From 0b60f71cb853b35e53d0b407493dbcfc098ed40e Mon Sep 17 00:00:00 2001 From: tobigun Date: Tue, 19 Oct 2010 16:39:31 +0000 Subject: initial commit git-svn-id: svn://svn.code.sf.net/p/ultrastardx/svn/branches/experimental@2684 b956fd51-792f-4845-bead-9b4dfca2ff2c --- mediaplugin/src/lib/midi/CIRCBUF.PAS | 183 +++++++++++++++++++++++++++++++++++ 1 file changed, 183 insertions(+) create mode 100644 mediaplugin/src/lib/midi/CIRCBUF.PAS (limited to 'mediaplugin/src/lib/midi/CIRCBUF.PAS') diff --git a/mediaplugin/src/lib/midi/CIRCBUF.PAS b/mediaplugin/src/lib/midi/CIRCBUF.PAS new file mode 100644 index 00000000..3ceb4c6e --- /dev/null +++ b/mediaplugin/src/lib/midi/CIRCBUF.PAS @@ -0,0 +1,183 @@ +{ $Header: /MidiComp/CIRCBUF.PAS 2 10/06/97 7:33 Davec $ } + +{ Written by David Churcher , + released to the public domain. } + + +{ A First-In First-Out circular buffer. + Port of circbuf.c from Microsoft's Windows MIDI monitor example. + I did do a version of this as an object (see Rev 1.1) but it was getting too + complicated and I couldn't see any real benefits to it so I dumped it + for an ordinary memory buffer with pointers. + + This unit is a bit C-like, everything is done with pointers and extensive + use is made of the undocumented feature of the Inc() function that + increments pointers by the size of the object pointed to. + All of this could probably be done using Pascal array notation with + range-checking turned off, but I'm not sure it's worth it. +} + +Unit Circbuf; + +interface + +{$IFDEF FPC} + {$MODE Delphi} + {$H+} // use long strings +{$ENDIF} + +Uses + Windows, + MMSystem; + +type + { MIDI input event } + TMidiBufferItem = record + timestamp: DWORD; { Timestamp in milliseconds after midiInStart } + data: DWORD; { MIDI message received } + sysex: PMidiHdr; { Pointer to sysex MIDIHDR, nil if not sysex } + end; + PMidiBufferItem = ^TMidiBufferItem; + + { MIDI input buffer } + TCircularBuffer = record + RecordHandle: HGLOBAL; { Windows memory handle for this record } + BufferHandle: HGLOBAL; { Windows memory handle for the buffer } + pStart: PMidiBufferItem; { ptr to start of buffer } + pEnd: PMidiBufferItem; { ptr to end of buffer } + pNextPut: PMidiBufferItem; { next location to fill } + pNextGet: PMidiBufferItem; { next location to empty } + Error: Word; { error code from MMSYSTEM functions } + Capacity: Word; { buffer size (in TMidiBufferItems) } + EventCount: Word; { Number of events in buffer } + end; + + PCircularBuffer = ^TCircularBuffer; + +function GlobalSharedLockedAlloc( Capacity: Word; var hMem: HGLOBAL ): Pointer; +procedure GlobalSharedLockedFree( hMem: HGLOBAL; ptr: Pointer ); + +function CircbufAlloc( Capacity: Word ): PCircularBuffer; +procedure CircbufFree( PBuffer: PCircularBuffer ); +function CircbufRemoveEvent( PBuffer: PCircularBuffer ): Boolean; +function CircbufReadEvent( PBuffer: PCircularBuffer; PEvent: PMidiBufferItem ): Boolean; +{ Note: The PutEvent function is in the DLL } + +implementation + +{ Allocates in global shared memory, returns pointer and handle } +function GlobalSharedLockedAlloc( Capacity: Word; var hMem: HGLOBAL ): Pointer; +var + ptr: Pointer; +begin + { Allocate the buffer memory } + hMem := GlobalAlloc(GMEM_SHARE Or GMEM_MOVEABLE Or GMEM_ZEROINIT, Capacity ); + + if (hMem = 0) then + ptr := Nil + else + begin + ptr := GlobalLock(hMem); + if (ptr = Nil) then + GlobalFree(hMem); + end; + + GlobalSharedLockedAlloc := Ptr; +end; + +procedure GlobalSharedLockedFree( hMem: HGLOBAL; ptr: Pointer ); +begin + if (hMem <> 0) then + begin + GlobalUnlock(hMem); + GlobalFree(hMem); + end; +end; + +function CircbufAlloc( Capacity: Word ): PCircularBuffer; +var + NewCircularBuffer: PCircularBuffer; + NewMIDIBuffer: PMidiBufferItem; + hMem: HGLOBAL; +begin + { TODO: Validate circbuf size, <64K } + NewCircularBuffer := + GlobalSharedLockedAlloc( Sizeof(TCircularBuffer), hMem ); + if (NewCircularBuffer <> Nil) then + begin + NewCircularBuffer^.RecordHandle := hMem; + NewMIDIBuffer := + GlobalSharedLockedAlloc( Capacity * Sizeof(TMidiBufferItem), hMem ); + if (NewMIDIBuffer = Nil) then + begin + { TODO: Exception here? } + GlobalSharedLockedFree( NewCircularBuffer^.RecordHandle, + NewCircularBuffer ); + NewCircularBuffer := Nil; + end + else + begin + NewCircularBuffer^.pStart := NewMidiBuffer; + { Point to item at end of buffer } + NewCircularBuffer^.pEnd := NewMidiBuffer; + Inc(NewCircularBuffer^.pEnd, Capacity); + { Start off the get and put pointers in the same position. These + will get out of sync as the interrupts start rolling in } + NewCircularBuffer^.pNextPut := NewMidiBuffer; + NewCircularBuffer^.pNextGet := NewMidiBuffer; + NewCircularBuffer^.Error := 0; + NewCircularBuffer^.Capacity := Capacity; + NewCircularBuffer^.EventCount := 0; + end; + end; + CircbufAlloc := NewCircularBuffer; +end; + +procedure CircbufFree( pBuffer: PCircularBuffer ); +begin + if (pBuffer <> Nil) then + begin + GlobalSharedLockedFree(pBuffer^.BufferHandle, pBuffer^.pStart); + GlobalSharedLockedFree(pBuffer^.RecordHandle, pBuffer); + end; +end; + +{ Reads first event in queue without removing it. + Returns true if successful, False if no events in queue } +function CircbufReadEvent( PBuffer: PCircularBuffer; PEvent: PMidiBufferItem ): Boolean; +var + PCurrentEvent: PMidiBufferItem; +begin + if (PBuffer^.EventCount <= 0) then + CircbufReadEvent := False + else + begin + PCurrentEvent := PBuffer^.PNextget; + + { Copy the object from the "tail" of the buffer to the caller's object } + PEvent^.Timestamp := PCurrentEvent^.Timestamp; + PEvent^.Data := PCurrentEvent^.Data; + PEvent^.Sysex := PCurrentEvent^.Sysex; + CircbufReadEvent := True; + end; +end; + +{ Remove current event from the queue } +function CircbufRemoveEvent(PBuffer: PCircularBuffer): Boolean; +begin + if (PBuffer^.EventCount > 0) then + begin + Dec( Pbuffer^.EventCount); + + { Advance the buffer pointer, with wrap } + Inc( Pbuffer^.PNextGet ); + If (PBuffer^.PNextGet = PBuffer^.PEnd) then + PBuffer^.PNextGet := PBuffer^.PStart; + + CircbufRemoveEvent := True; + end + else + CircbufRemoveEvent := False; +end; + +end. -- cgit v1.2.3