delphi 如何快速读取非常大的文本文件

代码仅供参考：

代码1

function R(const FileName: string): string;

var

M: TFileStream;

begin

M := TFileStream.Create(FileName, fmOpenRead);

try

SetLength(Result, M.Size);

M.Read(Result[1], M.Size);

finally

M.Free;

end;

代码2

function MMFileToString(const AFilename: string): string;

var

hFile: THandle;

hFileMap: THandle;

hiSize: DWORD;

loSize: DWORD;

text: string;

view: pointer;

begin

Result := '';

if AFilename = '' then

Exit;

if not FileExists(AFilename) then

Exit;

{Open the file}

hFile := CreateFile(

PChar(AFilename), GENERIC_READ, FILE_SHARE_READ, nil,

OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0

);

if hFile <> INVALID_HANDLE_VALUE then

begin

loSize := GetFileSize(hFile, @hiSize);

{File was opened successfully, now map it:}

hFileMap := CreateFileMapping(

hFile, nil, PAGE_READONLY, hiSize, loSize, 'TextForString'

);

if (hFileMap <> 0) then

begin

if (GetLastError() = ERROR_ALREADY_EXISTS) then

begin

MessageDlg(

'Mapping already exists - not created.', mtWarning, [mbOk], 0

);

CloseHandle(hFileMap)

end

else

begin

try

{File mapped successfully, now map a view of the file into the

address space:}

view := MapViewOfFile(hFileMap, FILE_MAP_READ, 0, 0, 0);

if (view <> nil) then

begin {View mapped successfully}

{Close file handle - as long is view is open it will persist}

CloseHandle(hFile);

SetLength(Result, loSize);

Move(view^, Result[1], loSize);

end

else

MessageDlg(

'Unable to map view of file. ' + SysErrorMessage(GetLastError),

mtWarning, [mbOk], 0

);

finally

UnmapViewOfFile(view); {Close view}

CloseHandle(hFileMap); {Close mapping}

end

else

begin

MessageDlg(

'Unable to create file mapping. ' + SysErrorMessage(GetLastError),

mtWarning, [mbOk], 0

);

end;

end

else

begin

MessageDlg(

'Unable to open file. ' + SysErrorMessage(GetLastError),

mtWarning, [mbOk], 0

);

end;

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