libcurl：如何下载原始文件名的URL？ (相当于“-O / – remote-name”)

http://tnerual.eriogerg.free.fr/vimqrc.pdf)

http://get.adobe.com/reader/download/?installer=Reader_10.1_Basque_for_Windows&standalone=1%22

//invoked as ./a.out #include #include char *location = "/tmp/test/out";size_t write_data(void *ptr, size_t size, size_t nmemb, FILE *stream) { size_t written = fwrite(ptr, size, nmemb, stream); return written; }int main(int argc, char *argv[]){ CURL *curl; CURLcode res; int ret = -1; if (argc!= 2) { //invoked as ./a.out  return -1; } curl = curl_easy_init(); if (!curl) { goto bail; } FILE *fp = fopen(location, "wb"); curl_easy_setopt(curl, CURLOPT_URL, argv[1]); //invoked as ./a.out  /* example.com is redirected, so we tell libcurl to follow redirection */ curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data); curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp); /* Perform the request, res will get the return code */ res = curl_easy_perform(curl); /* Check for errors */ if(res != CURLE_OK) fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res)); /* always cleanup */ curl_easy_cleanup(curl); ret = 0; fclose(fp); bail: return ret; }

我在libcurl源代码中找到了答案.看起来“远程名称”是标题中“content-disposition”标记的一部分. Libcurl正在解析标头并在content-disposition标签中查找“filename =”.此解析在通过CURLOPT_HEADERFUNCTION选项提供的回调中完成.最后,在写入数据的回调中(通过CURLOPT_WRITEFUNCTION提供),此远程名称用于创建输出文件.

如果缺少文件名,它只是从URL本身中找出它.这是从lib curl复制的相当多的代码,并且对我自己的修改很少,以使其更简单并符合我的要求.

#define _GNU_SOURCE #include #include #include #include #include #include typedef unsigned long uint64_t;typedef struct { char dnld_remote_fname[4096]; char dnld_url[4096]; FILE *dnld_stream; FILE *dbg_stream; uint64_t dnld_file_sz; } dnld_params_t;static int get_oname_from_cd(char const*const cd, char *oname){ char const*const cdtag = "Content-disposition:"; char const*const key = "filename="; int ret = 0; char *val = NULL; /* Example Content-Disposition: filename=name1367; charset=funny; option=strange */ /* If filename is present */ val = strcasestr(cd, key); if (!val) { printf("No key-value for \"%s\" in \"%s\"", key, cdtag); goto bail; } /* Move to value */ val += strlen(key); /* Copy value as oname */ while (*val != '\0' && *val != ';') { //printf (".... %c\n", *val); *oname++ = *val++; } *oname = '\0'; bail: return ret; }static int get_oname_from_url(char const* url, char *oname){ int ret = 0; char const *u = url; /* Remove "http(s)://" */ u = strstr(u, "://"); if (u) { u += strlen("://"); } u = strrchr(u, '/'); /* Remove last '/' */ u++; /* Copy value as oname */ while (*u != '\0') { //printf (".... %c\n", *u); *oname++ = *u++; } *oname = '\0'; return ret; }size_t dnld_header_parse(void *hdr, size_t size, size_t nmemb, void *userdata){ const size_t cb = size * nmemb; const char *hdr_str= hdr; dnld_params_t *dnld_params = (dnld_params_t*)userdata; char const*const cdtag = "Content-disposition:"; /* Example: * ... * Content-Type: text/html * Content-Disposition: filename=name1367; charset=funny; option=strange */ if (strstr(hdr_str, "Content-disposition:")) { printf ("has c-d: %s\n", hdr_str); } if (!strncasecmp(hdr_str, cdtag, strlen(cdtag))) { printf ("Found c-d: %s\n", hdr_str); int ret = get_oname_from_cd(hdr_str+strlen(cdtag), dnld_params->dnld_remote_fname); if (ret) { printf("ERR: bad remote name"); } } return cb; } FILE* get_dnld_stream(char const*const fname) { char const*const pre = "/tmp/"; char out[4096]; snprintf(out, sizeof(out), "%s/%s", pre, fname); FILE *fp = fopen(out, "wb"); if (!fp) { printf ("Could not create file %s\n", out); } return fp; }size_t write_cb(void *buffer, size_t sz, size_t nmemb, void *userdata){ int ret = 0; dnld_params_t *dnld_params = (dnld_params_t*)userdata; if (!dnld_params->dnld_remote_fname[0]) { ret = get_oname_from_url(dnld_params->dnld_url, dnld_params->dnld_remote_fname); } if (!dnld_params->dnld_stream) { dnld_params->dnld_stream = get_dnld_stream(dnld_params->dnld_remote_fname); } ret = fwrite(buffer, sz, nmemb, dnld_params->dnld_stream); if (ret == (sz*nmemb)) { dnld_params->dnld_file_sz += ret; } return ret; }int download_url(char const*const url){ CURL *curl; int ret = -1; CURLcode cerr = CURLE_OK; dnld_params_t dnld_params; memset(&dnld_params, 0, sizeof(dnld_params)); strncpy(dnld_params.dnld_url, url, strlen(url)); curl = curl_easy_init(); if (!curl) { goto bail; } cerr = curl_easy_setopt(curl, CURLOPT_URL, url); if (cerr) { printf ("%s: failed with err %d\n", "URL", cerr); goto bail;} cerr = curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, dnld_header_parse); if (cerr) { printf ("%s: failed with err %d\n", "HEADER", cerr); goto bail;} cerr = curl_easy_setopt(curl, CURLOPT_HEADERDATA, &dnld_params); if (cerr) { printf ("%s: failed with err %d\n", "HEADER DATA", cerr); goto bail;} cerr = curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_cb); if (cerr) { printf ("%s: failed with err %d\n", "WR CB", cerr); goto bail;} cerr = curl_easy_setopt(curl, CURLOPT_WRITEDATA, &dnld_params); if (cerr) { printf ("%s: failed with err %d\n", "WR Data", cerr); goto bail;} cerr = curl_easy_perform(curl); if(cerr != CURLE_OK) { fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(cerr)); } printf ("Remote name: %s\n", dnld_params.dnld_remote_fname); fclose(dnld_params.dnld_stream); /* always cleanup */ curl_easy_cleanup(curl); ret = 0; printf ("file size : %lu\n", dnld_params.dnld_file_sz); bail: return ret; }int main(int argc, char *argv[]){ if (argc != 2) { printf ("Bad args\n"); return -1; } return download_url(argv[1]); }