Declaration¶
Source position: bufstream.pp line 88
type
TBufferedFileStream = class(TFileStream)
public
constructor Create(const AFileName: string; Mode: Word);
constructor Create(const AFileName: string; Mode: Word;
Rights: Cardinal);
destructor Destroy;
function Seek(Offset: LongInt; Origin: Word) : LongInt; overload;
function Seek(const Offset: Int64; Origin: TSeekOrigin) : Int64; overload;
function Read : LongInt;
function Write : LongInt;
procedure Flush;
procedure InitializeCache;
end;
Inheritance¶
Description¶
TBufferedFileStream is a TFileStream descendant which implements a buffered file stream. It provides a buffer with multiple pages used for random read / write access in the file stream.
By default, It uses a fixed-size buffer consisting of 8 pages with a 4,096 bytes per page. Both page count and page size configurable using the InitializeCache method in the class. The buffer is automatically maintained when the stream size or position is changed, and when reading or writing content to/from the stream.
Pages which have been modified in the buffer are written to the file stream as needed (all pages are used and a read/write operation is performed), when the Flush method is called, and when the class instance is freed. Thus, the class will never use more than the total size obtained by multiplying the CacheBlockSize and aCacheBlockCount arguments to InitializeCache.
This class is suitable when you need to do a lot of random access to a file: hence the use of different pages of configurable size. If you simply wish to speed up sequential reads you better use TReadBufStream or TWriteBufStream for speeding up sequential writes.
Methods¶
| Member | Visibility | Description |
|---|---|---|
| Create | public | Constructor for the class instance. |
| Destroy | public | Destructor for the class instance. |
| Flush | public | Flushes modified pages in the buffer to the file stream. |
| InitializeCache | public | Re-initializes the internal buffer for the buffered file stream. |
| Read | public | Reads the specified number of bytes into the Buffer parameter. |
| Seek | public | Moves the position in the buffer relative to the specified origin. |
| Write | public | Writes the specified number of bytes in Buffer to the internal page buffer(s). |
See also¶
| Name | Description |
|---|---|
| TFileStream | |
| THandleStream | |
| TStream | |
| TReadBufStream | Read-only buffered stream. |
| TWriteBufStream | Write-only buffered stream. |