Method CreateSparseFile

src/PlatformSpecific.cpp:62–100

Create a file in sparse mode

// Create a file in sparse mode
bool PlatformSpecific::CreateSparseFile(const CPath& name, uint64_t size)
{
	DWORD dwReturnedBytes=0;

	HANDLE hd = CreateFileW(name.GetRaw().c_str(),
		GENERIC_READ | GENERIC_WRITE,
		0,       // share - not shareable
		NULL,    // security - not inheritable
		CREATE_ALWAYS,
		FILE_ATTRIBUTE_ARCHIVE,
		NULL);
	if (hd == INVALID_HANDLE_VALUE) {
		AddDebugLogLineC(logPartFile, CFormat("converting %s to sparse failed (OPEN): %s ") % name % SystemError());
		return false;
	}

	if (!DeviceIoControl(hd, FSCTL_SET_SPARSE, NULL, 0, NULL, 0, &dwReturnedBytes, NULL)) {
		AddDebugLogLineC(logPartFile, CFormat("converting %s to sparse failed (SET_SPARSE): %s ") % name % SystemError());
	} else {
		// FILE_ZERO_DATA_INFORMATION is not defined here
		struct {
			uint64 FileOffset;
			uint64 BeyondFinalZero;
		} fzdi;
		fzdi.FileOffset = 0;
		fzdi.BeyondFinalZero = size;
		LARGE_INTEGER largo;
		largo.QuadPart = size;

		// zero the data
		if (!DeviceIoControl(hd, FSCTL_SET_ZERO_DATA, (LPVOID) &fzdi, sizeof(fzdi), NULL, 0, &dwReturnedBytes, NULL)) {
			AddDebugLogLineC(logPartFile, CFormat("converting %s to sparse failed (ZERO): %s") % name % SystemError());
		} else if (!SetFilePointerEx(hd, largo, NULL, FILE_BEGIN) || !SetEndOfFile(hd)) {
			AddDebugLogLineC(logPartFile, CFormat("converting %s to sparse failed (SEEK): %s") % name % SystemError());
		}
	}
	CloseHandle(hd);
	return true;
}

#else  // non Windows systems don't need all this
#include "CFile.h"