如何删除 MemoryStream 中的起始 header 并将其余部分保存到文件中？

Question

我目前有一个 TMemoryStream，它通过读取一个 varbinary 字段来填充，该字段最初是由来自 MS SQL 服务器数据库 table.[=14= 的 UTF8 标准编码的]

varbinary 字段包含一个 header 部分，在将流的其余部分保存为文件之前需要将其删除。

我已经成功提取了所需的header信息，其中包括文件名，但还没有找到了将流的剩余部分保存为有效文件的解决方案。

数据最初被读入 TdxMemData 数据集。

procedure TBaseDataPump.SaveAttachments(mtblAttachmentInfo: TdxMemData);
var
  AFile: TMemoryStream;
  ANewFile: TStringStream;
  sFullPath: String;
  wsImageBlob, wsHeader, wsBody: WideString;
  iposition: Integer;
begin
  if mtblAttachmentInfo.Active then // TdxMemData filled with data
  begin
    with mtblAttachmentInfo do
    begin
      First;
      while NOT EOF do
      begin
        // Below code works fine to save the file without removing the data
        AFile := TMemoryStream.Create; // Create the memory stream
        TBlobField(FieldByName('ImageBlob')).SaveToStream(AFile);
        // load the file image from the data to the memory strem

        // Get the header content
        ANewFile := TStringStream.Create('');
        TBlobField(FieldByName('ImageBlob')).SaveToStream(ANewFile);
        // read  the filed again to a TStringStream

        wsImageBlob := UTF8ToString(ANewFile.DataString);
        // I can see the data as wide string and can find the header bit and its ending position on the 
        //  its ending position on the  string
        iposition := AnsiPos(#13#13#10, wsImageBlob); // find the header ending position

        // getting the header to another widestring
        wsHeader := AnsiLeftStr(wsImageBlob,position);
        wsHeader := AnsiLeftStr(wsImageBlob,POS(#9,wsHeader)-1);
        wsHeader := StringReplace(wsHeader,'''','',[rfReplaceall]);

        // need to save the stream from the position of the end of header as file
      end;
    end;

  end;
end;

Answer 1

用copyfrom方法找到了解决方案。它如下：

      // Create the  TStringStream
      ANewFile := TStringStream.Create('');

      try
        TBlobField(FieldByName('ImageBlob')).SaveToStream(ANewFile);

        // get the blob as a string so we can extract the header information
        wsImageBlob := UTF8ToString(ANewFile.DataString);

        position := AnsiPos(#13#13#10, wsImageBlob);

        if position <> 0 then begin
          // have header information to extract
          position := position + 2;

          wsHeader := AnsiLeftStr(wsImageBlob, position);
          wsHeader := AnsiLeftStr(wsImageBlob, POS(#9, wsHeader) - 1);
          wsHeader := StringReplace(wsHeader, '''', '', [rfReplaceall]);

          sFilePath := sDirectorypath + wsHeader;

          ANewFile.Position := position;     

          AFile := TMemoryStream.Create;
          try
            AFile.CopyFrom(ANewFile, ANewFile.Size - position);

            AFile.SaveToFile(sFilePath);
          finally
            FreeAndNil(AFile);
          end;
        end
      finally
        FreeAndNil(ANewFile);
      end;

如何删除 MemoryStream 中的起始 header 并将其余部分保存到文件中？

How to remove the starting header in a MemoryStream and save the rest to a file?

delphi

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