1 /***************************************************************************
2 * _ _ ____ _
3 * Project ___| | | | _ \| |
4 * / __| | | | |_) | |
5 * | (__| |_| | _ <| |___
6 * \___|\___/|_| \_\_____|
7 *
8 * Copyright (C) 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.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 * SPDX-License-Identifier: curl
22 *
23 ***************************************************************************/
24 /* <DESC>
25 * Stream-parse a document using the streaming Expat parser.
26 * </DESC>
27 */
28 /* Written by David Strauss
29 *
30 * Expat => https://libexpat.github.io/
31 *
32 * gcc -Wall -I/usr/local/include xmlstream.c -lcurl -lexpat -o xmlstream
33 *
34 */
35
36 #include <stdio.h>
37 #include <stdlib.h>
38 #include <string.h>
39 #include <assert.h>
40
41 #include <expat.h>
42 #include <curl/curl.h>
43
44 struct MemoryStruct {
45 char *memory;
46 size_t size;
47 };
48
49 struct ParserStruct {
50 int ok;
51 size_t tags;
52 size_t depth;
53 struct MemoryStruct characters;
54 };
55
startElement(void * userData,const XML_Char * name,const XML_Char ** atts)56 static void startElement(void *userData, const XML_Char *name,
57 const XML_Char **atts)
58 {
59 struct ParserStruct *state = (struct ParserStruct *) userData;
60 state->tags++;
61 state->depth++;
62
63 /* Get a clean slate for reading in character data. */
64 free(state->characters.memory);
65 state->characters.memory = NULL;
66 state->characters.size = 0;
67 }
68
characterDataHandler(void * userData,const XML_Char * s,int len)69 static void characterDataHandler(void *userData, const XML_Char *s, int len)
70 {
71 struct ParserStruct *state = (struct ParserStruct *) userData;
72 struct MemoryStruct *mem = &state->characters;
73
74 char *ptr = realloc(mem->memory, mem->size + len + 1);
75 if(!ptr) {
76 /* Out of memory. */
77 fprintf(stderr, "Not enough memory (realloc returned NULL).\n");
78 state->ok = 0;
79 return;
80 }
81
82 mem->memory = ptr;
83 memcpy(&(mem->memory[mem->size]), s, len);
84 mem->size += len;
85 mem->memory[mem->size] = 0;
86 }
87
endElement(void * userData,const XML_Char * name)88 static void endElement(void *userData, const XML_Char *name)
89 {
90 struct ParserStruct *state = (struct ParserStruct *) userData;
91 state->depth--;
92
93 printf("%5lu %10lu %s\n", state->depth, state->characters.size, name);
94 }
95
parseStreamCallback(void * contents,size_t length,size_t nmemb,void * userp)96 static size_t parseStreamCallback(void *contents, size_t length, size_t nmemb,
97 void *userp)
98 {
99 XML_Parser parser = (XML_Parser) userp;
100 size_t real_size = length * nmemb;
101 struct ParserStruct *state = (struct ParserStruct *) XML_GetUserData(parser);
102
103 /* Only parse if we are not already in a failure state. */
104 if(state->ok && XML_Parse(parser, contents, real_size, 0) == 0) {
105 int error_code = XML_GetErrorCode(parser);
106 fprintf(stderr, "Parsing response buffer of length %lu failed"
107 " with error code %d (%s).\n",
108 real_size, error_code, XML_ErrorString(error_code));
109 state->ok = 0;
110 }
111
112 return real_size;
113 }
114
main(void)115 int main(void)
116 {
117 CURL *curl_handle;
118 CURLcode res;
119 XML_Parser parser;
120 struct ParserStruct state;
121
122 /* Initialize the state structure for parsing. */
123 memset(&state, 0, sizeof(struct ParserStruct));
124 state.ok = 1;
125
126 /* Initialize a namespace-aware parser. */
127 parser = XML_ParserCreateNS(NULL, '\0');
128 XML_SetUserData(parser, &state);
129 XML_SetElementHandler(parser, startElement, endElement);
130 XML_SetCharacterDataHandler(parser, characterDataHandler);
131
132 /* Initialize a libcurl handle. */
133 curl_global_init(CURL_GLOBAL_DEFAULT);
134 curl_handle = curl_easy_init();
135 curl_easy_setopt(curl_handle, CURLOPT_URL,
136 "https://www.w3schools.com/xml/simple.xml");
137 curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, parseStreamCallback);
138 curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, (void *)parser);
139
140 printf("Depth Characters Closing Tag\n");
141
142 /* Perform the request and any follow-up parsing. */
143 res = curl_easy_perform(curl_handle);
144 if(res != CURLE_OK) {
145 fprintf(stderr, "curl_easy_perform() failed: %s\n",
146 curl_easy_strerror(res));
147 }
148 else if(state.ok) {
149 /* Expat requires one final call to finalize parsing. */
150 if(XML_Parse(parser, NULL, 0, 1) == 0) {
151 int error_code = XML_GetErrorCode(parser);
152 fprintf(stderr, "Finalizing parsing failed with error code %d (%s).\n",
153 error_code, XML_ErrorString(error_code));
154 }
155 else {
156 printf(" --------------\n");
157 printf(" %lu tags total\n", state.tags);
158 }
159 }
160
161 /* Clean up. */
162 free(state.characters.memory);
163 XML_ParserFree(parser);
164 curl_easy_cleanup(curl_handle);
165 curl_global_cleanup();
166
167 return 0;
168 }
169