输入文件保存在StrBlob中, 用一个StrBlobPtr打印出StrBlob中的每一个元素

本文介绍了一个使用C++实现的字符串容器类StrBlob的设计与实现细节，包括智能指针的应用、异常处理机制及迭代器的实现。通过具体代码示例展示了如何在类中运用shared_ptr和weak_ptr来管理资源，以及如何通过检查边界条件来避免运行时错误。

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Talk cheap, It's code:

#include "vld.h"
#define _CRTDBG_MAP_ALLOC
#include 
#include 
#include 
#include 
#include 
#include 

using namespace std;

class StrBlobPtr;
class StrBlob
{
public:
	friend class StrBlobPtr;
	typedef shared_ptr> shared_strVecP;
	typedef vector::size_type size_type;
	StrBlob ();
	StrBlob (initializer_list il);
	size_type size () const { return data->size (); }
	bool empty () const { return data->empty (); }

	//append & delete
	void push_back (const string &t) { data->push_back (t); }
	void pop_back ();

	//call elements
	string& front ();
	string& back ();
private:
	shared_strVecP data;
	//if input invailed, throw exception
	void check (size_type query_pos, const string &msg) const
	{
		try {
			if (query_pos >= data->size ())
				throw out_of_range (msg);
		}
		catch (out_of_range err) {
			cout << err.what () << endl;
		}
	}
};
StrBlob::StrBlob () :data (make_shared > ()) {}
StrBlob::StrBlob (initializer_listil) : data (make_shared> (il)) {}

string& StrBlob::front ()
{
	//if vector is empty, throw exception
	check (0, "front on empty StrBlob");
	return data->front ();
}

string& StrBlob::back ()
{
	//if vector is empty, throw exception
	check (0, "back on empty StrBlob");
	return data->back ();
}

void StrBlob::pop_back ()
{
	check (0, "pop_back on empty StrBlob");
	data->pop_back ();
}

class StrBlobPtr
{
public:
	typedef shared_ptr> shared_strVecP;
	StrBlobPtr () :pos (0) {}
	StrBlobPtr (StrBlob &a, size_t sz = 0) :wptr (a.data), pos (sz) {}
	StrBlobPtr& incr ();
	string& deref ()const;
private:
	shared_strVecP check (size_t, const string&)const;
	weak_ptr>wptr;
	size_t pos;
};

shared_ptr> StrBlobPtr::check (size_t query_pos, const string &msg)const
{
	typedef shared_ptr> shared_strVecP;
	auto ret = wptr.lock ();
	try {
		if (!ret)
			throw runtime_error ("unbound StrBlobPtr!");
		if (query_pos >= ret->size ())
			throw out_of_range (msg);
	}
	catch (runtime_error err) {
		cout << err.what () << endl;
	}
	catch (out_of_range err) {
		cout << err.what () << endl;
	}
	return ret;
}

string& StrBlobPtr::deref ()const
{
	auto p = check (pos, "dereference past end");
	return (*p)[pos];
}

StrBlobPtr& StrBlobPtr::incr ()
{
	check (pos, "incerement past end of StrBlobPtr");
	++pos;
	return *this;
}

int main (int argc, char* argv[])
{
	std::ios::sync_with_stdio (false);
	size_t times = 0;
	string word;
	StrBlob blob;
	while (cin >> word) {
		blob.push_back (word);
		++times;
	}
	StrBlobPtr blob_ptr (blob);
	for (size_t i = 0; i < times; ++i) {
		cout << blob_ptr.deref () << " ";
		blob_ptr.incr ();
		cout << endl;
	}
	system ("pause");
	return 0;
}

奇怪的是, VLD检查不出内存泄漏, 但使用VS2013自带的检测机制却显示内存泄漏, 希望以后可以得到答案.