c – 从二进制文件读取结构数据时获取垃圾值

大家好,在上一个问题中,我能够获取要加载到文件中的结构数据,但现在问题是我在检索它时会得到垃圾值.

文件内容：settings.bin

110#NormalCompression Level210#NormalCompression Level310#NormalCompression Level410#NormalCompression Level510#NormalCompression Level

码

#include<cstdlib>#include<iostream>#include<string>#include<iomanip>#include<fstream.h>using namespace std;const char* ErrorLogFilePath = "resources\\error.txt";const char* SettingsFilePath = "resources\\settings.bin";const int NoOfSettings = 5;struct Setting {    int SettingID;    int SettingINTValue;    double SettingDOUBLEValue;    char SettingCHARValue;    string SettingSTRINGValue;    string SettingName;};istream& operator>>(istream& _is, Setting& _s) {    _is>>_s.SettingID;    _is>>_s.SettingINTValue;    _is>>_s.SettingDOUBLEValue;    _is>>_s.SettingCHARValue;    _is>>_s.SettingSTRINGValue;    _is>>_s.SettingName;}ostream& operator<<(ostream& _os, const Setting& _s) {    _os<<_s.SettingID;    _os<<_s.SettingINTValue;    _os<<_s.SettingDOUBLEValue;    _os<<_s.SettingCHARValue;    _os<<_s.SettingSTRINGValue;    _os<<_s.SettingName;}class ErrorReport {public:    fstream ErrorFile;    void PostError(string Title,string Data,int ErrorID) {        ErrorFile.open(ErrorLogFilePath,ios::out);        ErrorFile.close();    }} Error;class SettingsClass {public:    Setting setting[NoOfSettings];    void ResetSettings() {        fstream SettingFile;        Setting defaultsetting[NoOfSettings];        for(int i=1; i<=NoOfSettings; i  ) {            defaultsetting[i-1].SettingID = i;            defaultsetting[i-1].SettingINTValue = 0;            defaultsetting[i-1].SettingDOUBLEValue = 0;            defaultsetting[i-1].SettingCHARValue = '#';            defaultsetting[i-1].SettingSTRINGValue = "null";            switch(i) {            default:                defaultsetting[i-1].SettingName = "Compression Level";                defaultsetting[i-1].SettingSTRINGValue = "Normal";                defaultsetting[i-1].SettingINTValue = 1;                break;            }        }        SettingFile.open(SettingsFilePath,ios::binary|ios::out);        if(SettingFile.is_open()) {            for(size_t i=0; i<NoOfSettings;   i) {                SettingFile<<defaultsetting[i];            }        } else {            cout<<"Error!";        }        SettingFile.close();    }    void _SettingsClass() {        fstream SettingFile;        SettingFile.open(SettingsFilePath,ios::binary|ios::in);        Setting TempSettings[NoOfSettings];        if(SettingFile.is_open()) {            for(size_t i=0; i<NoOfSettings;   i) {                SettingFile>>TempSettings[i];            }        } else {            cout<<"Error...";        }        SettingFile.close();        for(int i=0; i<NoOfSettings; i  ) {            cout<<TempSettings[i].SettingINTValue<<"\n";        }    }} Settings;int main(int argc, char *argv[]){    Settings._SettingsClass();//    cout<<Settings.GetSetting(1).SettingName;    system("PAUSE");    return EXIT_SUCCESS;}

产量

44730761302686384

现在为什么我得到那些垃圾值？任何人都可以帮助我,因为我认为它不应该像这样(？).我应该为该struct数组的每个元素得到1.

提前致谢！

解决方法:

格式化输入需要分隔符,因此它知道何时停止读取特定值.即使您以二进制模式打开文件,您所编写的内容本质上也是一个没有分隔符的文本文件,因此您无法将其读回.

如果你必须有一个二进制文件,那么这是使用你的结构读/写一个的方法：

#include <iostream>#include <string>#include <iomanip>#include <fstream>#include <vector>const char* SettingsFilePath = "settings.bin";struct Setting{    int SettingID;    int SettingINTValue;    double SettingDOUBLEValue;    char SettingCHARValue;    std::string SettingSTRINGValue;    std::string SettingName;    Setting()        : SettingID(0)        , SettingINTValue(0)        , SettingDOUBLEValue(0)        , SettingCHARValue(0)    {    }    void Write(std::fstream& out)    {        out.write(reinterpret_cast<const char*>(&SettingID), sizeof(SettingID));        out.write(reinterpret_cast<const char*>(&SettingINTValue), sizeof(SettingINTValue));        out.write(reinterpret_cast<const char*>(&SettingDOUBLEValue), sizeof(SettingDOUBLEValue));        out.write(reinterpret_cast<const char*>(&SettingCHARValue), sizeof(SettingCHARValue));        size_t str_size = SettingSTRINGValue.size();        out.write(reinterpret_cast<const char*>(&str_size), sizeof(str_size));        out.write(SettingSTRINGValue.c_str(), SettingSTRINGValue.size());        str_size = SettingName.size();        out.write(reinterpret_cast<const char*>(&str_size), sizeof(str_size));        out.write(SettingName.c_str(), SettingName.size());    }    void Read(std::fstream& in)    {        in.read(reinterpret_cast<char*>(&SettingID), sizeof(SettingID));        in.read(reinterpret_cast<char*>(&SettingINTValue), sizeof(SettingINTValue));        in.read(reinterpret_cast<char*>(&SettingDOUBLEValue), sizeof(SettingDOUBLEValue));        in.read(reinterpret_cast<char*>(&SettingCHARValue), sizeof(SettingCHARValue));        size_t str_size;        std::vector<char> str_data;        in.read(reinterpret_cast<char*>(&str_size), sizeof(str_size));        str_data.resize(str_size);        in.read(&str_data[0], str_size);        SettingSTRINGValue.assign(str_data.begin(), str_data.end());        in.read(reinterpret_cast<char*>(&str_size), sizeof(str_size));        str_data.resize(str_size);        in.read(&str_data[0], str_size);        SettingName.assign(str_data.begin(), str_data.end());    }    void Print(const std::string& title)    {        std::cout << title << "\n";        std::cout << std::string(title.size(), '-') << "\n";        const size_t w = 22;        std::cout << std::setw(w) << std::right << "SettingID : " << SettingID << "\n";        std::cout << std::setw(w) << std::right << "SettingINTValue : " << SettingINTValue << "\n";        std::cout << std::setw(w) << std::right << "SettingDOUBLEValue : " << SettingDOUBLEValue << "\n";        std::cout << std::setw(w) << std::right << "SettingCHARValue : " << SettingCHARValue << "\n";        std::cout << std::setw(w) << std::right << "SettingSTRINGValue : " << SettingSTRINGValue << "\n";        std::cout << std::setw(w) << std::right << "SettingName : " << SettingName << "\n";        std::cout << "\n";    }};int main(){    {        Setting s;        s.Print("Default before Write");        s.SettingID = 1;        s.SettingINTValue = 2;        s.SettingDOUBLEValue = 3.5;        s.SettingCHARValue = 'Z';        s.SettingSTRINGValue = "Blah Blah";        s.SettingName = "Some Settings";        std::fstream f(SettingsFilePath, std::ios::out | std::ios::binary);        s.Write(f);        s.Print("Values written to file");    }    {        Setting s;        s.Print("Default before read");        std::fstream f(SettingsFilePath, std::ios::in | std::ios::binary);        s.Read(f);        s.Print("Values after read");    }    return EXIT_SUCCESS;}

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