Exer14_27_StrBlob.h

#ifndef STRBLOB_H
#define STRBLOB_H
#include <cstddef>
#include <string>
#include <vector>
#include <initializer_list>
#include <memory>
#include <stdexcept>
using std::size_t;
using std::string;
using std::vector;
using std::initializer_list;
using std::shared_ptr;
using std::make_shared;
using std::weak_ptr;
using std::runtime_error;
using std::out_of_range;
class StrBlobPtr;
class ConstStrBlobPtr;
class StrBlob {
    friend class StrBlobPtr;
    friend class ConstStrBlobPtr;
    // overloaded equality operators required by exercise 14.16
    friend bool operator==(const StrBlob&, const StrBlob&);
    friend bool operator!=(const StrBlob&, const StrBlob&);
    // overloaded relational operator required by exercise 14.18
    friend bool operator<(const StrBlob&, const StrBlob&);
    friend bool operator<=(const StrBlob&, const StrBlob&);
    friend bool operator>(const StrBlob&, const StrBlob&);
    friend bool operator>=(const StrBlob&, const StrBlob&);
public:
    typedef vector<string>::size_type size_type;
    StrBlob();
    StrBlob(initializer_list<string> il);
    size_type size() const { return data->size(); }
    // add and remove elements
    void push_back(const string &t) { data->push_back(t); }
    void pop_back();
    // elements access
    string& front();
    string& back();
    // const versions of front and back required by exercise 12.2
    const string& front() const;
    const string& back() const;
    // return reference count
    const size_type use_count() const { return data.use_count(); }
    StrBlobPtr begin();
    StrBlobPtr end();
    ConstStrBlobPtr begin() const;
    ConstStrBlobPtr end() const;
    // access elements
    string& at(size_type) const;
    // subscript operator required by exercise 14.26
    // the difference between at and subscript is that subscript doesn't throw
    // exception if the index is out of range.
    string& operator[](size_t n)
    { return (*data)[n]; }
    const string& operator[](size_t n) const
    { return (*data)[n]; }
private:
    shared_ptr<vector<string>> data;
    // throws msg if data[i] isn't valid
    void check(size_type i, const string &msg) const;
};
// constructor
StrBlob::StrBlob() : data(make_shared<vector<string>>()) {}
StrBlob::StrBlob(initializer_list<string> il) :
    data(make_shared<vector<string>>(il)) {};
void StrBlob::check(size_type i, const string &msg) const
{
    if(i >= data->size())
        throw out_of_range(msg);
}
// add and remove elements
void StrBlob::pop_back()
{
    check(0, "pop_back on empty StrBlob");
    data->pop_back();
}
// elements access
string& StrBlob::front()
{
    check(0, "front on empty StrBlob");
    data->front();
}
string& StrBlob::back()
{
    check(0, "back on empty StrBlob");
    data->back();
}
const string& StrBlob::front() const
{
    check(0, "front on empty StrBlob");
    data->front();
}
const string& StrBlob::back() const
{
    check(0, "back on empty StrBlob");
    data->back();
}
string& StrBlob::at(size_type n) const
{
    check(n, "index out of range");
    return data->at(n);
}
// friend definition
bool operator==(const StrBlob &lhs, const StrBlob &rhs)
{
    return *lhs.data == *rhs.data;
}
bool operator!=(const StrBlob &lhs, const StrBlob &rhs)
{
    return !(lhs == rhs);
}
bool operator<(const StrBlob &lhs, const StrBlob &rhs)
{
    return *lhs.data < *rhs.data;
}
bool operator<=(const StrBlob &lhs, const StrBlob &rhs)
{
    return (lhs < rhs || lhs == rhs);
}
bool operator>(const StrBlob &lhs, const StrBlob &rhs)
{
    return !(lhs < rhs || lhs == rhs);
}
bool operator>=(const StrBlob &lhs, const StrBlob &rhs)
{
    return !(lhs < rhs);
}
// ******************************
// nonconst version of StrBlobPtr
// ******************************
class StrBlobPtr{
    // overloaded equality operators required by exercise 14.16
    friend bool operator==(const StrBlobPtr&, const StrBlobPtr&);
    friend bool operator!=(const StrBlobPtr&, const StrBlobPtr&);
    // overloaded relational operators required by exercise 14.18
    friend bool operator<(const StrBlobPtr&, const StrBlobPtr&);
    friend bool operator<=(const StrBlobPtr&, const StrBlobPtr&);
    friend bool operator>(const StrBlobPtr&, const StrBlobPtr&);
    friend bool operator>=(const StrBlobPtr&, const StrBlobPtr&);
public:
    StrBlobPtr() : curr(0) {}
    StrBlobPtr(StrBlob &a, size_t sz = 0) : wptr(a.data), curr(sz) {}
    string& deref() const;
    StrBlobPtr& incr();
    // subscript operator required by exercise 14.26
    string& operator[](size_t n);
    const string& operator[](size_t n) const;
    // increment and decrement operator required by exercise 14.27
    StrBlobPtr& operator++(); // prefix increment, return reference
    StrBlobPtr& operator--(); // prefix decrement
    StrBlobPtr operator++(int); // postfix increment, return value
    StrBlobPtr operator--(int); // postfix decrement
private:
    shared_ptr<vector<string>> check(size_t, const string&) const;
    weak_ptr<vector<string>> wptr;
    size_t curr;
};
shared_ptr<vector<string>> StrBlobPtr::check(size_t i, const string& msg) const
{
    auto ret = wptr.lock();
    if(!ret)
        throw runtime_error("unbound StrBlobPtr");
    if(i >= ret->size())
        throw out_of_range(msg);
    return ret;
}
string& StrBlobPtr::deref() const
{
    auto p = check(curr, "dereference past end");
    return (*p)[curr];
}
StrBlobPtr& StrBlobPtr::incr()
{
    check(curr, "increment past end of StrBlobPtr");
    ++curr;
    return *this;
}
// It should be curr + n, because this points to the position of index curr,
// if we dereference an element by index, we should get the element at the
// position of curr + n.
string& StrBlobPtr::operator[](size_t n)
{
    auto p = check(curr + n, "deference past end");
    return (*p)[curr + n];
}
const string& StrBlobPtr::operator[](size_t n) const
{
    auto p = check(curr + n, "deference past end");
    return (*p)[curr + n];
}
StrBlobPtr& StrBlobPtr::operator++()
{
    check(curr, "increment past end of StrBlobStr");
    ++curr; // advance the current state
    return *this;
}
StrBlobPtr& StrBlobPtr::operator--()
{
    --curr; // move the current state back one element
    check(curr, "decrement past begin of StrBlobPtr");
    return *this;
}
StrBlobPtr StrBlobPtr::operator++(int)
{
    auto ret = *this; // save the current value
    ++*this; // advance one element; prefix ++ checks the increment
    return ret; // return the saved value
}
StrBlobPtr StrBlobPtr::operator--(int)
{
    auto ret = *this; // save the current value
    --*this; // move backward one element; prefix -- checks the decrement
    return ret; // return the saved value
}
// definitions of friend operators
// shared_ptr has its overloaded version of equality and relational operators, but weak_ptr doesn't
// so we have to use lock() to compare
bool operator==(const StrBlobPtr &lhs, const StrBlobPtr &rhs)
{
    return lhs.curr == rhs.curr;
}
bool operator!=(const StrBlobPtr &lhs, const StrBlobPtr &rhs)
{
    return !(lhs == rhs);
}
bool operator<(const StrBlobPtr &lhs, const StrBlobPtr &rhs)
{
    return lhs.curr < rhs.curr;
}
bool operator<=(const StrBlobPtr &lhs, const StrBlobPtr &rhs)
{
    return (lhs < rhs || lhs == rhs);
}
bool operator>(const StrBlobPtr &lhs, const StrBlobPtr &rhs)
{
    return !(lhs < rhs || lhs == rhs);
}
bool operator>=(const StrBlobPtr &lhs, const StrBlobPtr &rhs)
{
    return !(lhs < rhs);
}
// ***************************
// const version of StrBlobPtr
// ***************************
class ConstStrBlobPtr{
    // overloaded equality operators required by exercise 14.16
    friend bool operator==(const ConstStrBlobPtr&, const ConstStrBlobPtr&);
    friend bool operator!=(const ConstStrBlobPtr&, const ConstStrBlobPtr&);
    // overloaded relational operators required by exercise 14.18
    friend bool operator<(const ConstStrBlobPtr&, const ConstStrBlobPtr&);
    friend bool operator<=(const ConstStrBlobPtr&, const ConstStrBlobPtr&);
    friend bool operator>(const ConstStrBlobPtr&, const ConstStrBlobPtr&);
    friend bool operator>=(const ConstStrBlobPtr&, const ConstStrBlobPtr&);
public:
    ConstStrBlobPtr() : curr(0) {}
    ConstStrBlobPtr(const StrBlob &a, size_t sz = 0) : wptr(a.data),curr(sz) {}
    string& deref() const;
    ConstStrBlobPtr& incr();
    // subscript operator required by exercise 14.26
    // ConstStrBlobPtr should only have const version of subscript operator
    string& operator[](size_t n) const;
private:
    shared_ptr<vector<string>> check(size_t, const string&) const;
    const weak_ptr<vector<string>> wptr;
    size_t curr;
};
shared_ptr<vector<string>> ConstStrBlobPtr::check(size_t i, const string& msg) const
{
    auto ret = wptr.lock();
    if(!ret)
        throw runtime_error("unbound StrBlobPtr");
    if(i >= ret->size())
        throw out_of_range(msg);
    return ret;
}
string& ConstStrBlobPtr::deref() const
{
    auto p = check(curr, "dereference past end");
    return (*p)[curr];
}
ConstStrBlobPtr& ConstStrBlobPtr::incr()
{
    check(curr, "increment past end of StrBlobPtr");
    ++curr;
    return *this;
}
string& ConstStrBlobPtr::operator[](size_t n) const
{
    auto p = check(curr + n, "deference past end");
    return (*p)[curr + n];
}
// definitions of friend operators
bool operator==(const ConstStrBlobPtr &lhs, const ConstStrBlobPtr &rhs)
{
    return lhs.wptr.lock() == rhs.wptr.lock() && lhs.curr == rhs.curr;
}
bool operator!=(const ConstStrBlobPtr &lhs, const ConstStrBlobPtr &rhs)
{
    return !(lhs == rhs);
}
bool operator<(const ConstStrBlobPtr &lhs, const ConstStrBlobPtr &rhs)
{
    return lhs.curr < rhs.curr;
}
bool operator<=(const ConstStrBlobPtr &lhs, const ConstStrBlobPtr &rhs)
{
    return lhs.curr <= rhs.curr;
}
bool operator>(const ConstStrBlobPtr &lhs, const ConstStrBlobPtr &rhs)
{
    return lhs.curr > rhs.curr;
}
bool operator>=(const ConstStrBlobPtr &lhs, const ConstStrBlobPtr &rhs)
{
    return lhs.curr >= rhs.curr;
}
// we have to define these member functions here, after the definition of StrBlobPtr
StrBlobPtr StrBlob::begin()
{
    return StrBlobPtr(*this);
}
StrBlobPtr StrBlob::end()
{
    auto ret = StrBlobPtr(*this, data->size());
    return ret;
}
ConstStrBlobPtr StrBlob::begin() const
{
    return ConstStrBlobPtr(*this);
}
ConstStrBlobPtr StrBlob::end() const
{
    auto ret = ConstStrBlobPtr(*this, data->size());
    return ret;
}
#endif
// Note: If two pointers point to two unrelated objects, the result of comparison
// is undefined(See page 120). Here we assume that lhs and rhs point to the same
// object, thus StrBlobPtr has consistent behaviour with built-in pointer. On the
// other hand, we can compare two pointers with == regardless whether they point
// to the same object. Thus it seems that equality and relational operators are
// not consistent with each other.