AK: Try to avoid String allocation in FlyString(StringView)

If we're constructing a FlyString from a StringView, and we already
have a matching StringImpl in the table, use HashTable::find() to
locate the existing string without creating a temporary String.

1 files changed, 15 insertions, 2 deletions

diff --git a/AK/FlyString.cpp b/AK/FlyString.cpp
index 128abcc6f7..8acc94d67a 100644
--- a/AK/FlyString.cpp
+++ b/AK/FlyString.cpp
@@ -55,9 +55,22 @@ FlyString::FlyString(const String& string)
     }
 }
 
-FlyString::FlyString(const StringView& string)
-    : FlyString(static_cast<String>(string))
+FlyString::FlyString(StringView const& string)
 {
+    if (string.is_null())
+        return;
+    auto it = fly_impls().find(string.hash(), [&](auto& candidate) {
+        return string == candidate;
+    });
+    if (it == fly_impls().end()) {
+        auto new_string = string.to_string();
+        fly_impls().set(new_string.impl());
+        new_string.impl()->set_fly({}, true);
+        m_impl = new_string.impl();
+    } else {
+        VERIFY((*it)->is_fly());
+        m_impl = *it;
+    }
 }
 
 FlyString::FlyString(const char* string)