將固定數量的字節復制到std :: deque中<char>

Question

我正在制作一個類，用於緩沖從std::cin讀取的一些二進制數據； 我需要一些有限的能力來回溯流。 更詳細地講，當我從流中read n個字節時，我希望能夠倒回流中的n個字節。

當前，我通過將單個字符追加到std::deque來追加到緩沖區，但是我希望有更好的方法將數據塊從std::istream復制到std::deque 。

基本上，有什么方法可以改善（刪除？）下面的load函數中的while循環嗎？

目前我有：

#include<algorithm>
#include<deque>

class BufferedStdIn{
public:

BufferedStdIn(): m_buffer(), m_cursor(0){
}

// copy data out from my internal buffer to the client's array
// format dictated by external interface requirement
void read(char* dest, size_t n){
    load(n)
    std::copy( m_buffer.begin(), m_buffer.begin()+n, dest );
    m_cursor+=n;
}

// Go backwards in the stream; return the number of bytes moved.
// @retval < input arg n indicates that we can't rewind as far as asked for
size_t rewind(size_t n){
    int final_pos=m_cursor-n;
    if( final_pos < 0 ){
        // can't go as far as the client wants, just go back to start of my buffer
        size_t moved=m_cursor;
        m_cursor=0;
        return moved;
    }
    else{ // can do what client wants
        m_cursor=final_pos;
        return n;
    }
}

void load(n){
    m_buffer.erase( m_buffer.begin(), m_buffer.begin()+m_cursor);
    m_cursor=0;
    while( m_buffer.size()<n){
        char c;
        std::cin.get(c);
        m_buffer.push_back(c);
    }
}

// SNIP: other functions that let clients look at m_buffer

std::deque<char> m_buffer;
size_t m_cursor;


}

Answer 1

也許效率不高，但更短：

void load(size_t n)
{
    m_buffer.erase( m_buffer.begin(), m_buffer.begin()+m_cursor);
    m_cursor=0;
    if(m_buffer.size() < n)
        std::copy_n(std::istream_iterator<char>(std::cin), n - m_buffer.size(), std::back_inserter(m_buffer));
}