added simple chkspeed sample.

docs/examples/chkspeed.c

+/*****************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * $Id$
+ *
+ * Example source code to show how the callback function can be used to
+ * download data into a chunk of memory instead of storing it in a file.
+ * After successful download we use curl_easy_getinfo() calls to get the
+ * amount of downloaded bytes, the time used for the whole download, and
+ * the average download speed.
+ * On Linux you can create the download test files with:
+ * dd if=/dev/urandom of=file_1M.bin bs=1M count=1
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#include <curl/curl.h>
+#include <curl/types.h>
+#include <curl/easy.h>
+
+#define URL_BASE "http://speedtest.your.domain/"
+#define URL_1M   URL_BASE "file_1M.bin"
+#define URL_2M   URL_BASE "file_2M.bin"
+#define URL_5M   URL_BASE "file_5M.bin"
+#define URL_10M  URL_BASE "file_10M.bin"
+#define URL_20M  URL_BASE "file_20M.bin"
+#define URL_50M  URL_BASE "file_50M.bin"
+#define URL_100M URL_BASE "file_100M.bin"
+
+#define CHKSPEED_VERSION "1.0"
+
+static size_t WriteCallback(void *ptr, size_t size, size_t nmemb, void *data)
+{
+  /* we are not interested in the downloaded bytes itself,
+     so we only return the size we would have saved ... */  
+  return (size_t)(size * nmemb);
+}
+
+int main(int argc, char *argv[])
+{
+  CURL *curl_handle;
+  CURLcode res;
+  int prtsep = 0, prttime = 0;
+  char *url = URL_1M;
+  char *appname = argv[0];
+
+  if (argc > 1) {
+    /* parse input parameters */
+    for (argc--, argv++; *argv; argc--, argv++) {
+      if (strncasecmp(*argv, "-", 1) == 0) {
+        if (strncasecmp(*argv, "-H", 2) == 0) {
+          fprintf(stderr, 
+                  "\rUsage: %s [-m=1|2|5|10|20|50|100] [-t] [-x] [url]\n",
+                  appname);
+          exit(1);
+        } else if (strncasecmp(*argv, "-V", 2) == 0) {
+          fprintf(stderr, "\r%s %s - %s\n",
+                  appname, CHKSPEED_VERSION, curl_version());
+          exit(1);
+        } else if (strncasecmp(*argv, "-X", 2) == 0) {
+          prtsep = 1;
+        } else if (strncasecmp(*argv, "-T", 2) == 0) {
+          prttime = 1;
+        } else if (strncasecmp(*argv, "-M=", 3) == 0) {
+          int m = atoi(*argv + 3);
+          switch(m) {
+            case   1: url = URL_1M;
+                      break;
+            case   2: url = URL_2M;
+                      break;
+            case   5: url = URL_5M;
+                      break;
+            case  10: url = URL_10M;
+                      break;
+            case  20: url = URL_20M;
+                      break;
+            case  50: url = URL_50M;
+                      break;
+            case 100: url = URL_100M;
+                      break;
+            default:  fprintf(stderr, "\r%s: invalid parameter %s\n",
+                              appname, *argv + 3);
+                      exit(1);
+          }
+        } else {
+          fprintf(stderr, "\r%s: invalid or unknown option %s\n",
+                  appname, *argv);
+          exit(1);
+        }
+      } else {
+        url = *argv;
+      }
+    }
+  }
+
+  /* print separator line */
+  if (prtsep) {
+    printf("-------------------------------------------------\n");
+  }
+  /* print localtime */
+  if (prttime) {
+    time_t t = time(NULL);
+    printf("Localtime: %s", ctime(&t));
+  }
+
+  /* init libcurl */
+  curl_global_init(CURL_GLOBAL_ALL);
+
+  /* init the curl session */
+  curl_handle = curl_easy_init();
+
+  /* specify URL to get */
+  curl_easy_setopt(curl_handle, CURLOPT_URL, url);
+
+  /* send all data to this function  */
+  curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, WriteCallback);
+
+  /* some servers don't like requests that are made without a user-agent
+     field, so we provide one */
+  curl_easy_setopt(curl_handle, CURLOPT_USERAGENT,
+                   "libcurl-speedchecker/" CHKSPEED_VERSION);
+
+  /* get it! */
+  res = curl_easy_perform(curl_handle);
+
+  if(CURLE_OK == res) {
+    double val;
+
+    /* check for bytes downloaded */
+    res = curl_easy_getinfo(curl_handle, CURLINFO_SIZE_DOWNLOAD, &val);
+    if((CURLE_OK == res) && val)
+      printf("Data downloaded: %0.0f bytes.\n", val);
+
+    /* check for total download time */
+    res = curl_easy_getinfo(curl_handle, CURLINFO_TOTAL_TIME, &val);
+    if((CURLE_OK == res) && val)
+      printf("Total download time: %0.3f sec.\n", val);
+
+    /* check for average download speed */
+    res = curl_easy_getinfo(curl_handle, CURLINFO_SPEED_DOWNLOAD, &val);
+    if((CURLE_OK == res) && val)
+      printf("Average download speed: %0.3f kbyte/sec.\n", val / 1024);
+
+  } else {
+    printf("Errror while fetching '%s' : %s\n", url, curl_easy_strerror(res));
+  }
+
+  /* cleanup curl stuff */
+  curl_easy_cleanup(curl_handle);
+
+  /* we're done with libcurl, so clean it up */
+  curl_global_cleanup();
+
+  return 0;
+}