我需要以递归方式为给定的根/父路径构建一个树结构.像“浏览文件夹”对话框.
Delphi的FindFirst(FindFirstFile API)不能与faDirectory一起使用,FindNext将获取所有文件(它使用faAnyFile而不管指定的faDirectory),而不仅仅是目录.这使得构建树的过程非常缓慢.
解决方法
绝对最快的方式,使用
NtQueryDirectoryFile api.有了这个我们可以一次查询不是单个文件而是多个文件.还可以选择要返回的信息(较小的信息 – 更高的速度).示例(完全递归)
// int nLevel,PSTR prefix for debug only
void ntTraverse(POBJECT_ATTRIBUTES poa,int nLevel,PSTR prefix)
{
enum { ALLOCSIZE = 0x10000 };//64kb
if (nLevel > MAXUCHAR)
{
DbgPrint("nLevel > MAXUCHAR\n");
return ;
}
NTSTATUS status;
IO_STATUS_BLOCK iosb;
UNICODE_STRING ObjectName;
OBJECT_ATTRIBUTES oa = { sizeof(oa),&ObjectName };
DbgPrint("%s[<%wZ>]\n",prefix,poa->ObjectName);
if (0 <= (status = NtOpenFile(&oa.RootDirectory,FILE_GENERIC_READ,poa,&iosb,FILE_SHARE_VALID_FLAGS,FILE_SYNCHRONOUS_IO_NONALERT|FILE_OPEN_REPARSE_POINT|FILE_OPEN_FOR_BACKUP_INTENT)))
{
if (PVOID buffer = new UCHAR[ALLOCSIZE])
{
union {
PVOID pv;
PBYTE pb;
PFILE_DIRECTORY_INFORMATION DirInfo;
};
while (0 <= (status = NtQueryDirectoryFile(oa.RootDirectory,NULL,pv = buffer,ALLOCSIZE,FileDirectoryInformation,FALSE)))
{
ULONG NextEntryOffset = 0;
do
{
pb += NextEntryOffset;
ObjectName.Buffer = DirInfo->FileName;
switch (ObjectName.Length = (USHORT)DirInfo->FileNameLength)
{
case 2*sizeof(WCHAR):
if (ObjectName.Buffer[1] != '.') break;
case sizeof(WCHAR):
if (ObjectName.Buffer[0] == '.') continue;
}
ObjectName.MaximumLength = ObjectName.Length;
if (DirInfo->FileAttributes & FILE_ATTRIBUTE_DIRECTORY)
{
ntTraverse(&oa,nLevel + 1,prefix - 1);
}
} while (NextEntryOffset = DirInfo->NextEntryOffset);
if (ALLOCSIZE - iosb.Information > (ULONG)FIELD_OFFSET(FILE_DIRECTORY_INFORMATION,FileName[256]))
{
break;//NO_MORE_FILES
}
}
delete [] buffer;
if (status == STATUS_NO_MORE_FILES)
{
status = STATUS_SUCCESS;
}
}
NtClose(oa.RootDirectory);
}
if (0 > status)
{
DbgPrint("---- %x %wZ\n",status,poa->ObjectName);
}
}
void ntTraverse()
{
BOOLEAN b;
RtlAdjustPrivilege(SE_BACKUP_PRIVILEGE,TRUE,FALSE,&b);
char prefix[MAXUCHAR + 1];
memset(prefix,'\t',MAXUCHAR);
prefix[MAXUCHAR] = 0;
STATIC_OBJECT_ATTRIBUTES(oa,"\\systemroot");
ntTraverse(&oa,prefix + MAXUCHAR);
}
但是如果您使用交互式树 – 您不需要一次扩展所有树,但只需要顶层,使用TVE_EXPAND处理TVN_ITEMEXPANDING,使用TVE_COLLAPSE处理TVN_ITEMEXPANDED,以便在用户点击时设置扩展/折叠节点并设置cChildren
如果将FindFirstFileExW与FIND_FIRST_EX_LARGE_FETCH和FindExInfoBasic一起使用,这会给N4QueryDirectoryFile提供近似性能,但要小一点：
WIN32_FIND_DATA fd;
HANDLE hFindFile = FindFirstFileExW(L"..\\*",FindExInfoBasic,&fd,FindExSearchLimitToDirectories,FIND_FIRST_EX_LARGE_FETCH);
if (hFindFile != INVALID_HANDLE_VALUE)
{
do
{
if (fd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
{
if (fd.cFileName[0] == '.')
{
switch (fd.cFileName[1])
{
case 0:
continue;
case '.':
if (fd.cFileName[2] == 0) continue;
break;
}
}
DbgPrint("%S\n",fd.cFileName);
}
} while (FindNextFile(hFindFile,&fd));
FindClose(hFindFile);
}
遗憾的是,FindExSearchLimitToDirectories目前尚未实现