extern HTInputSocket* HTInputSocket_new PARAMS((int file_number));
83:
84: </PRE>
85: <H3>Get next character from buffer</H3>
2.24 frystyk 86: <PRE>extern int HTInputSocket_getCharacter PARAMS((HTInputSocket* isoc));
2.17 luotonen 87:
88: </PRE>
2.22 timbl 89: <H3>Read block from input socket</H3>Read *len characters and return a
90: buffer (don't free) containing *len
91: characters ( *len may have changed).
92: Buffer is not NULL-terminated.
2.17 luotonen 93: <PRE>extern char * HTInputSocket_getBlock PARAMS((HTInputSocket * isoc,
94: int * len));
95:
96: </PRE>
97: <H3>Free input socket buffer</H3>
98: <PRE>extern void HTInputSocket_free PARAMS((HTInputSocket * isoc));
99:
2.22 timbl 100:
2.17 luotonen 101: PUBLIC char * HTInputSocket_getLine PARAMS((HTInputSocket * isoc));
102: PUBLIC char * HTInputSocket_getUnfoldedLine PARAMS((HTInputSocket * isoc));
103: PUBLIC char * HTInputSocket_getStatusLine PARAMS((HTInputSocket * isoc));
104: PUBLIC BOOL HTInputSocket_seemsBinary PARAMS((HTInputSocket * isoc));
105:
106: </PRE>
2.25 luotonen 107:
108:
109: <H3>Security Buffering</H3>
110:
111: When it's necessary to get e.g. the header section, or part of it,
112: exactly as it came from the client to calculate the message digest,
113: these functions turn buffering on and off. All the material returned
114: by <CODE>HTInputSocket_getStatusLine()</CODE>,
115: <CODE>HTInputSocket_getUnfoldedLine()</CODE> and
116: <CODE>HTInputSocket_getLine()</CODE> gets buffered after a call to
117: <CODE>HTInputSocket_startBuffering()</CODE> until either
118: <CODE>HTInputSocket_stopBuffering()</CODE> is called, or an empty line is
119: returned by any of these functions (end of body section).
120: <CODE>HTInputSocket_getBuffer()</CODE> returns the number of
121: characters buffered, and sets the given buffer pointer to point to
122: internal buffer. This buffer exists until <CODE>HTInputSocket</CODE>
123: object is freed.
124: <PRE>
125:
126: PUBLIC void HTInputSocket_startBuffering PARAMS((HTInputSocket * isoc));
127: PUBLIC void HTInputSocket_stopBuffering PARAMS((HTInputSocket * isoc));
128: PUBLIC int HTInputSocket_getBuffer PARAMS((HTInputSocket * isoc,
129: char ** buffer_ptr));
130: </PRE>
131:
2.1 timbl 132: <H2>The HTFormat type</H2>We use the HTAtom object for holding
133: representations. This allows faster
134: manipulation (comparison and copying)
2.14 timbl 135: that if we stayed with strings.<P>
136: The following have to be defined
137: in advance of the other include files
138: because of circular references.
2.1 timbl 139: <PRE>typedef HTAtom * HTFormat;
2.13 timbl 140:
2.14 timbl 141: #include <A
142: NAME="z14" HREF="HTAccess.html">"HTAccess.h"</A> /* Required for HTRequest definition */
143:
2.1 timbl 144: </PRE>These macros (which used to be constants)
145: define some basic internally referenced
2.13 timbl 146: representations.
147: <H3>Internal ones</H3>The www/xxx ones are of course not
148: MIME standard.<P>
2.20 frystyk 149: star/star is an output format which
2.1 timbl 150: leaves the input untouched. It is
151: useful for diagnostics, and for users
152: who want to see the original, whatever
153: it is.
2.13 timbl 154: <H3></H3>
2.20 frystyk 155: <PRE>#define WWW_SOURCE HTAtom_for("*/*") /* Whatever it was originally*/
2.1 timbl 156:
157: </PRE>www/present represents the user's
158: perception of the document. If you
159: convert to www/present, you present
160: the material to the user.
161: <PRE>#define WWW_PRESENT HTAtom_for("www/present") /* The user's perception */
162:
163: </PRE>The message/rfc822 format means a
164: MIME message or a plain text message
165: with no MIME header. This is what
166: is returned by an HTTP server.
167: <PRE>#define WWW_MIME HTAtom_for("www/mime") /* A MIME message */
2.10 timbl 168:
2.1 timbl 169: </PRE>www/print is like www/present except
170: it represents a printed copy.
171: <PRE>#define WWW_PRINT HTAtom_for("www/print") /* A printed copy */
172:
2.10 timbl 173: </PRE>www/unknown is a really unknown type.
2.11 timbl 174: Some default action is appropriate.
2.10 timbl 175: <PRE>#define WWW_UNKNOWN HTAtom_for("www/unknown")
176:
2.13 timbl 177:
178:
179: </PRE>
180: <H3>MIME ones (a few)</H3>These are regular MIME types. HTML
2.11 timbl 181: is assumed to be added by the W3
182: code. application/octet-stream was
183: mistakenly application/binary in
184: earlier libwww versions (pre 2.11).
2.10 timbl 185: <PRE>#define WWW_PLAINTEXT HTAtom_for("text/plain")
2.1 timbl 186: #define WWW_POSTSCRIPT HTAtom_for("application/postscript")
187: #define WWW_RICHTEXT HTAtom_for("application/rtf")
2.10 timbl 188: #define WWW_AUDIO HTAtom_for("audio/basic")
2.1 timbl 189: #define WWW_HTML HTAtom_for("text/html")
2.11 timbl 190: #define WWW_BINARY HTAtom_for("application/octet-stream")
2.26 ! frystyk 191: #define WWW_VIDEO HTAtom_for("video/mpeg")
2.7 timbl 192:
2.1 timbl 193: </PRE>We must include the following file
194: after defining HTFormat, to which
2.10 timbl 195: it makes reference.
196: <H2>The HTEncoding type</H2>
197: <PRE>typedef HTAtom* HTEncoding;
198:
199: </PRE>The following are values for the
200: MIME types:
201: <PRE>#define WWW_ENC_7BIT HTAtom_for("7bit")
202: #define WWW_ENC_8BIT HTAtom_for("8bit")
203: #define WWW_ENC_BINARY HTAtom_for("binary")
204:
205: </PRE>We also add
206: <PRE>#define WWW_ENC_COMPRESS HTAtom_for("compress")
207:
208: #include "HTAnchor.h"
2.1 timbl 209:
210: </PRE>
211: <H2>The HTPresentation and HTConverter
212: types</H2>This HTPresentation structure represents
213: a possible conversion algorithm from
214: one format to annother. It includes
215: a pointer to a conversion routine.
216: The conversion routine returns a
217: stream to which data should be fed.
218: See also <A
2.12 timbl 219: NAME="z5" HREF="#z3">HTStreamStack</A> which scans
2.1 timbl 220: the list of registered converters
221: and calls one. See the <A
2.10 timbl 222: NAME="z6" HREF="HTInit.html">initialisation
2.1 timbl 223: module</A> for a list of conversion routines.
224: <PRE>typedef struct _HTPresentation HTPresentation;
225:
2.13 timbl 226: typedef HTStream * <A
227: NAME="z12">HTConverter</A> PARAMS((
228: HTRequest * request,
229: void * param,
230: HTFormat input_format,
231: HTFormat output_format,
232: HTStream * output_stream));
2.1 timbl 233:
234: struct _HTPresentation {
2.13 timbl 235: HTAtom* rep; /* representation name atomized */
2.1 timbl 236: HTAtom* rep_out; /* resulting representation */
2.2 timbl 237: HTConverter *converter; /* The routine to gen the stream stack */
2.1 timbl 238: char * command; /* MIME-format string */
239: float quality; /* Between 0 (bad) and 1 (good) */
240: float secs;
241: float secs_per_byte;
242: };
243:
2.15 timbl 244: </PRE>A global list of converters is kept
2.1 timbl 245: by this module. It is also scanned
246: by modules which want to know the
247: set of formats supported. for example.
2.22 timbl 248: Note there is also an additional
2.15 timbl 249: list associated with each <A
2.22 timbl 250: NAME="z16" HREF="HTAccess.html#z5">request</A>
251: .
2.15 timbl 252: <PRE>extern HTList * <A
253: NAME="z17">HTConversions</A> ;
2.1 timbl 254:
2.12 timbl 255:
2.1 timbl 256: </PRE>
257: <H2>HTSetPresentation: Register a system
258: command to present a format</H2>
2.8 timbl 259: <H3>On entry,</H3>
2.1 timbl 260: <DL>
261: <DT>rep
262: <DD> is the MIME - style format name
263: <DT>command
264: <DD> is the MAILCAP - style command
265: template
266: <DT>quality
267: <DD> A degradation faction 0..1
268: <DT>maxbytes
269: <DD> A limit on the length acceptable
270: as input (0 infinite)
271: <DT>maxsecs
272: <DD> A limit on the time user
273: will wait (0 for infinity)
274: </DL>
275:
276: <PRE>extern void HTSetPresentation PARAMS((
2.13 timbl 277: HTList * conversions,
278: CONST char * representation,
279: CONST char * command,
280: float quality,
281: float secs,
282: float secs_per_byte
2.1 timbl 283: ));
284:
285:
286: </PRE>
287: <H2>HTSetConversion: Register a converstion
288: routine</H2>
2.8 timbl 289: <H3>On entry,</H3>
2.1 timbl 290: <DL>
291: <DT>rep_in
292: <DD> is the content-type input
293: <DT>rep_out
294: <DD> is the resulting content-type
295: <DT>converter
296: <DD> is the routine to make
297: the stream to do it
298: </DL>
299:
300: <PRE>
301: extern void HTSetConversion PARAMS((
2.13 timbl 302: HTList * conversions,
2.1 timbl 303: CONST char * rep_in,
304: CONST char * rep_out,
2.2 timbl 305: HTConverter * converter,
2.1 timbl 306: float quality,
307: float secs,
308: float secs_per_byte
309: ));
310:
311:
312: </PRE>
313: <H2><A
2.10 timbl 314: NAME="z3">HTStreamStack: Create a stack of
2.1 timbl 315: streams</A></H2>This is the routine which actually
316: sets up the conversion. It currently
317: checks only for direct conversions,
2.8 timbl 318: but multi-stage conversions are forseen.
2.2 timbl 319: It takes a stream into which the
2.1 timbl 320: output should be sent in the final
321: format, builds the conversion stack,
322: and returns a stream into which the
323: data in the input format should be
324: fed. The anchor is passed because
325: hypertxet objects load information
326: into the anchor object which represents
2.23 luotonen 327: them. <P>
328: If <CODE>guess</CODE> is true and input format is
329: <CODE>www/unknown</CODE>, try to guess the format
330: by looking at the first few butes of the stream. <P>
2.1 timbl 331: <PRE>extern HTStream * HTStreamStack PARAMS((
332: HTFormat format_in,
2.23 luotonen 333: HTRequest * request,
334: BOOL guess));
2.1 timbl 335:
336: </PRE>
337: <H2>HTStackValue: Find the cost of a
338: filter stack</H2>Must return the cost of the same
339: stack which HTStreamStack would set
340: up.
2.8 timbl 341: <H3>On entry,</H3>
2.1 timbl 342: <DL>
343: <DT>format_in
344: <DD> The fomat of the data to
345: be converted
346: <DT>format_out
347: <DD> The format required
348: <DT>initial_value
349: <DD> The intrinsic "value"
350: of the data before conversion on
351: a scale from 0 to 1
352: <DT>length
353: <DD> The number of bytes expected
354: in the input format
355: </DL>
356:
357: <PRE>extern float HTStackValue PARAMS((
2.13 timbl 358: HTList * conversions,
2.1 timbl 359: HTFormat format_in,
2.13 timbl 360: HTFormat format_out,
2.1 timbl 361: float initial_value,
362: long int length));
363:
364: #define NO_VALUE_FOUND -1e20 /* returned if none found */
365:
366: </PRE>
367: <H2><A
2.10 timbl 368: NAME="z1">HTCopy: Copy a socket to a stream</A></H2>This is used by the protocol engines
2.6 secret 369: to send data down a stream, typically
2.22 timbl 370: one which has been generated by HTStreamStack.
371: Returns the number of bytes transferred.
2.19 luotonen 372: <PRE>extern int HTCopy PARAMS((
2.1 timbl 373: int file_number,
374: HTStream* sink));
375:
376:
2.6 secret 377: </PRE>
378: <H2><A
2.10 timbl 379: NAME="c6">HTFileCopy: Copy a file to a stream</A></H2>This is used by the protocol engines
2.6 secret 380: to send data down a stream, typically
2.7 timbl 381: one which has been generated by HTStreamStack.
382: It is currently called by <A
2.12 timbl 383: NAME="z9" HREF="#c7">HTParseFile</A>
2.6 secret 384: <PRE>extern void HTFileCopy PARAMS((
385: FILE* fp,
386: HTStream* sink));
387:
388:
2.7 timbl 389: </PRE>
390: <H2><A
2.10 timbl 391: NAME="c2">HTCopyNoCR: Copy a socket to a stream,
2.7 timbl 392: stripping CR characters.</A></H2>It is slower than <A
2.12 timbl 393: NAME="z2" HREF="#z1">HTCopy</A> .
2.1 timbl 394: <PRE>
395: extern void HTCopyNoCR PARAMS((
396: int file_number,
397: HTStream* sink));
398:
2.16 luotonen 399:
400: </PRE>
2.1 timbl 401: <H2>HTParseSocket: Parse a socket given
402: its format</H2>This routine is called by protocol
403: modules to load an object. uses<A
2.12 timbl 404: NAME="z4" HREF="#z3">
2.1 timbl 405: HTStreamStack</A> and the copy routines
406: above. Returns HT_LOADED if succesful,
407: <0 if not.
408: <PRE>extern int HTParseSocket PARAMS((
409: HTFormat format_in,
410: int file_number,
2.13 timbl 411: HTRequest * request));
2.6 secret 412:
413: </PRE>
414: <H2><A
2.10 timbl 415: NAME="c1">HTParseFile: Parse a File through
2.7 timbl 416: a file pointer</A></H2>This routine is called by protocols
417: modules to load an object. uses<A
2.12 timbl 418: NAME="z4" HREF="#z3"> HTStreamStack</A>
2.7 timbl 419: and <A
2.12 timbl 420: NAME="c7" HREF="#c6">HTFileCopy</A> . Returns HT_LOADED
2.7 timbl 421: if succesful, <0 if not.
2.6 secret 422: <PRE>extern int HTParseFile PARAMS((
423: HTFormat format_in,
424: FILE *fp,
2.13 timbl 425: HTRequest * request));
2.8 timbl 426:
427: </PRE>
2.11 timbl 428: <H2><A
429: NAME="z11">HTNetToText: Convert Net ASCII to
430: local representation</A></H2>This is a filter stream suitable
431: for taking text from a socket and
432: passing it into a stream which expects
433: text in the local C representation.
434: It does ASCII and newline conversion.
435: As usual, pass its output stream
436: to it when creating it.
437: <PRE>extern HTStream * HTNetToText PARAMS ((HTStream * sink));
438:
439: </PRE>
2.8 timbl 440: <H2>HTFormatInit: Set up default presentations
441: and conversions</H2>These are defined in HTInit.c or
442: HTSInit.c if these have been replaced.
443: If you don't call this routine, and
444: you don't define any presentations,
445: then this routine will automatically
446: be called the first time a conversion
447: is needed. However, if you explicitly
448: add some conversions (eg using HTLoadRules)
449: then you may want also to explicitly
450: call this to get the defaults as
451: well.
2.20 frystyk 452: <PRE>
453: extern void HTFormatInit PARAMS((HTList * conversions));
2.22 timbl 454:
2.21 frystyk 455: </PRE>
2.22 timbl 456: <H2>HTFormatInitNIM: Set up default presentations
457: and conversions</H2>This is a slightly different version
458: of HTFormatInit, but without any
459: conversions that might use third
460: party programs. This is intended
461: for Non Interactive Mode.
462: <PRE>extern void HTFormatInitNIM PARAMS((HTList * conversions));
2.21 frystyk 463:
2.1 timbl 464: </PRE>
2.22 timbl 465: <H2>HTFormatDelete: Remove presentations
466: and conversions</H2>Deletes the list from HTFormatInit
467: or HTFormatInitNIM
468: <PRE>extern void HTFormatDelete PARAMS((HTList * conversions));
2.21 frystyk 469:
470: </PRE>
471:
2.1 timbl 472: <H2>Epilogue</H2>
473: <PRE>extern BOOL HTOutputSource; /* Flag: shortcut parser */
474: #endif
475:
2.22 timbl 476: </PRE>end</BODY>
2.10 timbl 477: </HTML>
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