summaryrefslogtreecommitdiff
path: root/docs/examples/htmltitle.cpp
blob: e31e3e3210ea5c385cebf5f98309127a594705a1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ***************************************************************************/
/* <DESC>
 * Get a web page, extract the title with libxml.
 * </DESC>

 Written by Lars Nilsson

 GNU C++ compile command line suggestion (edit paths accordingly):

 g++ -Wall -I/opt/curl/include -I/opt/libxml/include/libxml2 htmltitle.cpp \
 -o htmltitle -L/opt/curl/lib -L/opt/libxml/lib -lcurl -lxml2
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <string>
#include <curl/curl.h>
#include <libxml/HTMLparser.h>

//
//  Case-insensitive string comparison
//

#ifdef _MSC_VER
#define COMPARE(a, b) (!_stricmp((a), (b)))
#else
#define COMPARE(a, b) (!strcasecmp((a), (b)))
#endif

//
//  libxml callback context structure
//

struct Context
{
  Context(): addTitle(false) { }

  bool addTitle;
  std::string title;
};

//
//  libcurl variables for error strings and returned data

static char errorBuffer[CURL_ERROR_SIZE];
static std::string buffer;

//
//  libcurl write callback function
//

static int writer(char *data, size_t size, size_t nmemb,
                  std::string *writerData)
{
  if(writerData == NULL)
    return 0;

  writerData->append(data, size*nmemb);

  return size * nmemb;
}

//
//  libcurl connection initialization
//

static bool init(CURL *&conn, char *url)
{
  CURLcode code;

  conn = curl_easy_init();

  if(conn == NULL) {
    fprintf(stderr, "Failed to create CURL connection\n");
    exit(EXIT_FAILURE);
  }

  code = curl_easy_setopt(conn, CURLOPT_ERRORBUFFER, errorBuffer);
  if(code != CURLE_OK) {
    fprintf(stderr, "Failed to set error buffer [%d]\n", code);
    return false;
  }

  code = curl_easy_setopt(conn, CURLOPT_URL, url);
  if(code != CURLE_OK) {
    fprintf(stderr, "Failed to set URL [%s]\n", errorBuffer);
    return false;
  }

  code = curl_easy_setopt(conn, CURLOPT_FOLLOWLOCATION, 1L);
  if(code != CURLE_OK) {
    fprintf(stderr, "Failed to set redirect option [%s]\n", errorBuffer);
    return false;
  }

  code = curl_easy_setopt(conn, CURLOPT_WRITEFUNCTION, writer);
  if(code != CURLE_OK) {
    fprintf(stderr, "Failed to set writer [%s]\n", errorBuffer);
    return false;
  }

  code = curl_easy_setopt(conn, CURLOPT_WRITEDATA, &buffer);
  if(code != CURLE_OK) {
    fprintf(stderr, "Failed to set write data [%s]\n", errorBuffer);
    return false;
  }

  return true;
}

//
//  libxml start element callback function
//

static void StartElement(void *voidContext,
                         const xmlChar *name,
                         const xmlChar **attributes)
{
  Context *context = static_cast<Context *>(voidContext);

  if(COMPARE(reinterpret_cast<char *>(name), "TITLE")) {
    context->title = "";
    context->addTitle = true;
  }
  (void) attributes;
}

//
//  libxml end element callback function
//

static void EndElement(void *voidContext,
                       const xmlChar *name)
{
  Context *context = static_cast<Context *>(voidContext);

  if(COMPARE(reinterpret_cast<char *>(name), "TITLE"))
    context->addTitle = false;
}

//
//  Text handling helper function
//

static void handleCharacters(Context *context,
                             const xmlChar *chars,
                             int length)
{
  if(context->addTitle)
    context->title.append(reinterpret_cast<char *>(chars), length);
}

//
//  libxml PCDATA callback function
//

static void Characters(void *voidContext,
                       const xmlChar *chars,
                       int length)
{
  Context *context = static_cast<Context *>(voidContext);

  handleCharacters(context, chars, length);
}

//
//  libxml CDATA callback function
//

static void cdata(void *voidContext,
                  const xmlChar *chars,
                  int length)
{
  Context *context = static_cast<Context *>(voidContext);

  handleCharacters(context, chars, length);
}

//
//  libxml SAX callback structure
//

static htmlSAXHandler saxHandler =
{
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  StartElement,
  EndElement,
  NULL,
  Characters,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  cdata,
  NULL
};

//
//  Parse given (assumed to be) HTML text and return the title
//

static void parseHtml(const std::string &html,
                      std::string &title)
{
  htmlParserCtxtPtr ctxt;
  Context context;

  ctxt = htmlCreatePushParserCtxt(&saxHandler, &context, "", 0, "",
                                  XML_CHAR_ENCODING_NONE);

  htmlParseChunk(ctxt, html.c_str(), html.size(), 0);
  htmlParseChunk(ctxt, "", 0, 1);

  htmlFreeParserCtxt(ctxt);

  title = context.title;
}

int main(int argc, char *argv[])
{
  CURL *conn = NULL;
  CURLcode code;
  std::string title;

  // Ensure one argument is given

  if(argc != 2) {
    fprintf(stderr, "Usage: %s <url>\n", argv[0]);
    exit(EXIT_FAILURE);
  }

  curl_global_init(CURL_GLOBAL_DEFAULT);

  // Initialize CURL connection

  if(!init(conn, argv[1])) {
    fprintf(stderr, "Connection initializion failed\n");
    exit(EXIT_FAILURE);
  }

  // Retrieve content for the URL

  code = curl_easy_perform(conn);
  curl_easy_cleanup(conn);

  if(code != CURLE_OK) {
    fprintf(stderr, "Failed to get '%s' [%s]\n", argv[1], errorBuffer);
    exit(EXIT_FAILURE);
  }

  // Parse the (assumed) HTML code
  parseHtml(buffer, title);

  // Display the extracted title
  printf("Title: %s\n", title.c_str());

  return EXIT_SUCCESS;
}