util.hh: Move stuff to types.hh

Change-Id: Ia852306a4b8aac6856dc42bc69e4b58b53a0d67c

1 files changed, 111 insertions, 0 deletions

diff --git a/src/libutil/types.hh b/src/libutil/types.hh
index c86f52175..4974634d8 100644
--- a/src/libutil/types.hh
+++ b/src/libutil/types.hh
@@ -4,6 +4,7 @@
 #include "ref.hh"
 
 #include <list>
+#include <optional>
 #include <set>
 #include <string>
 #include <limits>
@@ -51,6 +52,116 @@ struct Explicit {
     }
 };
 
+/**
+ * Get a value for the specified key from an associate container.
+ */
+template <class T>
+const typename T::mapped_type * get(const T & map, const typename T::key_type & key)
+{
+    auto i = map.find(key);
+    if (i == map.end()) return nullptr;
+    return &i->second;
+}
+
+template <class T>
+typename T::mapped_type * get(T & map, const typename T::key_type & key)
+{
+    auto i = map.find(key);
+    if (i == map.end()) return nullptr;
+    return &i->second;
+}
+
+/**
+ * Get a value for the specified key from an associate container, or a default value if the key isn't present.
+ */
+template <class T>
+const typename T::mapped_type & getOr(T & map,
+    const typename T::key_type & key,
+    const typename T::mapped_type & defaultValue)
+{
+    auto i = map.find(key);
+    if (i == map.end()) return defaultValue;
+    return i->second;
+}
+
+/**
+ * Remove and return the first item from a container.
+ */
+template <class T>
+std::optional<typename T::value_type> remove_begin(T & c)
+{
+    auto i = c.begin();
+    if (i == c.end()) return {};
+    auto v = std::move(*i);
+    c.erase(i);
+    return v;
+}
+
+
+/**
+ * Remove and return the first item from a container.
+ */
+template <class T>
+std::optional<typename T::value_type> pop(T & c)
+{
+    if (c.empty()) return {};
+    auto v = std::move(c.front());
+    c.pop();
+    return v;
+}
+
+
+/**
+ * A RAII helper that increments a counter on construction and
+ * decrements it on destruction.
+ */
+template<typename T>
+struct MaintainCount
+{
+    T & counter;
+    long delta;
+    MaintainCount(T & counter, long delta = 1) : counter(counter), delta(delta) { counter += delta; }
+    ~MaintainCount() { counter -= delta; }
+};
+
+
+/**
+ * A Rust/Python-like enumerate() iterator adapter.
+ *
+ * Borrowed from http://reedbeta.com/blog/python-like-enumerate-in-cpp17.
+ */
+template <typename T,
+          typename TIter = decltype(std::begin(std::declval<T>())),
+          typename = decltype(std::end(std::declval<T>()))>
+constexpr auto enumerate(T && iterable)
+{
+    struct iterator
+    {
+        size_t i;
+        TIter iter;
+        constexpr bool operator != (const iterator & other) const { return iter != other.iter; }
+        constexpr void operator ++ () { ++i; ++iter; }
+        constexpr auto operator * () const { return std::tie(i, *iter); }
+    };
+
+    struct iterable_wrapper
+    {
+        T iterable;
+        constexpr auto begin() { return iterator{ 0, std::begin(iterable) }; }
+        constexpr auto end() { return iterator{ 0, std::end(iterable) }; }
+    };
+
+    return iterable_wrapper{ std::forward<T>(iterable) };
+}
+
+
+/**
+ * C++17 std::visit boilerplate
+ */
+template<class... Ts> struct overloaded : Ts... { using Ts::operator()...; };
+template<class... Ts> overloaded(Ts...) -> overloaded<Ts...>;
+
+
 
 /**
  * This wants to be a little bit like rust's Cow type.