Move the ringbuffer to common

2 files changed, 337 insertions, 0 deletions

diff --git a/common/ringbuffer.cpp b/common/ringbuffer.cpp
new file mode 100644
index 00000000..91857499
--- /dev/null
+++ b/common/ringbuffer.cpp
@@ -0,0 +1,224 @@
+/**
+ * OpenAL cross platform audio library
+ * Copyright (C) 1999-2007 by authors.
+ * This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Library General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ *  Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ *  License along with this library; if not, write to the
+ *  Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ * Or go to http://www.gnu.org/copyleft/lgpl.html
+ */
+
+#include "config.h"
+
+#include "ringbuffer.h"
+
+#include <algorithm>
+#include <climits>
+#include <stdexcept>
+
+#include "almalloc.h"
+
+
+RingBufferPtr RingBuffer::Create(size_t sz, size_t elem_sz, int limit_writes)
+{
+    size_t power_of_two{0u};
+    if(sz > 0)
+    {
+        power_of_two = sz;
+        power_of_two |= power_of_two>>1;
+        power_of_two |= power_of_two>>2;
+        power_of_two |= power_of_two>>4;
+        power_of_two |= power_of_two>>8;
+        power_of_two |= power_of_two>>16;
+#if SIZE_MAX > UINT_MAX
+        power_of_two |= power_of_two>>32;
+#endif
+    }
+    ++power_of_two;
+    if(power_of_two <= sz || power_of_two > std::numeric_limits<size_t>::max()/elem_sz)
+        throw std::overflow_error{"Ring buffer size overflow"};
+
+    const size_t bufbytes{power_of_two * elem_sz};
+    RingBufferPtr rb{new(FamCount(bufbytes)) RingBuffer{bufbytes}};
+    rb->mWriteSize = limit_writes ? sz : (power_of_two-1);
+    rb->mSizeMask = power_of_two - 1;
+    rb->mElemSize = elem_sz;
+
+    return rb;
+}
+
+void RingBuffer::reset() noexcept
+{
+    mWritePtr.store(0, std::memory_order_relaxed);
+    mReadPtr.store(0, std::memory_order_relaxed);
+    std::fill_n(mBuffer.begin(), (mSizeMask+1)*mElemSize, al::byte{});
+}
+
+
+size_t RingBuffer::read(void *dest, size_t cnt) noexcept
+{
+    const size_t free_cnt{readSpace()};
+    if(free_cnt == 0) return 0;
+
+    const size_t to_read{std::min(cnt, free_cnt)};
+    size_t read_ptr{mReadPtr.load(std::memory_order_relaxed) & mSizeMask};
+
+    size_t n1, n2;
+    const size_t cnt2{read_ptr + to_read};
+    if(cnt2 > mSizeMask+1)
+    {
+        n1 = mSizeMask+1 - read_ptr;
+        n2 = cnt2 & mSizeMask;
+    }
+    else
+    {
+        n1 = to_read;
+        n2 = 0;
+    }
+
+    auto outiter = std::copy_n(mBuffer.begin() + read_ptr*mElemSize, n1*mElemSize,
+        static_cast<al::byte*>(dest));
+    read_ptr += n1;
+    if(n2 > 0)
+    {
+        std::copy_n(mBuffer.begin(), n2*mElemSize, outiter);
+        read_ptr += n2;
+    }
+    mReadPtr.store(read_ptr, std::memory_order_release);
+    return to_read;
+}
+
+size_t RingBuffer::peek(void *dest, size_t cnt) const noexcept
+{
+    const size_t free_cnt{readSpace()};
+    if(free_cnt == 0) return 0;
+
+    const size_t to_read{std::min(cnt, free_cnt)};
+    size_t read_ptr{mReadPtr.load(std::memory_order_relaxed) & mSizeMask};
+
+    size_t n1, n2;
+    const size_t cnt2{read_ptr + to_read};
+    if(cnt2 > mSizeMask+1)
+    {
+        n1 = mSizeMask+1 - read_ptr;
+        n2 = cnt2 & mSizeMask;
+    }
+    else
+    {
+        n1 = to_read;
+        n2 = 0;
+    }
+
+    auto outiter = std::copy_n(mBuffer.begin() + read_ptr*mElemSize, n1*mElemSize,
+        static_cast<al::byte*>(dest));
+    if(n2 > 0)
+        std::copy_n(mBuffer.begin(), n2*mElemSize, outiter);
+    return to_read;
+}
+
+size_t RingBuffer::write(const void *src, size_t cnt) noexcept
+{
+    const size_t free_cnt{writeSpace()};
+    if(free_cnt == 0) return 0;
+
+    const size_t to_write{std::min(cnt, free_cnt)};
+    size_t write_ptr{mWritePtr.load(std::memory_order_relaxed) & mSizeMask};
+
+    size_t n1, n2;
+    const size_t cnt2{write_ptr + to_write};
+    if(cnt2 > mSizeMask+1)
+    {
+        n1 = mSizeMask+1 - write_ptr;
+        n2 = cnt2 & mSizeMask;
+    }
+    else
+    {
+        n1 = to_write;
+        n2 = 0;
+    }
+
+    auto srcbytes = static_cast<const al::byte*>(src);
+    std::copy_n(srcbytes, n1*mElemSize, mBuffer.begin() + write_ptr*mElemSize);
+    write_ptr += n1;
+    if(n2 > 0)
+    {
+        std::copy_n(srcbytes + n1*mElemSize, n2*mElemSize, mBuffer.begin());
+        write_ptr += n2;
+    }
+    mWritePtr.store(write_ptr, std::memory_order_release);
+    return to_write;
+}
+
+
+ll_ringbuffer_data_pair RingBuffer::getReadVector() const noexcept
+{
+    ll_ringbuffer_data_pair ret;
+
+    size_t w{mWritePtr.load(std::memory_order_acquire)};
+    size_t r{mReadPtr.load(std::memory_order_acquire)};
+    w &= mSizeMask;
+    r &= mSizeMask;
+    const size_t free_cnt{(w-r) & mSizeMask};
+
+    const size_t cnt2{r + free_cnt};
+    if(cnt2 > mSizeMask+1)
+    {
+        /* Two part vector: the rest of the buffer after the current read ptr,
+         * plus some from the start of the buffer. */
+        ret.first.buf = const_cast<al::byte*>(mBuffer.data() + r*mElemSize);
+        ret.first.len = mSizeMask+1 - r;
+        ret.second.buf = const_cast<al::byte*>(mBuffer.data());
+        ret.second.len = cnt2 & mSizeMask;
+    }
+    else
+    {
+        /* Single part vector: just the rest of the buffer */
+        ret.first.buf = const_cast<al::byte*>(mBuffer.data() + r*mElemSize);
+        ret.first.len = free_cnt;
+        ret.second.buf = nullptr;
+        ret.second.len = 0;
+    }
+
+    return ret;
+}
+
+ll_ringbuffer_data_pair RingBuffer::getWriteVector() const noexcept
+{
+    ll_ringbuffer_data_pair ret;
+
+    size_t w{mWritePtr.load(std::memory_order_acquire)};
+    size_t r{mReadPtr.load(std::memory_order_acquire) + mWriteSize - mSizeMask};
+    w &= mSizeMask;
+    r &= mSizeMask;
+    const size_t free_cnt{(r-w-1) & mSizeMask};
+
+    const size_t cnt2{w + free_cnt};
+    if(cnt2 > mSizeMask+1)
+    {
+        /* Two part vector: the rest of the buffer after the current write ptr,
+         * plus some from the start of the buffer. */
+        ret.first.buf = const_cast<al::byte*>(mBuffer.data() + w*mElemSize);
+        ret.first.len = mSizeMask+1 - w;
+        ret.second.buf = const_cast<al::byte*>(mBuffer.data());
+        ret.second.len = cnt2 & mSizeMask;
+    }
+    else
+    {
+        ret.first.buf = const_cast<al::byte*>(mBuffer.data() + w*mElemSize);
+        ret.first.len = free_cnt;
+        ret.second.buf = nullptr;
+        ret.second.len = 0;
+    }
+
+    return ret;
+}
diff --git a/common/ringbuffer.h b/common/ringbuffer.h
new file mode 100644
index 00000000..fa8fce10
--- /dev/null
+++ b/common/ringbuffer.h
@@ -0,0 +1,113 @@
+#ifndef RINGBUFFER_H
+#define RINGBUFFER_H
+
+#include <atomic>
+#include <memory>
+#include <stddef.h>
+#include <utility>
+
+#include "albyte.h"
+#include "almalloc.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
+ * single-consumer/single-provider operation.
+ */
+
+struct ll_ringbuffer_data {
+    al::byte *buf;
+    size_t len;
+};
+using ll_ringbuffer_data_pair = std::pair<ll_ringbuffer_data,ll_ringbuffer_data>;
+
+
+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};
+
+    al::FlexArray<al::byte, 16> mBuffer;
+
+public:
+    RingBuffer(const size_t count) : mBuffer{count} { }
+
+    /** Reset the read and write pointers to zero. This is not thread safe. */
+    void reset() noexcept;
+
+    /**
+     * 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.
+     */
+    ll_ringbuffer_data_pair getReadVector() const noexcept;
+    /**
+     * 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.
+     */
+    ll_ringbuffer_data_pair 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
+    {
+        const size_t w{mWritePtr.load(std::memory_order_acquire)};
+        const size_t r{mReadPtr.load(std::memory_order_acquire)};
+        return (w-r) & mSizeMask;
+    }
+
+    /**
+     * 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); }
+
+    /**
+     * 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).
+     */
+    static std::unique_ptr<RingBuffer> Create(size_t sz, size_t elem_sz, int limit_writes);
+
+    DEF_FAM_NEWDEL(RingBuffer, mBuffer)
+};
+using RingBufferPtr = std::unique_ptr<RingBuffer>;
+
+#endif /* RINGBUFFER_H */