Mutable String Class

Question

Here is a String class that I've made for fun in my spare time, for myself. I have a few concerns about it, and am considering going immutable or a mix of the two where the string would be immutable when initialized from a constant, and then mutable when changed.

Also I am considering how to implement Unicode. I could prefer not to have a default format such as always translating to UTF32 internally, but rather to be flexible and to have each instance keep its source format unless told otherwise. But then I would need a Char class to abstract the difference between formats, and I find it very fun to keep things optimized for performance as well.

1. How would you go about this?
2. Is there something very wrong in my class?

Please be criticize my code so that I can improve on it.

Header

/*
    String defaults to String::Empty
*/

#pragma once
#include "../Types.hpp"
#include "../DataStruct/Vector.hpp"

namespace Core
{
    class String
    {
        static UInt NewLineLength;

        public:
        static CStr const Empty;

        private:
        typedef DataStruct::Vector<TChar> Vector;
        Vector _vctr;

        public:
        /* StrPtrVec internal class */
        class StrPtrVec : public DataStruct::Vector<String*>
        {
            public:
            StrPtrVec();
            StrPtrVec(UInt capacity);
            ~StrPtrVec();
        };

        /* public static */
        static UInt CStrLength(CStr);
        static UInt CStrByteSize(CStr);
        static void FormatToBuffer(TChar* buffer, UInt buffer_size, CStr format, ...);
        static String FormatToString(CStr format, ...);
        static Int Compare(CStr source, CStr target);
        static Bool StartsWith(CStr text, UInt textLength, CStr value);
        static Bool StartsWith(CStr text, CStr value);
        static Bool EndsWith(CStr text, UInt textLength, CStr value);
        static Bool EndsWith(CStr text, CStr value);
        static UInt IndexOf(CStr text, UInt textLength, CStr value, UInt valueLength, UInt start = 0);
        static UInt IndexOf(CStr text, UInt textLength, CStr value, UInt start = 0);
        static UInt IndexOf(CStr text, CStr value, UInt start = 0);
        static UInt LastIndexOf(CStr text, UInt textLength, CStr value, UInt valueLength, UInt start = Default);
        static UInt LastIndexOf(CStr text, UInt textLength, CStr value, UInt start = Default);
        static UInt LastIndexOf(CStr text, CStr value, UInt start = Default);
        static String SubString(CStr text, UInt textLength, UInt start, UInt length);
        static String SubString(CStr text, UInt start, UInt length);

        //StrPtrVec* must be manually deleted to avoir leaks
        static StrPtrVec* Split(CStr text, UInt textLength, CStr delimiters, UInt delimitersLength);
        static StrPtrVec* Split(CStr text, UInt textLength, CStr delimiters);
        static StrPtrVec* Split(CStr text, CStr delimiters);

        static Bool IsDigit(TChar chr);
        static Bool IsDigit(CStr text, UInt textLength);
        static Bool IsDigit(CStr text);
        static const UInt NoMatch = (UInt)-1;
        static const UInt Default = NoMatch;
        static const UInt MaxSize = NoMatch - 1;

        /* Constructors && Destructor */
        String();
        String(UInt capacity);
        String(CStr value);
        String(CStr value, UInt length);
        String(CStr begin, CStr end);
        String(String const & value);
        String(String && value);
        ~String();

        /* Operators */
        operator CStr () const;
        String& operator=(CStr text);
        String& operator=(String const &text);
        String& operator=(String && text);
        String& operator+=(CStr text);
        String& operator+=(String const & text);
        String operator+(CStr text) const;
        String operator+(String const & text) const;
        Bool operator==(CStr text) const;
        Bool operator!=(CStr text) const;
        Bool operator>(CStr text) const;
        Bool operator<(CStr text) const;
        Bool operator>=(CStr text) const;
        Bool operator<=(CStr text) const;
        TChar operator[](UInt index) const;

        /* Public Const Functions */
        Bool IsEmpty() const;
        UInt Capacity() const;
        UInt Length() const;
        UInt ByteSize() const;
        CStr CStrPtr() const;
        Int Compare(CStr value) const;
        Bool StartsWith(CStr value);
        Bool EndsWith(CStr value);
        UInt IndexOf(CStr value, UInt start = 0) const;
        UInt LastIndexOf(CStr value, UInt start = Default) const;
        String SubString(UInt start, UInt length) const;
        StrPtrVec* Split(CStr delimiters) const;

        /* Public No-Const Functions */
        void Clear();
        void Reserve(UInt capacity);
        void Shrink();
        String& Append(CStr value);
        String& Append(String const & value);
        String& AppendLine(CStr value = String::Empty);
        String& AppendLine(String const & value);
        TChar* DrivePointer(UInt future_length);
        String& TrimLeft();
        String& TrimRight();
        String& Trim();
        Bool IsDigit();
        String& Overwrite(UInt start, CStr begin, CStr end);
        String& Replace(CStr oldValue, CStr newValue);
    };
}

Implementation

#include <stdarg.h>
#include "String.hpp"
#include "../Assert/Assert.hpp"

void FormatImpl(Core::TChar* buffer, Core::UInt buffer_size, Core::CStr format, va_list args);
Core::UInt FormatImplGetRequiredSize(Core::CStr format, va_list args);

namespace Core
{
    UInt String::NewLineLength = String::CStrLength(NewLine);
    CStr const String::Empty = Text("");

    /******************************************************************************/
    /* StrPtrVec internal class ***************************************************/
    /******************************************************************************/

    String::StrPtrVec::StrPtrVec() : DataStruct::Vector<String*>(Pod)
    {
    }

    String::StrPtrVec::StrPtrVec(UInt capacity) : DataStruct::Vector<String*>(capacity, Pod)
    {
    }

    String::StrPtrVec::~StrPtrVec()
    {
        auto it = Begin();
        auto end = End();
        while(it < end)
        {
            delete *it;
            ++it;
        }
    }

    /******************************************************************************/
    /* public static **************************************************************/
    /******************************************************************************/

    UInt String::CStrLength(CStr text)
    {
        ASSERT_PARAMETER(text);

        UInt length = 0U;

        if(text)
            while(*text != '\0')
            {
                ++text;
                ++length;
            }

        return length;
    }

    UInt String::CStrByteSize(CStr text)
    {
        ASSERT_PARAMETER(text);
        return CStrLength(text) * sizeof(TChar);
    }

    void String::FormatToBuffer(TChar* buffer, UInt buffer_size, CStr format, ...)
    {
        ASSERT_PARAMETER(buffer);
        ASSERT_PARAMETER(format);

        va_list args;
        va_start(args, format);
        FormatImpl(buffer, buffer_size, format, args);
        va_end(args);
    }

    String String::FormatToString(CStr format, ...)
    {
        ASSERT_PARAMETER(format);

        va_list args;
        UInt size;
        String value;

        va_start(args, format);
        size = FormatImplGetRequiredSize(format, args);
        va_end(args);

        value.Reserve(size);

        va_start(args, format);
        FormatImpl(value._vctr.DrivePointer(size), size, format, args);
        va_end(args);

        return value;
    }

    Int String::Compare(CStr source, CStr target)
    {
        //Return
        //   0 when source == target
        //   1 when source >  target
        //  -1 when source <  target

        ASSERT_PARAMETER(source);
        ASSERT_PARAMETER(target);

        while(true)
        {
            if(*source == '\0' && *target == '\0') return 0;
            if(*source == '\0') return -1;
            if(*target == '\0') return 1;
            if(*source < *target) return -1;
            if(*source > *target) return 1;
            ++source;
            ++target;
        }

        return 0;
    }

    Bool String::StartsWith(CStr text, UInt textLength, CStr value)
    {
        ASSERT_PARAMETER(text);
        ASSERT_PARAMETER(value);

        CStr end = text + textLength;

        while(text < end && *value && *text == *value)
        {
            ++text;
            ++value;
        }

        return !*value;
    }

    Bool String::StartsWith(CStr text, CStr value)
    {
        ASSERT_PARAMETER(text);
        ASSERT_PARAMETER(value);

        while(*text && *value && *text == *value)
        {
            ++text;
            ++value;
        }

        return !*value;
    }

    Bool String::EndsWith(CStr text, UInt textLength, CStr value)
    {
        ASSERT_PARAMETER(text);
        ASSERT_PARAMETER(value);
        CStr it = text + textLength - CStrLength(value);
        return it >= text ? StartsWith(it, value) : false;
    }

    Bool String::EndsWith(CStr text, CStr value)
    {
        ASSERT_PARAMETER(text);
        ASSERT_PARAMETER(value);
        return EndsWith(text, CStrLength(text), value);
    }

    UInt String::IndexOf(CStr text, UInt textLength, CStr value, UInt valueLength, UInt start)
    {
        ASSERT_PARAMETER(text);
        ASSERT_PARAMETER(value);

        CStr it, end;

        if(start >= textLength || textLength < valueLength)
            return NoMatch;

        it = text + start;
        end = text + textLength;

        while(it < end)
        {
            if(valueLength == 1 ? *it == *value : StartsWith(it, value))
                return it - text;
            ++it;
        }

        return NoMatch;
    }

    UInt String::IndexOf(CStr text, UInt textLength, CStr value, UInt start)
    {
        ASSERT_PARAMETER(text);
        ASSERT_PARAMETER(value);
        return IndexOf(text, textLength, value, CStrLength(value), start);
    }

    UInt String::IndexOf(CStr text, CStr value, UInt start)
    {
        ASSERT_PARAMETER(text);
        ASSERT_PARAMETER(value);
        return IndexOf(text, CStrLength(text), value, CStrLength(value), start);
    }

    UInt String::LastIndexOf(CStr text, UInt textLength, CStr value, UInt valueLength, UInt start)
    {
        ASSERT_PARAMETER(text);
        ASSERT_PARAMETER(value);

        if(start != Default)
        {
            if(start > textLength)
                return NoMatch;
            else
                textLength = start;
        }

        if(valueLength > textLength)
            return NoMatch;

        CStr rend = text - 1;
        CStr it = text + textLength - valueLength;

        while(rend < it)
        {
            if(valueLength == 1 ? *it == *value : StartsWith(it, valueLength, value))
                return it - text;
            --it;
        }

        return NoMatch;
    }

    UInt String::LastIndexOf(CStr text, UInt textLength, CStr value, UInt start)
    {
        ASSERT_PARAMETER(text);
        ASSERT_PARAMETER(value);
        return LastIndexOf(text, textLength, value, CStrLength(value), start);
    }

    UInt String::LastIndexOf(CStr text, CStr value, UInt start)
    {
        ASSERT_PARAMETER(text);
        ASSERT_PARAMETER(value);
        return LastIndexOf(text, CStrLength(text), value, CStrLength(value), start);
    }

    String String::SubString(CStr text, UInt textLength, UInt start, UInt length)
    {
        ASSERT_PARAMETER(text);

        if(length > textLength) length = textLength;
        if(!text || !length || start + length > textLength) return String();
        return String(text + start, text + start + length);
    }

    String String::SubString(CStr text, UInt start, UInt length)
    {
        ASSERT_PARAMETER(text);
        return SubString(text, CStrLength(text), start, length);
    }

    //delimiters is a list of TChar separators and not a single string separator
    String::StrPtrVec* String::Split(CStr text, UInt textLength, CStr delimiters, UInt delimitersLength)
    {
        ASSERT_PARAMETER(text);
        ASSERT_PARAMETER(delimiters);

        StrPtrVec* vStr;
        CStr begin, it, end;
        UInt count;

        vStr = new StrPtrVec();

        if(!textLength)
            return vStr;

        if(!delimitersLength)
        {
            vStr->Add(new String(text));
            return vStr;
        }

        begin = text;
        it = text;
        end = text + textLength;
        count = 0U;

        while(it < end)
        {
            if(delimitersLength == 1 ? *it == *delimiters : IndexOf(delimiters, delimitersLength, it, 1U, 0U) != NoMatch)
            {
                if(begin != it)
                {
                    vStr->Add(new String(begin, it));
                    begin = it + 1;
                    ++count;
                }
                else
                    ++begin;
            }
            ++it;
        }

        if(begin != end)
        {
            vStr->Add(new String(begin, end));
            ++count;
        }

        return vStr;
    }

    String::StrPtrVec* String::Split(CStr text, UInt textLength, CStr delimiters)
    {
        ASSERT_PARAMETER(text);
        ASSERT_PARAMETER(delimiters);
        return Split(text, textLength, delimiters, CStrLength(delimiters));
    }

    String::StrPtrVec* String::Split(CStr text, CStr delimiters)
    {
        ASSERT_PARAMETER(text);
        ASSERT_PARAMETER(delimiters);
        return Split(text, CStrLength(text), delimiters, CStrLength(delimiters));
    }

    //Digits are 0123456789
    Bool String::IsDigit(TChar chr)
    {
        TChar const value[2] = {chr, 0};
        return String::IndexOf(Text("0123456789"), 10U, value) != String::NoMatch;
    }

    Bool String::IsDigit(CStr text, UInt textLength)
    {
        ASSERT_PARAMETER(text);
        CStr it = text;
        CStr end = text + textLength;

        while(it < end)
            if(!IsDigit(*it++))
                return false;

        return true;
    }

    Bool String::IsDigit(CStr text)
    {
        ASSERT_PARAMETER(text);
        return IsDigit(text, CStrLength(text));
    }

    /******************************************************************************/
    /* Constructors && Destructor *************************************************/
    /******************************************************************************/

    String::String() : _vctr(Vector::CtorModeEnum::Pod)
    {
    }

    String::String(UInt capacity) : _vctr(capacity, Vector::CtorModeEnum::Pod)
    {
    }

    //value must be null terminated
    String::String(CStr value) : _vctr(Vector::CtorModeEnum::Pod)
    {
        ASSERT_PARAMETER(value);
        UInt length = CStrLength(value);
        if(length)
            _vctr.AddRange(value, value + length + 1);
    }

    //if length > 0 value must not be null
    String::String(CStr value, UInt length) : _vctr(Vector::CtorModeEnum::Pod)
    {
        ASSERT_PARAMETER(length == 0 || value);
        if(length)
            _vctr.AddRange(value, value + length + 1);
    }

    String::String(CStr begin, CStr end) : _vctr(Vector::CtorModeEnum::Pod)
    {
        ASSERT_PARAMETER(begin);
        ASSERT_PARAMETER(end);
        ASSERT(begin <= end);

        if(begin != end)
            _vctr.AddRange(begin, end);

        _vctr.Add(Text('\0'));
    }

    String::String(String const & value) : _vctr(value._vctr)
    {
    }

    String::String(String && value) : _vctr((Vector&&)value)
    {
    }

    String::~String()
    {
    }

    /******************************************************************************/
    /* Operators ******************************************************************/
    /******************************************************************************/

    String::operator CStr () const
    {
        return CStrPtr();
    }

    String& String::operator=(CStr text)
    {
        ASSERT_PARAMETER(text);

        UInt n = CStrLength(text);
        _vctr.Clear();

        if(n)
            _vctr.AddRange(text, text + n + 1);

        return *this;
    }

    String& String::operator=(String const & text)
    {
        if(this != &text)
        {
            if(text.IsEmpty())
                _vctr.Clear();
            else
                *this = text.CStrPtr();
        }

        return *this;
    }

    String& String::operator=(String && text)
    {
        _vctr.operator=((Vector&&)text);
        return *this;
    }

    String& String::operator+=(CStr text)
    {
        //ASSERT_PARAMETER(text);
        UInt length = CStrLength(text);
        UInt current_length, new_length;
        Bool max_size_overflowing;

        if(length)
        {
            //Check for MaxSize overflow
            current_length = _vctr.Length();
            new_length = current_length + length;
            max_size_overflowing = new_length >= MaxSize || new_length < current_length;
            ASSERT(!max_size_overflowing);

            _vctr.Remove(current_length - 1);
            _vctr.AddRange(text, text + length + 1);
        }
        return *this;
    }

    String& String::operator+=(String const & text)
    {
        if(!text.IsEmpty())
        {
            _vctr.Remove(_vctr.Length() - 1);
            _vctr.operator+=(text._vctr);
        }
        return *this;
    }

    String String::operator+(CStr text) const
    {
        ASSERT_PARAMETER(text);
        return String(*this) += text;
    }

    String String::operator+(String const & text) const
    {
        return String(*this) += text;
    }

    Bool String::operator==(CStr text) const { ASSERT_PARAMETER(text); return Compare(text) ==  0; }
    Bool String::operator!=(CStr text) const { ASSERT_PARAMETER(text); return Compare(text) !=  0; }
    Bool String::operator> (CStr text) const { ASSERT_PARAMETER(text); return Compare(text) ==  1; }
    Bool String::operator< (CStr text) const { ASSERT_PARAMETER(text); return Compare(text) == -1; }
    Bool String::operator>=(CStr text) const { ASSERT_PARAMETER(text); return Compare(text) >=  0; }
    Bool String::operator<=(CStr text) const { ASSERT_PARAMETER(text); return Compare(text) <=  0; }

    TChar String::operator[](UInt index) const
    {
        return _vctr.operator[](index);
    }

    /******************************************************************************/
    /* Public Const Functions *****************************************************/
    /******************************************************************************/

    Bool String::IsEmpty() const
    {
        return _vctr.IsEmpty();
    }

    UInt String::Capacity() const
    {
        return _vctr.Capacity();
    }

    UInt String::Length() const
    {
        return _vctr.IsEmpty() ? 0U : _vctr.Length() - 1;
    }

    UInt String::ByteSize() const
    {
        return Length() * sizeof(TChar);
    }

    CStr String::CStrPtr() const
    {
        return IsEmpty() ? String::Empty : _vctr.Begin();
    }

    Int String::Compare(CStr value) const
    {
        ASSERT_PARAMETER(value);
        return Compare(CStrPtr(), value);
    }

    Bool String::StartsWith(CStr value)
    {
        ASSERT_PARAMETER(value);
        return StartsWith(CStrPtr(), value);
    }

    Bool String::EndsWith(CStr value)
    {
        ASSERT_PARAMETER(value);
        return EndsWith(CStrPtr(), Length(), value);
    }

    UInt String::IndexOf(CStr value, UInt start) const
    {
        ASSERT_PARAMETER(value);
        return IndexOf(CStrPtr(), Length(), value, CStrLength(value), start);
    }

    UInt String::LastIndexOf(CStr value, UInt start) const
    {
        ASSERT_PARAMETER(value);
        return LastIndexOf(CStrPtr(), Length(), value, CStrLength(value), start);
    }

    String String::SubString(UInt start, UInt length) const
    {
        return SubString(CStrPtr(), Length(), start, length);
    }

    String::StrPtrVec* String::Split(CStr delimiters) const
    {
        ASSERT_PARAMETER(delimiters);
        return Split(CStrPtr(), Length(), delimiters);
    }

    /******************************************************************************/
    /* Public Functions ***********************************************************/
    /******************************************************************************/

    //Clear does not deallocate memorys
    void String::Clear()
    {
        _vctr.Clear();
    }

    void String::Reserve(UInt capacity)
    {
        _vctr.Reserve(capacity + sizeof(TChar));
    }

    void String::Shrink()
    {
        _vctr.Shrink();
    }

    String& String::Append(CStr value)
    {
        ASSERT_PARAMETER(value);
        *this += value;
        return *this;
    }

    String& String::Append(String const & value)
    {
        *this += value;
        return *this;
    }

    String& String::AppendLine(CStr value)
    {
        ASSERT_PARAMETER(value);
        *this += value;
        *this += NewLine;
        return *this;
    }

    String& String::AppendLine(String const & value)
    {
        *this += value;
        *this += NewLine;
        return *this;
    }

    TChar* String::DrivePointer(UInt future_length)
    {
        auto buffer = _vctr.DrivePointer(future_length + 1);
        buffer[future_length] = Text('\0');
        return buffer;
    }

    String& String::TrimLeft()
    {
        auto it = _vctr.Begin();
        UInt size;

        while(it < _vctr.End() && *it == 32)
            ++it;

        if(it != _vctr.Begin())
        {
            size = _vctr.End() - it;
            Memory::Move(it, _vctr.DrivePointer(size), size * sizeof(TChar));
        }

        return *this;
    }

    String& String::TrimRight()
    {
        Vector::Element* it;

        while((it = _vctr.RBegin() - 1) > _vctr.REnd() && *it == 32)
            _vctr.Remove(*it);

        return *this;
    }

    String& String::Trim()
    {
        return TrimRight().TrimLeft();
    }

    Bool String::IsDigit()
    {
        return IsDigit(CStr(), Length());
    }

    UInt HowManyThereIs(CStr text, UInt textLength, CStr value, UInt valueLength)
    {
        UInt it = 0U, idx;
        UInt count = 0U;

        while(it < textLength)
        {
            idx = String::IndexOf(text, textLength, value, valueLength, it);
            if(idx != String::NoMatch)
            {
                it = idx + valueLength;
                ++count;
            }
            else
                break;
        }

        return count;
    }

    String& _ReplaceRightToLeft(String& stringRef, UInt length, CStr oldValue, UInt oldValueLength, CStr newValue, UInt newValueLength)
    {
        Int diff = Int(newValueLength - oldValueLength);
        Int offset = diff ? diff * HowManyThereIs(stringRef.CStrPtr(), length, oldValue, oldValueLength) : 0;

        UInt newLength = length + offset;
        stringRef.Reserve(newLength);

        CStr text = stringRef.CStrPtr();
        CStr tail = text + length;

        UInt idx;
        UInt lengthToMove;
        VoidPtr source, target;

        while(length && String::NoMatch != (idx = String::LastIndexOf(text, length, oldValue, oldValueLength, String::Default)))
        {
            lengthToMove = length - (idx + oldValueLength);

            if(lengthToMove)
            {
                source = VoidPtr(text + idx + oldValueLength);
                target = VoidPtr(tail - lengthToMove + offset);
                Memory::Move(source, target, lengthToMove * sizeof(TChar));
            }

            offset -= diff;
            source = VoidPtr(newValue);
            target = VoidPtr(text + idx + offset);
            Memory::Move(source, target, newValueLength * sizeof(TChar));

            tail -= lengthToMove + oldValueLength;
            length = tail - text;
        }

        stringRef.DrivePointer(newLength);
        return stringRef;
    }

    String& _ReplaceLeftToRight(String& stringRef, UInt length, CStr oldValue, UInt oldValueLength, CStr newValue, UInt newValueLength)
    {
        /*
        ### DF ### best ###
        !## DF ### best ###
        ! DF F ### best ###
        ! DF ! ### best ###
        ! DF ! best est ###
        ! DF ! best !st ###
        ! DF ! best !
        */

        CStr text = stringRef.CStrPtr();
        CStr it_source = text;
        CStr it_target = text;
        UInt idx;

        while(String::NoMatch != (idx = String::IndexOf(it_source, length, oldValue, oldValueLength, 0U)))
        {
            if(idx)
            {
                Memory::Move((VoidPtr)it_source, (VoidPtr)it_target, idx * sizeof(TChar));
                it_source += idx;
                it_target += idx;
            }

            Memory::Move(VoidPtr(newValue), VoidPtr(it_target), newValueLength * sizeof(TChar));
            it_source += oldValueLength; // 3
            it_target += newValueLength; // 1
        }

        idx = text + length - it_source;
        if(idx)
        {
            Memory::Move((VoidPtr)it_source, (VoidPtr)it_target, idx * sizeof(TChar));
            it_source += idx;
            it_target += idx;
        }

        stringRef.DrivePointer(it_target - text);
        return stringRef;
    }

    //TASK TODO Switch Memory::Move by Memory::Copy when applicable
    //TASK TODO The start param of IndexOf default to 0 and not to String::Default, unlike LastIndexOf.
    //          I called IndexOf with start = String::Default while meaning 0
    //          Maybe the start param should default to String::Default instead of 0
    //TASK TODO Minimise and Optimise String::Replace
    //          consider a function for oldValueLength == newValueLength
    //          reconsider one function for all cases

    String& _Replace(String& stringRef, UInt length, CStr oldValue, UInt oldValueLength, CStr newValue, UInt newValueLength)
    {
        Int diff = Int(newValueLength - oldValueLength);
        if(diff >= 0)
            return _ReplaceRightToLeft(stringRef, length, oldValue, oldValueLength, newValue, newValueLength);
        else
            return _ReplaceLeftToRight(stringRef, length, oldValue, oldValueLength, newValue, newValueLength);
    }

    String& String::Replace(CStr oldValue, CStr newValue)
    {
        ASSERT_PARAMETER(oldValue);
        ASSERT_PARAMETER(newValue);

        UInt oldValueLength, length;

        if(IndexOf(oldValue) == NoMatch)
            return *this;

        oldValueLength = CStrLength(oldValue);
        length = Length();

        if(oldValueLength > length)
            return *this;

        return _Replace(*this, length, oldValue, oldValueLength, newValue, CStrLength(newValue));
    }
}

Units Tests are also present in the CoreSpecimen project on GitHub. I am limited to two links per post at this time so it's not linked here.

Answer 1

A few points open to improvement:

• In your implementation file, you have two functions, _ReplaceRightToLeft() and _ReplaceLeftToRight() that are using a technically ilegal naming. Names starting with an underscore, followed by an uppercase letter are reserved by the C++ standard.

• You are dealing with raw pointers here and there (Split() raises a few red flags), which is not ideal, since no information about ownership is implied. Ideally, you should give preference to smart pointers.

• Personally, I think you are abusing a bit with the typedefs for every native type. This is the convention in a lot of Windows code, but is it really necessary in your case to typedef VoidPtr, Bool, Int? I sort of understand the reason, keeping an uniform naming for everything, but as time goes by, you are likely to get tired or hitting SHIFT every time you want to declare a simple int. So my suggestion is for you to rethink that and be less pedantic with the type naming, in exchange for more straightforwardness when writing code.

• Another piece of personal advice: YMMV, but I have recently decided to stop indenting namespaces, after many years of doing so. I have come to the conclusion that this adds little to nothing to the readability of the code, at the expense of a default level of indentation everywhere. This is another case to weight pedantry vs practicality.

• What's a CStr? Took me a while to realize that it must be char *. This typedef is only obfuscating the code. Even though more verbose, const char * (or const TChar * if you prefer), would make things a lot clearer.

• Instead of doing something awkward like this:

  _vctr.operator=((Vector&&)text);
  

  Use std::move() instead.

• Minor aspect: your naming convention for function parameters is apparently camelCase, though you have one or two instances of snake_case. I.e.: In FormatToBuffer() and DrivePointer(), that I've been able to notice.

Answer 2

Use of Vector for multiple concepts can be misleading. I would replace

    typedef DataStruct::Vector<TChar> Vector;
    Vector _vctr;

by

    typedef DataStruct::Vector<TChar> StringData;
    StringData _sdata;

Majority of the static functions that operate with CStr don't use String in their interface. I would move them to be extern functions in Core namespace.

It's not clear what the purpose of the static member variable Empty is. It's better to have a function that returns an empty String rather than be committed to a member variable. I would change:

    static CStr const Empty;

to

    static CStr const& GetEmpty();

For the same reason, I would move NewLineLength to be a member function.

    static UInt GetNewLineLength();

Answer 3

am considering going immutable or a mix of the two where the string would be immutable when initialized from a constant, and then mutable when changed.

I'm not quite sure this is a good idea.

C++'s concept of const correctness makes immutability as done in other languages pretty rare for C++. Basically, by making all of the mutating methods non-const, you can make a const instance of your class immutable. This means that you don't need to two classes for both cases of mutable/immutable.

By having a const version that returns a copy and a non-const version that operates in place, you can have the best of both worlds while keeping all of your code in one place. The downside of course is that you have to get kind of strange with the naming scheme in this situation or it can become confusing which one you're calling.

Or, there's also the option that the standard library takes. When an instance is immutable, you could disallow any kind of mutatation on it. The consumer of the class would then have to manually make a copy and mutate that if required. While it's a bit more tedious as a consumer, it's much less code for you, and I think explicit copies would end up being pretty rare (for example, a consumer planning to copy a string can just accept it by value instead of const-ref).

Anyway, just something to be aware of. I'm not sure if C++ can even support a compile time version of what you're considering (at least not without quite a bit of template specialization magic, and even then I'm unsure).

---

Empty doesn't need to be exposed in the header (nor should it likely exist).

---

What type is NewLine? Assuming it's a char*, having it be a char[] would mean instead of a constant for the size, you could just use sizeof.

---

I'm not sure from a design perspective if a string class should have a concept of lines. Seems that might be better off left to some kind of reader/writer + stream system. There's a fine line between where storage and common usage of storage should be split, but I tend to tend towards storage being a very separate concern.

---

/* StrPtrVec internal class */

That's a lie. It's a publically exposed class, and it's a return type of a few of your functions. There's nothing 'internal' about it, and treating it as such will lead you to reasonining about it differently than if you thought it was an exposed class.

---

If DataStruct::Vector is implementated as a curiosity, that's great. If this were to end up being used for real though, unless you had some very specific reason, it would be much better to use std::vector.

---

//StrPtrVec* must be manually deleted to avoir leaks
static StrPtrVec* Split(CStr text, UInt textLength, CStr delimiters, UInt delimitersLength);
static StrPtrVec* Split(CStr text, UInt textLength, CStr delimiters);
static StrPtrVec* Split(CStr text, CStr delimiters);

... What!? A raw owning pointer should be considered unacceptable as a return in modern C++ code. There's a host of better options:

1. Return a vector of Strings instead of C-strings. Note: Can be done with no overhead with copy-on-write, but COW has it's own disadvantages.
2. Return a vector of pairs where each is a begin/end index
3. Return a vector of std::unique_ptr (or some other smart pointer)

Also, why is the vector returned by pointer?

---

I'm a bit confused by your class. Or rather, I don't like that C-string and a C++ data type are mixed. C-strings are C-strings, and your String class is your String class. If you want to make convenience methods for C-string manipulation, go ahead, but don't mix it together with your class (perhaps free functions in a StringUtil namespace). Or, if you do, at least use your class in situations that make sense (return types, etc). You could even go as far as making a copy-on-write style String that can wrap a C-string with no cost (though once again, COW has some disadvantages).

---

I have mixed feelings about your equality operators asserting that the provided C-string is non-null. Clear, unambigious semantics can be provided with a null c-string, so I'm not sure if the restriction is really necessary.

---

What is DrivePointer? Why is it named like it is? Is the call responsible for freeing it?

---

That reminds me, your class is in pretty desperate need of documentation in a few places.

---

while(it < _vctr.End() && *it == 32)

Use character literals instead of ASCII values. Not only is it easier to read, but you've made the assumption that the system is using ASCII and thus limited your code's portability for no reason.

---

Declare variables as tightly scoped as possible. It helps the reader see where things are used and determine what they are.

For example, in TrimLeft, size could be declared inside of the block in which it's used.

---

This is just a guess, but I'm going to imagine that your IsDigit(TChar chr) can be made many, many times faster than your current implementation by either either a switch or a range:

switch (chr) {
    case '0':
    case '1':
    case '2':
    ...
    case '9':
        return true;
    default:
        return false;
}

Or:

return (chr >= '0' && chr <= '9');

Note that the range based approach assumes that 0, 1, 2, ..., 9 are contiguous in the character set. As odd a thought as it is, that's actually not guaranteed to be true, so you would technically be sacrificing a bit of portability with that. In practice, it likely wouldn't be much of an issue, but just one of those rather sneaky C++ portability gotchas.

---

This comes down to personal style, but I'm a fan of SCREAMING_CAPS_CONSTANTS rather than PascalCaseConstants. Screaming constants are very clearly constants, they're a pretty well established pattern in the C++ world (and pretty much every other language), and they're very hard to confuse with anything else (local variable, method name, etc).

---

While I'm spewing opinions about style, I'm also not a fan of omitted braces. It's a bit paranoid, but I think it's better to err on the side of always adding them. It only takes a few extra keystrokes, and it means that the chances of someone messing up the code in the future are vastly reduced.

It's fairly easy in theory to notice if braces are missing or not, but imagine a beginner developer coming along, or imagine a diff going horribly wrong... Not all that hard to imagine that the missing braces could come back to bite you.

---

Implicit conversions to a pointer type can result in some very, very weird statements being valid:

String s;
s + 3; // Valid
s - 2; // Valid
delete s; // Wait, what?!

char* f() {
    return String(); // Dangling pointer
}

In other words, this is probably a bad idea. Though it would be incredibly convenient, there's a reason std::string and most smart pointer implementations require an explicit conversion to a raw pointer.

---

Speaking of pointer gotchas, CStrPtr() needs two versions. The const version should return a pointer to const, and the non-const version should return a non-const pointer. As it currently stands, provided CStr is non constant (I have no idea what it actually is), you can mutate a const String by converting it to a CStr. At best this is stupid on the part of the consumer, and at worst, it's a segfault. The interface shouldn't make this mistake possible.

---

Just a thought: your class is just a template parameter or two away from being generalized to any kind of underlying char type.