Annotation of libwww/Library/src/SGML.html, revision 2.13
2.4 timbl 1: <HTML>
2: <HEAD>
3: <TITLE>SGML parse and stream definition for libwww</TITLE></HEAD>
2.1 timbl 4: <BODY>
5: <H1>SGML and Structured streams</H1>The SGML parser is a state machine.
2.11 frystyk 6: It is called for every character of the input stream. The DTD data
7: structure contains pointers to functions which are called to
8: implement the actual effect of the text read. When these functions are
9: called, the attribute structures pointed to by the DTD are valid,
10: and the function is parsed a pointer to the curent tag structure, and
11: an "element stack" which represents the state of nesting within SGML
2.13 ! frystyk 12: elements. See also the <A HREF="HTStream.html">the generic Stream
! 13: definition</A><P>
2.11 frystyk 14:
2.1 timbl 15: The following aspects are from Dan
16: Connolly's suggestions: Binary search,
17: Strcutured object scheme basically,
18: SGML content enum type.<P>
2.11 frystyk 19:
20: The module is a part of the <A HREF="Overview">CERN Common WWW Library</A>
2.1 timbl 21: (c) Copyright CERN 1991 - See Copyright.html
2.11 frystyk 22:
23: <PRE>
24: #ifndef SGML_H
2.1 timbl 25: #define SGML_H
26:
27: #include "HTUtils.h"
28: #include "HTStream.h"
29:
30: </PRE>
31: <H2>SGML content types</H2>
32: <PRE>typedef enum _SGMLContent{
33: SGML_EMPTY, /* no content */
2.8 timbl 34: SGML_LITERAL, /* character data. Recognized exact close tag only.
2.1 timbl 35: Old www server compatibility only! Not SGML */
36: SGML_CDATA, /* character data. recognize </ only */
37: SGML_RCDATA, /* replaceable character data. recognize </ and &ref; */
38: SGML_MIXED, /* elements and parsed character data. recognize all markup */
39: SGML_ELEMENT /* any data found will be returned as an error*/
40: } SGMLContent;
41:
42:
43: typedef struct {
44: char * name; /* The (constant) name of the attribute */
45: /* Could put type info in here */
46: } attr;
47:
48:
49: /* A tag structure describes an SGML element.
50: ** -----------------------------------------
51: **
52: **
53: ** name is the string which comes after the tag opener "<".
54: **
55: ** attributes points to a zero-terminated array
56: ** of attribute names.
57: **
58: ** litteral determines how the SGML engine parses the charaters
59: ** within the element. If set, tag openers are ignored
60: ** except for that which opens a matching closing tag.
61: **
62: */
63: typedef struct _tag HTTag;
64: struct _tag{
65: char * name; /* The name of the tag */
66: attr * attributes; /* The list of acceptable attributes */
67: int number_of_attributes; /* Number of possible attributes */
68: SGMLContent contents; /* End only on end tag @@ */
69: };
70:
71:
72:
73:
74: /* DTD Information
75: ** ---------------
76: **
77: ** Not the whole DTD, but all this parser usues of it.
78: */
79: typedef struct {
2.2 timbl 80: HTTag * tags; /* Must be in strcmp order by name */
81: int number_of_tags;
82: CONST char ** entity_names; /* Must be in strcmp order by name */
83: int number_of_entities;
2.1 timbl 84: } SGML_dtd;
85:
2.9 frystyk 86: #define MAX_ATTRIBUTES 20 /* Max number of attributes per element */
2.1 timbl 87:
88: /* SGML context passed to parsers
89: */
90: typedef struct _HTSGMLContext *HTSGMLContext; /* Hidden */
91:
92:
93: /*__________________________________________________________________________
94: */
95:
2.6 timbl 96: </PRE>
97: <H2>Structured Object definition</H2>A structured object is something
98: which can reasonably be represented
99: in SGML. I'll rephrase that. A
100: structured object is am ordered tree-structured
101: arrangement of data which is representable
102: as text.The SGML parer outputs to
103: a Structured object. A Structured
104: object can output its contents to
105: another Structured Object. It's a
106: kind of typed stream. The architecure
107: is largely Dan Conolly's. Elements
108: and entities are passed to the sob
109: by number, implying a knowledge of
110: the DTD. Knowledge of the SGML syntax
111: is not here, though.<P>
112: Superclass: HTStream<P>
113: The creation methods will vary on
114: the type of Structured Object.Maybe
115: the callerData is enough info to
2.13 ! frystyk 116: pass along. <P>
! 117:
! 118: <B>NOTE: </B>The <CODE>put_block</CODE> method was <CODE>write</CODE>,
! 119: but this upset systems which had macros for <CODE>write()</CODE>. See
! 120: <A HREF="HTStream.html">the generic stream definition</A> for valid
! 121: return codes.<P>
! 122:
2.6 timbl 123: <PRE>typedef struct _HTStructured HTStructured;
2.1 timbl 124:
125: typedef struct _HTStructuredClass{
126:
127: char* name; /* Just for diagnostics */
128:
2.13 ! frystyk 129: int (*_free) PARAMS((
2.1 timbl 130: HTStructured* me));
131:
2.13 ! frystyk 132: int (*abort) PARAMS((
2.5 timbl 133: HTStructured* me,
134: HTError e));
2.1 timbl 135:
136: void (*put_character) PARAMS((
137: HTStructured* me,
138: char ch));
139:
140: void (*put_string) PARAMS((
141: HTStructured* me,
142: CONST char * str));
143:
2.13 ! frystyk 144: void (*put_block) PARAMS((
2.2 timbl 145: HTStructured* me,
2.1 timbl 146: CONST char * str,
147: int len));
148:
149: void (*start_element) PARAMS((
150: HTStructured* me,
151: int element_number,
2.2 timbl 152: CONST BOOL* attribute_present,
153: CONST char** attribute_value));
2.1 timbl 154:
155: void (*end_element) PARAMS((
156: HTStructured* me,
157: int element_number));
158:
159: void (*put_entity) PARAMS((
160: HTStructured* me,
161: int entity_number));
162:
2.13 ! frystyk 163: } HTStructuredClass;
2.1 timbl 164:
2.6 timbl 165: </PRE>
166: <H2>Find a Tag by Name</H2>Returns a pointer to the tag within
167: the DTD.
2.7 timbl 168: <PRE>extern HTTag * SGMLFindTag PARAMS((CONST SGML_dtd* dtd, CONST char * string));
2.1 timbl 169:
170:
2.6 timbl 171: </PRE>
2.10 timbl 172: <H2>Find a Attribute by Name</H2>Returns the number of the
173: atribute or -1 if failure.
174: <PRE>extern int SGMLFindAttribute PARAMS((HTTag* tag, CONST char * string));
175:
176:
177: </PRE>
2.6 timbl 178: <H2>Create an SGML parser</H2>
179: <PRE>/*
2.1 timbl 180: ** On entry,
181: ** dtd must point to a DTD structure as defined above
182: ** callbacks must point to user routines.
183: ** callData is returned in callbacks transparently.
184: ** On exit,
185: ** The default tag starter has been processed.
186: */
187:
188:
189: extern HTStream* SGML_new PARAMS((
190: CONST SGML_dtd * dtd,
191: HTStructured * target));
192:
2.2 timbl 193: extern CONST HTStreamClass SGMLParser;
2.1 timbl 194:
195:
196: #endif /* SGML_H */
2.7 timbl 197:
2.1 timbl 198:
2.3 timbl 199:
200:
2.4 timbl 201:
2.6 timbl 202:
203:
204:
205:
2.8 timbl 206:
207: </PRE></BODY>
2.4 timbl 208: </HTML>
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