Use a different method for storing and looking up buffers

Rather than each buffer being individually allocated with a generated 'thunk'
ID that's used with a uint:ptr map, buffers are allocated in arrays of 64
within a vector. Each group of 64 has an associated 64-bit mask indicating
which are free to use, and the buffer ID is comprised of the two array indices
which directly locate the buffer (no searching, binary or otherwise).

Currently no buffers are actually deallocated after being allocated, though
they are reused. So an app that creates a ton of buffers once, then deletes
them all and uses only a couple from then on, will have a bit of waste, while
an app that's more consistent with the number of used buffers won't be a
problem. This can be improved by removing elements of the containing vector
that contain all-free buffers while there are plenty of other free buffers.

Also, this method can easily be applied to other resources, like sources.

1 files changed, 61 insertions, 8 deletions

diff --git a/OpenAL32/Include/alMain.h b/OpenAL32/Include/alMain.h
index bf7d2559..f3ffac29 100644
--- a/OpenAL32/Include/alMain.h
+++ b/OpenAL32/Include/alMain.h
@@ -12,6 +12,9 @@
 #ifdef HAVE_STRINGS_H
 #include <strings.h>
 #endif
+#ifdef HAVE_INTRIN_H
+#include <intrin.h>
+#endif
 
 #include "AL/al.h"
 #include "AL/alc.h"
@@ -83,6 +86,51 @@ typedef ALuint64SOFT ALuint64;
 #define FAM_SIZE(T, M, N)  (offsetof(T, M) + sizeof(((T*)NULL)->M[0])*(N))
 
 
+/* Define a CTZ64 macro (count trailing zeros, for 64-bit integers). The result
+ * is *UNDEFINED* if the value is 0.
+ */
+#ifdef __GNUC__
+
+#if SIZEOF_LONG == 8
+#define CTZ64(x) __builtin_ctzl(x)
+#else
+#define CTZ64(x) __builtin_ctzll(x)
+#endif
+
+#elif defined(_MSC_VER)
+
+static inline int msvc_ctz64(ALuint64 v)
+{
+    unsigned long idx = 0;
+    _BitScanForward64(&idx, v);
+    return idx;
+}
+#define CTZ64(x) msvc_ctz64(x)
+
+#else
+
+/* There be black magics here. The popcnt64 method is derived from
+ * https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
+ * while the ctz-utilizing-popcnt algorithm is shown here
+ * http://www.hackersdelight.org/hdcodetxt/ntz.c.txt
+ * as the ntz2 variant. These likely aren't the most efficient methods, but
+ * they're good enough if the GCC or MSVC intrinsics aren't available.
+ */
+static inline int fallback_popcnt64(ALuint64 v)
+{
+    v = v - ((v >> 1) & U64(0x5555555555555555));
+    v = (v & U64(0x3333333333333333)) + ((v >> 2) & U64(0x3333333333333333));
+    v = (v + (v >> 4)) & U64(0x0f0f0f0f0f0f0f0f);
+    return (v * U64(0x0101010101010101)) >> 56;
+}
+
+static inline int fallback_ctz64(ALuint64 value)
+{
+    return fallback_popcnt64(~value & (value - 1));
+}
+#define CTZ64(x) fallback_ctz64(x)
+#endif
+
 static const union {
     ALuint u;
     ALubyte b[sizeof(ALuint)];
@@ -312,6 +360,13 @@ typedef union AmbiConfig {
 } AmbiConfig;
 
 
+typedef struct BufferSubList {
+    ALuint64 FreeMask;
+    struct ALbuffer *Buffers; /* 64 */
+} BufferSubList;
+TYPEDEF_VECTOR(BufferSubList, vector_BufferSubList)
+
+
 typedef struct EnumeratedHrtf {
     al_string name;
 
@@ -399,7 +454,8 @@ struct ALCdevice_struct
     ALsizei NumAuxSends;
 
     // Map of Buffers for this device
-    UIntMap BufferMap;
+    vector_BufferSubList BufferList;
+    almtx_t BufferLock;
 
     // Map of Effects for this device
     UIntMap EffectMap;
@@ -620,13 +676,10 @@ inline ALint GetChannelIdxByName(const RealMixParams *real, enum Channel chan)
 { return GetChannelIndex(real->ChannelName, chan); }
 
 
-inline void LockBuffersRead(ALCdevice *device)
-{ LockUIntMapRead(&device->BufferMap); }
-inline void UnlockBuffersRead(ALCdevice *device)
-{ UnlockUIntMapRead(&device->BufferMap); }
-
-inline struct ALbuffer *LookupBuffer(ALCdevice *device, ALuint id)
-{ return (struct ALbuffer*)LookupUIntMapKeyNoLock(&device->BufferMap, id); }
+inline void LockBufferList(ALCdevice *device)
+{ almtx_lock(&device->BufferLock); }
+inline void UnlockBufferList(ALCdevice *device)
+{ almtx_unlock(&device->BufferLock); }
 
 
 vector_al_string SearchDataFiles(const char *match, const char *subdir);