C++ has no coroutines (yet), and the ones of boost are so ugly

passphrase_cache.cc

@@ -43,5 +43,26 @@ namespace pEp {
         entry->tp = clock::now();
         _cache.splice(_cache.end(), _cache, entry);
     }
+
+    std::string PassphraseCache::latest_passphrase()
+    {
+        std::lock_guard<std::mutex> lock(_mtx);
+        cleanup();
+        _which = _cache.end();
+        return "";
+    }
+
+    std::string PassphraseCache::next_passphrase()
+    {
+        std::lock_guard<std::mutex> lock(_mtx);
+
+        if (_cache.empty() || _which == _cache.begin()) {
+            return "";
+        }
+        else {
+            --_which;
+            return _which->passphrase;
+        }
+    }
 };
 

passphrase_cache.hh

@@ -28,6 +28,8 @@ namespace pEp {
         int _max_size;
         duration _timeout;
 
+        cache::iterator _which;
+
     public:
         PassphraseCache(int max_size=20, duration timeout =
                 std::chrono::minutes(10)) : _max_size(max_size),
@@ -49,6 +51,15 @@ namespace pEp {
         using passphrase_callee = std::function<bool(std::string)>;
         bool for_each_passphrase(const passphrase_callee& callee);
 
+        // get all passphrases in cache from latest to oldest
+        // always returns ""
+
+        std::string latest_passphrase();
+
+        // get next passphrase; returns "" when no passphrases are left
+
+        std::string next_passphrase();
+
         // convenience functions
         // i.e.
         // status = cache.api(::encrypt_message, session, src, extra, dst, enc_format, flags)

test/test_passphrase_cache.cc

@@ -49,6 +49,15 @@ int main()
     status = cache.api(api_test2, session, n, str, bytes, sl);
     assert(status == PEP_STATUS_OK);
 
+    std::cout << "expected: two passphrases in order\n";
+
+    pEp::PassphraseCache _cache = cache;
+    _cache.latest_passphrase();
+    for (std::string passphrase = _cache.next_passphrase(); passphrase != "" ;
+            passphrase = _cache.next_passphrase()) {
+        std::cout << passphrase << "\n";
+    }
+
     sleep(2);
 
     std::cout << "expected: no passphrase\n";
@@ -59,8 +68,6 @@ int main()
     status = cache.api(api_test2, session, 23, str, bytes, sl);
     assert(status == PEP_STATUS_OK);
 
-    pEp::PassphraseCache _cache = cache;
-
     ::release(session);
     return 0;
 }