Source code of Windows XP (NT5)
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262 lines
6.3 KiB

Conversion of mci midi sequencer.
Originals on \\sysuk1\data\win31mm\src\sonic\mciseq
List utility
------------
LIST H 1238 - List management definitions
LIST C 5648 - Memory management
SUPPORT C ** NEW FOR NT ** (replace .asm etc).
Common header file
------------------
MMSYS H 7810 - Common definitions for MCI and SEQ
MCI processing
--------------
MCISEQ H 5410 - Definitions for MCI part of driver
MCICMDS C 23354 - Commands from mciDriverEntry - msXxx
MCISEQ C 36751 - DriverProc -> mciDriverEntry
CALLBACK C 2147 - Sequencer callback
FORMATS C 10845 - Time formats
-- Convert to passing around MMTIME structures ?
Sequencer
---------
MMSEQI H 13524 - Definitions local to mmseq.c (internal sequencer)
MMSEQ C 63220 - midiSeqMessage - the sequencer
MMSEQ D 3116 - Doc
UTIL C 21200 - callback, track and timer helpers for sequencer
Other bits (not reqd for NT)
----------------------------
TASK ASM 2856 - interface to mmTask (why ?)
CRIT ASM 1895 - critical sections
MCISEQ DEF 304 - def file
DATA FLOW
==================================================================
MCI (MMSYS.H) SEQ
midiSeqMessage
(SEQ_...)
--------------------->
MIDISEQINFO
MIDISEQOPEN
MIDISEQHDR
MIDISEQCALLBACK
(MIDISEQ_...)
DONE -> TaskSignal - TO stream task
DONEPLAY -> TaskSignal - TO stream task
RESET -> StreamTrackReset -> TaskSignal
<---------------------
MIDISEQERR_...
<---------------------
==================================================================
Notes :
mciGetDriverData returns a pointer to the stream - SeqStreamType so
the stream is equated to a logical device.
GETMOTWORD = 'Get Motorola word' (!)
Within the timer interrupt routine use the critical section to get
the other side of the mutual exclusion.
SERIALIZATION : A critical section is used which is held over calls
to mciDriverEntry and in the sequencer tasks but released when
getting messages (blocking) or temporarily while yielding.
STRUCTURE
=========
DRV_... + MCI_... messages
(mciseq.c!DriverEntry)
|
V
MCI messages :
(mciseq.c!mciDriverEntry)
MCI_OPEN_DRIVER
mcicmds.c!msOpen
MCI_CLOSE_DRIVER
mcicmds.c!msClose
MCI_PLAY
mcicmds.c!msPlay
MCI_PAUSE
MCI_STOP
mmseq.c!midiSeqMessage SEQ_SETPORTOFF
MCI_SEEK
mcicmds.c!msSeek
MCI_STATUS
mcicmds.c!msStatus
MCI_GETDEVCAPS
mcicmds.c!msGetDevCaps
MCI_INFO
mcicmds.c!msInfo
MCI_SET
mcicmds.c!msSet
Rest unsupported
MMSEQ messages :
(mmseq.c!midiSeqMessage)
SEQ_OPEN
....................................................................
Tasking structure :
-------------------
Application task :
mcicmds.c!msOpen
|
V
mciseq.c!msOpenStream -> mmTaskCreate with routine mciStreamCycle
|
V
TaskSignal
PostAppMessage
.
. WTM_QUITTASK, WTM_DONEPLAY, WTM_FILLBUFFER
.
Sequencer task :
GetMessage
TaskBlock
|
V
mciseq.c!mciStreamCycle
|
V
mmseq.c!midiSeqMessage - SEQ_TRACKDATA, SEQ_SETPORTOFF
| SEQ_GETINFO
V
NewTrackData
mciStreamCycle just keeps the buffers for the current stream stoked up.
Thus : there is 1 (extra) task PER LOGICAL DEVICE.
There is 1 SEQ structure per task and 1 stream structure per task (which
contains an HMIDISEQ handle hSeq to the SEQ structure). The SEQ
structure remembers the HTASK.
The SeqStreamType structure is the per-stream data on the MCI side.
This is unfortunately shared between application and stream tasks.
There is no need to inhibit threading between sequencer tasks, only
between the main task and associated sequencer tasks.
Use of Yield etc :
mciseq.c!msOpenStream - appears to have a spurious yield near the start
mcicmds.c!msOpen - calls Yield to allow the stream task to start
properly. We need to force this to happen now. Note that this
is subtle because multiple people might be running - so we
probably need a special event per task.
mcicmds.c!msPlay - sits in a loop at the moment ! Need the event
again.
mmseq NEVER yields or blocks
mciseq.c!mciStreamCycle :
TaskBlock near start when finished init - other side of
Yield in msOpen. Also later Blocks again for more work.
This is the other side of msPlay ?
mmTaskYeild - probably unnecessary since nothing was kicked off ?
......................................................................
MIDISEQ_DONE
Timers :
========
util.c!OneShotTimer has pointer to NPSEQ structure passed to it.
|
--> mmseq.c!TimerIntRoutine
|
|
util.c!MIDICallback
Conversion Issues
tasking
File format
Seems OK because :
1. mmio... is used to get at the chunks
2. The data is in big-endian format and macros are used which will
work for either format (GETMODWORD, GETMOTDWORD etc).
file access
OK - via MMIO
parameter sizes
api
build
globals
list.c - arrayOfLists
window messages
alignment / structure packing / structure overlays
Comments :
==========
1. This code is essentially uncommented. On the positive side the
structure is reasonably clean (though overcomplex and relying
on 'messages' (untyped calls) rather than subroutine calls which
means many bugs will get by the compiler into runtime code.
BUGS
====
Pointer to MMIOPROC in mcicmds.c should be pointer to pointer to.