使用ifstream的時候，可以用seekg進行重定位，但有一個需要注意的地方。
如果想重定位到文件頭，應該用：
mFile.seekg(0, ios_base::beg);
而不是
mFile.seekg(ios_base::beg);
我實驗的結果是，后者會定位到文件頭后面一個字符，也就是說，第一個字符被吃掉了。
我要記得,每一個指針在申明d時候就必須要初始化啊初始化,調試了1個工作日.
讀日志文件的一個類
//pchar.hpp
?1?#include?<string.h>
?2?
?3?void?trimLeft(char?*?p_char){
?4???char?szBuff[1024];
?5???memset(szBuff,?0,?sizeof(szBuff));
?6???char?*pBuff?=?p_char;
?7???while(?*pBuff?==?'?'){
?8?????++?pBuff;
?9???}
10?
11???strncpy(szBuff,?pBuff,?sizeof(szBuff)?-1);
12???strncpy(p_char,?szBuff,?strlen(szBuff));
13???p_char[strlen(szBuff)]?=?0x0;
14?}
15?
16?
17?void?trimRight(char?*?p_char){
18???for(int?i?=?strlen(p_char)?-?1;?i?>=?0;?i--?){
19?????if(?*(p_char?+?i)?==?'?')?{
20???????*(p_char?+?i?)?=?'\0';
21?????}else?break;
22???}
23?}
24?
25?void?trim(char?*?p_char){
26???trimLeft(p_char);
27???trimRight(p_char);
28?}
29?
30?
?1?//IniFile.hpp
?2?
?3?#include?<unistd.h>
?4?#include?<stdio.h>
?5?#include?<stdlib.h>
?6?#include?<string>
?7?#include?<fstream>
?8?
?9?using?namespace?std;
10?
11?#ifndef?INIFILE_HPP_
12?#define?INIFILE_HPP_
13?
14?
15?class?IniFile?{
16?
17???public:
18?????IniFile(){?m_bOpened=?false;}
19?
20?????IniFile(const?char?*?p_szFileName);
21?????~IniFile();
22?
23???public:
24?????void?setFileName(const?char?*?p_szFileName);
25?????int?openIni();
26?????int?getPchar?(const?char?*p_szSection,?const?char?*p_szKey,?char?*p_szDefaultValue);
27?????int?getInt???(const?char?*p_szSection,?const?char?*p_szKey,?int&?p_iDefaultValue);
28?????int?getBool??(const?char?*p_szSection,?const?char?*p_szKey,?int&?p_iDefaultValue);
29?????int?getString(string?p_strSection,?string?p_strKey,?string&?p_strDefaultValue);
30?
31???protected:
32?
33?
34???private:
35?????ifstream?inFile;
36?????char?m_szFileName[256];
37?????char?m_szSection[32];
38?????bool?m_bOpened;
39?};
40?
41?#endif?//INIFILE_HPP_
42?
43?
??1?//IniFile.cpp
??2?
??3?#include?"../include/IniFile.hpp"
??4?#include?"../include/pchar.hpp"
??5?
??6?
??7?IniFile::IniFile(const?char?*?p_szFileName){
??8???m_bOpened?=?false;
??9???setFileName(p_szFileName);
?10?}
?11?
?12?IniFile::~IniFile(){
?13???inFile.close();
?14???printf("ini文件句柄釋放!\n");
?15?}
?16??????????????????????????
?17?void?IniFile::setFileName(const?char?*?p_szFileName){
?18???memset(?m_szFileName,?0,?sizeof(m_szFileName)?);
?19???strncpy(?m_szFileName,?p_szFileName,?sizeof(m_szFileName)-1?);
?20?}
?21?
?22?
?23?
?24?
?25?int?IniFile::openIni(){
?26???inFile.open(m_szFileName,?ios::in);
?27???if?(!?inFile.good()){
?28?????return?-1;
?29?????m_bOpened=?false;
?30???}
?31?
?32???m_bOpened=?true;
?33???return?0;
?34?}
?35?
?36?
?37?int?IniFile::getPchar(const?char?*p_szSection,?const?char?*p_szKey,?char?*p_szDefaultValue){
?38???char?szBuff[1024];
?39???char?szKey[32]?;
?40???char?szDefaultValue[64]?;
?41???char?szCurrentSection[32];
?42???string?strLine;
?43???int?iLen?=?0,?bInSelfSection?=?0?;
?44???char?*?pStrValue?=?NULL?;
?45????????????????????????????????????????
?46???memset(m_szSection,?0,?sizeof(m_szSection)?)?;
?47???strncpy(m_szSection,?p_szSection,?sizeof(m_szSection)-1);
?48???
?49???memset(szKey,?0,?sizeof(szKey));
?50???strncpy(szKey,?p_szKey,?sizeof(szKey)?-?1);
?51?
?52???memset(szDefaultValue,?0,?sizeof(szDefaultValue));
?53???strncpy(szDefaultValue,?p_szDefaultValue,?sizeof(szDefaultValue)-1);
?54?
?55???inFile.seekg(0,?ios_base::beg);?//將文件指針指向最開始d位置
?56???while(!inFile.eof()){
?57?????getline(inFile,?strLine);
?58?
?59?????memset(szBuff,?0,?sizeof(szBuff));
?60?????snprintf(szBuff,?sizeof(szBuff)-1,?"%s",?strLine.c_str());
?61?????trim(szBuff);
?62?
?63?????if?(?(szBuff[0]?==?'#')?||?(strlen(szBuff)?<?3)?)?{?//取消對注釋和無用數據的解析,
?64???????continue;
?65?????}
?66?
?67?????iLen?=?strlen(szBuff);
?68?????if?(szBuff[iLen-1]?==?0x0D)?//將每一行配置的換行符后數據去掉
?69???????szBuff[iLen-1]?=?0x0;
?70?
?71?????iLen?=?strlen(szBuff);
?72?????if?(szBuff[0]?==?'['?&&?szBuff[iLen-1]?==?']')?{?//判斷是否為Section??[MOSERVER]
?73???????if?(bInSelfSection)
?74?????????bInSelfSection?=?0;
?75?
?76???????szBuff[iLen-1]?=?0x0;
?77???????memset(szCurrentSection,?0,?sizeof(szCurrentSection));
?78???????strcpy(szCurrentSection,?szBuff?+?1);?//取出section名
?79?
?80???????if?(strcasecmp(m_szSection,?szCurrentSection)?==?0)?{??//如果是自己需要的section則做好標記
?81?????????bInSelfSection?=?1;
?82?????????continue;
?83???????}
?84?????}
?85?
?86?????if?(!bInSelfSection)??//如果沒有讀到需要的section則繼續找
?87???????continue;
?88?
?89?????if?(pStrValue?==?NULL){
?90???????pStrValue?=?strchr(szBuff,?'=');??//查找'='的位置,沒有找到則讀下一條
?91?????}
?92?
?93?????if?(pStrValue?==?NULL){
?94???????continue;
?95?????}
?96?????*pStrValue?=?0;?//將'='變為'0'來分割value和key
?97?????pStrValue++;
?98?????if?(*pStrValue?==?0){//如果沒有讀到value則繼續讀下一條
?99???????continue;
100?????}
101?????if?(bInSelfSection)?{
102???????if(strcasecmp(szKey,szBuff)==0){
103?????????strncpy(p_szDefaultValue,?pStrValue,?64?-?1);
104?????????return?0;
105???????}
106?????}
107?????pStrValue?=?NULL;
108???}
109???return?-1;
110?}
111?
112?
113?int?IniFile::getString(string?p_strSection,?string?p_strKey,?string&?p_strDefaultValue){
114???inFile.seekg(0,?ios_base::beg);
115???char?szDefaultValue[64];
116???memset(szDefaultValue,?0,?sizeof(szDefaultValue));
117???getPchar(p_strSection.c_str(),?p_strKey.c_str(),?szDefaultValue);
118???getPchar("MOSERVER",?"TIMEOUT",?szDefaultValue);
119???//printf("getchar:?%s\n",?szDefaultValue);//
120???p_strDefaultValue?=?szDefaultValue;
121???return?0;
122?}?
123?
124?
?1?//測試程序
?2?
?3?#include?"../include/IniFile.hpp"
?4?
?5?int?main(){
?6???printf("開始分析ini文件!\n");
?7???IniFile?ini;
?8???char?szPort[64];
?9???memset(szPort,?0,?sizeof(szPort));
10?
11???ini.setFileName("../config/inifile.ini");
12???ini.openIni();
13???ini.getPchar("MOSERVER",?"MAXCONNECTED",?szPort);
14???printf("ini文件裝載完成!\n");
15?
16???string?timeout;
17???ini.getString("MOSERVER",?"TIMEOUT",?timeout);
18?
19???printf("MAXCONNECTED:%s\n",?szPort);
20???printf("TIMEOUT:%s\n",?timeout.c_str());
21?
22???return?0;
23?}
inifile.ini文件格式
#為注釋,處理時自動去掉前后空格
#######################################################################
# the configuration for MOServer
# by Khan.Lau (Lau.Khan#gmail.com)
# 2006-04-12
#######################################################################
[MOSERVER]
LISTENPORT=8097
WHITEIP=192.168.1.122;127.0.0.1;
MAXCONNECTED=50
MAXCONSINGLEIP=5
TIMEOUT=60
DBHOST=127.0.0.1
DBNAME=smstest
DBPORT=9055
DBUID=postgres
DBPWD=