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