Allow storing multiple buffers in a ALbufferlistitem

This will be to allow buffer layering, multiple buffers of the same format and
sample rate that are mixed together prior to resampling, filtering, and
panning. This will allow composing sounds from individual components that can
be swapped around on different invocations (e.g. layer SoundA and SoundB on one
instance and SoundA and SoundC on a different instance for a slightly different
sound, then just SoundA for a third instance, and so on). The longest buffer
within the list item determines the length of the list item.

More work needs to be done to fully support it, namely the ability to specity
multiple buffers to layer for static and streaming sources. Also the behavior
of loop points for layered static sources should be worked out. Should also
consider allowing each layer to have a sample offset.

4 files changed, 153 insertions, 72 deletions

diff --git a/Alc/ALu.c b/Alc/ALu.c
index 0da610d1..5f0c556a 100644
--- a/Alc/ALu.c
+++ b/Alc/ALu.c
@@ -1450,7 +1450,7 @@ static void CalcSourceParams(ALvoice *voice, ALCcontext *context, bool force)
     while(BufferListItem != NULL)
     {
         const ALbuffer *buffer;
-        if((buffer=BufferListItem->buffer) != NULL)
+        if(BufferListItem->num_buffers >= 1 && (buffer=BufferListItem->buffers[0]) != NULL)
         {
             if(props->SpatializeMode == SpatializeOn ||
                (props->SpatializeMode == SpatializeAuto && buffer->FmtChannels == FmtMono))
diff --git a/Alc/mixer.c b/Alc/mixer.c
index c77488bc..37bdf6ac 100644
--- a/Alc/mixer.c
+++ b/Alc/mixer.c
@@ -362,9 +362,13 @@ ALboolean MixSource(ALvoice *voice, ALsource *Source, ALCdevice *Device, ALsizei
             memcpy(SrcData, voice->PrevSamples[chan], MAX_PRE_SAMPLES*sizeof(ALfloat));
             SrcDataSize = MAX_PRE_SAMPLES;
 
+            /* TODO: Handle multi-buffer items by adding them together in
+             * SrcData. Need to work out how to deal with looping (loop
+             * points).
+             */
             if(isstatic)
             {
-                const ALbuffer *ALBuffer = BufferListItem->buffer;
+                const ALbuffer *ALBuffer = BufferListItem->buffers[0];
                 const ALubyte *Data = ALBuffer->data;
                 ALsizei DataSize;
 
@@ -421,7 +425,7 @@ ALboolean MixSource(ALvoice *voice, ALsource *Source, ALCdevice *Device, ALsizei
                 while(tmpiter && SrcBufferSize > SrcDataSize)
                 {
                     const ALbuffer *ALBuffer;
-                    if((ALBuffer=tmpiter->buffer) != NULL)
+                    if(tmpiter->num_buffers >= 1 && (ALBuffer=tmpiter->buffers[0]) != NULL)
                     {
                         const ALubyte *Data = ALBuffer->data;
                         ALsizei DataSize = ALBuffer->SampleLen;
@@ -637,7 +641,7 @@ ALboolean MixSource(ALvoice *voice, ALsource *Source, ALCdevice *Device, ALsizei
             ALsizei LoopStart = 0;
             ALsizei LoopEnd = 0;
 
-            if((ALBuffer=BufferListItem->buffer) != NULL)
+            if(BufferListItem->num_buffers >= 1 && (ALBuffer=BufferListItem->buffers[0]) != NULL)
             {
                 DataSize = ALBuffer->SampleLen;
                 LoopStart = ALBuffer->LoopStart;
diff --git a/OpenAL32/Include/alSource.h b/OpenAL32/Include/alSource.h
index 03034ce8..970ea07c 100644
--- a/OpenAL32/Include/alSource.h
+++ b/OpenAL32/Include/alSource.h
@@ -19,8 +19,9 @@ struct ALsource;
 
 
 typedef struct ALbufferlistitem {
-    struct ALbuffer *buffer;
     ATOMIC(struct ALbufferlistitem*) next;
+    ALsizei num_buffers;
+    struct ALbuffer *buffers[];
 } ALbufferlistitem;
 
 
diff --git a/OpenAL32/alSource.c b/OpenAL32/alSource.c
index cc19a0c3..f4d82c68 100644
--- a/OpenAL32/alSource.c
+++ b/OpenAL32/alSource.c
@@ -774,9 +774,11 @@ static ALboolean SetSourceiv(ALsource *Source, ALCcontext *Context, SourceProp p
             if(buffer != NULL)
             {
                 /* Add the selected buffer to a one-item queue */
-                ALbufferlistitem *newlist = al_calloc(DEF_ALIGN, sizeof(ALbufferlistitem));
-                newlist->buffer = buffer;
+                ALbufferlistitem *newlist = al_calloc(DEF_ALIGN,
+                    FAM_SIZE(ALbufferlistitem, buffers, 1));
                 ATOMIC_INIT(&newlist->next, NULL);
+                newlist->num_buffers = 1;
+                newlist->buffers[0] = buffer;
                 IncrementRef(&buffer->ref);
 
                 /* Source is now Static */
@@ -795,11 +797,15 @@ static ALboolean SetSourceiv(ALsource *Source, ALCcontext *Context, SourceProp p
             /* Delete all elements in the previous queue */
             while(oldlist != NULL)
             {
+                ALsizei i;
                 ALbufferlistitem *temp = oldlist;
                 oldlist = ATOMIC_LOAD(&temp->next, almemory_order_relaxed);
 
-                if(temp->buffer)
-                    DecrementRef(&temp->buffer->ref);
+                for(i = 0;i < temp->num_buffers;i++)
+                {
+                    if(temp->buffers[i])
+                        DecrementRef(&temp->buffers[i]->ref);
+                }
                 al_free(temp);
             }
             return AL_TRUE;
@@ -1219,12 +1225,18 @@ static ALboolean GetSourcedv(ALsource *Source, ALCcontext *Context, SourceProp p
                 ALint length = 0;
                 ALsizei freq = 1;
                 do {
-                    ALbuffer *buffer = BufferList->buffer;
-                    if(buffer && buffer->SampleLen > 0)
+                    ALsizei max_len = 0;
+                    ALsizei i;
+                    for(i = 0;i < BufferList->num_buffers;i++)
                     {
-                        freq = buffer->Frequency;
-                        length += buffer->SampleLen;
+                        ALbuffer *buffer = BufferList->buffers[i];
+                        if(buffer && buffer->SampleLen > 0)
+                        {
+                            freq = buffer->Frequency;
+                            max_len = maxi(max_len, buffer->SampleLen);
+                        }
                     }
+                    length += max_len;
                     BufferList = ATOMIC_LOAD(&BufferList->next, almemory_order_relaxed);
                 } while(BufferList != NULL);
                 *values = (ALdouble)length / (ALdouble)freq;
@@ -1344,7 +1356,8 @@ static ALboolean GetSourceiv(ALsource *Source, ALCcontext *Context, SourceProp p
         case AL_BUFFER:
             ReadLock(&Source->queue_lock);
             BufferList = (Source->SourceType == AL_STATIC) ? Source->queue : NULL;
-            *values = (BufferList && BufferList->buffer) ? BufferList->buffer->id : 0;
+            *values = (BufferList && BufferList->num_buffers >= 1 && BufferList->buffers[0]) ?
+                      BufferList->buffers[0]->id : 0;
             ReadUnlock(&Source->queue_lock);
             return AL_TRUE;
 
@@ -1360,31 +1373,38 @@ static ALboolean GetSourceiv(ALsource *Source, ALCcontext *Context, SourceProp p
             {
                 ALint length = 0;
                 do {
-                    ALbuffer *buffer = BufferList->buffer;
-                    if(buffer && buffer->SampleLen > 0)
+                    ALsizei max_len = 0;
+                    ALsizei i;
+                    for(i = 0;i < BufferList->num_buffers;i++)
                     {
-                        ALuint byte_align, sample_align;
-                        if(buffer->OriginalType == UserFmtIMA4)
-                        {
-                            ALsizei align = (buffer->OriginalAlign-1)/2 + 4;
-                            byte_align = align * ChannelsFromFmt(buffer->FmtChannels);
-                            sample_align = buffer->OriginalAlign;
-                        }
-                        else if(buffer->OriginalType == UserFmtMSADPCM)
-                        {
-                            ALsizei align = (buffer->OriginalAlign-2)/2 + 7;
-                            byte_align = align * ChannelsFromFmt(buffer->FmtChannels);
-                            sample_align = buffer->OriginalAlign;
-                        }
-                        else
+                        ALbuffer *buffer = BufferList->buffers[i];
+                        if(buffer && buffer->SampleLen > 0)
                         {
-                            ALsizei align = buffer->OriginalAlign;
-                            byte_align = align * ChannelsFromFmt(buffer->FmtChannels);
-                            sample_align = buffer->OriginalAlign;
+                            ALuint byte_align, sample_align;
+                            if(buffer->OriginalType == UserFmtIMA4)
+                            {
+                                ALsizei align = (buffer->OriginalAlign-1)/2 + 4;
+                                byte_align = align * ChannelsFromFmt(buffer->FmtChannels);
+                                sample_align = buffer->OriginalAlign;
+                            }
+                            else if(buffer->OriginalType == UserFmtMSADPCM)
+                            {
+                                ALsizei align = (buffer->OriginalAlign-2)/2 + 7;
+                                byte_align = align * ChannelsFromFmt(buffer->FmtChannels);
+                                sample_align = buffer->OriginalAlign;
+                            }
+                            else
+                            {
+                                ALsizei align = buffer->OriginalAlign;
+                                byte_align = align * ChannelsFromFmt(buffer->FmtChannels);
+                                sample_align = buffer->OriginalAlign;
+                            }
+
+                            max_len = maxi(max_len, buffer->SampleLen / sample_align * byte_align);
                         }
-
-                        length += buffer->SampleLen / sample_align * byte_align;
                     }
+                    length += max_len;
+
                     BufferList = ATOMIC_LOAD(&BufferList->next, almemory_order_relaxed);
                 } while(BufferList != NULL);
                 *values = length;
@@ -1400,8 +1420,14 @@ static ALboolean GetSourceiv(ALsource *Source, ALCcontext *Context, SourceProp p
             {
                 ALint length = 0;
                 do {
-                    ALbuffer *buffer = BufferList->buffer;
-                    if(buffer) length += buffer->SampleLen;
+                    ALsizei max_len = 0;
+                    ALsizei i;
+                    for(i = 0;i < BufferList->num_buffers;i++)
+                    {
+                        ALbuffer *buffer = BufferList->buffers[i];
+                        if(buffer) max_len = maxi(max_len, buffer->SampleLen);
+                    }
+                    length += max_len;
                     BufferList = ATOMIC_LOAD(&BufferList->next, almemory_order_relaxed);
                 } while(BufferList != NULL);
                 *values = length;
@@ -2503,8 +2529,13 @@ AL_API ALvoid AL_APIENTRY alSourcePlayv(ALsizei n, const ALuint *sources)
         BufferList = source->queue;
         while(BufferList)
         {
-            if((buffer=BufferList->buffer) != NULL && buffer->SampleLen > 0)
-                break;
+            ALsizei b;
+            for(b = 0;b < BufferList->num_buffers;b++)
+            {
+                buffer = BufferList->buffers[b];
+                if(buffer && buffer->SampleLen > 0) break;
+            }
+            if(buffer && buffer->SampleLen > 0) break;
             BufferList = ATOMIC_LOAD(&BufferList->next, almemory_order_relaxed);
         }
 
@@ -2804,11 +2835,12 @@ AL_API ALvoid AL_APIENTRY alSourceQueueBuffers(ALuint src, ALsizei nb, const ALu
     BufferList = source->queue;
     while(BufferList)
     {
-        if(BufferList->buffer)
+        for(i = 0;i < BufferList->num_buffers;i++)
         {
-            BufferFmt = BufferList->buffer;
-            break;
+            if((BufferFmt=BufferList->buffers[i]) != NULL)
+                break;
         }
+        if(BufferFmt) break;
         BufferList = ATOMIC_LOAD(&BufferList->next, almemory_order_relaxed);
     }
 
@@ -2826,17 +2858,20 @@ AL_API ALvoid AL_APIENTRY alSourceQueueBuffers(ALuint src, ALsizei nb, const ALu
 
         if(!BufferListStart)
         {
-            BufferListStart = al_calloc(DEF_ALIGN, sizeof(ALbufferlistitem));
+            BufferListStart = al_calloc(DEF_ALIGN,
+                FAM_SIZE(ALbufferlistitem, buffers, 1));
             BufferList = BufferListStart;
         }
         else
         {
-            ALbufferlistitem *item = al_calloc(DEF_ALIGN, sizeof(ALbufferlistitem));
+            ALbufferlistitem *item = al_calloc(DEF_ALIGN,
+                FAM_SIZE(ALbufferlistitem, buffers, 1));
             ATOMIC_STORE(&BufferList->next, item, almemory_order_relaxed);
             BufferList = item;
         }
-        BufferList->buffer = buffer;
         ATOMIC_INIT(&BufferList->next, NULL);
+        BufferList->num_buffers = 1;
+        BufferList->buffers[0] = buffer;
         if(!buffer) continue;
 
         /* Hold a read lock on each buffer being queued while checking all
@@ -2861,10 +2896,13 @@ AL_API ALvoid AL_APIENTRY alSourceQueueBuffers(ALuint src, ALsizei nb, const ALu
             {
                 ALbufferlistitem *next = ATOMIC_LOAD(&BufferListStart->next,
                                                      almemory_order_relaxed);
-                if((buffer=BufferListStart->buffer) != NULL)
+                for(i = 0;i < BufferListStart->num_buffers;i++)
                 {
-                    DecrementRef(&buffer->ref);
-                    ReadUnlock(&buffer->lock);
+                    if((buffer=BufferListStart->buffers[i]) != NULL)
+                    {
+                        DecrementRef(&buffer->ref);
+                        ReadUnlock(&buffer->lock);
+                    }
                 }
                 al_free(BufferListStart);
                 BufferListStart = next;
@@ -2877,8 +2915,11 @@ AL_API ALvoid AL_APIENTRY alSourceQueueBuffers(ALuint src, ALsizei nb, const ALu
     BufferList = BufferListStart;
     while(BufferList != NULL)
     {
-        ALbuffer *buffer = BufferList->buffer;
-        if(buffer) ReadUnlock(&buffer->lock);
+        for(i = 0;i < BufferList->num_buffers;i++)
+        {
+            ALbuffer *buffer = BufferList->buffers[i];
+            if(buffer) ReadUnlock(&buffer->lock);
+        }
         BufferList = ATOMIC_LOAD(&BufferList->next, almemory_order_relaxed);
     }
     UnlockBuffersRead(device);
@@ -2940,12 +2981,12 @@ AL_API ALvoid AL_APIENTRY alSourceUnqueueBuffers(ALuint src, ALsizei nb, ALuint
         Current = ATOMIC_LOAD_SEQ(&voice->current_buffer);
     else if(ATOMIC_LOAD_SEQ(&source->state) == AL_INITIAL)
         Current = OldTail;
-    if(OldTail != Current)
+    if(OldTail != Current && OldTail->num_buffers == 1)
     {
         for(i = 1;i < nb;i++)
         {
             ALbufferlistitem *next = ATOMIC_LOAD(&OldTail->next, almemory_order_relaxed);
-            if(!next || next == Current) break;
+            if(!next || next == Current || next->num_buffers != 1) break;
             OldTail = next;
         }
     }
@@ -2964,7 +3005,7 @@ AL_API ALvoid AL_APIENTRY alSourceUnqueueBuffers(ALuint src, ALsizei nb, ALuint
     while(OldHead != NULL)
     {
         ALbufferlistitem *next = ATOMIC_LOAD(&OldHead->next, almemory_order_relaxed);
-        ALbuffer *buffer = OldHead->buffer;
+        ALbuffer *buffer = OldHead->buffers[0];
 
         if(!buffer)
             *(buffers++) = 0;
@@ -3073,8 +3114,11 @@ static void DeinitSource(ALsource *source, ALsizei num_sends)
     while(BufferList != NULL)
     {
         ALbufferlistitem *next = ATOMIC_LOAD(&BufferList->next, almemory_order_relaxed);
-        if(BufferList->buffer != NULL)
-            DecrementRef(&BufferList->buffer->ref);
+        for(i = 0;i < BufferList->num_buffers;i++)
+        {
+            if(BufferList->buffers[i] != NULL)
+                DecrementRef(&BufferList->buffers[i]->ref);
+        }
         al_free(BufferList);
         BufferList = next;
     }
@@ -3235,8 +3279,15 @@ static ALint64 GetSourceSampleOffset(ALsource *Source, ALCcontext *context, ALui
         const ALbufferlistitem *BufferList = Source->queue;
         while(BufferList && BufferList != Current)
         {
-            if(BufferList->buffer)
-                readPos += (ALuint64)BufferList->buffer->SampleLen << 32;
+            ALsizei max_len = 0;
+            ALsizei i;
+
+            for(i = 0;i < BufferList->num_buffers;i++)
+            {
+                ALbuffer *buffer = BufferList->buffers[i];
+                if(buffer) max_len = maxi(max_len, buffer->SampleLen);
+            }
+            readPos += (ALuint64)max_len << 32;
             BufferList = ATOMIC_LOAD(&CONST_CAST(ALbufferlistitem*,BufferList)->next,
                                      almemory_order_relaxed);
         }
@@ -3288,19 +3339,28 @@ static ALdouble GetSourceSecOffset(ALsource *Source, ALCcontext *context, ALuint
         const ALbuffer *BufferFmt = NULL;
         while(BufferList && BufferList != Current)
         {
-            const ALbuffer *buffer = BufferList->buffer;
-            if(buffer != NULL)
+            ALsizei max_len = 0;
+            ALsizei i;
+
+            for(i = 0;i < BufferList->num_buffers;i++)
             {
-                if(!BufferFmt) BufferFmt = buffer;
-                readPos += (ALuint64)buffer->SampleLen << FRACTIONBITS;
+                ALbuffer *buffer = BufferList->buffers[i];
+                if(buffer)
+                {
+                    if(!BufferFmt) BufferFmt = buffer;
+                    max_len = maxi(max_len, buffer->SampleLen);
+                }
             }
+            readPos += (ALuint64)max_len << FRACTIONBITS;
             BufferList = ATOMIC_LOAD(&CONST_CAST(ALbufferlistitem*,BufferList)->next,
                                      almemory_order_relaxed);
         }
 
         while(BufferList && !BufferFmt)
         {
-            BufferFmt = BufferList->buffer;
+            ALsizei i;
+            for(i = 0;i < BufferList->num_buffers && !BufferFmt;i++)
+                BufferFmt = BufferList->buffers[i];
             BufferList = ATOMIC_LOAD(&CONST_CAST(ALbufferlistitem*,BufferList)->next,
                                      almemory_order_relaxed);
         }
@@ -3357,14 +3417,22 @@ static ALdouble GetSourceOffset(ALsource *Source, ALenum name, ALCcontext *conte
 
         while(BufferList != NULL)
         {
-            const ALbuffer *buffer;
+            ALsizei max_len = 0;
+            ALsizei i;
+
             readFin = readFin || (BufferList == Current);
-            if((buffer=BufferList->buffer) != NULL)
+            for(i = 0;i < BufferList->num_buffers;i++)
             {
-                if(!BufferFmt) BufferFmt = buffer;
-                totalBufferLen += buffer->SampleLen;
-                if(!readFin) readPos += buffer->SampleLen;
+                ALbuffer *buffer = BufferList->buffers[i];
+                if(buffer)
+                {
+                    if(!BufferFmt) BufferFmt = buffer;
+                    max_len = maxi(max_len, buffer->SampleLen);
+                }
             }
+            totalBufferLen += max_len;
+            if(!readFin) readPos += max_len;
+
             BufferList = ATOMIC_LOAD(&CONST_CAST(ALbufferlistitem*,BufferList)->next,
                                      almemory_order_relaxed);
         }
@@ -3432,7 +3500,6 @@ static ALdouble GetSourceOffset(ALsource *Source, ALenum name, ALCcontext *conte
 static ALboolean ApplyOffset(ALsource *Source, ALvoice *voice)
 {
     ALbufferlistitem *BufferList;
-    const ALbuffer *Buffer;
     ALuint bufferLen, totalBufferLen;
     ALuint offset = 0;
     ALsizei frac = 0;
@@ -3445,8 +3512,15 @@ static ALboolean ApplyOffset(ALsource *Source, ALvoice *voice)
     BufferList = Source->queue;
     while(BufferList && totalBufferLen <= offset)
     {
-        Buffer = BufferList->buffer;
-        bufferLen = Buffer ? Buffer->SampleLen : 0;
+        ALsizei max_len = 0;
+        ALsizei i;
+
+        for(i = 0;i < BufferList->num_buffers;i++)
+        {
+            ALbuffer *buffer = BufferList->buffers[i];
+            if(buffer) max_len = maxi(max_len, buffer->SampleLen);
+        }
+        bufferLen = max_len;
 
         if(bufferLen > offset-totalBufferLen)
         {
@@ -3483,8 +3557,10 @@ static ALboolean GetSampleOffset(ALsource *Source, ALuint *offset, ALsizei *frac
     BufferList = Source->queue;
     while(BufferList)
     {
-        if((BufferFmt=BufferList->buffer) != NULL)
-            break;
+        ALsizei i;
+        for(i = 0;i < BufferList->num_buffers && !BufferFmt;i++)
+            BufferFmt = BufferList->buffers[i];
+        if(BufferFmt) break;
         BufferList = ATOMIC_LOAD(&CONST_CAST(ALbufferlistitem*,BufferList)->next,
                                  almemory_order_relaxed);
     }