1 /**
2  * section: InputOutput
3  * synopsis: Example of custom Input/Output
4  * purpose: Demonstrate the use of xmlRegisterInputCallbacks
5  *          to build a custom I/O layer, this is used in an
6  *          XInclude method context to show how dynamic document can
7  *          be built in a clean way.
8  * usage: io1
9  * test: io1 > io1.tmp && diff io1.tmp $(srcdir)/io1.res
10  * author: Daniel Veillard
11  * copy: see Copyright for the status of this software.
12  */
13 
14 #include <stdio.h>
15 #include <string.h>
16 #include <libxml/parser.h>
17 #include <libxml/tree.h>
18 #include <libxml/xinclude.h>
19 #include <libxml/xmlIO.h>
20 
21 #ifdef LIBXML_XINCLUDE_ENABLED
22 static const char *result = "<list><people>a</people><people>b</people></list>";
23 static const char *cur = NULL;
24 static int rlen;
25 
26 /**
27  * sqlMatch:
28  * @URI: an URI to test
29  *
30  * Check for an sql: query
31  *
32  * Returns 1 if yes and 0 if another Input module should be used
33  */
34 static int
sqlMatch(const char * URI)35 sqlMatch(const char * URI) {
36     if ((URI != NULL) && (!strncmp(URI, "sql:", 4)))
37         return(1);
38     return(0);
39 }
40 
41 /**
42  * sqlOpen:
43  * @URI: an URI to test
44  *
45  * Return a pointer to the sql: query handler, in this example simply
46  * the current pointer...
47  *
48  * Returns an Input context or NULL in case or error
49  */
50 static void *
sqlOpen(const char * URI)51 sqlOpen(const char * URI) {
52     if ((URI == NULL) || (strncmp(URI, "sql:", 4)))
53         return(NULL);
54     cur = result;
55     rlen = strlen(result);
56     return((void *) cur);
57 }
58 
59 /**
60  * sqlClose:
61  * @context: the read context
62  *
63  * Close the sql: query handler
64  *
65  * Returns 0 or -1 in case of error
66  */
67 static int
sqlClose(void * context)68 sqlClose(void * context) {
69     if (context == NULL) return(-1);
70     cur = NULL;
71     rlen = 0;
72     return(0);
73 }
74 
75 /**
76  * sqlRead:
77  * @context: the read context
78  * @buffer: where to store data
79  * @len: number of bytes to read
80  *
81  * Implement an sql: query read.
82  *
83  * Returns the number of bytes read or -1 in case of error
84  */
85 static int
sqlRead(void * context,char * buffer,int len)86 sqlRead(void * context, char * buffer, int len) {
87    const char *ptr = (const char *) context;
88 
89    if ((context == NULL) || (buffer == NULL) || (len < 0))
90        return(-1);
91 
92    if (len > rlen) len = rlen;
93    memcpy(buffer, ptr, len);
94    rlen -= len;
95    return(len);
96 }
97 
98 const char *include = "<?xml version='1.0'?>\n\
99 <document xmlns:xi=\"http://www.w3.org/2003/XInclude\">\n\
100   <p>List of people:</p>\n\
101   <xi:include href=\"sql:select_name_from_people\"/>\n\
102 </document>\n";
103 
main(void)104 int main(void) {
105     xmlDocPtr doc;
106 
107     /*
108      * this initialize the library and check potential ABI mismatches
109      * between the version it was compiled for and the actual shared
110      * library used.
111      */
112     LIBXML_TEST_VERSION
113 
114     /*
115      * register the new I/O handlers
116      */
117     if (xmlRegisterInputCallbacks(sqlMatch, sqlOpen, sqlRead, sqlClose) < 0) {
118         fprintf(stderr, "failed to register SQL handler\n");
119 	exit(1);
120     }
121     /*
122      * parse include into a document
123      */
124     doc = xmlReadMemory(include, strlen(include), "include.xml", NULL, 0);
125     if (doc == NULL) {
126         fprintf(stderr, "failed to parse the including file\n");
127 	exit(1);
128     }
129 
130     /*
131      * apply the XInclude process, this should trigger the I/O just
132      * registered.
133      */
134     if (xmlXIncludeProcess(doc) <= 0) {
135         fprintf(stderr, "XInclude processing failed\n");
136 	exit(1);
137     }
138 
139 #ifdef LIBXML_OUTPUT_ENABLED
140     /*
141      * save the output for checking to stdout
142      */
143     xmlDocDump(stdout, doc);
144 #endif
145 
146     /*
147      * Free the document
148      */
149     xmlFreeDoc(doc);
150 
151     /*
152      * Cleanup function for the XML library.
153      */
154     xmlCleanupParser();
155     /*
156      * this is to debug memory for regression tests
157      */
158     xmlMemoryDump();
159     return(0);
160 }
161 #else
main(void)162 int main(void) {
163     fprintf(stderr, "XInclude support not compiled in\n");
164     exit(1);
165 }
166 #endif
167