xmlstream: XML stream parsing example source code

Add an XML stream parsing example using Expat. Add missing ignore for
the binary from an unrelated example.

docs/examples/.gitignore

@@ -43,3 +43,5 @@ simplessl
 smtp-multi
 smtp-tls
 url2file
+usercertinmem
+xmlstream

docs/examples/README

@@ -78,4 +78,5 @@ simplepost.c   - HTTP POST
 simplessl.c    - HTTPS example with certificates many options set
 synctime.c     - Sync local time by extracting date from remote HTTP servers
 url2file.c     - download a document and store it in a file
+xmlstream.c    - Stream-parse a document using the streaming Expat parser
 10-at-a-time.c - Download many files simultaneously, 10 at a time.

docs/examples/xmlstream.c

@@ -0,0 +1,158 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2013, 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 http://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.
+ *
+ ***************************************************************************/
+/* Stream-parse a document using the streaming Expat parser.
+ * Written by David Strauss
+ *
+ * Expat => http://www.libexpat.org/
+ *
+ * gcc -Wall -I/usr/local/include xmlstream.c -lcurl -lexpat -o xmlstream
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#include <expat.h>
+#include <curl/curl.h>
+
+struct MemoryStruct {
+  char *memory;
+  size_t size;
+};
+
+struct ParserStruct {
+  int ok;
+  size_t tags;
+  size_t depth;
+  struct MemoryStruct characters;
+};
+
+static void startElement(void *userData, const XML_Char *name, const XML_Char **atts)
+{
+  struct ParserStruct *state = (struct ParserStruct *) userData;
+  state->tags++;
+  state->depth++;
+
+  /* Get a clean slate for reading in character data. */
+  free(state->characters.memory);
+  state->characters.memory = NULL;
+  state->characters.size = 0;
+}
+
+static void characterDataHandler(void *userData, const XML_Char *s, int len)
+{
+  struct ParserStruct *state = (struct ParserStruct *) userData;
+  struct MemoryStruct *mem = &state->characters;
+
+  mem->memory = realloc(mem->memory, mem->size + len + 1);
+  if(mem->memory == NULL) {
+    /* Out of memory. */
+    fprintf(stderr, "Not enough memory (realloc returned NULL).\n");
+    state->ok = 0;
+    return;
+  }
+
+  memcpy(&(mem->memory[mem->size]), s, len);
+  mem->size += len;
+  mem->memory[mem->size] = 0;
+}
+
+static void endElement(void *userData, const XML_Char *name)
+{
+  struct ParserStruct *state = (struct ParserStruct *) userData;
+  state->depth--;
+
+  printf("%5lu   %10lu   %s\n", state->depth, state->characters.size, name);
+}
+
+static size_t parseStreamCallback(void *contents, size_t length, size_t nmemb, void *userp)
+{
+  XML_Parser parser = (XML_Parser) userp;
+  size_t real_size = length * nmemb;
+  struct ParserStruct *state = (struct ParserStruct *) XML_GetUserData(parser);
+
+  /* Only parse if we're not already in a failure state. */
+  if (state->ok && XML_Parse(parser, contents, real_size, 0) == 0) {
+    int error_code = XML_GetErrorCode(parser);
+    fprintf(stderr, "Parsing response buffer of length %lu failed with error code %d (%s).\n",
+            real_size, error_code, XML_ErrorString(error_code));
+    state->ok = 0;
+  }
+
+  return real_size;
+}
+
+int main(void)
+{
+  CURL *curl_handle;
+  CURLcode res;
+  XML_Parser parser;
+  struct ParserStruct state;
+
+  /* Initialize the state structure for parsing. */
+  memset(&state, 0, sizeof(struct ParserStruct));
+  state.ok = 1;
+
+  /* Initialize a namespace-aware parser. */
+  parser = XML_ParserCreateNS(NULL, '\0');
+  XML_SetUserData(parser, &state);
+  XML_SetElementHandler(parser, startElement, endElement);
+  XML_SetCharacterDataHandler(parser, characterDataHandler);
+
+  /* Initalize a libcurl handle. */
+  curl_global_init(CURL_GLOBAL_ALL ^ CURL_GLOBAL_SSL);
+  curl_handle = curl_easy_init();
+  curl_easy_setopt(curl_handle, CURLOPT_URL, "http://www.w3schools.com/xml/simple.xml");
+  curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, parseStreamCallback);
+  curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, (void *)parser);
+
+  printf("Depth   Characters   Closing Tag\n");
+
+  /* Perform the request and any follow-up parsing. */
+  res = curl_easy_perform(curl_handle);
+  if(res != CURLE_OK) {
+    fprintf(stderr, "curl_easy_perform() failed: %s\n",
+            curl_easy_strerror(res));
+  }
+  else if (state.ok) {
+    /* Expat requires one final call to finalize parsing. */
+    if (XML_Parse(parser, NULL, 0, 1) == 0) {
+      int error_code = XML_GetErrorCode(parser);
+      fprintf(stderr, "Finalizing parsing failed with error code %d (%s).\n",
+              error_code, XML_ErrorString(error_code));
+    }
+    else {
+      printf("                     --------------\n");
+      printf("                     %lu tags total\n", state.tags);
+    }
+  }
+
+  /* Clean up. */
+  free(state.characters.memory);
+  XML_ParserFree(parser);
+  curl_easy_cleanup(curl_handle);
+  curl_global_cleanup();
+
+  return 0;
+}