Question

我看不出我做错了什么。我认为它可能是三种规则之一。 Codepad link

#include    <deque>
//#include  <string>
//#include  <utility>
//#include  <cstdlib>
#include    <cstring>
#include    <iostream>
//#include  <algorithm> // I use sort(), so why does this still compile when commented out?

#include    <boost/filesystem.hpp>
#include    <boost/foreach.hpp>

using namespace std;

namespace fs = boost::filesystem;

class Page
{
    public:
        // constructor
        Page(const char* path, const char* data, int size) :
            path_(fs::path(path)),
            size_(size),
            data_(new char[size])
        {
//          cout    << "Creating Page..." << endl;
            strncpy(data_, data, size);
//          cout    << "done creating Page..." << endl;
        }
        // copy constructor
        Page(const Page& other) :
            path_(fs::path(other.path())),
            size_(other.size()),
            data_(new char[other.size()])
        {
//          cout    << "Copying Page..." << endl;
            strncpy(data_, other.data(), size_);
//          cout    << "done copying Page..." << endl;
        }
        // destructor
        ~Page() { delete[] data_; }
        // accessors
        const fs::path& path() const { return path_; }
        const char* data() const { return data_; }
        int size() const { return size_; }
        // operators
        Page& operator = (const Page& other) {
            if (this == &other)
                return *this;
            char* newImage = new char[other.size()];
            strncpy(newImage, other.data(), other.size());
            delete[] data_;
            data_ = newImage;
            return *this;
        }
        bool operator < (const Page& other) const { return path_ < other.path();    }
    private:
        fs::path path_;
        int size_;
        char* data_;
};

class Book
{
    public:
        Book(const char* path) :
            path_(fs::path(path))
        {
            cout    << "Creating Book..." << endl;
            cout    << "pushing back #1" << endl;
            pages_.push_back(Page("image1.jpg", "firstImage", 10));
            cout    << "pushing back #3" << endl;
            pages_.push_back(Page("image3.jpg", "thirdImage", 10));
            cout    << "pushing back #2" << endl;
            pages_.push_back(Page("image2.jpg", "secondImage", 11));

            cout    << "testing operator <" << endl;
            cout    << pages_[0].path().string() << (pages_[0] < pages_[1]? " < " : " > ") << pages_[1].path().string() << endl;
            cout    << pages_[1].path().string() << (pages_[1] < pages_[2]? " < " : " > ") << pages_[2].path().string() << endl;
            cout    << pages_[0].path().string() << (pages_[0] < pages_[2]? " < " : " > ") << pages_[2].path().string() << endl;

            cout    << "sorting" << endl;
            BOOST_FOREACH (Page p, pages_)
                cout    << p.path().string() << endl;
            sort(pages_.begin(), pages_.end());
            cout << "done sorting\n";
            BOOST_FOREACH (Page p, pages_)
                cout    << p.path().string() << endl;

            cout    << "done Creating Book" << endl;
        }
    private:
        deque<Page> pages_;
        fs::path path_;
};

int main() {
    Book* book = new Book("/some/path/");
}

Answer 1

我一直在搞乱，并意识到我的赋值操作符也需要复制所有其他参数，而不仅仅是堆分配的参数。

男人我感到愚蠢。＆GT; _＆LT;

Btw后续问题：有没有办法在不需要strncpy（）所有缓冲区的情况下进行排序，而只需交换指针地址？

编辑：

tnx dirkgently。是的，就是这样，在我发布之前，sry没有看到你的评论。

容器不会排序，包括测试用例，（简单问题？）

1 个答案: