[base] ControlFlowWrapper.

base/base_tests/CMakeLists.txt

@@ -13,6 +13,7 @@ set(
   collection_cast_test.cpp
   condition_test.cpp
   containers_test.cpp
+  control_flow_tests.cpp
   levenshtein_dfa_test.cpp
   logging_test.cpp
   math_test.cpp

base/base_tests/base_tests.pro

@@ -23,6 +23,7 @@ SOURCES += \
   collection_cast_test.cpp \
   condition_test.cpp \
   containers_test.cpp \
+  control_flow_tests.cpp \
   levenshtein_dfa_test.cpp \
   logging_test.cpp \
   newtype_test.cpp \

base/base_tests/control_flow_tests.cpp

@@ -0,0 +1,57 @@
+#include "testing/testing.hpp"
+
+#include "base/control_flow.hpp"
+
+#include <cstdint>
+
+using namespace base;
+
+namespace
+{
+struct Repeater
+{
+  explicit Repeater(uint32_t repetitions) : m_repetitions(repetitions) {}
+
+  template <typename Fn>
+  void ForEach(Fn && fn)
+  {
+    ControlFlowWrapper<Fn> wrapper(std::forward<Fn>(fn));
+    for (uint32_t i = 0; i < m_repetitions; ++i)
+    {
+      ++m_calls;
+      if (wrapper() == ControlFlow::Break)
+        break;
+    }
+  }
+
+  uint32_t m_repetitions = 0;
+  uint32_t m_calls = 0;
+};
+}  // namespace
+
+UNIT_TEST(ControlFlow_Smoke)
+{
+  {
+    Repeater repeater(10);
+    uint32_t c = 0;
+    repeater.ForEach([&c] { ++c; });
+
+    TEST_EQUAL(c, 10, ());
+    TEST_EQUAL(c, repeater.m_repetitions, ());
+    TEST_EQUAL(c, repeater.m_calls, ());
+  }
+
+  {
+    Repeater repeater(10);
+    uint32_t c = 0;
+    repeater.ForEach([&c] {
+      ++c;
+      if (c == 5)
+        return ControlFlow::Break;
+      return ControlFlow::Continue;
+    });
+
+    TEST_EQUAL(c, 5, ());
+    TEST_EQUAL(c, repeater.m_calls, ());
+  }
+}

base/control_flow.hpp

@@ -1,5 +1,7 @@
 #pragma once
 
+#include <utility>
+
 namespace base
 {
 // This enum is used to control the flow of ForEach invocations.
@@ -8,4 +10,36 @@ enum class ControlFlow
   Break,
   Continue
 };
+
+// A wrapper that calls |fn| with arguments |args|.
+// To avoid excessive calls, |fn| may signal the end of execution via its return value,
+// which should then be checked by the wrapper's user.
+template <typename Fn>
+struct ControlFlowWrapper
+{
+  template <typename Gn>
+  explicit ControlFlowWrapper(Gn && gn) : m_fn(std::forward<Gn>(gn))
+  {
+  }
+
+  template <typename... Args>
+  typename std::enable_if<
+      std::is_same<typename std::result_of<Fn(Args...)>::type, base::ControlFlow>::value,
+      base::ControlFlow>::type
+  operator()(Args &&... args)
+  {
+    return m_fn(std::forward<Args>(args)...);
+  }
+
+  template <typename... Args>
+  typename std::enable_if<std::is_same<typename std::result_of<Fn(Args...)>::type, void>::value,
+                          base::ControlFlow>::type
+  operator()(Args &&... args)
+  {
+    m_fn(std::forward<Args>(args)...);
+    return ControlFlow::Continue;
+  }
+
+  Fn m_fn;
+};
 }  // namespace base

coding/multilang_utf8_string.hpp

@@ -88,37 +88,21 @@ public:
       AddString(l, utf8s);
   }
 
-  // Calls |fn| for each pair of |lang| and |utf8s| stored in this multilang string.
-  // To avoid excessive calls, |fn| may signal the end of execution via its return value.
   template <typename Fn>
-  typename enable_if<
-      is_same<typename result_of<Fn(int8_t, std::string)>::type, base::ControlFlow>::value,
-      void>::type
-  ForEach(Fn && fn) const
+  void ForEach(Fn && fn) const
   {
     size_t i = 0;
     size_t const sz = m_s.size();
+    base::ControlFlowWrapper<Fn> wrapper(std::forward<Fn>(fn));
     while (i < sz)
     {
       size_t const next = GetNextIndex(i);
-      if (fn((m_s[i] & 0x3F), m_s.substr(i + 1, next - i - 1)) == base::ControlFlow::Break)
-        return;
+      if (wrapper((m_s[i] & 0x3F), m_s.substr(i + 1, next - i - 1)) == base::ControlFlow::Break)
+        break;
       i = next;
     }
   }
 
-  // Calls |fn| for each pair of |lang| and |utf8s| stored in this multilang string.
-  template <typename Fn>
-  typename enable_if<is_same<typename result_of<Fn(int8_t, std::string)>::type, void>::value,
-                     void>::type
-  ForEach(Fn && fn) const
-  {
-    ForEach([&](int8_t lang, std::string utf8s) {
-      fn(lang, utf8s);
-      return base::ControlFlow::Continue;
-    });
-  }
-
   bool GetString(int8_t lang, string & utf8s) const;
   bool GetString(string const & lang, string & utf8s) const
   {

xcode/base/base.xcodeproj/project.pbxproj

@@ -16,6 +16,7 @@
 		3446C67D1DDCAA4900146687 /* uni_string_dfa_test.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 3446C6791DDCAA2500146687 /* uni_string_dfa_test.cpp */; };
 		3446C6821DDCAA7400146687 /* newtype_test.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 3446C67E1DDCAA6E00146687 /* newtype_test.cpp */; };
 		3446C6831DDCAA7800146687 /* ref_counted_tests.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 3446C67F1DDCAA6E00146687 /* ref_counted_tests.cpp */; };
+		39B89C3A1FD1898A001104AF /* control_flow_tests.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 39B89C391FD1898A001104AF /* control_flow_tests.cpp */; };
 		39BC0FD01FD057FA00B6C276 /* control_flow.hpp in Headers */ = {isa = PBXBuildFile; fileRef = 39BC0FCF1FD057F900B6C276 /* control_flow.hpp */; };
 		39FD271E1CC65AD000AFF551 /* testingmain.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 39FD27011CC65A2800AFF551 /* testingmain.cpp */; };
 		39FD271F1CC65AD000AFF551 /* assert_test.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 39FD26C81CC65A0E00AFF551 /* assert_test.cpp */; };
@@ -143,6 +144,7 @@
 		3446C67F1DDCAA6E00146687 /* ref_counted_tests.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = ref_counted_tests.cpp; sourceTree = "<group>"; };
 		34BA2D6A1DBE169E00FAB345 /* common-debug.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; name = "common-debug.xcconfig"; path = "../common-debug.xcconfig"; sourceTree = "<group>"; };
 		34BA2D6B1DBE169E00FAB345 /* common-release.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; name = "common-release.xcconfig"; path = "../common-release.xcconfig"; sourceTree = "<group>"; };
+		39B89C391FD1898A001104AF /* control_flow_tests.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = control_flow_tests.cpp; sourceTree = "<group>"; };
 		39BC0FCF1FD057F900B6C276 /* control_flow.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = control_flow.hpp; sourceTree = "<group>"; };
 		39FD26C81CC65A0E00AFF551 /* assert_test.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = assert_test.cpp; sourceTree = "<group>"; };
 		39FD26CA1CC65A0E00AFF551 /* bits_test.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = bits_test.cpp; sourceTree = "<group>"; };
@@ -286,6 +288,7 @@
 		39FD26C71CC659D200AFF551 /* base_tests */ = {
 			isa = PBXGroup;
 			children = (
+				39B89C391FD1898A001104AF /* control_flow_tests.cpp */,
 				67E40EC71E4DC0D500A6D200 /* small_set_test.cpp */,
 				3446C67E1DDCAA6E00146687 /* newtype_test.cpp */,
 				3446C67F1DDCAA6E00146687 /* ref_counted_tests.cpp */,
@@ -674,6 +677,7 @@
 				3D3731FE1F9A445500D2121B /* url_helpers.cpp in Sources */,
 				675341F91A3F57E400A0A8C3 /* src_point.cpp in Sources */,
 				675342031A3F57E400A0A8C3 /* strings_bundle.cpp in Sources */,
+				39B89C3A1FD1898A001104AF /* control_flow_tests.cpp in Sources */,
 				3D74EF141F8B902C0081202C /* bwt.cpp in Sources */,
 				3D74EF131F8B902C0081202C /* move_to_front.cpp in Sources */,
 				675341CD1A3F57E400A0A8C3 /* base.cpp in Sources */,