Implementing erase/erase_if functions from library fundamentals ts:

base/stl_util.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Derived from google3/util/gtl/stl_util.h
 
 #ifndef BASE_STL_UTIL_H_
 #define BASE_STL_UTIL_H_
 
 #include <algorithm>
+#include <deque>

[danakj, 2017/03/03 23:51:22]

What is including all of these headers together so commonly going to do to
compile time, anything?

[dyaroshev, 2017/03/04 00:32:49]

Good point. I will do the measurements and come back to you.

[dyaroshev, 2017/03/05 10:49:59]

Doesn't seem to affect build times. Checked on mac. I've tried to provide as
much of the same environment as I could - nothing else was running, after recent
restart. Unfortunately I forgot -k parameter the second time but I don't think
it should significantly affect time.

// master -------------------------------------------------------------------

time ninja -k 1000000 -C out/gn/ chrome
...

real  172m47.963s
user  1292m6.310s
sys 61m58.296s

// with changes --------------------------------------------------------------

time ninja -C out/gn chrome
...

real  168m0.094s
user  1258m49.411s
sys 58m40.793s

+#include <forward_list>
 #include <functional>
 #include <iterator>
+#include <list>
+#include <map>
+#include <set>
 #include <string>
+#include <unordered_map>
+#include <unordered_set>
 #include <vector>
 
 #include "base/logging.h"
 
 namespace base {
 
+namespace internal {
+
+// Calls erase on iterators of matching elements.
+template <typename Container, typename Predicate>
+void IterateAndEraseIf(Container& container, Predicate pred) {
+  for (auto it = std::begin(container); it != std::end(container);) {

[danakj, 2017/03/03 23:51:22]

you could use container.begin()/end() here too right, there's no arrays.

[dyaroshev, 2017/03/04 00:32:49]

Done.

+    if (pred(*it))
+      it = container.erase(it);
+    else
+      ++it;
+  }
+}
+
+}  // namespace internal
+
 // Clears internal memory of an STL object.
 // STL clear()/reserve(0) does not always free internal memory allocated
 // This function uses swap/destructor to ensure the internal memory is freed.
 template<class T>
 void STLClearObject(T* obj) {
   T tmp;
   tmp.swap(*obj);
   // Sometimes "T tmp" allocates objects with memory (arena implementation?).
   // Hence using additional reserve(0) even if it doesn't always work.
   obj->reserve(0);
@@ skipping 89 matching lines @@
 // Returns true if the sorted container |a1| contains all elements of the sorted
 // container |a2|.
 template <typename Arg1, typename Arg2>
 bool STLIncludes(const Arg1& a1, const Arg2& a2) {
   DCHECK(STLIsSorted(a1));
   DCHECK(STLIsSorted(a2));
   return std::includes(a1.begin(), a1.end(),
                        a2.begin(), a2.end());
 }
 
+// Erase/EraseIf are based on library fundamentals ts v2 erase/erase_if
+// http://en.cppreference.com/w/cpp/experimental/lib_extensions_2
+// They provide a generic way to erase elements from a container.
+// The functions here implement these for the standard containers until those
+// functions are available in the C++ standard.
+// For Chromium containers overloads should be defined in their own headers
+// (like standard containers).
+// Note: there is no std::erase for standard associative containers so we don't
+// have it either.
+
+template <typename CharT, typename Traits, typename Allocator, typename Value>
+void Erase(std::basic_string<CharT, Traits, Allocator>& container,
+           const Value& value) {
+  container.erase(
+      std::remove(std::begin(container), std::end(container), value),

[danakj, 2017/03/03 23:51:22]

same for these, you don't need std::begin/end right?

[dyaroshev, 2017/03/04 00:32:49]

Done.

+      std::end(container));
+}
+
+template <typename CharT, typename Traits, typename Allocator, class Predicate>
+void EraseIf(std::basic_string<CharT, Traits, Allocator>& container,
+             Predicate pred) {
+  container.erase(
+      std::remove_if(std::begin(container), std::end(container), pred),
+      std::end(container));
+}
+
+template <class T, class Allocator, class Value>
+void Erase(std::deque<T, Allocator>& container, const Value& value) {
+  container.erase(
+      std::remove(std::begin(container), std::end(container), value),
+      std::end(container));
+}
+
+template <class T, class Allocator, class Predicate>
+void EraseIf(std::deque<T, Allocator>& container, Predicate pred) {
+  container.erase(
+      std::remove_if(std::begin(container), std::end(container), pred),
+      std::end(container));
+}
+
+template <class T, class Allocator, class Value>
+void Erase(std::vector<T, Allocator>& container, const Value& value) {
+  container.erase(
+      std::remove(std::begin(container), std::end(container), value),
+      std::end(container));
+}
+
+template <class T, class Allocator, class Predicate>
+void EraseIf(std::vector<T, Allocator>& container, Predicate pred) {
+  container.erase(
+      std::remove_if(std::begin(container), std::end(container), pred),
+      std::end(container));
+}
+
+template <class T, class Allocator, class Value>
+void Erase(std::forward_list<T, Allocator>& container, const Value& value) {
+  // Unlike std::forward_list::remove, this function template accepts
+  // heterogeneous types and does not force a conversion to the container's
+  // value type before invoking the == operator.
+  container.remove_if([&](const T& cur) { return cur == value; });
+}
+
+template <class T, class Allocator, class Predicate>
+void EraseIf(std::forward_list<T, Allocator>& container, Predicate pred) {
+  container.remove_if(pred);
+}
+
+template <class T, class Allocator, class Value>
+void Erase(std::list<T, Allocator>& container, const Value& value) {
+  // Unlike std::list::remove, this function template accepts heterogeneous
+  // types and does not force a conversion to the container's value type before
+  // invoking the == operator.
+  container.remove_if([&](const T& cur) { return cur == value; });
+}
+
+template <class T, class Allocator, class Predicate>
+void EraseIf(std::list<T, Allocator>& container, Predicate pred) {
+  container.remove_if(pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void EraseIf(std::map<T, Allocator>& container, Predicate pred) {
+  internal::IterateAndEraseIf(container, pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void EraseIf(std::multimap<T, Allocator>& container, Predicate pred) {
+  internal::IterateAndEraseIf(container, pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void EraseIf(std::set<T, Allocator>& container, Predicate pred) {
+  internal::IterateAndEraseIf(container, pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void EraseIf(std::multiset<T, Allocator>& container, Predicate pred) {
+  internal::IterateAndEraseIf(container, pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void EraseIf(std::unordered_map<T, Allocator>& container, Predicate pred) {
+  internal::IterateAndEraseIf(container, pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void EraseIf(std::unordered_multimap<T, Allocator>& container, Predicate pred) {
+  internal::IterateAndEraseIf(container, pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void EraseIf(std::unordered_set<T, Allocator>& container, Predicate pred) {
+  internal::IterateAndEraseIf(container, pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void EraseIf(std::unordered_multiset<T, Allocator>& container, Predicate pred) {
+  internal::IterateAndEraseIf(container, pred);
+}
+
 }  // namespace base
 
 #endif  // BASE_STL_UTIL_H_