C++文本處理_文件讀寫

QT在進行文本讀寫時和C++一樣，是基於文本流操作的。

QT在讀取全部文本時，相對比較便捷。使用readAll()函數，配合split()進行分隔符的拆分（例如行結束符"\n"），可將拆分結果賦值給list，然后進行后續的數據處理。

ringRoadDistList = ringRoadDistStream.readAll().split("\n",QString::SkipEmptyParts);

在C++中也可以實現類似的效果：

    list<string> strList;
    char line[100];
    while (false == staEnLane2Stream.eof())
    {
        staEnLane2Stream.getline(line, sizeof(line));  //c從staEnLane2Stream按行讀取sizeof(line)個數到緩沖區line中（遇到"\n"，將提前截止）
        strList.push_back(line);
    }

如果遇到換行符'\n'（第一種形式）或delim（第二種形式），則讀取終止，'\n'或delim都不會被保存進s對應的數組中。

基於文本流的輸出，兩個類似：

ofstream resultStream;
resultStream.open(staEnLane3Path.c_str(), ios_base::out);
    if (false == resultStream.is_open())
    {
        cerr << "error: unable to open output file: " << staEnLane3Path << endl;
        return 2;
    }
while (lane2Map.end() != j)
    {
        cout << (*j).first << " " << (*j).second << endl;
        resultStream << (*j).first << " " << (*j).second << endl;
        ++j;
    }

舉個栗子：

// ringRoadTime.cpp : 定義控制台應用程序的入口點。

#include "stdafx.h"
#include <string>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <iostream>
#include <list>
#include <map>
using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
    string rootPath = "E:/superHighway/ringRoadData/GC/GC_Entry/";
    string staEnLane2Name = "GC_stationEntryLane2.csv";
    string staEnLane3Name = "GC_stationEntryLane.csv";
    string staEnLane2Path = rootPath + staEnLane2Name;
    string staEnLane3Path = rootPath + staEnLane3Name;
    //ifstream staEnLane2Stream(staEnLane2Path.c_str(), ios::in);
    ifstream staEnLane2Stream;
    ofstream resultStream;

    //文件打開，保存數據到list，關閉文件
    staEnLane2Stream.open(staEnLane2Path.c_str(), ios_base::in);
    if (false == staEnLane2Stream.is_open())
    {
        cerr << "error: unable to open input file: " << staEnLane2Path << endl;
        return 1;
    }
    list<string> strList;
    char line[100];
    while (false == staEnLane2Stream.eof())
    {
        staEnLane2Stream.getline(line, sizeof(line));
        strList.push_back(line);
    }
    staEnLane2Stream.close();
    resultStream.open(staEnLane3Path.c_str(), ios_base::out);
    if (false == resultStream.is_open())
    {
        cerr << "error: unable to open output file: " << staEnLane3Path << endl;
        return 2;
    }

    //數據插入map中，進行匹配
    map<string, string> lane2Map;
    list<string>::iterator k = strList.begin();
    for (; k != strList.end(); ++k)
    {
         size_t i = (*k).find_first_of(",");
        lane2Map.insert(pair<string, string>((*k).substr(0,i), (*k).substr(i+1)));
    }
    map<string, string>::iterator j = lane2Map.begin();
    while (lane2Map.end() != j)
    {
        cout << (*j).first << " " << (*j).second << endl;
        resultStream << (*j).first << " " << (*j).second << endl;    //基於文本流的數據寫入
        ++j;
    }
    resultStream.close();

    system("pause");
    return 0;
}