LibCurl get/set: use lock

cpp/include/kvikio/remote_handle.hpp

@@ -52,6 +52,7 @@ namespace detail {
  */
 class LibCurl {
  private:
+ std::mutex _mutex{};
  std::stack<CURL*> _free_curl_handles{};
 
  LibCurl()
@@ -81,8 +82,6 @@ class LibCurl {
  LibCurl& operator=(LibCurl&& o) = delete;
 
  public:
- void put(CURL* handle) { _free_curl_handles.push(handle); }
-
  static LibCurl& instance()
  {
  static LibCurl _instance;
@@ -92,17 +91,28 @@ class LibCurl {
  CURL* get()
  {
  // Check if we have a handle available.
- if (!_free_curl_handles.empty()) {
- CURL* ret = _free_curl_handles.top();
- _free_curl_handles.pop();
- curl_easy_reset(ret);
- return ret;
+ CURL* ret = nullptr;
+ {
+ std::lock_guard const lock(_mutex);
+ if (!_free_curl_handles.empty()) {
+ ret = _free_curl_handles.top();
+ _free_curl_handles.pop();
+ }
  }
  // If not, we create a new handle.
- CURL* ret = curl_easy_init();
- if (ret == nullptr) { throw std::runtime_error("libcurl: call to curl_easy_init() failed"); }
+ if (ret == nullptr) {
+ ret = curl_easy_init();
+ if (ret == nullptr) { throw std::runtime_error("libcurl: call to curl_easy_init() failed"); }
+ }
+ curl_easy_reset(ret);
  return ret;
  }
+
+ void put(CURL* handle)
+ {
+ std::lock_guard const lock(_mutex);
+ _free_curl_handles.push(handle);
+ }
 };
 
 /**
@@ -142,7 +152,17 @@ class CurlHandle {
  }
  void perform()
  {
+ // Need CURLOPT_NOSIGNAL to support threading, see
+ // <https://curl.se/libcurl/c/CURLOPT_NOSIGNAL.html>
+ setopt(CURLOPT_NOSIGNAL, 1L);
+
+ // We always set CURLOPT_ERRORBUFFER to get better error messages.
  setopt(CURLOPT_ERRORBUFFER, _errbuf);
+
+ // Make curl_easy_perform() fail when receiving HTTP code errors.
+ setopt(CURLOPT_FAILONERROR, 1L);
+
+ // Perform and check for errors.
  CURLcode err = curl_easy_perform(handle());
  if (err != CURLE_OK) {
  std::string msg(_errbuf);
@@ -156,6 +176,7 @@ class CurlHandle {
  throw std::runtime_error(ss.str());
  }
  }
+
  template <typename INFO, typename VALUE>
  void getinfo(INFO info, VALUE value)
  {
@@ -179,7 +200,6 @@ inline std::size_t get_file_size(std::string url)
 
  curl.setopt(CURLOPT_URL, url.c_str());
  curl.setopt(CURLOPT_NOBODY, 1L);
- curl.setopt(CURLOPT_FAILONERROR, 1L);
  curl.perform();
 
  curl_off_t cl;
@@ -305,7 +325,6 @@ class RemoteHandle {
  auto curl = create_curl_handle();
 
  curl.setopt(CURLOPT_URL, _url.c_str());
- curl.setopt(CURLOPT_FAILONERROR, 1L);
 
  std::string const byte_range =
  std::to_string(file_offset) + "-" + std::to_string(file_offset + size - 1);