Simplify string adapters

Author: bblanchon

extras/tests/Misc/StringAdapters.cpp

@@ -4,7 +4,6 @@
 
 #include <Arduino.h>
 
-#include <ArduinoJson/Strings/IsString.hpp>
 #include <ArduinoJson/Strings/StringAdapters.hpp>
 
 #include <catch.hpp>

src/ArduinoJson/Strings/Adapters/FlashString.hpp

@@ -5,7 +5,6 @@
 #pragma once
 
 #include <ArduinoJson/Polyfills/pgmspace.hpp>
-#include <ArduinoJson/Strings/StringAdapter.hpp>
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
@@ -72,22 +71,12 @@ class FlashString {
   size_t size_;
 };
 
-template <>
-struct StringAdapter<const __FlashStringHelper*, void> {
-  using AdaptedString = FlashString;
+inline FlashString adaptString(const __FlashStringHelper* s) {
+  return FlashString(s, s ? strlen_P(reinterpret_cast<const char*>(s)) : 0);
+}
 
-  static AdaptedString adapt(const __FlashStringHelper* s) {
-    return AdaptedString(s, s ? strlen_P(reinterpret_cast<const char*>(s)) : 0);
-  }
-};
-
-template <>
-struct SizedStringAdapter<const __FlashStringHelper*, void> {
-  using AdaptedString = FlashString;
-
-  static AdaptedString adapt(const __FlashStringHelper* s, size_t n) {
-    return AdaptedString(s, n);
-  }
-};
+inline FlashString adaptString(const __FlashStringHelper* s, size_t n) {
+  return FlashString(s, n);
+}
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Strings/Adapters/JsonString.hpp

@@ -6,17 +6,11 @@
 
 #include <ArduinoJson/Strings/Adapters/RamString.hpp>
 #include <ArduinoJson/Strings/JsonString.hpp>
-#include <ArduinoJson/Strings/StringAdapter.hpp>
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
-template <>
-struct StringAdapter<JsonString> {
-  using AdaptedString = RamString;
-
-  static AdaptedString adapt(const JsonString& s) {
-    return AdaptedString(s.c_str(), s.size(), s.isLinked());
-  }
-};
+inline RamString adaptString(const JsonString& s) {
+  return RamString(s.c_str(), s.size(), s.isLinked());
+}
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Strings/Adapters/RamString.hpp

@@ -9,13 +9,15 @@
 
 #include <ArduinoJson/Polyfills/assert.hpp>
 #include <ArduinoJson/Polyfills/attributes.hpp>
-#include <ArduinoJson/Strings/StringAdapter.hpp>
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
 template <typename T>
 struct IsChar
-    : integral_constant<bool, is_integral<T>::value && sizeof(T) == 1> {};
+    : integral_constant<bool,
+                        is_same<remove_cv_t<T>, char>::value ||
+                            is_same<remove_cv_t<T>, signed char>::value ||
+                            is_same<remove_cv_t<T>, unsigned char>::value> {};
 
 class RamString {
  public:
@@ -52,42 +54,27 @@ class RamString {
   bool linked_;  // TODO: merge with size_
 };
 
-template <typename TChar>
-struct StringAdapter<TChar*, enable_if_t<IsChar<TChar>::value>> {
-  using AdaptedString = RamString;
-
-  static AdaptedString adapt(const TChar* p) {
-    auto str = reinterpret_cast<const char*>(p);
-    return AdaptedString(str, str ? ::strlen(str) : 0);
-  }
-};
+template <typename TChar, typename = enable_if_t<IsChar<TChar>::value>>
+inline RamString adaptString(TChar* p) {
+  auto str = reinterpret_cast<const char*>(p);
+  return RamString(str, str ? ::strlen(str) : 0);
+}
 
-template <typename TChar, size_t N>
-struct StringAdapter<TChar[N], enable_if_t<IsChar<TChar>::value>> {
-  using AdaptedString = RamString;
-
-  static AdaptedString adapt(const TChar* p) {
-    auto str = reinterpret_cast<const char*>(p);
-    return AdaptedString(str, str ? ::strlen(str) : 0);
-  }
-};
+template <
+    typename TChar, size_t N,
+    typename = enable_if_t<IsChar<TChar>::value && !is_const<TChar>::value>>
+inline RamString adaptString(TChar p[N]) {
+  auto str = reinterpret_cast<const char*>(p);
+  return RamString(str, str ? ::strlen(str) : 0);
+}
 
-template <>
-struct StringAdapter<const char*, void> {
-  using AdaptedString = RamString;
-
-  static AdaptedString adapt(const char* p) {
-    return AdaptedString(p, p ? ::strlen(p) : 0, true);
-  }
-};
+inline RamString adaptString(const char* p) {
+  return RamString(p, p ? ::strlen(p) : 0, true);
+}
 
 template <typename TChar>
-struct SizedStringAdapter<TChar*, enable_if_t<IsChar<TChar>::value>> {
-  using AdaptedString = RamString;
-
-  static AdaptedString adapt(const TChar* p, size_t n) {
-    return AdaptedString(reinterpret_cast<const char*>(p), n);
-  }
-};
+inline RamString adaptString(const TChar* p, size_t n) {
+  return RamString(reinterpret_cast<const char*>(p), n);
+}
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Strings/Adapters/StringObject.hpp

@@ -5,44 +5,40 @@
 #pragma once
 
 #include <ArduinoJson/Strings/Adapters/RamString.hpp>
-#include <ArduinoJson/Strings/StringAdapter.hpp>
 #include <ArduinoJson/Strings/StringTraits.hpp>
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
-template <typename T>
-struct StringAdapter<
-    T,
-    enable_if_t<(string_traits<T>::has_cstr || string_traits<T>::has_data) &&
-                (string_traits<T>::has_length || string_traits<T>::has_size)>> {
-  using AdaptedString = RamString;
-
-  static AdaptedString adapt(const T& s) {
-    return AdaptedString(get_data(s), get_size(s));
-  }
-
- private:
-  template <typename U>
-  static enable_if_t<string_traits<U>::has_size, size_t> get_size(const U& s) {
-    return s.size();
-  }
-
-  template <typename U>
-  static enable_if_t<!string_traits<U>::has_size, size_t> get_size(const U& s) {
-    return s.length();
-  }
-
-  template <typename U>
-  static enable_if_t<string_traits<U>::has_data, const char*> get_data(
-      const U& s) {
-    return s.data();
-  }
-
-  template <typename U>
-  static enable_if_t<!string_traits<U>::has_data, const char*> get_data(
-      const U& s) {
-    return s.c_str();
-  }
-};
+namespace string_helpers {
+template <typename U>
+static enable_if_t<string_traits<U>::has_size, size_t> get_size(const U& s) {
+  return s.size();
+}
+
+template <typename U>
+static enable_if_t<!string_traits<U>::has_size, size_t> get_size(const U& s) {
+  return s.length();
+}
+
+template <typename U>
+static enable_if_t<string_traits<U>::has_data, const char*> get_data(
+    const U& s) {
+  return s.data();
+}
+
+template <typename U>
+static enable_if_t<!string_traits<U>::has_data, const char*> get_data(
+    const U& s) {
+  return s.c_str();
+}
+}  // namespace string_helpers
+
+template <typename T,
+          typename = enable_if_t<
+              (string_traits<T>::has_cstr || string_traits<T>::has_data) &&
+              (string_traits<T>::has_length || string_traits<T>::has_size)>>
+inline RamString adaptString(const T& s) {
+  return RamString(string_helpers::get_data(s), string_helpers::get_size(s));
+}
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Strings/IsString.hpp

@@ -70,4 +70,13 @@ static void stringGetChars(TAdaptedString s, char* p, size_t n) {
   }
 }
 
+template <typename TString>
+using AdaptedString = decltype(adaptString(declval<TString>()));
+
+template <typename T, typename Enable = void>
+struct IsString : false_type {};
+
+template <typename T>
+struct IsString<T, void_t<AdaptedString<T>>> : true_type {};
+
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Strings/StringAdapter.hpp

@@ -5,7 +5,6 @@
 #pragma once
 
 #include <ArduinoJson/Strings/Adapters/RamString.hpp>
-#include <ArduinoJson/Strings/StringAdapter.hpp>
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 

src/ArduinoJson/Strings/StringAdapters.hpp

@@ -9,7 +9,6 @@
 
 #include <ArduinoJson/Memory/ResourceManager.hpp>
 #include <ArduinoJson/Polyfills/type_traits.hpp>
-#include <ArduinoJson/Strings/IsString.hpp>
 #include <ArduinoJson/Strings/StringAdapters.hpp>
 #include <ArduinoJson/Variant/VariantAttorney.hpp>
 #include <ArduinoJson/Variant/VariantOperators.hpp>