CString tidy cleanup and rvalue methods

We add rvalue version of append/insert/replace so that calling
those on a temporary yields to a temporary.

Also add string literal versions of those so that we can 
append/insert/replace a literal without allocation, e.g.:

`CString foo = CString{ bar }.append("baz");`

This will not end-up creating a temporary CString for "baz".

Author: pixelflinger

libs/utils/include/utils/CString.h

@@ -23,6 +23,7 @@
 #include <utils/ostream.h>
 
 #include <string_view>
+#include <utility>
 
 #include <assert.h>
 #include <stddef.h>
@@ -97,11 +98,7 @@ class UTILS_PUBLIC CString {
         return *this;
     }
 
-    ~CString() noexcept {
-        if (mData) {
-            free(mData - 1);
-        }
-    }
+    ~CString() noexcept;
 
     void swap(CString& other) noexcept {
         // don't use std::swap(), we don't want an STL dependency in this file
@@ -110,42 +107,98 @@ class UTILS_PUBLIC CString {
         other.mCStr = temp;
     }
 
-    const_pointer c_str() const noexcept { return mCStr; }
     pointer c_str() noexcept { return mCStr; }
+    const_pointer c_str() const noexcept { return const_cast<CString*>(this)->c_str(); }
     const_pointer c_str_safe() const noexcept { return mData ? c_str() : ""; }
     const_pointer data() const noexcept { return c_str(); }
     pointer data() noexcept { return c_str(); }
     size_type size() const noexcept { return mData ? mData[-1].length : 0; }
     size_type length() const noexcept { return size(); }
     bool empty() const noexcept { return size() == 0; }
 
-    iterator begin() noexcept { return mCStr; }
+    iterator begin() noexcept { return c_str(); }
     iterator end() noexcept { return begin() + length(); }
     const_iterator begin() const noexcept { return data(); }
     const_iterator end() const noexcept { return begin() + length(); }
     const_iterator cbegin() const noexcept { return begin(); }
     const_iterator cend() const noexcept { return end(); }
 
-    CString& replace(size_type pos, size_type len, const CString& str) noexcept;
-    CString& insert(size_type pos, const CString& str) noexcept { return replace(pos, 0, str); }
-    CString& append(const CString& str) noexcept { return insert(length(), str); }
+    // replace
+    template<size_t N>
+    CString& replace(size_type const pos,
+            size_type const len, const StringLiteral<N>& str) & noexcept {
+        return replace(pos, len, str, N - 1);
+    }
+
+    CString& replace(size_type const pos, size_type const len, const CString& str) & noexcept {
+        return replace(pos, len, str.c_str_safe(), str.size());
+    }
+
+    template<size_t N>
+    CString&& replace(size_type const pos,
+            size_type const len, const StringLiteral<N>& str) && noexcept {
+        return std::move(replace(pos, len, str));
+    }
 
-    const_reference operator[](size_type pos) const noexcept {
+    CString&& replace(size_type const pos, size_type const len, const CString& str) && noexcept {
+        return std::move(replace(pos, len, str));
+    }
+
+    // insert
+    template<size_t N>
+    CString& insert(size_type const pos, const StringLiteral<N>& str) & noexcept {
+        return replace(pos, 0, str);
+    }
+
+    CString& insert(size_type const pos, const CString& str) & noexcept {
+        return replace(pos, 0, str);
+    }
+
+    template<size_t N>
+    CString&& insert(size_type const pos, const StringLiteral<N>& str) && noexcept {
+        return std::move(*this).replace(pos, 0, str);
+    }
+
+    CString&& insert(size_type const pos, const CString& str) && noexcept {
+        return std::move(*this).replace(pos, 0, str);
+    }
+
+    // append
+    template<size_t N>
+    CString& append(const StringLiteral<N>& str) & noexcept {
+        return insert(length(), str);
+    }
+
+    CString& append(const CString& str) & noexcept {
+        return insert(length(), str);
+    }
+
+    template<size_t N>
+    CString&& append(const StringLiteral<N>& str) && noexcept {
+        return std::move(*this).insert(length(), str);
+    }
+
+    CString&& append(const CString& str) && noexcept {
+        return std::move(*this).insert(length(), str);
+    }
+
+
+    const_reference operator[](size_type const pos) const noexcept {
         assert(pos < size());
         return begin()[pos];
     }
 
-    reference operator[](size_type pos) noexcept {
+    reference operator[](size_type const pos) noexcept {
         assert(pos < size());
         return begin()[pos];
     }
 
-    const_reference at(size_type pos) const noexcept {
+    const_reference at(size_type const pos) const noexcept {
         assert(pos < size());
         return begin()[pos];
     }
 
-    reference at(size_type pos) noexcept {
+    reference at(size_type const pos) noexcept {
         assert(pos < size());
         return begin()[pos];
     }
@@ -171,7 +224,7 @@ class UTILS_PUBLIC CString {
     }
 
     // placement new declared as "throw" to avoid the compiler's null-check
-    inline void* operator new(size_t, void* ptr) {
+    void* operator new(size_t, void* ptr) {
         assert(ptr);
         return ptr;
     }
@@ -185,6 +238,8 @@ class UTILS_PUBLIC CString {
     };
 
 private:
+    CString& replace(size_type pos, size_type len, char const* str, size_t l) & noexcept;
+
 #if !defined(NDEBUG)
     friend io::ostream& operator<<(io::ostream& out, const CString& rhs);
 #endif
@@ -225,7 +280,7 @@ class UTILS_PUBLIC CString {
     }
 };
 
-// implement this for your type for automatic conversion to CString. Failing to do so leads
+// Implement this for your type for automatic conversion to CString. Failing to do so leads
 // to a compile-time failure.
 template<typename T>
 CString to_string(T value) noexcept;
@@ -249,7 +304,7 @@ class UTILS_PUBLIC FixedSizeString {
     pointer c_str() noexcept { return mData; }
 
 private:
-    value_type mData[N] = {0};
+    value_type mData[N] = {};
 };
 
 } // namespace utils

libs/utils/src/CString.cpp

@@ -20,27 +20,30 @@
 #include <utils/ostream.h>
 
 #include <algorithm>
+#include <cstdlib>
 #include <memory>
 
+
 namespace utils {
 
 UTILS_NOINLINE
-CString::CString(const char* cstr, size_t length) {
+CString::CString(const char* cstr, size_t const length) {
     if (length && cstr) {
-        Data* p = (Data*)malloc(sizeof(Data) + length + 1);
-        p->length = (size_type)length;
-        mCStr = (value_type*)(p + 1);
+
+        Data* const p = static_cast<Data*>(std::malloc(sizeof(Data) + length + 1));
+        p->length = size_type(length);
+        mCStr = reinterpret_cast<value_type*>(p + 1);
         // we don't use memcpy here to avoid a call to libc, the generated code is pretty good.
         std::uninitialized_copy_n(cstr, length, mCStr);
         mCStr[length] = '\0';
     }
 }
 
-CString::CString(size_t length) {
+CString::CString(size_t const length) {
     if (length) {
-        Data* p = (Data*)malloc(sizeof(Data) + length + 1);
-        p->length = (size_type)length;
-        mCStr = (value_type*)(p + 1);
+        Data* const p = static_cast<Data*>(std::malloc(sizeof(Data) + length + 1));
+        p->length = size_type(length);
+        mCStr = reinterpret_cast<value_type*>(p + 1);
         std::fill_n(mCStr, length, 0);
         mCStr[length] = '\0';
     }
@@ -58,24 +61,30 @@ CString& CString::operator=(const CString& rhs) {
     if (this != &rhs) {
         auto *const p = mData ? mData - 1 : nullptr;
         new(this) CString(rhs);
-        free(p);
+        std::free(p);
     }
     return *this;
 }
 
-CString& CString::replace(size_type pos, size_type len, const CString& str) noexcept {
+CString::~CString() noexcept {
+    if (mData) {
+        std::free(mData - 1);
+    }
+}
+
+CString& CString::replace(size_type const pos, size_type len, char const* str, size_t const l) & noexcept {
     assert(pos <= size());
 
     len = std::min(len, size() - pos);
 
     // The new size of the string, after the replacement.
-    const size_type newSize = size() - len + str.size();
+    const size_type newSize = size() - len + l;
 
     // Allocate enough memory to hold the new string.
-    Data* p = (Data*) malloc(sizeof(Data) + newSize + 1);
+    Data* const p = static_cast<Data*>(std::malloc(sizeof(Data) + newSize + 1));
     assert(p);
     p->length = newSize;
-    value_type* newStr = (value_type*) (p + 1);
+    value_type* newStr = reinterpret_cast<value_type*>(p + 1);
 
     const value_type* beginning = mCStr;
     const value_type* replacementStart = mCStr + pos;
@@ -84,22 +93,22 @@ CString& CString::replace(size_type pos, size_type len, const CString& str) noex
 
     value_type* ptr = newStr;
     ptr = std::uninitialized_copy(beginning, replacementStart, ptr);
-    ptr = std::uninitialized_copy_n(str.c_str_safe(), str.length(), ptr);
+    ptr = std::uninitialized_copy_n(str, l, ptr);
     ptr = std::uninitialized_copy(replacementEnd, end, ptr);
 
     // null-terminator
     *ptr = 0;
 
     std::swap(mCStr, newStr);
     if (newStr) {
-        free((Data*) newStr - 1);
+        std::free(reinterpret_cast<Data*>(newStr) - 1);
     }
 
     return *this;
 }
 
 #if !defined(NDEBUG)
-io::ostream& operator<<(io::ostream& out, const utils::CString& rhs) {
+io::ostream& operator<<(io::ostream& out, const CString& rhs) {
     return out << rhs.c_str_safe();
 }
 #endif