C++流,函数声明和其他问题

Question

Iobuffer.cpp

#include "Iobuffer.h"

    IOBuffer::IOBuffer (int maxBytes){
    Init (maxBytes);
    }

    IOBuffer & IOBuffer :: operator = (const IOBuffer & buffer){
        if(MaxBytes< buffer.BufferSize) return *this;//fail
        Initialized = buffer.Initialized;
        BufferSize = buffer.BufferSize;
        memcpy(Buffer, buffer.Buffer, buffer.BufferSize);
        NextByte = buffer.NextByte;
        Packing = Packing;
        return *this;
    }

    void IOBuffer::Clear(){
        NextByte = 0;
        Packing = true;
    }

    void IOBuffer::Print(ostream & stream) const{
        stream<<"MaxBytes "<<MaxBytes<<" BufferSize "<<BufferSize;
    }

    int IOBuffer::Init (int maxBytes){
        Initialized = false;
        if (maxBytes < 0) maxBytes = 0;
        MaxBytes = maxBytes;
        Buffer = new char[MaxBytes];
        BufferSize = 0;
        Clear ();
        return 1;
    }

    int IOBuffer::DRead(istream & stream, int recref){
        stream.seekp(recref, ios::beg);
        if(stream.tellp() != recref) return -1;
        return Write(stream);
    }

    static const char * headerStr = "IOBuffer";
    static const int headerSize = strlen(headerStr);

    int IOBuffer::ReadHeader(istream & stream){
        char str[9];
        stream.seekg(0, ios::beg);
        stream.read(str, headerSize);
        if(!stream.good()) return -1;
        if(strncmp(str,headerStr, headerSize)==0) return headerSize;
        else return -1;
}

    int IOBuffer::WriteHeader (ostream & stream) const{
        stream.seekp(0, ios::beg);
        stream.write(headerStr, headerSize);
        if(!stream.good()) return -1;
        return headerSize;
}

它伴随着Iobuffer.h

#include <cstring>
#include <iostream>
    class IOBuffer{
    public:
        IOBuffer (int maxBytes = 1000);
        IOBuffer & operator = (const IOBuffer &);
        virtual void Clear ();
        virtual int Pack (const void * field, int size = -1) = 0;
        virtual int Unpack (void * field, int maxbytes = -1) = 0;
        virtual void Print(ostream &) const;
        int Init (int maxBytes);
        virtual int Read (istream & x) = 0;
        virtual int Write (ostream & x) const = 0;
        virtual int DRead(istream &, int recref);
        virtual int DWrite(ostream &, int recref) const;
        virtual int ReadHeader (istream &);
        virtual int WriteHeader (ostream *);
    protected:
        int Initialized;
        char * Buffer;
        int BufferSize;
        int MaxBytes;
        int NextByte;
        int Packing;
    };

这是我的文件系统课程的作业.在Iobuffer.h中,#include <iostream>是因为我认为它会修复"ostream"或"istream""尚未声明"我从虚拟中得到的错误; 打印,读取,写入,DRead,DWrite,ReadHeader和WriteHeader函数原型.这些是该文件中唯一的错误..cpp文件中的错误有些相关,我得到相同的"istream"和"ostream尚未声明"错误.任何帮助都非常感谢,如果需要进一步的细节,请告诉我.

-Macaire 更新,查尔斯沃思爵士的建议以指数方式减少错误.在WriteHeader的头文件中,生成了虚函数原型"candidate is:virtual int IOBuffer :: WriteHeader(std :: ostream)"错误.其余5个错误在.cpp文件中,其中三个来自DRead的定义(每行一个).第一行说

‘struct std::basic_istream<char, std::char_traits<char> >’ has no member named ‘seekp’

另外请注意为什么格式化如此陌生？我在cplusplus.com上查了ostream 一下,我想这可能是因为我使用整数作为我的搜索偏移量.继续,以下一行说

‘struct std::basic_istream<char, std::char_traits<char> >’ has no member named ‘tellp’

返回声明说的很奇怪,

no matching function for call to ‘IOBuffer::Write(std::basic_istream<char, std::char_traits<char> >&)’

最后的错误是原型

‘int IOBuffer::WriteHeader(std::ostream&) const’ does not match any in class ‘IOBuffer’

是的,这是5不是6错误.

Answer 1

标准库中的大多数名称都位于命名空间内std.因此,通常的做法就是在使用它们时完全限定它们(std::ostream而不是ostream等等).

一种不太推荐的方法是声明using namespace std;,这会将整个std命名空间拉到你当前所处的任何范围内(为了节省你std::每次写入的麻烦).请注意,在头文件中声明是非常糟糕的做法using namespace ....这些应仅保留给源文件.

UPDATE

您的大多数新错误消息都是因为您感到困惑istream和ostream. istream有一个叫做的函数,例如seekg,没有seekp.