Question

我有一个实用程序，用于比较源文件日期/时间。这在大多数情况下都有效，但在比较不同时区的文件的日期/时间时会失败。所以我需要一个UTC日期时间例程。

从环顾四周看来，Windows API GetFileTime似乎支持这一点。我也找到了这个包装程序，但是在Delphi 2010下编译时，它在GetFileTime调用时崩溃。

有什么想法吗？或者是否有人有一段处理UTC时区等的代码，我可以通过2个文件名来告诉我它们是否不同？

function CompareFileTimes(File1, File2 : String) : LongInt;
var
  F1, F2          : THandle;
  F1_CreateTime,
  F1_LastAccess,
  F1_LastWrite,
  F2_CreateTime,
  F2_LastAccess,
  F2_LastWrite    : PFileTime;
begin
  //Initialize all variables
  F1 := 0;
  F2 := 0;

  //Since these are pointers, we have to
  //allocate memory for the FileTime structures
  GetMem(F1_CreateTime, SizeOf(TFileTime));
  GetMem(F1_LastAccess, SizeOf(TFileTime));
  GetMem(F1_LastWrite, SizeOf(TFileTime));
  GetMem(F2_CreateTime, SizeOf(TFileTime));
  GetMem(F2_LastAccess, SizeOf(TFileTime));
  GetMem(F2_LastWrite, SizeOf(TFileTime));

  //Fill the structures with nulls for now
  FillChar(F1_CreateTime, SizeOf(TFileTime), #0);
  FillChar(F1_LastAccess, SizeOf(TFileTime), #0);
  FillChar(F1_LastWrite, SizeOf(TFileTime), #0);
  FillChar(F2_CreateTime, SizeOf(TFileTime), #0);
  FillChar(F2_LastAccess, SizeOf(TFileTime), #0);
  FillChar(F2_LastWrite, SizeOf(TFileTime), #0);

  //Get file handles for the files in question
  //Notice that even though we're using CreateFile
  //the open disposition for the file is OPEN_EXISTING
  F1 := CreateFile(PChar(F1), 0, FILE_SHARE_READ, nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
  F2 := CreateFile(PChar(F2), 0, FILE_SHARE_READ, nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);

  //Get the file times for the files.
  GetFileTime(F1, F1_CreateTime, F1_LastAccess, F1_LastWrite);
  GetFileTime(F2, F2_CreateTime, F2_LastAccess, F2_LastWrite);

  //Assign the function's result to comparison
  //-1, File1 is younger than File2
  //0, File1 is the same as File2
  //+1 File1 is older than File2
  Result := CompareFileTime(F1_CreateTime^, F2_CreateTime^);

  //Free the memory allocated to the pointers
  FreeMem(F1_CreateTime, SizeOf(TFileTime));
  FreeMem(F1_LastAccess, SizeOf(TFileTime));
  FreeMem(F1_LastWrite, SizeOf(TFileTime));
  FreeMem(F2_CreateTime, SizeOf(TFileTime));
  FreeMem(F2_LastAccess, SizeOf(TFileTime));
  FreeMem(F2_LastWrite, SizeOf(TFileTime));
end;

非常感谢任何帮助。

Answer 1

Delphi 2010已经包含一个简单的包装器，用于在ioutils.pas中获取UTC时间。这是一段比较文件的UTC创建时间的代码。

uses
  IOUtils, DateUtils;

function CompareFileCreationTimeUtc(const aFile1, aFile2: String): integer;
var
  lCreationTime1: TDateTime;
  lCreationTime2: TDateTime;
begin

  lCreationTime1 := TFile.GetCreationTimeUtc(aFile1);
  lCreationTime2 := TFile.GetCreationTimeUtc(aFile2);

  Result := CompareDateTime(lCreationTime1, lCreationTime2);

end;

Answer 2

如果您不想使用IOUtils例程并且喜欢自己做，那么您的功能应该像（未经测试）一样进行更正：

function CompareFileTimes(File1, File2 : String) : LongInt;
var
  F1, F2: THandle;
  F1_CreateTime, F2_CreateTime: TFileTime;
begin
  //Fill the structures with nulls for now
  ZeroMemory(@F1_CreateTime, SizeOf(TFileTime));
  ZeroMemory(@F2_CreateTime, SizeOf(TFileTime));

  //Get file handles for the files in question
  //Notice that even though we're using CreateFile
  //the open disposition for the file is OPEN_EXISTING
  F1 := CreateFile(PChar(File1), 0, FILE_SHARE_READ , nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
  F2 := CreateFile(PChar(File2), 0, FILE_SHARE_READ, nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);

  if (F1=INVALID_HANDLE_VALUE) or (F1=INVALID_HANDLE_VALUE) then
    RaiseLastOSError;

  //Get the file times for the files.
  if not GetFileTime(F1, @F1_CreateTime, nil, nil) or
     not GetFileTime(F2, @F2_CreateTime, nil, nil) then
    RaiseLastOSError;
  //Assign the function's result to comparison
  //-1, File1 is younger than File2
  //0, File1 is the same as File2
  //+1 File1 is older than File2
  Result := CompareFileTime(F1_CreateTime, F2_CreateTime);
end;

UTC支持比较2个文件的日期/时间

2 个答案: