1 files changed, 165 insertions, 0 deletions
diff --git a/src/base/URingBuffer.pas b/src/base/URingBuffer.pas
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+++ b/src/base/URingBuffer.pas
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+{* UltraStar Deluxe - Karaoke Game
+ *
+ * UltraStar Deluxe is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING. If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ *
+ * $URL$
+ * $Id$
+ *}
+
+unit URingBuffer;
+
+interface
+
+{$IFDEF FPC}
+  {$MODE Delphi}
+{$ENDIF}
+
+{$I switches.inc}
+
+uses
+  SysUtils;
+
+type
+  TRingBuffer = class
+    private
+      RingBuffer: PByteArray;
+      BufferCount: integer;
+      BufferSize: integer;
+      WritePos: integer;
+      ReadPos: integer;
+    public
+      constructor Create(Size: integer);
+      destructor Destroy; override;
+      function Read(Buffer: PByteArray; Count: integer): integer;
+      function Write(Buffer: PByteArray; Count: integer): integer;
+      function Size(): integer;
+      function Available(): integer;
+      procedure Flush();
+  end;
+
+implementation
+
+uses
+  Math;
+
+constructor TRingBuffer.Create(Size: integer);
+begin
+  BufferSize := Size;
+
+  GetMem(RingBuffer, Size);
+  if (RingBuffer = nil) then
+    raise Exception.Create('No memory');
+end;
+
+destructor TRingBuffer.Destroy;
+begin
+  FreeMem(RingBuffer);
+end;
+
+function TRingBuffer.Read(Buffer: PByteArray; Count: integer): integer;
+var
+  PartCount: integer;
+begin
+  // adjust output count
+  if (Count > BufferCount) then
+  begin
+    //DebugWriteln('Read too much: ' + inttostr(count) +',count:'+ inttostr(BufferCount) + '/size:' + inttostr(BufferSize));
+    Count := BufferCount;
+  end;
+
+  // check if there is something to do
+  if (Count <= 0) then
+  begin
+    Result := Count;
+    Exit;
+  end;
+
+  // copy data to output buffer
+
+  // first step: copy from the area between the read-position and the end of the buffer
+  PartCount := Min(Count, BufferSize - ReadPos);
+  Move(RingBuffer[ReadPos], Buffer[0], PartCount);
+
+  // second step: if we need more data, copy from the beginning of the buffer
+  if (PartCount < Count) then
+    Move(RingBuffer[0], Buffer[0], Count-PartCount);
+
+  // mark the copied part of the buffer as free
+  BufferCount := BufferCount - Count;
+  ReadPos := (ReadPos + Count) mod BufferSize;
+
+  Result := Count;
+end;
+
+function TRingBuffer.Write(Buffer: PByteArray; Count: integer): integer;
+var
+  PartCount: integer;
+begin
+  // check for a reasonable request
+  if (Count <= 0) then
+  begin
+    Result := Count;
+    Exit;
+  end;
+
+  // skip input data if the input buffer is bigger than the ring-buffer
+  if (Count > BufferSize) then
+  begin
+    //DebugWriteln('Write skip data:' + inttostr(count) +',count:'+ inttostr(BufferCount) + '/size:' + inttostr(BufferSize));
+    Buffer := @Buffer[Count - BufferSize];
+    Count := BufferSize;
+  end;
+
+  // first step: copy to the area between the write-position and the end of the buffer
+  PartCount := Min(Count, BufferSize - WritePos);
+  Move(Buffer[0], RingBuffer[WritePos], PartCount);
+
+  // second step: copy data to front of buffer
+  if (PartCount < Count) then
+    Move(Buffer[PartCount], RingBuffer[0], Count-PartCount);
+
+  // update info
+  BufferCount := Min(BufferCount + Count, BufferSize);
+  WritePos := (WritePos + Count) mod BufferSize;
+  // if the buffer is full, we have to reposition the read-position
+  if (BufferCount = BufferSize) then
+    ReadPos := WritePos;
+
+  Result := Count;
+end;
+
+function TRingBuffer.Available(): integer;
+begin
+  Result := BufferCount;
+end;
+
+function TRingBuffer.Size(): integer;
+begin
+  Result := BufferSize;
+end;
+
+procedure TRingBuffer.Flush();
+begin
+  ReadPos := 0;
+  WritePos := 0;
+  BufferCount := 0;
+end;
+
+end.