update openal

Engine/lib/openal-soft/common/ringbuffer.h

@@ -2,111 +2,133 @@
 #define RINGBUFFER_H
 
 #include <atomic>
+#include <cassert>
+#include <cstddef>
 #include <memory>
-#include <stddef.h>
+#include <new>
 #include <utility>
 
-#include "albyte.h"
 #include "almalloc.h"
+#include "flexarray.h"
 
 
 /* NOTE: This lockless ringbuffer implementation is copied from JACK, extended
  * to include an element size. Consequently, parameters and return values for a
- * size or count is in 'elements', not bytes. Additionally, it only supports
+ * size or count are in 'elements', not bytes. Additionally, it only supports
  * single-consumer/single-provider operation.
  */
 
 struct RingBuffer {
 private:
-    std::atomic<size_t> mWritePtr{0u};
-    std::atomic<size_t> mReadPtr{0u};
-    size_t mWriteSize{0u};
-    size_t mSizeMask{0u};
-    size_t mElemSize{0u};
+#if defined(__cpp_lib_hardware_interference_size) && !defined(_LIBCPP_VERSION)
+    static constexpr std::size_t sCacheAlignment{std::hardware_destructive_interference_size};
+#else
+    /* Assume a 64-byte cache line, the most common/likely value. */
+    static constexpr std::size_t sCacheAlignment{64};
+#endif
+    alignas(sCacheAlignment) std::atomic<std::size_t> mWriteCount{0u};
+    alignas(sCacheAlignment) std::atomic<std::size_t> mReadCount{0u};
 
-    al::FlexArray<al::byte, 16> mBuffer;
+    alignas(sCacheAlignment) const std::size_t mWriteSize;
+    const std::size_t mSizeMask;
+    const std::size_t mElemSize;
+
+    al::FlexArray<std::byte, 16> mBuffer;
 
 public:
     struct Data {
-        al::byte *buf;
-        size_t len;
+        std::byte *buf;
+        std::size_t len;
     };
     using DataPair = std::pair<Data,Data>;
 
-
-    RingBuffer(const size_t count) : mBuffer{count} { }
+    RingBuffer(const std::size_t writesize, const std::size_t mask, const std::size_t elemsize,
+        const std::size_t numbytes)
+        : mWriteSize{writesize}, mSizeMask{mask}, mElemSize{elemsize}, mBuffer{numbytes}
+    { }
 
     /** Reset the read and write pointers to zero. This is not thread safe. */
-    void reset() noexcept;
+    auto reset() noexcept -> void;
+
+    /**
+     * Return the number of elements available for reading. This is the number
+     * of elements in front of the read pointer and behind the write pointer.
+     */
+    [[nodiscard]] auto readSpace() const noexcept -> std::size_t
+    {
+        const std::size_t w{mWriteCount.load(std::memory_order_acquire)};
+        const std::size_t r{mReadCount.load(std::memory_order_acquire)};
+        /* mWriteCount is never more than mWriteSize greater than mReadCount. */
+        return w - r;
+    }
+
+    /**
+     * The copying data reader. Copy at most `count' elements into `dest'.
+     * Returns the actual number of elements copied.
+     */
+    [[nodiscard]] auto read(void *dest, std::size_t count) noexcept -> std::size_t;
+    /**
+     * The copying data reader w/o read pointer advance. Copy at most `count'
+     * elements into `dest'. Returns the actual number of elements copied.
+     */
+    [[nodiscard]] auto peek(void *dest, std::size_t count) const noexcept -> std::size_t;
 
     /**
      * The non-copying data reader. Returns two ringbuffer data pointers that
      * hold the current readable data. If the readable data is in one segment
      * the second segment has zero length.
      */
-    DataPair getReadVector() const noexcept;
+    [[nodiscard]] auto getReadVector() noexcept -> DataPair;
+    /** Advance the read pointer `count' places. */
+    auto readAdvance(std::size_t count) noexcept -> void
+    {
+        const std::size_t w{mWriteCount.load(std::memory_order_acquire)};
+        const std::size_t r{mReadCount.load(std::memory_order_relaxed)};
+        [[maybe_unused]] const std::size_t readable{w - r};
+        assert(readable >= count);
+        mReadCount.store(r+count, std::memory_order_release);
+    }
+
+
+    /**
+     * Return the number of elements available for writing. This is the total
+     * number of writable elements excluding what's readable (already written).
+     */
+    [[nodiscard]] auto writeSpace() const noexcept -> std::size_t
+    { return mWriteSize - readSpace(); }
+
+    /**
+     * The copying data writer. Copy at most `count' elements from `src'. Returns
+     * the actual number of elements copied.
+     */
+    [[nodiscard]] auto write(const void *src, std::size_t count) noexcept -> std::size_t;
+
     /**
      * The non-copying data writer. Returns two ringbuffer data pointers that
      * hold the current writeable data. If the writeable data is in one segment
      * the second segment has zero length.
      */
-    DataPair getWriteVector() const noexcept;
-
-    /**
-     * Return the number of elements available for reading. This is the number
-     * of elements in front of the read pointer and behind the write pointer.
-     */
-    size_t readSpace() const noexcept
+    [[nodiscard]] auto getWriteVector() noexcept -> DataPair;
+    /** Advance the write pointer `count' places. */
+    auto writeAdvance(std::size_t count) noexcept -> void
     {
-        const size_t w{mWritePtr.load(std::memory_order_acquire)};
-        const size_t r{mReadPtr.load(std::memory_order_acquire)};
-        return (w-r) & mSizeMask;
+        const std::size_t w{mWriteCount.load(std::memory_order_relaxed)};
+        const std::size_t r{mReadCount.load(std::memory_order_acquire)};
+        [[maybe_unused]] const std::size_t writable{mWriteSize - (w - r)};
+        assert(writable >= count);
+        mWriteCount.store(w+count, std::memory_order_release);
     }
 
-    /**
-     * The copying data reader. Copy at most `cnt' elements into `dest'.
-     * Returns the actual number of elements copied.
-     */
-    size_t read(void *dest, size_t cnt) noexcept;
-    /**
-     * The copying data reader w/o read pointer advance. Copy at most `cnt'
-     * elements into `dest'. Returns the actual number of elements copied.
-     */
-    size_t peek(void *dest, size_t cnt) const noexcept;
-    /** Advance the read pointer `cnt' places. */
-    void readAdvance(size_t cnt) noexcept
-    { mReadPtr.fetch_add(cnt, std::memory_order_acq_rel); }
-
-
-    /**
-     * Return the number of elements available for writing. This is the number
-     * of elements in front of the write pointer and behind the read pointer.
-     */
-    size_t writeSpace() const noexcept
-    {
-        const size_t w{mWritePtr.load(std::memory_order_acquire)};
-        const size_t r{mReadPtr.load(std::memory_order_acquire) + mWriteSize - mSizeMask};
-        return (r-w-1) & mSizeMask;
-    }
-
-    /**
-     * The copying data writer. Copy at most `cnt' elements from `src'. Returns
-     * the actual number of elements copied.
-     */
-    size_t write(const void *src, size_t cnt) noexcept;
-    /** Advance the write pointer `cnt' places. */
-    void writeAdvance(size_t cnt) noexcept
-    { mWritePtr.fetch_add(cnt, std::memory_order_acq_rel); }
-
-    size_t getElemSize() const noexcept { return mElemSize; }
+    [[nodiscard]] auto getElemSize() const noexcept -> std::size_t { return mElemSize; }
 
     /**
      * Create a new ringbuffer to hold at least `sz' elements of `elem_sz'
-     * bytes. The number of elements is rounded up to the next power of two
-     * (even if it is already a power of two, to ensure the requested amount
-     * can be written).
+     * bytes. The number of elements is rounded up to a power of two. If
+     * `limit_writes' is true, the writable space will be limited to `sz'
+     * elements regardless of the rounded size.
      */
-    static std::unique_ptr<RingBuffer> Create(size_t sz, size_t elem_sz, int limit_writes);
+    [[nodiscard]] static
+    auto Create(std::size_t sz, std::size_t elem_sz, bool limit_writes) -> std::unique_ptr<RingBuffer>;
 
     DEF_FAM_NEWDEL(RingBuffer, mBuffer)
 };