X-Git-Url: http://plrg.eecs.uci.edu/git/?p=folly.git;a=blobdiff_plain;f=folly%2FMapUtil.h;h=7bdb60b734618f9300a456d5bc11078016f7145d;hp=227a1297f060d86df3d33aa3661300405cbd344f;hb=7da4ef82aee382777bb50aadd4af14a482739d10;hpb=546bd3f5f2ed1fdf3a0f5c2b6737a20c4bc2f561

diff --git a/folly/MapUtil.h b/folly/MapUtil.h
index 227a1297..7bdb60b7 100644
--- a/folly/MapUtil.h
+++ b/folly/MapUtil.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014 Facebook, Inc.
+ * Copyright 2012-present Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,8 +14,12 @@
  * limitations under the License.
  */
 
-#ifndef FOLLY_MAPUTIL_H_
-#define FOLLY_MAPUTIL_H_
+#pragma once
+
+#include <folly/Conv.h>
+#include <folly/Optional.h>
+#include <folly/functional/Invoke.h>
+#include <tuple>
 
 namespace folly {
 
@@ -23,13 +27,88 @@ namespace folly {
  * Given a map and a key, return the value corresponding to the key in the map,
  * or a given default value if the key doesn't exist in the map.
  */
-template <class Map>
-typename Map::mapped_type get_default(
-    const Map& map, const typename Map::key_type& key,
-    const typename Map::mapped_type& dflt =
-    typename Map::mapped_type()) {
+template <typename Map, typename Key>
+typename Map::mapped_type get_default(const Map& map, const Key& key) {
   auto pos = map.find(key);
-  return (pos != map.end() ? pos->second : dflt);
+  return (pos != map.end()) ? (pos->second) : (typename Map::mapped_type{});
+}
+template <
+    class Map,
+    typename Key = typename Map::key_type,
+    typename Value = typename Map::mapped_type,
+    typename std::enable_if<!is_invocable<Value>::value>::type* = nullptr>
+typename Map::mapped_type
+get_default(const Map& map, const Key& key, Value&& dflt) {
+  using M = typename Map::mapped_type;
+  auto pos = map.find(key);
+  return (pos != map.end()) ? (pos->second) : M(std::forward<Value>(dflt));
+}
+
+/**
+ * Give a map and a key, return the value corresponding to the key in the map,
+ * or a given default value if the key doesn't exist in the map.
+ */
+template <
+    class Map,
+    typename Key = typename Map::key_type,
+    typename Func,
+    typename = typename std::enable_if<std::is_convertible<
+        typename std::result_of<Func()>::type,
+        typename Map::mapped_type>::value>::type>
+typename Map::mapped_type
+get_default(const Map& map, const Key& key, Func&& dflt) {
+  auto pos = map.find(key);
+  return pos != map.end() ? pos->second : dflt();
+}
+
+/**
+ * Given a map and a key, return the value corresponding to the key in the map,
+ * or throw an exception of the specified type.
+ */
+template <
+    class E = std::out_of_range,
+    class Map,
+    typename Key = typename Map::key_type>
+const typename Map::mapped_type& get_or_throw(
+    const Map& map,
+    const Key& key,
+    const std::string& exceptionStrPrefix = std::string()) {
+  auto pos = map.find(key);
+  if (pos != map.end()) {
+    return pos->second;
+  }
+  throw E(folly::to<std::string>(exceptionStrPrefix, key));
+}
+
+template <
+    class E = std::out_of_range,
+    class Map,
+    typename Key = typename Map::key_type>
+typename Map::mapped_type& get_or_throw(
+    Map& map,
+    const Key& key,
+    const std::string& exceptionStrPrefix = std::string()) {
+  auto pos = map.find(key);
+  if (pos != map.end()) {
+    return pos->second;
+  }
+  throw E(folly::to<std::string>(exceptionStrPrefix, key));
+}
+
+/**
+ * Given a map and a key, return a Optional<V> if the key exists and None if the
+ * key does not exist in the map.
+ */
+template <class Map, typename Key = typename Map::key_type>
+folly::Optional<typename Map::mapped_type> get_optional(
+    const Map& map,
+    const Key& key) {
+  auto pos = map.find(key);
+  if (pos != map.end()) {
+    return folly::Optional<typename Map::mapped_type>(pos->second);
+  } else {
+    return folly::none;
+  }
 }
 
 /**
@@ -37,21 +116,59 @@ typename Map::mapped_type get_default(
  * key in the map, or the given default reference if the key doesn't exist in
  * the map.
  */
-template <class Map>
+template <class Map, typename Key = typename Map::key_type>
 const typename Map::mapped_type& get_ref_default(
-    const Map& map, const typename Map::key_type& key,
+    const Map& map,
+    const Key& key,
     const typename Map::mapped_type& dflt) {
   auto pos = map.find(key);
   return (pos != map.end() ? pos->second : dflt);
 }
 
+/**
+ * Passing a temporary default value returns a dangling reference when it is
+ * returned. Lifetime extension is broken by the indirection.
+ * The caller must ensure that the default value outlives the reference returned
+ * by get_ref_default().
+ */
+template <class Map, typename Key = typename Map::key_type>
+const typename Map::mapped_type& get_ref_default(
+    const Map& map,
+    const Key& key,
+    typename Map::mapped_type&& dflt) = delete;
+
+template <class Map, typename Key = typename Map::key_type>
+const typename Map::mapped_type& get_ref_default(
+    const Map& map,
+    const Key& key,
+    const typename Map::mapped_type&& dflt) = delete;
+
+/**
+ * Given a map and a key, return a reference to the value corresponding to the
+ * key in the map, or the given default reference if the key doesn't exist in
+ * the map.
+ */
+template <
+    class Map,
+    typename Key = typename Map::key_type,
+    typename Func,
+    typename = typename std::enable_if<std::is_convertible<
+        typename std::result_of<Func()>::type,
+        const typename Map::mapped_type&>::value>::type,
+    typename = typename std::enable_if<
+        std::is_reference<typename std::result_of<Func()>::type>::value>::type>
+const typename Map::mapped_type&
+get_ref_default(const Map& map, const Key& key, Func&& dflt) {
+  auto pos = map.find(key);
+  return (pos != map.end() ? pos->second : dflt());
+}
+
 /**
  * Given a map and a key, return a pointer to the value corresponding to the
  * key in the map, or nullptr if the key doesn't exist in the map.
  */
-template <class Map>
-const typename Map::mapped_type* get_ptr(
-    const Map& map, const typename Map::key_type& key) {
+template <class Map, typename Key = typename Map::key_type>
+const typename Map::mapped_type* get_ptr(const Map& map, const Key& key) {
   auto pos = map.find(key);
   return (pos != map.end() ? &pos->second : nullptr);
 }
@@ -59,13 +176,117 @@ const typename Map::mapped_type* get_ptr(
 /**
  * Non-const overload of the above.
  */
-template <class Map>
-typename Map::mapped_type* get_ptr(
-    Map& map, const typename Map::key_type& key) {
+template <class Map, typename Key = typename Map::key_type>
+typename Map::mapped_type* get_ptr(Map& map, const Key& key) {
   auto pos = map.find(key);
   return (pos != map.end() ? &pos->second : nullptr);
 }
 
-}  // namespace folly
+// TODO: Remove the return type computations when clang 3.5 and gcc 5.1 are
+// the minimum supported versions.
+namespace detail {
+template <
+    class T,
+    size_t pathLength,
+    class = typename std::enable_if<(pathLength > 0)>::type>
+struct NestedMapType {
+  using type = typename NestedMapType<T, pathLength - 1>::type::mapped_type;
+};
+
+template <class T>
+struct NestedMapType<T, 1> {
+  using type = typename T::mapped_type;
+};
+
+template <typename... KeysDefault>
+struct DefaultType;
+
+template <typename Default>
+struct DefaultType<Default> {
+  using type = Default;
+};
+
+template <typename Key, typename... KeysDefault>
+struct DefaultType<Key, KeysDefault...> {
+  using type = typename DefaultType<KeysDefault...>::type;
+};
+
+template <class... KeysDefault>
+auto extract_default(const KeysDefault&... keysDefault) ->
+    typename DefaultType<KeysDefault...>::type const& {
+  return std::get<sizeof...(KeysDefault)-1>(std::tie(keysDefault...));
+}
+} // namespace detail
+
+/**
+ * Given a map of maps and a path of keys, return a pointer to the nested value,
+ * or nullptr if the key doesn't exist in the map.
+ */
+template <class Map, class Key1, class Key2, class... Keys>
+auto get_ptr(
+    const Map& map,
+    const Key1& key1,
+    const Key2& key2,
+    const Keys&... keys) ->
+    typename detail::NestedMapType<Map, 2 + sizeof...(Keys)>::type const* {
+  auto pos = map.find(key1);
+  return pos != map.end() ? get_ptr(pos->second, key2, keys...) : nullptr;
+}
+
+template <class Map, class Key1, class Key2, class... Keys>
+auto get_ptr(Map& map, const Key1& key1, const Key2& key2, const Keys&... keys)
+    -> typename detail::NestedMapType<Map, 2 + sizeof...(Keys)>::type* {
+  auto pos = map.find(key1);
+  return pos != map.end() ? get_ptr(pos->second, key2, keys...) : nullptr;
+}
+
+/**
+ * Given a map and a path of keys, return the value corresponding to the nested
+ * value, or a given default value if the path doesn't exist in the map.
+ * The default value is the last parameter, and is copied when returned.
+ */
+template <
+    class Map,
+    class Key1,
+    class Key2,
+    class... KeysDefault,
+    typename = typename std::enable_if<sizeof...(KeysDefault) != 0>::type>
+auto get_default(
+    const Map& map,
+    const Key1& key1,
+    const Key2& key2,
+    const KeysDefault&... keysDefault) ->
+    typename detail::NestedMapType<Map, 1 + sizeof...(KeysDefault)>::type {
+  if (const auto* ptr = get_ptr(map, key1)) {
+    return get_default(*ptr, key2, keysDefault...);
+  }
+  return detail::extract_default(keysDefault...);
+}
 
-#endif /* FOLLY_MAPUTIL_H_ */
+/**
+ * Given a map and a path of keys, return a reference to the value corresponding
+ * to the nested value, or the given default reference if the path doesn't exist
+ * in the map.
+ * The default value is the last parameter, and must be a lvalue reference.
+ */
+template <
+    class Map,
+    class Key1,
+    class Key2,
+    class... KeysDefault,
+    typename = typename std::enable_if<sizeof...(KeysDefault) != 0>::type,
+    typename = typename std::enable_if<std::is_lvalue_reference<
+        typename detail::DefaultType<KeysDefault...>::type>::value>::type>
+auto get_ref_default(
+    const Map& map,
+    const Key1& key1,
+    const Key2& key2,
+    KeysDefault&&... keysDefault) ->
+    typename detail::NestedMapType<Map, 1 + sizeof...(KeysDefault)>::type
+    const& {
+  if (const auto* ptr = get_ptr(map, key1)) {
+    return get_ref_default(*ptr, key2, keysDefault...);
+  }
+  return detail::extract_default(keysDefault...);
+}
+} // namespace folly