using libcurl to download files
July 25th, 2010
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this example shows how to use curl for downloading a file in c++ with a class and a progress callback.
this is pseudocode, means you need some header for this to work, etc 
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 | #define CURL_STATICLIB #include <stdio.h> #include <curl/curl.h> #include <curl/types.h> #include <curl/easy.h> #include <string> class MyClass; typedef struct job_info_t { int jobID; MyClass *parent; } struct job_info_t; int progress_callback(void *data, double download_total_size, double download_total_size_done, double ultotal, double uldone) { job_info_t *jinfo = (job_info_t *)data; if(!jinfo) return 1; jinfo->parent->reportProgress(jinfo->jobID, download_total_size, download_total_size_done); return 0; } void MyClass::reportProgress(int jobID, double download_total_size, double download_total_size_done) { printf("DLFile-%04d|progress: %0.3f\n", jobID, download_total_size_done / download_total_size); } int MyClass::downloadFile(int jobID, std::string localFile, string url) { job_info jinfo; jinfo.parent = this; jinfo.jobID = jobID; CURL *curl = curl_easy_init(); if(!curl) { printf("DLFile-%04d|error creating curl: %s\n", jobID, localFile.string().c_str()); printf("DLFile-%04d|download URL: %s\n", jobID, url.c_str()); return 1; } FILE *outFile = fopen(localFile.string().c_str(), "wb"); if(!outFile) { perror("error opening file"); printf("DLFile-%04d|error opening local file: %s.\n", jobID, localFile.string().c_str()); printf("DLFile-%04d|download URL: %s\n", jobID, url.c_str()); return 2; } char *curl_err_str[CURL_ERROR_SIZE]; memset(curl_err_str, 0, CURL_ERROR_SIZE); CURLcode res; curl_easy_setopt(curl, CURLOPT_URL, url.c_str()); // logging stuff // curl_easy_setopt(curl, CURLOPT_STDERR, InstallerLog::getSingleton()->getLogFilePtr()); curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, curl_err_str[0]); // progess stuff curl_easy_setopt(curl, CURLOPT_NOPROGRESS, 0); curl_easy_setopt(curl, CURLOPT_PROGRESSDATA, &jinfo); curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, &progress_callback); curl_easy_setopt(curl, CURLOPT_WRITEDATA, outFile); // http related settings curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1); // follow redirects curl_easy_setopt(curl, CURLOPT_AUTOREFERER, 1); // set the Referer: field in requests where it follows a Location: redirect. curl_easy_setopt(curl, CURLOPT_MAXREDIRS, 20); curl_easy_setopt(curl, CURLOPT_USERAGENT, "YourUserAgent"); curl_easy_setopt(curl, CURLOPT_FILETIME, 1); res = curl_easy_perform(curl); curl_easy_cleanup(curl); fclose(outFile); // print curl error if existing if(res != CURLE_OK) { printf("DLFile-%04d| CURL returned: %d\n", jobID, res); printf("DLFile-%04d| CURL error: %s\n", jobID, curl_err_str); return 3; } return 0; } |