[triplet] Use pointer to instance-controlled strings and cache hashcode

2 files changed, 46 insertions, 27 deletions

diff --git a/toolsrc/include/triplet.h b/toolsrc/include/triplet.h
index e634afd3f..be3bcf5b3 100644
--- a/toolsrc/include/triplet.h
+++ b/toolsrc/include/triplet.h
@@ -4,8 +4,13 @@
 
 namespace vcpkg
 {
+    struct TripletInstance;
+
     struct Triplet
     {
+    public:
+        constexpr Triplet() : m_instance(&default_instance) {}
+
         static Triplet from_canonical_name(const std::string& triplet_as_string);
 
         static const Triplet X86_WINDOWS;
@@ -16,28 +21,23 @@ namespace vcpkg
 
         const std::string& canonical_name() const;
         const std::string& to_string() const;
+        size_t hash_code() const;
+
+        bool operator==(const Triplet& other) const;
 
     private:
-        std::string m_canonical_name;
-    };
+        static const TripletInstance default_instance;
 
-    bool operator==(const Triplet& left, const Triplet& right);
+        constexpr Triplet(const TripletInstance* ptr) : m_instance(ptr) {}
+
+        const TripletInstance* m_instance;
+    };
 
     bool operator!=(const Triplet& left, const Triplet& right);
 }
 
-namespace std
+template<>
+struct std::hash<vcpkg::Triplet>
 {
-    template<>
-    struct hash<vcpkg::Triplet>
-    {
-        size_t operator()(const vcpkg::Triplet& t) const
-        {
-            std::hash<std::string> hasher;
-            size_t hash = 17;
-            hash = hash * 31 + hasher(t.canonical_name());
-            return hash;
-        }
-    };
-
-} // namespace std
+    size_t operator()(const vcpkg::Triplet& t) const { return t.hash_code(); }
+};
diff --git a/toolsrc/src/triplet.cpp b/toolsrc/src/triplet.cpp
index ff41ce77d..451deb040 100644
--- a/toolsrc/src/triplet.cpp
+++ b/toolsrc/src/triplet.cpp
@@ -6,31 +6,50 @@
 
 namespace vcpkg
 {
+    struct TripletInstance
+    {
+        TripletInstance(std::string&& s) : value(std::move(s)), hash(std::hash<std::string>()(value)) {}
+
+        const std::string value;
+        const size_t hash = 0;
+
+        bool operator==(const TripletInstance& o) const { return o.value == value; }
+    };
+    const TripletInstance Triplet::default_instance({});
+}
+
+template<>
+struct std::hash<vcpkg::TripletInstance>
+{
+    size_t operator()(const vcpkg::TripletInstance& t) const { return t.hash; }
+};
+
+namespace vcpkg
+{
+    static std::unordered_set<TripletInstance> g_triplet_instances;
+
     const Triplet Triplet::X86_WINDOWS = from_canonical_name("x86-windows");
     const Triplet Triplet::X64_WINDOWS = from_canonical_name("x64-windows");
     const Triplet Triplet::X86_UWP = from_canonical_name("x86-uwp");
     const Triplet Triplet::X64_UWP = from_canonical_name("x64-uwp");
     const Triplet Triplet::ARM_UWP = from_canonical_name("arm-uwp");
 
-    bool operator==(const Triplet& left, const Triplet& right)
-    {
-        return left.canonical_name() == right.canonical_name();
-    }
+    bool Triplet::operator==(const Triplet& other) const { return this->m_instance == other.m_instance; }
 
     bool operator!=(const Triplet& left, const Triplet& right) { return !(left == right); }
 
     Triplet Triplet::from_canonical_name(const std::string& triplet_as_string)
     {
-        const std::string s(Strings::ascii_to_lowercase(triplet_as_string));
+        std::string s(Strings::ascii_to_lowercase(triplet_as_string));
         auto it = std::find(s.cbegin(), s.cend(), '-');
         Checks::check_exit(VCPKG_LINE_INFO, it != s.cend(), "Invalid triplet: %s", triplet_as_string);
 
-        Triplet t;
-        t.m_canonical_name = s;
-        return t;
+        auto p = g_triplet_instances.emplace(std::move(s));
+        return &*p.first;
     }
 
-    const std::string& Triplet::canonical_name() const { return this->m_canonical_name; }
+    const std::string& Triplet::canonical_name() const { return this->m_instance->value; }
 
-    const std::string& Triplet::to_string() const { return this->m_canonical_name; }
+    const std::string& Triplet::to_string() const { return this->canonical_name(); }
+    size_t Triplet::hash_code() const { return m_instance->hash; }
 }