Annotation of libwww/Library/src/SGML.html, revision 2.14.2.1
2.4 timbl 1: <HTML>
2: <HEAD>
2.14 frystyk 3: <TITLE>SGML parse and stream definition for libwww</TITLE>
4: </HEAD>
2.1 timbl 5: <BODY>
2.11 frystyk 6:
2.14 frystyk 7: <H1>SGML and Structured streams</H1>
2.11 frystyk 8:
2.14 frystyk 9: <PRE>
10: /*
11: ** (c) COPYRIGHT CERN 1994.
12: ** Please first read the full copyright statement in the file COPYRIGH.
13: */
14: </PRE>
15:
16: The SGML parser is a state machine. It is called for every character
17: of the input stream. The DTD data structure contains pointers to
18: functions which are called to implement the actual effect of the text
19: read. When these functions are called, the attribute structures
20: pointed to by the DTD are valid, and the function is parsed a pointer
21: to the curent tag structure, and an "element stack" which represents
22: the state of nesting within SGML elements. See also the <A
23: HREF="HTStream.html">the generic Stream definition</A><P>
24:
25: The following aspects are from Dan Connolly's suggestions: Binary
26: search, Strcutured object scheme basically, SGML content enum type.<P>
27:
28: This module is implemented by <A HREF="SGML.c">SGML.c</A>, and it is a
29: part of the <A
30: HREF="http://info.cern.ch/hypertext/WWW/Library/User/Guide/Guide.html">
31: Library of Common Code</A>.
2.11 frystyk 32:
33: <PRE>
34: #ifndef SGML_H
2.1 timbl 35: #define SGML_H
36:
37: #include "HTStream.h"
38: </PRE>
2.14.2.1! frystyk 39:
2.1 timbl 40: <H2>SGML content types</H2>
41: <PRE>typedef enum _SGMLContent{
42: SGML_EMPTY, /* no content */
2.8 timbl 43: SGML_LITERAL, /* character data. Recognized exact close tag only.
2.1 timbl 44: Old www server compatibility only! Not SGML */
45: SGML_CDATA, /* character data. recognize </ only */
46: SGML_RCDATA, /* replaceable character data. recognize </ and &ref; */
47: SGML_MIXED, /* elements and parsed character data. recognize all markup */
48: SGML_ELEMENT /* any data found will be returned as an error*/
49: } SGMLContent;
50:
51:
52: typedef struct {
53: char * name; /* The (constant) name of the attribute */
54: /* Could put type info in here */
55: } attr;
56:
57:
58: /* A tag structure describes an SGML element.
59: ** -----------------------------------------
60: **
61: **
62: ** name is the string which comes after the tag opener "<".
63: **
64: ** attributes points to a zero-terminated array
65: ** of attribute names.
66: **
67: ** litteral determines how the SGML engine parses the charaters
68: ** within the element. If set, tag openers are ignored
69: ** except for that which opens a matching closing tag.
70: **
71: */
72: typedef struct _tag HTTag;
73: struct _tag{
74: char * name; /* The name of the tag */
75: attr * attributes; /* The list of acceptable attributes */
76: int number_of_attributes; /* Number of possible attributes */
77: SGMLContent contents; /* End only on end tag @@ */
78: };
79:
80: /* DTD Information
81: ** ---------------
82: **
83: ** Not the whole DTD, but all this parser usues of it.
84: */
85: typedef struct {
2.2 timbl 86: HTTag * tags; /* Must be in strcmp order by name */
87: int number_of_tags;
88: CONST char ** entity_names; /* Must be in strcmp order by name */
89: int number_of_entities;
2.1 timbl 90: } SGML_dtd;
91:
2.9 frystyk 92: #define MAX_ATTRIBUTES 20 /* Max number of attributes per element */
2.1 timbl 93:
94: /* SGML context passed to parsers
95: */
96: typedef struct _HTSGMLContext *HTSGMLContext; /* Hidden */
97:
98:
99: /*__________________________________________________________________________
100: */
101:
2.6 timbl 102: </PRE>
103: <H2>Structured Object definition</H2>A structured object is something
104: which can reasonably be represented
105: in SGML. I'll rephrase that. A
106: structured object is am ordered tree-structured
107: arrangement of data which is representable
108: as text.The SGML parer outputs to
109: a Structured object. A Structured
110: object can output its contents to
111: another Structured Object. It's a
112: kind of typed stream. The architecure
113: is largely Dan Conolly's. Elements
114: and entities are passed to the sob
115: by number, implying a knowledge of
116: the DTD. Knowledge of the SGML syntax
117: is not here, though.<P>
118: Superclass: HTStream<P>
119: The creation methods will vary on
120: the type of Structured Object.Maybe
121: the callerData is enough info to
2.13 frystyk 122: pass along. <P>
123:
124: <B>NOTE: </B>The <CODE>put_block</CODE> method was <CODE>write</CODE>,
125: but this upset systems which had macros for <CODE>write()</CODE>. See
126: <A HREF="HTStream.html">the generic stream definition</A> for valid
127: return codes.<P>
128:
2.6 timbl 129: <PRE>typedef struct _HTStructured HTStructured;
2.1 timbl 130:
131: typedef struct _HTStructuredClass{
132:
133: char* name; /* Just for diagnostics */
134:
2.13 frystyk 135: int (*_free) PARAMS((
2.1 timbl 136: HTStructured* me));
137:
2.13 frystyk 138: int (*abort) PARAMS((
2.5 timbl 139: HTStructured* me,
140: HTError e));
2.1 timbl 141:
142: void (*put_character) PARAMS((
143: HTStructured* me,
144: char ch));
145:
146: void (*put_string) PARAMS((
147: HTStructured* me,
148: CONST char * str));
149:
2.13 frystyk 150: void (*put_block) PARAMS((
2.2 timbl 151: HTStructured* me,
2.1 timbl 152: CONST char * str,
153: int len));
154:
155: void (*start_element) PARAMS((
156: HTStructured* me,
157: int element_number,
2.2 timbl 158: CONST BOOL* attribute_present,
159: CONST char** attribute_value));
2.1 timbl 160:
161: void (*end_element) PARAMS((
162: HTStructured* me,
163: int element_number));
164:
165: void (*put_entity) PARAMS((
166: HTStructured* me,
167: int entity_number));
168:
2.13 frystyk 169: } HTStructuredClass;
2.1 timbl 170:
2.6 timbl 171: </PRE>
172: <H2>Find a Tag by Name</H2>Returns a pointer to the tag within
173: the DTD.
2.7 timbl 174: <PRE>extern HTTag * SGMLFindTag PARAMS((CONST SGML_dtd* dtd, CONST char * string));
2.1 timbl 175:
176:
2.6 timbl 177: </PRE>
2.10 timbl 178: <H2>Find a Attribute by Name</H2>Returns the number of the
179: atribute or -1 if failure.
180: <PRE>extern int SGMLFindAttribute PARAMS((HTTag* tag, CONST char * string));
181:
182:
183: </PRE>
2.6 timbl 184: <H2>Create an SGML parser</H2>
185: <PRE>/*
2.1 timbl 186: ** On entry,
187: ** dtd must point to a DTD structure as defined above
188: ** callbacks must point to user routines.
189: ** callData is returned in callbacks transparently.
190: ** On exit,
191: ** The default tag starter has been processed.
192: */
193:
194:
195: extern HTStream* SGML_new PARAMS((
196: CONST SGML_dtd * dtd,
197: HTStructured * target));
198:
2.2 timbl 199: extern CONST HTStreamClass SGMLParser;
2.1 timbl 200:
201:
202: #endif /* SGML_H */
2.7 timbl 203:
2.1 timbl 204:
2.3 timbl 205:
206:
2.4 timbl 207:
2.6 timbl 208:
209:
210:
211:
2.8 timbl 212:
213: </PRE></BODY>
2.4 timbl 214: </HTML>
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