我正在编写一个便携式Socket类,它支持发送和接收的超时…为了实现这些超时,我正在使用select()….但是,我有时需要知道我在select()中阻塞了多长时间当然在Linux上我会通过在调用select()之前和之后调用gettimeofday()然后使用timersub()来计算delta来实现…
鉴于Windows上的select()接受struct timeval的超时,我应该用什么方法替换Windows上的gettimeofday()？
我最终找到了这个页面：windows上的gettimeofday()[编辑：删除了链接,因为它现在指向一个广告网站].在Windows上有一个方便,花花公子的gettimeofday()实现.它使用GetSystemTimeAsFileTime()方法获得准确的时钟.
更新：这是一个活动链接[编辑：删除链接,因为它现在指向一个广告网站]指向OP所指的实现.另请注意链接实现中存在拼写错误：
#if defined(_MSC_VER) || defined(_MSC_EXTENSIONS) #define DELTA_EPOCH_IN_MICROSECS 11644473600000000Ui64 // WRONG #else #define DELTA_EPOCH_IN_MICROSECS 11644473600000000ULL // WRONG #endif
显示的值在结尾处缺少额外的0(它们假定为微秒,而不是100纳秒间隔的数量).这个拼写错误是在Google代码项目页面上通过this comment找到的.要使用的正确值如下所示：
#if defined(_MSC_VER) || defined(_MSC_EXTENSIONS) #define DELTA_EPOCH_IN_MICROSECS 116444736000000000Ui64 // CORRECT #else #define DELTA_EPOCH_IN_MICROSECS 116444736000000000ULL // CORRECT #endif
Postgresql为windows实现gettimeofday：
/*
* gettimeofday.c
* Win32 gettimeofday() replacement
*
* src/port/gettimeofday.c
*
* Copyright (c) 2003 SRA,Inc.
* Copyright (c) 2003 SKC,Inc.
*
* Permission to use,copy,modify,and distribute this software and
* its documentation for any purpose,without fee,and without a
* written agreement is hereby granted,provided that the above
* copyright notice and this paragraph and the following two
* paragraphs appear in all copies.
*
* IN NO EVENT SHALL THE AUTHOR BE LIABLE TO ANY PARTY FOR DIRECT,* INDIRECT,SPECIAL,INCIDENTAL,OR CONSEQUENTIAL DAMAGES,INCLUDING
* LOST PROFITS,ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
* DOCUMENTATION,EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
* THE AUTHOR SPECIFICALLY DISCLAIMS ANY WARRANTIES,INCLUDING,BUT NOT
* LIMITED TO,THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS
* IS" BASIS,AND THE AUTHOR HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE,* SUPPORT,UPDATES,ENHANCEMENTS,OR MODIFICATIONS.
*/
#include "c.h"
#include <sys/time.h>
/* FILETIME of Jan 1 1970 00:00:00. */
static const unsigned __int64 epoch = ((unsigned __int64) 116444736000000000ULL);
/*
* timezone information is stored outside the kernel so tzp isn't used anymore.
*
* Note: this function is not for Win32 high precision timing purpose. See
* elapsed_time().
*/
int
gettimeofday(struct timeval * tp,struct timezone * tzp)
{
FILETIME file_time;
SYSTEMTIME system_time;
ULARGE_INTEGER ularge;
GetSystemTime(&system_time);
SystemTimeToFileTime(&system_time,&file_time);
ularge.LowPart = file_time.dwLowDateTime;
ularge.HighPart = file_time.dwHighDateTime;
tp->tv_sec = (long) ((ularge.QuadPart - epoch) / 10000000L);
tp->tv_usec = (long) (system_time.wMilliseconds * 1000);
return 0;
}
