Utils: Modernize SmallString

Use more C++ api and constexpr. With C++ 17 we can use even more.

Change-Id: I33934cd7e087c311bf98501442df848bdb108279
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/libs/utils/smallstring.h

@@ -90,39 +90,35 @@ public:
     constexpr
     BasicSmallString(const char(&string)[ArraySize])
         : m_data(string)
-    {
+    {}
-    }
 
     BasicSmallString(const char *string, size_type size, size_type capacity)
     {
         if (Q_LIKELY(capacity <= shortStringCapacity())) {
-            std::memcpy(m_data.shortString.string, string, size);
+            std::char_traits<char>::copy(m_data.shortString.string, string, size);
             m_data.shortString.string[size] = 0;
             m_data.shortString.control.setShortStringSize(size);
             m_data.shortString.control.setIsShortString(true);
             m_data.shortString.control.setIsReadOnlyReference(false);
         } else {
             m_data.allocated.data.pointer = Memory::allocate(capacity + 1);
-            std::memcpy(m_data.allocated.data.pointer, string, size);
+            std::char_traits<char>::copy(m_data.allocated.data.pointer, string, size);
             initializeLongString(size, capacity);
         }
     }
 
     explicit BasicSmallString(SmallStringView stringView)
         : BasicSmallString(stringView.data(), stringView.size(), stringView.size())
-    {
+    {}
-    }
 
     BasicSmallString(const char *string, size_type size)
         : BasicSmallString(string, size, size)
     {
     }
 
-    template<typename Type,
+    template<typename Type, typename = std::enable_if_t<std::is_pointer<Type>::value>>
-             typename = std::enable_if_t<std::is_pointer<Type>::value>
-             >
     BasicSmallString(Type characterPointer)
-        : BasicSmallString(characterPointer, std::strlen(characterPointer))
+        : BasicSmallString(characterPointer, std::char_traits<char>::length(characterPointer))
     {
         static_assert(!std::is_array<Type>::value, "Input type is array and not char pointer!");
     }
@@ -253,7 +249,7 @@ public:
     static
     BasicSmallString fromUtf8(const char *characterPointer)
     {
-        return BasicSmallString(characterPointer, std::strlen(characterPointer));
+        return BasicSmallString(characterPointer, std::char_traits<char>::length(characterPointer));
     }
 
     void reserve(size_type newCapacity)
@@ -271,7 +267,7 @@ public:
                 const char *oldData = data();
 
                 char *newData = Memory::allocate(newCapacity + 1);
-                std::memcpy(newData, oldData, oldSize);
+                std::char_traits<char>::copy(newData, oldData, oldSize);
                 m_data.allocated.data.pointer = newData;
                 initializeLongString(oldSize, newCapacity);
             }
@@ -380,7 +376,7 @@ public:
 
     bool contains(char characterToSearch) const
     {
-        auto found = std::memchr(data(), characterToSearch, size());
+        auto found = std::char_traits<char>::find(data(), size(), characterToSearch);
 
         return found != nullptr;
     }
@@ -388,7 +384,9 @@ public:
     bool startsWith(SmallStringView subStringToSearch) const noexcept
     {
         if (size() >= subStringToSearch.size())
-            return !std::memcmp(data(), subStringToSearch.data(), subStringToSearch.size());
+            return !std::char_traits<char>::compare(data(),
+                                                    subStringToSearch.data(),
+                                                    subStringToSearch.size());
 
         return false;
     }
@@ -401,7 +399,8 @@ public:
     bool endsWith(SmallStringView subStringToSearch) const noexcept
     {
         if (size() >= subStringToSearch.size()) {
-            const int comparison = std::memcmp(end().data() - subStringToSearch.size(),
+            const int comparison = std::char_traits<char>::compare(end().data()
+                                                                       - subStringToSearch.size(),
                                                                    subStringToSearch.data(),
                                                                    subStringToSearch.size());
             return comparison == 0;
@@ -462,7 +461,7 @@ public:
         size_type newSize = oldSize + string.size();
 
         reserve(optimalCapacity(newSize));
-        std::memcpy(data() + oldSize, string.data(), string.size());
+        std::char_traits<char>::copy(data() + oldSize, string.data(), string.size());
         at(newSize) = 0;
         setSize(newSize);
     }
@@ -724,7 +723,7 @@ private:
         at(size) = 0;
     }
 
-    void initializeLongString(size_type size, size_type capacity)
+    constexpr void initializeLongString(size_type size, size_type capacity)
     {
         m_data.allocated.data.pointer[size] = 0;
         m_data.allocated.data.size = size;
@@ -757,7 +756,7 @@ private:
         while (found != end()) {
             start = found + toText.size();
 
-            std::memcpy(found.data(), toText.data(), toText.size());
+            std::char_traits<char>::copy(found.data(), toText.data(), toText.size());
 
             found = std::search(start,
                                      end(),

src/libs/utils/smallstringfwd.h

@@ -25,6 +25,18 @@
 
 #pragma once
 
+#if __cplusplus >= 201703L
+#define constexpr17 constexpr
+#else
+#define constexpr17 inline
+#endif
+
+#if __cplusplus >= 202002L
+#define constexpr20 constexpr
+#else
+#define constexpr20 inline
+#endif
+
 using uint = unsigned int;
 
 namespace Utils {
@@ -35,9 +47,4 @@ class BasicSmallString;
 using SmallString = BasicSmallString<31>;
 using PathString = BasicSmallString<190>;
 
-inline
-int compare(SmallStringView first, SmallStringView second) noexcept;
-inline
-int reverseCompare(SmallStringView first, SmallStringView second) noexcept;
-
 } // namespace Utils

src/libs/utils/smallstringiterator.h

@@ -37,118 +37,89 @@ template <class Category,
          typename DistanceType = ptrdiff_t,
          typename Pointer = Type *,
          typename Reference = Type &>
-struct SmallStringIterator : public  std::iterator<Category, Type, DistanceType, Pointer, Reference>
+struct SmallStringIterator
 {
-    constexpr
+    using iterator_category = Category;
-    SmallStringIterator() noexcept = default;
+    using value_type = Type;
+    using difference_type = DistanceType;
+    using pointer = Pointer;
+    using reference = Reference;
 
-    constexpr
+    constexpr SmallStringIterator() noexcept = default;
-    SmallStringIterator(Pointer ptr) noexcept : pointer_(ptr)
-    {
-    }
 
-    SmallStringIterator operator++() noexcept
+    constexpr SmallStringIterator(Pointer ptr) noexcept
-    {
+        : pointer_(ptr)
-        return ++pointer_;
+    {}
-    }
 
-    SmallStringIterator operator++(int) noexcept
+    constexpr SmallStringIterator operator++() noexcept { return ++pointer_; }
-    {
-        return pointer_++;
-    }
 
-    SmallStringIterator operator--() noexcept
+    constexpr SmallStringIterator operator++(int) noexcept { return pointer_++; }
-    {
-        return --pointer_;
-    }
 
-    SmallStringIterator operator--(int) noexcept
+    constexpr SmallStringIterator operator--() noexcept { return --pointer_; }
-    {
-        return pointer_--;
-    }
 
-    SmallStringIterator operator+(DistanceType difference) const noexcept
+    constexpr SmallStringIterator operator--(int) noexcept { return pointer_--; }
+
+    constexpr SmallStringIterator operator+(DistanceType difference) const noexcept
     {
         return pointer_ + difference;
     }
 
-    SmallStringIterator operator-(DistanceType difference) const noexcept
+    constexpr SmallStringIterator operator-(DistanceType difference) const noexcept
     {
         return pointer_ - difference;
     }
 
-    SmallStringIterator operator+(std::size_t difference) const noexcept
+    constexpr SmallStringIterator operator+(std::size_t difference) const noexcept
     {
         return pointer_ + difference;
     }
 
-    SmallStringIterator operator-(std::size_t difference) const noexcept
+    constexpr SmallStringIterator operator-(std::size_t difference) const noexcept
     {
         return pointer_ - difference;
     }
 
-    DistanceType operator-(SmallStringIterator other) const noexcept
+    constexpr DistanceType operator-(SmallStringIterator other) const noexcept
     {
         return pointer_ - other.data();
     }
 
-    SmallStringIterator operator+=(DistanceType difference) noexcept
+    constexpr SmallStringIterator operator+=(DistanceType difference) noexcept
     {
         return pointer_ += difference;
     }
 
-    SmallStringIterator operator-=(DistanceType difference) noexcept
+    constexpr SmallStringIterator operator-=(DistanceType difference) noexcept
     {
         return pointer_ -= difference;
     }
 
-    Reference operator*() noexcept
+    constexpr Reference operator*() noexcept { return *pointer_; }
-    {
-        return *pointer_;
-    }
 
-    const Reference operator*() const noexcept
+    const Reference operator*() const noexcept { return *pointer_; }
-    {
-        return *pointer_;
-    }
 
-    Pointer operator->() noexcept
+    constexpr Pointer operator->() noexcept { return pointer_; }
-    {
-        return pointer_;
-    }
 
-    const Pointer operator->() const noexcept
+    constexpr const Pointer operator->() const noexcept { return pointer_; }
-    {
-        return pointer_;
-    }
 
-    constexpr
+    constexpr bool operator==(SmallStringIterator other) const noexcept
-    bool operator==(SmallStringIterator other) const noexcept
     {
         return pointer_ == other.pointer_;
     }
 
-    constexpr
+    constexpr bool operator!=(SmallStringIterator other) const noexcept
-    bool operator!=(SmallStringIterator other) const noexcept
     {
         return pointer_ != other.pointer_;
     }
 
-    constexpr
+    constexpr bool operator<(SmallStringIterator other) const noexcept
-    bool operator<(SmallStringIterator other) const noexcept
     {
         return pointer_ < other.pointer_;
     }
 
-    Pointer data() noexcept
+    constexpr Pointer data() noexcept { return pointer_; }
-    {
-        return pointer_;
-    }
 
-    const Pointer data() const noexcept
+    constexpr const Pointer data() const noexcept { return pointer_; }
-    {
-        return pointer_;
-    }
 
 private:
     Pointer pointer_ = nullptr;

src/libs/utils/smallstringlayout.h

@@ -49,30 +49,21 @@ struct ControlBlock
             m_isReference(isReference)
     {}
 
-    void setShortStringSize(size_type size)
+    constexpr void setShortStringSize(size_type size)
     {
        m_shortStringSize = static_cast<SizeType>(size);
     }
 
-    size_type shortStringSize() const
+    constexpr size_type shortStringSize() const { return m_shortStringSize; }
-    {
-        return m_shortStringSize;
-    }
 
-    void setIsReadOnlyReference(bool isReadOnlyReference)
+    constexpr void setIsReadOnlyReference(bool isReadOnlyReference)
     {
         m_isReadOnlyReference = isReadOnlyReference;
     }
 
-    void setIsReference(bool isReference)
+    constexpr void setIsReference(bool isReference) { m_isReference = isReference; }
-    {
-        m_isReference = isReference;
-    }
 
-    void setIsShortString(bool isShortString)
+    constexpr void setIsShortString(bool isShortString) { m_isReference = !isShortString; }
-    {
-        m_isReference = !isShortString;
-    }
 
     constexpr
     SizeType stringSize() const
@@ -168,7 +159,7 @@ struct StringDataLayout {
 
     template<size_type Size,
              typename std::enable_if_t<Size <= MaximumShortStringDataAreaSize, int> = 0>
-    StringDataLayout(const char(&string)[Size]) noexcept
+    constexpr StringDataLayout(const char (&string)[Size]) noexcept
         : shortString(ShortStringLayout<MaximumShortStringDataAreaSize>{})
     {
        for (size_type i = 0; i < Size; ++i)

src/libs/utils/smallstringview.h

@@ -25,6 +25,7 @@
 
 #pragma once
 
+#include "smallstringfwd.h"
 #include "smallstringiterator.h"
 
 #include <QString>
@@ -53,36 +54,32 @@ public:
 
     constexpr SmallStringView() = default;
 
-    SmallStringView(const char *characterPointer) noexcept
+    constexpr17 SmallStringView(const char *characterPointer) noexcept
         : m_pointer(characterPointer)
-        , m_size(std::strlen(characterPointer))
+        , m_size(std::char_traits<char>::length(characterPointer))
-    {
-    }
-
-    constexpr
-    SmallStringView(const char *const string, const size_type size) noexcept
-        : m_pointer(string),
-          m_size(size)
-    {
-    }
-
-    SmallStringView(const const_iterator begin, const const_iterator end) noexcept
-        : m_pointer(begin.data()),
-          m_size(std::size_t(end - begin))
-    {
-    }
-
-    template<typename String,
-             typename Utils::enable_if_has_char_data_pointer<String> = 0>
-    SmallStringView(const String &string) noexcept
-        : m_pointer(string.data()),
-          m_size(string.size())
     {}
 
-    static
+    constexpr SmallStringView(const char *const string, const size_type size) noexcept
-    SmallStringView fromUtf8(const char *const characterPointer)
+        : m_pointer(string)
+        , m_size(size)
     {
-        return SmallStringView(characterPointer, std::strlen(characterPointer));
+    }
+
+    constexpr SmallStringView(const const_iterator begin, const const_iterator end) noexcept
+        : m_pointer(begin.data())
+        , m_size(std::size_t(end - begin))
+    {
+    }
+
+    template<typename String, typename Utils::enable_if_has_char_data_pointer<String> = 0>
+    constexpr SmallStringView(const String &string) noexcept
+        : m_pointer(string.data())
+        , m_size(string.size())
+    {}
+
+    static constexpr17 SmallStringView fromUtf8(const char *const characterPointer)
+    {
+        return SmallStringView(characterPointer);
     }
 
     constexpr
@@ -133,93 +130,85 @@ public:
         return data() + size();
     }
 
-    const_reverse_iterator rbegin() const noexcept
+    constexpr17 const_reverse_iterator rbegin() const noexcept
     {
         return const_reverse_iterator(end());
     }
 
-    const_reverse_iterator rend() const noexcept
+    constexpr17 const_reverse_iterator rend() const noexcept
     {
         return const_reverse_iterator(begin());
     }
 
-    operator std::string() const
+    constexpr20 operator std::string() const { return std::string(data(), size()); }
-    {
-        return std::string(data(), size());
-    }
 
     explicit operator QString() const
     {
         return QString::fromUtf8(data(), int(size()));
     }
 
-    bool startsWith(SmallStringView subStringToSearch) const noexcept
+    constexpr17 bool startsWith(SmallStringView subStringToSearch) const noexcept
     {
         if (size() >= subStringToSearch.size())
-            return !std::memcmp(m_pointer, subStringToSearch.data(), subStringToSearch.size());
+            return !std::char_traits<char>::compare(m_pointer,
+                                                    subStringToSearch.data(),
+                                                    subStringToSearch.size());
 
         return false;
     }
 
-    bool startsWith(char characterToSearch) const noexcept
+    constexpr bool startsWith(char characterToSearch) const noexcept
     {
         return m_pointer[0] == characterToSearch;
     }
 
-    char back() const { return m_pointer[m_size - 1]; }
+    constexpr char back() const { return m_pointer[m_size - 1]; }
 
-    char operator[](std::size_t index) { return m_pointer[index]; }
+    constexpr char operator[](std::size_t index) { return m_pointer[index]; }
 
 private:
     const char *m_pointer = "";
     size_type m_size = 0;
 };
 
-inline
+constexpr17 bool operator==(SmallStringView first, SmallStringView second) noexcept
-bool operator==(SmallStringView first, SmallStringView second) noexcept
 {
-    return first.size() == second.size() && std::memcmp(first.data(), second.data(), first.size()) == 0;
+    return first.size() == second.size()
+           && std::char_traits<char>::compare(first.data(), second.data(), first.size()) == 0;
 }
 
-inline
+constexpr17 bool operator!=(SmallStringView first, SmallStringView second) noexcept
-bool operator!=(SmallStringView first, SmallStringView second) noexcept
 {
     return !(first == second);
 }
 
-inline
+constexpr17 int compare(SmallStringView first, SmallStringView second) noexcept
-int compare(SmallStringView first, SmallStringView second) noexcept
 {
     int sizeDifference = int(first.size() - second.size());
 
     if (sizeDifference == 0)
-        return std::memcmp(first.data(), second.data(), first.size());
+        return std::char_traits<char>::compare(first.data(), second.data(), first.size());
 
     return sizeDifference;
 }
 
-inline
+constexpr17 bool operator<(SmallStringView first, SmallStringView second) noexcept
-bool operator<(SmallStringView first, SmallStringView second) noexcept
 {
     return compare(first, second) < 0;
 }
 
-inline
+constexpr17 bool operator>(SmallStringView first, SmallStringView second) noexcept
-bool operator>(SmallStringView first, SmallStringView second) noexcept
 {
     return second < first;
 }
 
 namespace Internal {
-inline
+constexpr int reverse_memcmp(const char *first, const char *second, size_t n)
-int reverse_memcmp(const char *first, const char *second, size_t n)
 {
-
     const char *currentFirst = first + n - 1;
     const char *currentSecond = second + n - 1;
 
-    while (n > 0)
+    while (n > 0) {
-    {
         // If the current characters differ, return an appropriately signed
         // value; otherwise, keep searching backwards
         int difference = *currentFirst - *currentSecond;
@@ -233,10 +222,9 @@ int reverse_memcmp(const char *first, const char *second, size_t n)
 
     return 0;
 }
-}
+} // namespace Internal
 
-inline
+constexpr int reverseCompare(SmallStringView first, SmallStringView second) noexcept
-int reverseCompare(SmallStringView first, SmallStringView second) noexcept
 {
     int sizeDifference = int(first.size() - second.size());
 
@@ -248,10 +236,7 @@ int reverseCompare(SmallStringView first, SmallStringView second) noexcept
 
 } // namespace Utils
 
-#ifdef __cpp_user_defined_literals
-inline
 constexpr Utils::SmallStringView operator""_sv(const char *const string, size_t size)
 {
     return Utils::SmallStringView(string, size);
 }
-#endif