在Win32時(shí)間類型有這樣幾種類型
FILETIME/SYSTEMTIME/WINDOWSTIME
先提個(gè)問題，如何計(jì)算當(dāng)前時(shí)間100天以后的時(shí)間，在win32中。
1.SYSTEMTIME
SYSTEMTIME的定義是這樣
typedef?struct??_SYSTEMTIME
????{
????WORD?wYear;
????WORD?wMonth;
????WORD?wDayOfWeek;
????WORD?wDay;
????WORD?wHour;
????WORD?wMinute;
????WORD?wSecond;
????WORD?wMilliseconds;
????}?SYSTEMTIME;
很大，總共16個(gè)字節(jié)。你可以調(diào)用GetSystemTime來取得當(dāng)前的時(shí)間
SYSTEMTIME?st;
::GetSystemTime(&st);
但是如果你調(diào)用 st.wDay += 100;是達(dá)不到效果的，將會(huì)得到一個(gè)無效的時(shí)間格式
2. FILETIME
FILETIME的定義是這樣的
typedef?struct??_FILETIME
????{
????DWORD?dwLowDateTime;
????DWORD?dwHighDateTime;
????}?FILETIME;
FILETIME這個(gè)名字很奇怪，其實(shí)他跟FILE并沒有直接關(guān)系，只是很多File的API中，都以這個(gè)為時(shí)間的類型，比如你可以調(diào)用GetFileTime來取得File的創(chuàng)建/修改/訪問時(shí)間。
FILETIME是一個(gè)__int64。可以這樣轉(zhuǎn)化成__int64
__int64?d?=?*(__int64?*)&st;
//or
__int64?d2;
memcpy(&d2,&st,sizeof(d2));
轉(zhuǎn)化為__int64是一個(gè)以100納秒為單位的值
補(bǔ)習(xí)一下時(shí)間單位(
http://blog.vckbase.com/zaboli/archive/2005/06/29/8969.aspx)
| 1ms (毫秒) | 1毫秒=0.001秒=10-3秒(millisecond) |
| 1μs (微秒) | 1微秒=0.000001=10-6秒(microsecond) |
| 1ns (納秒) | 1納秒=0.000000001秒=10-9秒（nanosecond) |
| 1ps (皮秒) | 1皮秒=0.000000000001秒=10-12秒 |
| 1fs (飛秒) | 1飛秒=0.00000000000001秒=10-15秒 |
SYSTEMTIME可以通過SystemTimeToFileTime來轉(zhuǎn)化為FILETIME
3.Window Time
::GetTickCount()可以返回當(dāng)前的以微秒為單位的時(shí)間，用在精度要求不高的場合，返回的只是一個(gè)DWORD，四字節(jié)。高一點(diǎn)的使用timeGetTime
如何計(jì)算當(dāng)前時(shí)間100天以后的時(shí)間，在win32中。
應(yīng)該這樣寫
const?__int64?nano100SecInDay=(__int64)10000000*60*60*24;
SYSTEMTIME?st;
::GetSystemTime(&st);
FILETIME?f;
::SystemTimeToFileTime(&st,&f);
ULARGE_INTEGER?now;
memcpy(&now,&f,sizeof(now));
now?+=?100*nano100SecInDay;
memcpy(&f,&now,sizeof(f));
FileTimeToSystemTime(&f,&st);
最后：附上我寫的一個(gè)小工具，刪除指定文件夾下面的過期文件的一個(gè)工具，并可以備份，支持子文件夾嵌套。
#include?<windows.h>
#include?<cstdio>
#include?<string>
using?namespace?std;
const?__int64?nano100SecInDay=(__int64)10000000*60*60*24;
ULARGE_INTEGER?now;
int?days?=?14;
bool?backup?=?false;
string?dst_dir;
string?backup_dir;
void?make_sure_dir_exist(string?&?file)
{
????int?tag?=?2;
????while(true)
????{
????????tag?=?file.find_first_of("\\",tag+1);
????????if(tag!=-1)
????????{
????????????string?tmp?=?file.substr(0,tag);
????????????::CreateDirectory(tmp.c_str(),NULL);
????????}
????????else
????????{
????????????break;
????????}
????}
}
void?xdel(const?char?*dir)
{
????char?tempFileFind[1024];
????sprintf(tempFileFind,"%s\\*.*",dir);
????
????WIN32_FIND_DATA?ffd;
????HANDLE?hFind;
????hFind?=?::FindFirstFile(tempFileFind,&ffd);
????
????if(hFind?==?INVALID_HANDLE_VALUE)
????{
????????printf("can't?find?%s\n",dir);
????????return;
????}
????
????while(true)
????{
????????//printf("find?%s\n",ffd.cFileName);
????????FILETIME?&ft?=?ffd.ftLastWriteTime;
????????ULARGE_INTEGER?ui;
????????memcpy(&ui,&ft,sizeof(ui));
????????__int64?t?=?now.QuadPart-ui.QuadPart;
????????
????????if(ffd.dwFileAttributes&FILE_ATTRIBUTE_DIRECTORY)
????????{
????????????if(strcmp(ffd.cFileName,?".")?&&?strcmp(ffd.cFileName,?".."))
????????????{
????????????????char?temp[1024];
????????????????sprintf(temp,"%s\\%s",dir,ffd.cFileName);
????????????????xdel(temp);
????????????????
????????????????if(t>=nano100SecInDay*days)
????????????????{
????????????????????if(::RemoveDirectory(temp))
????????????????????{
????????????????????????printf("del?dir?%s?ok\n",temp);
????????????????????}
????????????????????else
????????????????????{
????????????????????????printf("del?dir?%s?failed\n",temp);
????????????????????}
????????????????}
????????????}
????????}
????????else
????????{
????????????char?temp[1024];
????????????sprintf(temp,"%s\\%s",dir,ffd.cFileName);
????????????
????????????if(t>=nano100SecInDay*days)
????????????{
????????????????if(backup)
????????????????{
????????????????????string?backup_file?=?temp;
????????????????????backup_file.replace(0,dst_dir.length(),backup_dir.c_str());
????????????????????make_sure_dir_exist(backup_file);
????????????????????if(::MoveFile(temp,backup_file.c_str()))
????????????????????{
????????????????????????printf("backup?file?%s?ok\n",temp);
????????????????????}
????????????????????else
????????????????????{
????????????????????????printf("backup?file?%s?failed\n",temp);
????????????????????}
????????????????}
????????????????else
????????????????{
????????????????????SetFileAttributes(temp,FILE_ATTRIBUTE_NORMAL);
????????????????????if(::DeleteFile(temp))
????????????????????{
????????????????????????printf("del?file?%s?ok\n",temp);
????????????????????}
????????????????????else
????????????????????{
????????????????????????printf("del?file?%s?failed\n",temp);
????????????????????}
????????????????}
????????????}
????????}
????????if?(!FindNextFile(hFind,?&ffd))?
????????{
????????????break;
????????}
????}
????FindClose(hFind);
}
int?main(int?argc,char?**?argv)
{
????if(argc<2)
????{
????????printf("usage:?xdel?directory?/d=?/m=\n");
????????printf("[optional]?/d:?config?the?expired?days,default?is?14?days\n");
????????printf("[optional]?/m:?config?the?backup?directory\n");?
????????printf("for?example:?xdel?d:\\test?/d=10?/m=d:\\backup");
????????return?1;
????}
????
????for(int?i=1;i<argc;++i)
????{
????????string?tmp?=?argv[i];
????????if(tmp.find("/d=")!=-1)
????????{
????????????int?d?=?atoi(tmp.substr(3).c_str());
????????????if(d!=0)
????????????{
????????????????days?=d;
????????????}
????????}
????????else?if(tmp.find("/m=")!=-1)
????????{
????????????backup?=?true;
????????????backup_dir?=?tmp.substr(3);
????????}
????????else
????????{
????????????dst_dir?=?tmp;
????????}
????}
????
????//Get?system?time
????SYSTEMTIME?st;
????::GetSystemTime(&st);
????FILETIME?f;
????::SystemTimeToFileTime(&st,&f);
????memcpy(&now,&f,sizeof(now));
????
????xdel(argv[1]);
????
????return?0;
}