在unique_ptr<>中使用自定义删除程序 (curl_formfree())
using custom deleter (curl_formfree()) in unique_ptr<>
我有下面的代码来使用 libcurl 发布文件。
bool FileUploadDownload::upload(const std::string& filename, const std::string& url) {
CURLcode res;
CURLFORMcode form_res;
curl_off_t speed_upload = 0;
struct curl_httppost* form_post = nullptr;
struct curl_httppost* last_ptr = nullptr;
struct curl_slist* header_list = nullptr;
static const char buf[] = "Expect: 100-continue";
std::string pure_fname = filename.substr(filename.find_last_of("/\") + 1);
res = curl_global_init(CURL_GLOBAL_ALL);
if (res != CURLE_OK) {
m_logger->errorf("curl_global_init(CURL_GLOBAL_ALL) failed: %s", curl_easy_strerror(res));
return false;
}
form_res = curl_formadd(&form_post,
&last_ptr,
CURLFORM_COPYNAME, "file",
CURLFORM_FILENAME, pure_fname.c_str(),
CURLFORM_FILE, filename.c_str(),
CURLFORM_CONTENTTYPE, "text/plain",
CURLFORM_END);
if (form_res != 0) {
m_logger->errorf("curl_formadd() failed: %s", curl_easy_strerror((CURLcode)form_res));
curl_formfree(form_post);
return false;
}
form_res = curl_formadd(&form_post,
&last_ptr,
CURLFORM_COPYNAME, "submit",
CURLFORM_COPYCONTENTS, "send",
CURLFORM_END);
if (form_res != 0) {
m_logger->errorf("curl_formadd() failed: %s", curl_easy_strerror((CURLcode)form_res));
curl_formfree(form_post);
return false;
}
if (m_curl) {
header_list = curl_slist_append(header_list, buf);
if(nullptr == header_list){
return false;
}
res = curl_easy_setopt(m_curl, CURLOPT_URL, url.c_str());
if (res != CURLE_OK) {
m_logger->errorf("curl_easy_setopt(CURLOPT_URL) failed: %s", curl_easy_strerror(res));
curl_formfree(form_post);
curl_slist_free_all(header_list);
return false;
}
res = curl_easy_setopt(m_curl, CURLOPT_HTTPHEADER, header_list);
if (res != CURLE_OK) {
m_logger->errorf("curl_easy_setopt(CURLOPT_HTTPHEADER) failed: %s", curl_easy_strerror(res));
curl_formfree(form_post);
curl_slist_free_all(header_list);
return false;
}
res = curl_easy_setopt(m_curl, CURLOPT_HTTPPOST, form_post);
if (res != CURLE_OK) {
m_logger->errorf("curl_easy_setopt(CURLOPT_HTTPPOST) failed: %s", curl_easy_strerror(res));
curl_formfree(form_post);
curl_slist_free_all(header_list);
return false;
}
res = curl_easy_setopt(m_curl, CURLOPT_VERBOSE, 1L);
if (res != CURLE_OK) {
m_logger->errorf("curl_easy_setopt(CURLOPT_VERBOSE) failed: %s", curl_easy_strerror(res));
curl_formfree(form_post);
curl_slist_free_all(header_list);
return false;
}
res = curl_easy_perform(m_curl);
if (res != CURLE_OK) {
m_logger->errorf("curl_easy_perform() failed: %s", curl_easy_strerror(res));
curl_formfree(form_post);
curl_slist_free_all(header_list);
return false;
}
res = curl_easy_getinfo(m_curl, CURLINFO_SPEED_UPLOAD, &speed_upload);
if (res != CURLE_OK) {
m_logger->errorf("curl_easy_getinfo(CURLINFO_SPEED_UPLOAD) failed: %s", curl_easy_strerror(res));
curl_formfree(form_post);
curl_slist_free_all(header_list);
return false;
}
m_logger->infof("Average upload speed: %" CURL_FORMAT_CURL_OFF_T
" megabyte/sec.n", speed_upload / (1024 * 1024));
curl_formfree(form_post);
curl_slist_free_all(header_list);
return true;
}
return false;
}
在很多情况下，上述函数失败并返回 false。在所有这些情况下，我需要打电话给curl_formfree()并curl_slist_free_all()。
我想使用std::unique_ptr<>来优化它
我已经重写了上面的函数，如下所示。
bool FileUploadDownload::upload(const std::string& filename, const std::string& url) {
CURLcode res;
CURLFORMcode form_res;
curl_off_t speed_upload = 0;
auto form_delete = [&](curl_httppost * p) {
curl_formfree(p);
};
//struct curl_httppost* form_post = nullptr;
//struct curl_httppost* last_ptr = nullptr;
std::unique_ptr<curl_httppost*, decltype(form_delete)> form_post;
std::unique_ptr<curl_httppost*, decltype(form_delete)> last_ptr;
struct curl_slist* header_list = nullptr;
static const char buf[] = "Expect: 100-continue";
std::string pure_fname = filename.substr(filename.find_last_of("/\") + 1);
res = curl_global_init(CURL_GLOBAL_ALL);
if (res != CURLE_OK) {
m_logger->errorf("curl_global_init(CURL_GLOBAL_ALL) failed: %s", curl_easy_strerror(res));
return false;
}
form_res = curl_formadd(form_post.get(),
last_ptr.get(),
CURLFORM_COPYNAME, "file",
CURLFORM_FILENAME, pure_fname.c_str(),
CURLFORM_FILE, filename.c_str(),
CURLFORM_CONTENTTYPE, "text/plain",
CURLFORM_END);
if (form_res != 0) {
m_logger->errorf("curl_formadd() failed: %s", curl_easy_strerror((CURLcode)form_res));
//curl_formfree(form_post);
return false;
}
form_res = curl_formadd(form_post.get(),
last_ptr.get(),
CURLFORM_COPYNAME, "submit",
CURLFORM_COPYCONTENTS, "send",
CURLFORM_END);
if (form_res != 0) {
m_logger->errorf("curl_formadd() failed: %s", curl_easy_strerror((CURLcode)form_res));
//curl_formfree(form_post);
return false;
}
if (m_curl) {
header_list = curl_slist_append(header_list, buf);
if(nullptr == header_list){
return false;
}
res = curl_easy_setopt(m_curl, CURLOPT_URL, url.c_str());
if (res != CURLE_OK) {
m_logger->errorf("curl_easy_setopt(CURLOPT_URL) failed: %s", curl_easy_strerror(res));
//curl_formfree(form_post);
curl_slist_free_all(header_list);
return false;
}
res = curl_easy_setopt(m_curl, CURLOPT_HTTPHEADER, header_list);
if (res != CURLE_OK) {
m_logger->errorf("curl_easy_setopt(CURLOPT_HTTPHEADER) failed: %s", curl_easy_strerror(res));
//curl_formfree(form_post);
curl_slist_free_all(header_list);
return false;
}
res = curl_easy_setopt(m_curl, CURLOPT_HTTPPOST, form_post.get());
if (res != CURLE_OK) {
m_logger->errorf("curl_easy_setopt(CURLOPT_HTTPPOST) failed: %s", curl_easy_strerror(res));
//curl_formfree(form_post);
curl_slist_free_all(header_list);
return false;
}
res = curl_easy_setopt(m_curl, CURLOPT_VERBOSE, 1L);
if (res != CURLE_OK) {
m_logger->errorf("curl_easy_setopt(CURLOPT_VERBOSE) failed: %s", curl_easy_strerror(res));
//curl_formfree(form_post);
curl_slist_free_all(header_list);
return false;
}
res = curl_easy_perform(m_curl);
if (res != CURLE_OK) {
m_logger->errorf("curl_easy_perform() failed: %s", curl_easy_strerror(res));
//curl_formfree(form_post);
curl_slist_free_all(header_list);
return false;
}
res = curl_easy_getinfo(m_curl, CURLINFO_SPEED_UPLOAD, &speed_upload);
if (res != CURLE_OK) {
m_logger->errorf("curl_easy_getinfo(CURLINFO_SPEED_UPLOAD) failed: %s", curl_easy_strerror(res));
//curl_formfree(form_post);
curl_slist_free_all(header_list);
return false;
}
m_logger->infof("Average upload speed: %" CURL_FORMAT_CURL_OFF_T
" megabyte/sec.n", speed_upload / (1024 * 1024));
//curl_formfree(form_post);
curl_slist_free_all(header_list);
return true;
}
return false;
}
我收到以下编译错误。
error: no match for call to ‘(std::unique_ptr<curl_httppost*, FileUploadDownload::upload(const string&, const string&)::<lambda(curl_httppost*)> >::deleter_type {aka FileUploadDownload::upload(const string&, const string&)::<lambda(curl_httppost*)>}) (curl_httppost**&)’
get_deleter()(__ptr);
你必须初始化指针。此外，lambda 的参数或指针的第一个参数也是错误的。unique_ptr需要它引用的类型，而删除程序接受指向该类型的指针。
std::unique_ptr<curl_httppost, decltype(form_delete)>
form_post( nullptr /* required by first call of curl_formadd */,
form_delete);
也许您想创建自己的"make"函数来用更少的代码构造这些指针。
curl_formadd需要访问指针进行初始化，并且它的第一个参数是curl_httppost**，因此使用.get()不会削减它。你要么必须使用中间指针(这违背了重构的目的？(，要么在这些指针周围创建一个包装器。注意，curl_formadd已弃用。尴尬的解决方法是管理指向指针的指针。
auto form_delete = [&](curl_httppost ** p) {
curl_formfree(*p);
delete p;
};
std::unique_ptr<curl_httppost*, decltype(form_delete)>
form_post( new curl_httppost*(nullptr) /* required by first call of curl_formadd */,
form_delete);
form_res = curl_formadd(form_post.get(),
这不会消除重置指针的要求，因为基础指针是非托管的。
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