trunk/src/diskthread.cpp

/***************************************************************************
 *                                                                         *
 *   LinuxSampler - modular, streaming capable sampler                     *
 *                                                                         *
 *   Copyright (C) 2003 by Benno Senoner                                   *
 *                                                                         *
 *   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; if not, write to the Free Software           *
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston,                 *
 *   MA  02111-1307  USA                                                   *
 ***************************************************************************/

#include "diskthread.h"


// *********** DiskThread **************
// *


// just a placeholder to mark a cell in the pickup array as 'reserved'
Stream* DiskThread::SLOT_RESERVED = (Stream*) &SLOT_RESERVED;


// #########################################################################
// # Foreign Thread Section
// #         (following code intended to be interface for audio thread)


/**
 * Returns -1 if command queue or pickup pool is full, 0 on success (will be
 * called by audio thread within the voice class).
 */
int DiskThread::OrderNewStream(Stream::reference_t* pStreamRef, gig::Sample* pSample, unsigned long SampleOffset, bool DoLoop) {
    dmsg(4,("Disk Thread: new stream ordered\n"));
    if (CreationQueue->write_space() < 1) {
        dmsg(1,("DiskThread: Order queue full!\n"));
        return -1;
    }

    pStreamRef->State   = Stream::state_active;
    pStreamRef->OrderID = CreateOrderID();
    pStreamRef->hStream = CreateHandle();
    pStreamRef->pStream = NULL; // a stream has to be activated by the disk thread first

    if (!pStreamRef->OrderID) return -1; // there was no free slot

    create_command_t cmd;
    cmd.OrderID      = pStreamRef->OrderID;
    cmd.hStream      = pStreamRef->hStream;
    cmd.pStreamRef   = pStreamRef;
    cmd.pSample      = pSample;
    cmd.SampleOffset = SampleOffset;
    cmd.DoLoop       = DoLoop;

    CreationQueue->push(&cmd);
    return 0;
}

/**
 * Returns -1 if command queue is full, 0 on success (will be called by audio
 * thread within the voice class).
 */
int DiskThread::OrderDeletionOfStream(Stream::reference_t* pStreamRef) {
    dmsg(4,("Disk Thread: stream deletion ordered\n"));
    if (DeletionQueue->write_space() < 1) {
        dmsg(1,("DiskThread: Deletion queue full!\n"));
        return -1;
    }

    delete_command_t cmd;
    cmd.pStream = pStreamRef->pStream;
    cmd.hStream = pStreamRef->hStream;
    cmd.OrderID = pStreamRef->OrderID;

    DeletionQueue->push(&cmd);
    return 0;
}

/**
 * Returns the pointer to a disk stream if the ordered disk stream
 * represented by the \a StreamOrderID was already activated by the disk
 * thread, returns NULL otherwise. If the call was successful, thus if it
 * returned a valid stream pointer, the caller has to the store that pointer
 * by himself, because it's not possible to call this method again with the
 * same used order ID; this method is just intended for picking up an ordered
 * disk stream. This method will usually be called by the voice class (within
 * the audio thread).
 *
 * @param StreamOrderID - ID previously returned by OrderNewStream()
 * @returns               pointer to created stream object, NULL otherwise
 */
Stream* DiskThread::AskForCreatedStream(Stream::OrderID_t StreamOrderID) {
    dmsg(4,("Disk Thread: been asked if stream already created, OrderID=%x ", StreamOrderID));
    Stream* pStream = pCreatedStreams[StreamOrderID];
    if (pStream && pStream != SLOT_RESERVED) {
        dmsg(4,("(yes created)\n"));
        pCreatedStreams[StreamOrderID] = NULL; // free the slot for a new order
    }
    else dmsg(4,("(no not yet created)\n"));
    return pStream;
}


// #########################################################################
// # Disk Thread Only Section
// #         (following code should only be executed by the disk thread)


DiskThread::DiskThread(uint BufferWrapElements) : Thread(false, 1, -2) {
    CreationQueue       = new RingBuffer<create_command_t>(1024);
    DeletionQueue       = new RingBuffer<delete_command_t>(1024);
    GhostQueue          = new RingBuffer<Stream::Handle>(MAX_INPUT_STREAMS);
    Streams             = MAX_INPUT_STREAMS;
    RefillStreamsPerRun = REFILL_STREAMS_PER_RUN;
    for (int i = 0; i < MAX_INPUT_STREAMS; i++) {
        pStreams[i] = new Stream(STREAM_BUFFER_SIZE, BufferWrapElements); // 131072 sample words
    }
    for (int i = 1; i <= MAX_INPUT_STREAMS; i++) {
        pCreatedStreams[i] = NULL;
    }
}

DiskThread::~DiskThread() {
    for (int i = 0; i < MAX_INPUT_STREAMS; i++) {
        if (pStreams[i]) delete pStreams[i];
    }
    if (CreationQueue) delete CreationQueue;
    if (DeletionQueue) delete DeletionQueue;
    if (GhostQueue)    delete GhostQueue;
}

int DiskThread::Main() {
    dmsg(3,("Disk thread running\n"));
    while (true) {
        IsIdle = true; // will be set to false if a stream got filled

        // if there are ghost streams, delete them
        for (int i = 0; i < GhostQueue->read_space(); i++) { //FIXME: unefficient
            Stream::Handle hGhostStream;
            GhostQueue->pop(&hGhostStream);
            bool found = false;
            for (int i = 0; i < this->Streams; i++) {
                if (pStreams[i]->GetHandle() == hGhostStream) {
                    pStreams[i]->Kill();
                    found = true;
                    break;
                }
            }
            if (!found) GhostQueue->push(&hGhostStream); // put ghost stream handle back to the queue
        }

        // if there are creation commands, create new streams
        while (Stream::UnusedStreams > 0 && CreationQueue->read_space() > 0) {
            create_command_t command;
            CreationQueue->pop(&command);
            CreateStream(command);
        }

        // if there are deletion commands, delete those streams
        while (Stream::UnusedStreams < Streams && DeletionQueue->read_space() > 0) {
            delete_command_t command;
            DeletionQueue->pop(&command);
            DeleteStream(command);
        }

        RefillStreams(); // refill the most empty streams

        // if nothing was done during this iteration (eg no streambuffer
        // filled with data) then sleep for 50ms
        if (IsIdle) usleep(30000);

        int streamsInUsage = 0;
        for (int i = Streams - 1; i >= 0; i--) {
            if (pStreams[i]->GetState() != Stream::state_unused) streamsInUsage++;
        }
        ActiveStreamCount = streamsInUsage;
        if (streamsInUsage > ActiveStreamCountMax) ActiveStreamCountMax = streamsInUsage;
    }

    return EXIT_FAILURE;
}

void DiskThread::CreateStream(create_command_t& Command) {
    // search for unused stream
    Stream* newstream = NULL;
    for (int i = Streams - 1; i >= 0; i--) {
        if (pStreams[i]->GetState() == Stream::state_unused) {
            newstream = pStreams[i];
            break;
        }
    }
    if (!newstream) {
        std::cerr << "No unused stream found (OrderID:" << Command.OrderID << ") - report if this happens, this is a bug!\n" << std::flush;
        return;
    }
    newstream->Launch(Command.hStream, Command.pStreamRef, Command.pSample, Command.SampleOffset, Command.DoLoop);
    dmsg(4,("new Stream launched by disk thread (OrderID:%d,StreamHandle:%d)\n", Command.OrderID, Command.hStream));
    if (pCreatedStreams[Command.OrderID] != SLOT_RESERVED) {
        std::cerr << "DiskThread: Slot " << Command.OrderID << " already occupied! Please report this!\n" << std::flush;
        newstream->Kill();
        return;
    }
    pCreatedStreams[Command.OrderID] = newstream;
}

void DiskThread::DeleteStream(delete_command_t& Command) {
    if (Command.pStream) Command.pStream->Kill();
    else { // the stream wasn't created by disk thread or picked up by audio thread yet

        // if stream was created but not picked up yet
        Stream* pStream = pCreatedStreams[Command.OrderID];
        if (pStream && pStream != SLOT_RESERVED) {
            pStream->Kill();
            pCreatedStreams[Command.OrderID] = NULL; // free slot for new order
            return;
        }

        // the stream was not created yet
        if (GhostQueue->write_space() > 0) {
            GhostQueue->push(&Command.hStream);
        }
        else dmsg(1,("DiskThread: GhostQueue full!\n"));
    }
}

void DiskThread::RefillStreams() {
    // sort the streams by most empty stream
    qsort(pStreams, Streams, sizeof(Stream*), CompareStreamWriteSpace);

    // refill the most empty streams
    for (uint i = 0; i < RefillStreamsPerRun; i++) {
        if (pStreams[i]->GetState() == Stream::state_active) {

            //float filledpercentage = (float) pStreams[i]->GetReadSpace() / 131072.0 * 100.0;
            //dmsg(("\nbuffer fill: %.1f%\n", filledpercentage));

            int writespace = pStreams[i]->GetWriteSpaceToEnd();
            if (writespace == 0) break;

            int capped_writespace = writespace;
            // if there is too much buffer space available then cut the read/write
            // size to MAX_REFILL_SIZE which is by default 65536 samples = 256KBytes
            if (writespace > MAX_REFILL_SIZE) capped_writespace = MAX_REFILL_SIZE;

            // adjust the amount to read in order to ensure that the buffer wraps correctly
            int read_amount = pStreams[i]->AdjustWriteSpaceToAvoidBoundary(writespace, capped_writespace);
            // if we wasn't able to refill one of the stream buffers by more than
            // MIN_REFILL_SIZE we'll send the disk thread to sleep later
            if (pStreams[i]->ReadAhead(read_amount) > MIN_REFILL_SIZE) this->IsIdle = false;
        }
    }
}

/// Handle Generator
Stream::Handle DiskThread::CreateHandle() {
    static uint32_t counter = 0;
    if (counter == 0xffffffff) counter = 1; // we use '0' as 'invalid handle' only, so we skip 0
    else                       counter++;
    return counter;
}

/// order ID Generator
Stream::OrderID_t DiskThread::CreateOrderID() {
    static uint32_t counter = 0;
    for (int i = 0; i < MAX_INPUT_STREAMS; i++) {
        if (counter == MAX_INPUT_STREAMS) counter = 1; // we use '0' as 'invalid order' only, so we skip 0
        else                              counter++;
        if (!pCreatedStreams[counter]) {
            pCreatedStreams[counter] = SLOT_RESERVED; // mark this slot as reserved
            return counter;                           // found empty slot
        }
    }
    return 0; // no free slot
}


// *********** C functions **************
// *

/**
 * This is the comparison function the qsort algo uses to determine if a value is
 * bigger than another one or special in our case; if the writespace of a stream
 * is bigger than another one.
 */
int CompareStreamWriteSpace(const void* A, const void* B) {
    Stream* a = *(Stream**) A;
    Stream* b = *(Stream**) B;
    return b->GetWriteSpace() - a->GetWriteSpace();
}
1	schoenebeck	9	/***************************************************************************
2			* *
3			* LinuxSampler - modular, streaming capable sampler *
4			* *
5			* Copyright (C) 2003 by Benno Senoner *
6			* *
7			* This program is free software; you can redistribute it and/or modify *
8			* it under the terms of the GNU General Public License as published by *
9			* the Free Software Foundation; either version 2 of the License, or *
10			* (at your option) any later version. *
11			* *
12			* This program is distributed in the hope that it will be useful, *
13			* but WITHOUT ANY WARRANTY; without even the implied warranty of *
14			* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
15			* GNU General Public License for more details. *
16			* *
17			* You should have received a copy of the GNU General Public License *
18			* along with this program; if not, write to the Free Software *
19			* Foundation, Inc., 59 Temple Place, Suite 330, Boston, *
20			* MA 02111-1307 USA *
21			***************************************************************************/
22
23			#include "diskthread.h"
24
25
26			// ********* DiskThread ************
27			// *
28
29
30	schoenebeck	18	// just a placeholder to mark a cell in the pickup array as 'reserved'
31			Stream* DiskThread::SLOT_RESERVED = (Stream*) &SLOT_RESERVED;
32
33
34	schoenebeck	9	// #########################################################################
35			// # Foreign Thread Section
36			// # (following code intended to be interface for audio thread)
37
38
39			/**
40	schoenebeck	18	* Returns -1 if command queue or pickup pool is full, 0 on success (will be
41			* called by audio thread within the voice class).
42	schoenebeck	9	*/
43	schoenebeck	26	int DiskThread::OrderNewStream(Stream::reference_t* pStreamRef, gig::Sample* pSample, unsigned long SampleOffset, bool DoLoop) {
44	schoenebeck	12	dmsg(4,("Disk Thread: new stream ordered\n"));
45	schoenebeck	18	if (CreationQueue->write_space() < 1) {
46			dmsg(1,("DiskThread: Order queue full!\n"));
47			return -1;
48			}
49	schoenebeck	9
50			pStreamRef->State = Stream::state_active;
51			pStreamRef->OrderID = CreateOrderID();
52			pStreamRef->hStream = CreateHandle();
53			pStreamRef->pStream = NULL; // a stream has to be activated by the disk thread first
54
55	schoenebeck	18	if (!pStreamRef->OrderID) return -1; // there was no free slot
56
57	schoenebeck	9	create_command_t cmd;
58	schoenebeck	18	cmd.OrderID = pStreamRef->OrderID;
59			cmd.hStream = pStreamRef->hStream;
60	schoenebeck	9	cmd.pStreamRef = pStreamRef;
61			cmd.pSample = pSample;
62			cmd.SampleOffset = SampleOffset;
63	schoenebeck	26	cmd.DoLoop = DoLoop;
64	schoenebeck	9
65	schoenebeck	18	CreationQueue->push(&cmd);
66	schoenebeck	9	return 0;
67			}
68
69			/**
70			* Returns -1 if command queue is full, 0 on success (will be called by audio
71			* thread within the voice class).
72			*/
73			int DiskThread::OrderDeletionOfStream(Stream::reference_t* pStreamRef) {
74	schoenebeck	12	dmsg(4,("Disk Thread: stream deletion ordered\n"));
75	schoenebeck	18	if (DeletionQueue->write_space() < 1) {
76			dmsg(1,("DiskThread: Deletion queue full!\n"));
77			return -1;
78			}
79	schoenebeck	9
80			delete_command_t cmd;
81			cmd.pStream = pStreamRef->pStream;
82			cmd.hStream = pStreamRef->hStream;
83			cmd.OrderID = pStreamRef->OrderID;
84
85	schoenebeck	18	DeletionQueue->push(&cmd);
86	schoenebeck	9	return 0;
87			}
88
89			/**
90			* Returns the pointer to a disk stream if the ordered disk stream
91			* represented by the \a StreamOrderID was already activated by the disk
92			* thread, returns NULL otherwise. If the call was successful, thus if it
93			* returned a valid stream pointer, the caller has to the store that pointer
94			* by himself, because it's not possible to call this method again with the
95			* same used order ID; this method is just intended for picking up an ordered
96			* disk stream. This method will usually be called by the voice class (within
97			* the audio thread).
98			*
99			* @param StreamOrderID - ID previously returned by OrderNewStream()
100			* @returns pointer to created stream object, NULL otherwise
101			*/
102			Stream* DiskThread::AskForCreatedStream(Stream::OrderID_t StreamOrderID) {
103	schoenebeck	12	dmsg(4,("Disk Thread: been asked if stream already created, OrderID=%x ", StreamOrderID));
104	schoenebeck	9	Stream* pStream = pCreatedStreams[StreamOrderID];
105	schoenebeck	18	if (pStream && pStream != SLOT_RESERVED) {
106			dmsg(4,("(yes created)\n"));
107			pCreatedStreams[StreamOrderID] = NULL; // free the slot for a new order
108			}
109			else dmsg(4,("(no not yet created)\n"));
110	schoenebeck	9	return pStream;
111			}
112
113
114
115			// #########################################################################
116			// # Disk Thread Only Section
117			// # (following code should only be executed by the disk thread)
118
119
120			DiskThread::DiskThread(uint BufferWrapElements) : Thread(false, 1, -2) {
121			CreationQueue = new RingBuffer<create_command_t>(1024);
122			DeletionQueue = new RingBuffer<delete_command_t>(1024);
123	schoenebeck	18	GhostQueue = new RingBuffer<Stream::Handle>(MAX_INPUT_STREAMS);
124	schoenebeck	9	Streams = MAX_INPUT_STREAMS;
125	schoenebeck	18	RefillStreamsPerRun = REFILL_STREAMS_PER_RUN;
126	schoenebeck	9	for (int i = 0; i < MAX_INPUT_STREAMS; i++) {
127	schoenebeck	18	pStreams[i] = new Stream(STREAM_BUFFER_SIZE, BufferWrapElements); // 131072 sample words
128	schoenebeck	9	}
129			for (int i = 1; i <= MAX_INPUT_STREAMS; i++) {
130			pCreatedStreams[i] = NULL;
131			}
132			}
133
134			DiskThread::~DiskThread() {
135			for (int i = 0; i < MAX_INPUT_STREAMS; i++) {
136			if (pStreams[i]) delete pStreams[i];
137			}
138			if (CreationQueue) delete CreationQueue;
139			if (DeletionQueue) delete DeletionQueue;
140	schoenebeck	18	if (GhostQueue) delete GhostQueue;
141	schoenebeck	9	}
142
143			int DiskThread::Main() {
144	schoenebeck	12	dmsg(3,("Disk thread running\n"));
145	schoenebeck	9	while (true) {
146			IsIdle = true; // will be set to false if a stream got filled
147
148	schoenebeck	18	// if there are ghost streams, delete them
149			for (int i = 0; i < GhostQueue->read_space(); i++) { //FIXME: unefficient
150			Stream::Handle hGhostStream;
151			GhostQueue->pop(&hGhostStream);
152			bool found = false;
153			for (int i = 0; i < this->Streams; i++) {
154			if (pStreams[i]->GetHandle() == hGhostStream) {
155			pStreams[i]->Kill();
156			found = true;
157			break;
158			}
159			}
160			if (!found) GhostQueue->push(&hGhostStream); // put ghost stream handle back to the queue
161			}
162
163	schoenebeck	9	// if there are creation commands, create new streams
164			while (Stream::UnusedStreams > 0 && CreationQueue->read_space() > 0) {
165			create_command_t command;
166	schoenebeck	18	CreationQueue->pop(&command);
167	schoenebeck	9	CreateStream(command);
168			}
169
170			// if there are deletion commands, delete those streams
171			while (Stream::UnusedStreams < Streams && DeletionQueue->read_space() > 0) {
172			delete_command_t command;
173	schoenebeck	18	DeletionQueue->pop(&command);
174	schoenebeck	9	DeleteStream(command);
175			}
176
177			RefillStreams(); // refill the most empty streams
178
179			// if nothing was done during this iteration (eg no streambuffer
180			// filled with data) then sleep for 50ms
181			if (IsIdle) usleep(30000);
182	senoner	10
183	schoenebeck	13	int streamsInUsage = 0;
184	senoner	10	for (int i = Streams - 1; i >= 0; i--) {
185	schoenebeck	13	if (pStreams[i]->GetState() != Stream::state_unused) streamsInUsage++;
186	senoner	10	}
187	schoenebeck	13	ActiveStreamCount = streamsInUsage;
188			if (streamsInUsage > ActiveStreamCountMax) ActiveStreamCountMax = streamsInUsage;
189	schoenebeck	9	}
190
191			return EXIT_FAILURE;
192			}
193
194			void DiskThread::CreateStream(create_command_t& Command) {
195			// search for unused stream
196			Stream* newstream = NULL;
197			for (int i = Streams - 1; i >= 0; i--) {
198			if (pStreams[i]->GetState() == Stream::state_unused) {
199			newstream = pStreams[i];
200			break;
201			}
202			}
203			if (!newstream) {
204	schoenebeck	18	std::cerr << "No unused stream found (OrderID:" << Command.OrderID << ") - report if this happens, this is a bug!\n" << std::flush;
205	schoenebeck	9	return;
206			}
207	schoenebeck	26	newstream->Launch(Command.hStream, Command.pStreamRef, Command.pSample, Command.SampleOffset, Command.DoLoop);
208	schoenebeck	18	dmsg(4,("new Stream launched by disk thread (OrderID:%d,StreamHandle:%d)\n", Command.OrderID, Command.hStream));
209			if (pCreatedStreams[Command.OrderID] != SLOT_RESERVED) {
210			std::cerr << "DiskThread: Slot " << Command.OrderID << " already occupied! Please report this!\n" << std::flush;
211			newstream->Kill();
212			return;
213			}
214			pCreatedStreams[Command.OrderID] = newstream;
215	schoenebeck	9	}
216
217			void DiskThread::DeleteStream(delete_command_t& Command) {
218			if (Command.pStream) Command.pStream->Kill();
219			else { // the stream wasn't created by disk thread or picked up by audio thread yet
220
221	schoenebeck	18	// if stream was created but not picked up yet
222	schoenebeck	9	Stream* pStream = pCreatedStreams[Command.OrderID];
223	schoenebeck	18	if (pStream && pStream != SLOT_RESERVED) {
224	schoenebeck	9	pStream->Kill();
225			pCreatedStreams[Command.OrderID] = NULL; // free slot for new order
226			return;
227			}
228
229	schoenebeck	18	// the stream was not created yet
230			if (GhostQueue->write_space() > 0) {
231			GhostQueue->push(&Command.hStream);
232	schoenebeck	9	}
233	schoenebeck	18	else dmsg(1,("DiskThread: GhostQueue full!\n"));
234	schoenebeck	9	}
235			}
236
237			void DiskThread::RefillStreams() {
238			// sort the streams by most empty stream
239			qsort(pStreams, Streams, sizeof(Stream*), CompareStreamWriteSpace);
240
241			// refill the most empty streams
242			for (uint i = 0; i < RefillStreamsPerRun; i++) {
243			if (pStreams[i]->GetState() == Stream::state_active) {
244
245			//float filledpercentage = (float) pStreams[i]->GetReadSpace() / 131072.0 * 100.0;
246			//dmsg(("\nbuffer fill: %.1f%\n", filledpercentage));
247
248			int writespace = pStreams[i]->GetWriteSpaceToEnd();
249			if (writespace == 0) break;
250
251			int capped_writespace = writespace;
252			// if there is too much buffer space available then cut the read/write
253			// size to MAX_REFILL_SIZE which is by default 65536 samples = 256KBytes
254			if (writespace > MAX_REFILL_SIZE) capped_writespace = MAX_REFILL_SIZE;
255
256			// adjust the amount to read in order to ensure that the buffer wraps correctly
257			int read_amount = pStreams[i]->AdjustWriteSpaceToAvoidBoundary(writespace, capped_writespace);
258			// if we wasn't able to refill one of the stream buffers by more than
259			// MIN_REFILL_SIZE we'll send the disk thread to sleep later
260			if (pStreams[i]->ReadAhead(read_amount) > MIN_REFILL_SIZE) this->IsIdle = false;
261			}
262			}
263			}
264
265			/// Handle Generator
266			Stream::Handle DiskThread::CreateHandle() {
267			static uint32_t counter = 0;
268			if (counter == 0xffffffff) counter = 1; // we use '0' as 'invalid handle' only, so we skip 0
269			else counter++;
270			return counter;
271			}
272
273			/// order ID Generator
274			Stream::OrderID_t DiskThread::CreateOrderID() {
275			static uint32_t counter = 0;
276	schoenebeck	18	for (int i = 0; i < MAX_INPUT_STREAMS; i++) {
277	schoenebeck	9	if (counter == MAX_INPUT_STREAMS) counter = 1; // we use '0' as 'invalid order' only, so we skip 0
278			else counter++;
279	schoenebeck	18	if (!pCreatedStreams[counter]) {
280			pCreatedStreams[counter] = SLOT_RESERVED; // mark this slot as reserved
281			return counter; // found empty slot
282			}
283			}
284			return 0; // no free slot
285	schoenebeck	9	}
286
287
288
289			// ********* C functions ************
290			// *
291
292			/**
293			* This is the comparison function the qsort algo uses to determine if a value is
294			* bigger than another one or special in our case; if the writespace of a stream
295			* is bigger than another one.
296			*/
297			int CompareStreamWriteSpace(const void* A, const void* B) {
298			Stream* a = (Stream*) A;
299			Stream* b = (Stream*) B;
300			return b->GetWriteSpace() - a->GetWriteSpace();
301			}