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  SQL Server Tips by Gama and Naughter


The XP calls the function GetDiskFreeSpaceEx to obtain information about the amount of space available on a disk volume. GetDiskFreeSpaceEx has four parameters: the first one is the path for a directory on the disk to be examined; this is a pointer to a null-terminated string. The second is the total number of free bytes on the disk and this is a pointer to an unsigned large integer (64 bits). The third is the total number of available bytes on the disk and this is a pointer like the one for the second parameter. Finally, the fourth is the total number of free bytes on the disk and this is a pointer like the ones from parameters two and three. XP_DISKSPACE will divide the number of free bytes on the disk by 1,048,576 (2 to the 20th power); this will result in a value measured in megabytes.

The DLL exposes 1 XP using the following XP++ code:

IMPLEMENT_XP(XP_DISKSPACE, CDiskSpaceExtendedStoredProcedure)

This is the code for calling GetDiskFreeSpaceEx and calculating the result in megabytes:

ULARGE_INTEGER i64FreeBytesToCaller;
BOOL bSuccess = GetDiskFreeSpaceEx(pszDriveLetter, &i64FreeBytesToCaller, &i64TotalBytes, &i64FreeBytes);
if (bSuccess)
DBINT nSpaceLeft = (DBINT) (((__int64) i64FreeBytes.QuadPart) / 1048576);

The above book excerpt is from:

Super SQL Server Systems
Turbocharge Database Performance with C++ External Procedures

ISBN: 0-9761573-2-2
Joseph Gama, P. J. Naughter  



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