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