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1 /***************************************************************************
2  *                                  _   _ ____  _
3  *  Project                     ___| | | |  _ \| |
4  *                             / __| | | | |_) | |
5  *                            | (__| |_| |  _ <| |___
6  *                             \___|\___/|_| \_\_____|
7  *
8  * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
9  *
10  * This software is licensed as described in the file COPYING, which
11  * you should have received as part of this distribution. The terms
12  * are also available at https://curl.haxx.se/docs/copyright.html.
13  *
14  * You may opt to use, copy, modify, merge, publish, distribute and/or sell
15  * copies of the Software, and permit persons to whom the Software is
16  * furnished to do so, under the terms of the COPYING file.
17  *
18  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
19  * KIND, either express or implied.
20  *
21  ***************************************************************************/
22 /* <DESC>
23  * Stream-parse a document using the streaming Expat parser.
24  * </DESC>
25  */
26 /* Written by David Strauss
27  *
28  * Expat => http://www.libexpat.org/
29  *
30  * gcc -Wall -I/usr/local/include xmlstream.c -lcurl -lexpat -o xmlstream
31  *
32  */
33 
34 #include <stdio.h>
35 #include <stdlib.h>
36 #include <string.h>
37 #include <assert.h>
38 
39 #include <expat.h>
40 #include <curl/curl.h>
41 
42 struct MemoryStruct {
43   char *memory;
44   size_t size;
45 };
46 
47 struct ParserStruct {
48   int ok;
49   size_t tags;
50   size_t depth;
51   struct MemoryStruct characters;
52 };
53 
startElement(void * userData,const XML_Char * name,const XML_Char ** atts)54 static void startElement(void *userData, const XML_Char *name,
55                          const XML_Char **atts)
56 {
57   struct ParserStruct *state = (struct ParserStruct *) userData;
58   state->tags++;
59   state->depth++;
60 
61   /* Get a clean slate for reading in character data. */
62   free(state->characters.memory);
63   state->characters.memory = NULL;
64   state->characters.size = 0;
65 }
66 
characterDataHandler(void * userData,const XML_Char * s,int len)67 static void characterDataHandler(void *userData, const XML_Char *s, int len)
68 {
69   struct ParserStruct *state = (struct ParserStruct *) userData;
70   struct MemoryStruct *mem = &state->characters;
71 
72   mem->memory = realloc(mem->memory, mem->size + len + 1);
73   if(mem->memory == NULL) {
74     /* Out of memory. */
75     fprintf(stderr, "Not enough memory (realloc returned NULL).\n");
76     state->ok = 0;
77     return;
78   }
79 
80   memcpy(&(mem->memory[mem->size]), s, len);
81   mem->size += len;
82   mem->memory[mem->size] = 0;
83 }
84 
endElement(void * userData,const XML_Char * name)85 static void endElement(void *userData, const XML_Char *name)
86 {
87   struct ParserStruct *state = (struct ParserStruct *) userData;
88   state->depth--;
89 
90   printf("%5lu   %10lu   %s\n", state->depth, state->characters.size, name);
91 }
92 
parseStreamCallback(void * contents,size_t length,size_t nmemb,void * userp)93 static size_t parseStreamCallback(void *contents, size_t length, size_t nmemb,
94                                   void *userp)
95 {
96   XML_Parser parser = (XML_Parser) userp;
97   size_t real_size = length * nmemb;
98   struct ParserStruct *state = (struct ParserStruct *) XML_GetUserData(parser);
99 
100   /* Only parse if we're not already in a failure state. */
101   if(state->ok && XML_Parse(parser, contents, real_size, 0) == 0) {
102     int error_code = XML_GetErrorCode(parser);
103     fprintf(stderr, "Parsing response buffer of length %lu failed"
104             " with error code %d (%s).\n",
105             real_size, error_code, XML_ErrorString(error_code));
106     state->ok = 0;
107   }
108 
109   return real_size;
110 }
111 
main(void)112 int main(void)
113 {
114   CURL *curl_handle;
115   CURLcode res;
116   XML_Parser parser;
117   struct ParserStruct state;
118 
119   /* Initialize the state structure for parsing. */
120   memset(&state, 0, sizeof(struct ParserStruct));
121   state.ok = 1;
122 
123   /* Initialize a namespace-aware parser. */
124   parser = XML_ParserCreateNS(NULL, '\0');
125   XML_SetUserData(parser, &state);
126   XML_SetElementHandler(parser, startElement, endElement);
127   XML_SetCharacterDataHandler(parser, characterDataHandler);
128 
129   /* Initialize a libcurl handle. */
130   curl_global_init(CURL_GLOBAL_ALL ^ CURL_GLOBAL_SSL);
131   curl_handle = curl_easy_init();
132   curl_easy_setopt(curl_handle, CURLOPT_URL,
133                    "http://www.w3schools.com/xml/simple.xml");
134   curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, parseStreamCallback);
135   curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, (void *)parser);
136 
137   printf("Depth   Characters   Closing Tag\n");
138 
139   /* Perform the request and any follow-up parsing. */
140   res = curl_easy_perform(curl_handle);
141   if(res != CURLE_OK) {
142     fprintf(stderr, "curl_easy_perform() failed: %s\n",
143             curl_easy_strerror(res));
144   }
145   else if(state.ok) {
146     /* Expat requires one final call to finalize parsing. */
147     if(XML_Parse(parser, NULL, 0, 1) == 0) {
148       int error_code = XML_GetErrorCode(parser);
149       fprintf(stderr, "Finalizing parsing failed with error code %d (%s).\n",
150               error_code, XML_ErrorString(error_code));
151     }
152     else {
153       printf("                     --------------\n");
154       printf("                     %lu tags total\n", state.tags);
155     }
156   }
157 
158   /* Clean up. */
159   free(state.characters.memory);
160   XML_ParserFree(parser);
161   curl_easy_cleanup(curl_handle);
162   curl_global_cleanup();
163 
164   return 0;
165 }
166