Difference between revisions of "TBufStream"

From Free Pascal wiki
Jump to navigationJump to search
(TBufFileStream)
Line 7: Line 7:
 
And example is presented below where a TStringList contained a large number of strings totaling about 100,000 characters was to be saved to disk. Using TWriteBufStream (instead of StringList.SaveToFile) reduced to time required by a factor of four. In this example, the StringList already contains it's data and for clarity try/finally structures have not been used. Your production code should differ ...
 
And example is presented below where a TStringList contained a large number of strings totaling about 100,000 characters was to be saved to disk. Using TWriteBufStream (instead of StringList.SaveToFile) reduced to time required by a factor of four. In this example, the StringList already contains it's data and for clarity try/finally structures have not been used. Your production code should differ ...
  
−
<syntaxhighlight lang="pascal">var
+
<syntaxhighlight lang="pascal">
 +
uses bufstream;
 +
 
 +
var
 
   WBufStream: TWriteBufStream;
 
   WBufStream: TWriteBufStream;
 
   FileStream: TFileStream;  
 
   FileStream: TFileStream;  
Line 22: Line 25:
  
 
In the same unit is '''TBufferedFileStream''' that appears to be even more suited to our need here -
 
In the same unit is '''TBufferedFileStream''' that appears to be even more suited to our need here -
−
<syntaxhighlight lang="pascal">var
+
<syntaxhighlight lang="pascal">uses bufstream;
 +
 
 +
var
 
   BufFileStream: TBufferedFileStream;
 
   BufFileStream: TBufferedFileStream;
  
Line 31: Line 36:
 
   BufFileStream.Free;
 
   BufFileStream.Free;
 
</syntaxhighlight>
 
</syntaxhighlight>
−
 
+
Note that BufferedFileStream has a fixed 32k buffer, TReadBufStream and TWriteBufStream buffer size can be set in the Create call.
  
 
==See Also==
 
==See Also==

Revision as of 15:03, 2 July 2021

TBufStream

TBufStream is the common ancestor for the TReadBufStream and TWriteBufStream streams. It completely handles the buffer memory management and position management. An instance of TBufStream should never be created directly. It also keeps the instance of the source stream.

TReadBufStream and TWriteBufStream can be used to speed up (or reduce memory consumption) of I/O processes where your application is reading or writing small 'lumps' of data and the underlying operating system is far more efficient handling data in sizable 'lumps'.

And example is presented below where a TStringList contained a large number of strings totaling about 100,000 characters was to be saved to disk. Using TWriteBufStream (instead of StringList.SaveToFile) reduced to time required by a factor of four. In this example, the StringList already contains it's data and for clarity try/finally structures have not been used. Your production code should differ ... 

uses bufstream;

var
  WBufStream: TWriteBufStream;
  FileStream: TFileStream; 
begin
  ....
  FileStream := TFileStream.Create('somefile.text', fmCreate);
  WBufStream := TWriteBufStream.Create(FileStream);
  StringList.SaveToStream(WBufStream);
  WBufStream.Free;
  FileStream.Free;

In use, the WBufStream will accept and store strings from the StringList, one by one, until its buffer is full (default 16k), it then uses the FileStream to write that content to disk, emptying its own buffer and starts again.

In the same unit is TBufferedFileStream that appears to be even more suited to our need here - 

uses bufstream;

var
  BufFileStream: TBufferedFileStream;

begin
  ....
  BufFileStream := TBufferedFileStream.Create('somefile.text', fmCreate);
  StringList.SaveToStream(BufFileStream);
  BufFileStream.Free;

Note that BufferedFileStream has a fixed 32k buffer, TReadBufStream and TWriteBufStream buffer size can be set in the Create call.

See Also

Retrieved from "http://wiki.freepascal.org/index.php?title=TBufStream&oldid=145612"