317 lines
12 KiB
C
317 lines
12 KiB
C
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/*
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==============================================================================
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This file is part of the JUCE library.
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Copyright (c) 2017 - ROLI Ltd.
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JUCE is an open source library subject to commercial or open-source
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licensing.
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The code included in this file is provided under the terms of the ISC license
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http://www.isc.org/downloads/software-support-policy/isc-license. Permission
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To use, copy, modify, and/or distribute this software for any purpose with or
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without fee is hereby granted provided that the above copyright notice and
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this permission notice appear in all copies.
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JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
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EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
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DISCLAIMED.
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==============================================================================
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*/
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namespace juce
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{
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//==============================================================================
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/**
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Encapsulates the logic required to implement a lock-free FIFO.
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This class handles the logic needed when building a single-reader, single-writer FIFO.
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It doesn't actually hold any data itself, but your FIFO class can use one of these to manage
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its position and status when reading or writing to it.
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To use it, you can call prepareToWrite() to determine the position within your own buffer that
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an incoming block of data should be stored, and prepareToRead() to find out when the next
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outgoing block should be read from.
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e.g.
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@code
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class MyFifo
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{
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public:
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MyFifo() : abstractFifo (1024)
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{
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}
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void addToFifo (const int* someData, int numItems)
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{
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int start1, size1, start2, size2;
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abstractFifo.prepareToWrite (numItems, start1, size1, start2, size2);
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if (size1 > 0)
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copySomeData (myBuffer + start1, someData, size1);
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if (size2 > 0)
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copySomeData (myBuffer + start2, someData + size1, size2);
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abstractFifo.finishedWrite (size1 + size2);
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}
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void readFromFifo (int* someData, int numItems)
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{
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int start1, size1, start2, size2;
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abstractFifo.prepareToRead (numItems, start1, size1, start2, size2);
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if (size1 > 0)
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copySomeData (someData, myBuffer + start1, size1);
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if (size2 > 0)
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copySomeData (someData + size1, myBuffer + start2, size2);
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abstractFifo.finishedRead (size1 + size2);
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}
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private:
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AbstractFifo abstractFifo;
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int myBuffer [1024];
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};
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@endcode
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@tags{Core}
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*/
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class JUCE_API AbstractFifo
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{
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public:
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//==============================================================================
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/** Creates a FIFO to manage a buffer with the specified capacity. */
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AbstractFifo (int capacity) noexcept;
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/** Destructor */
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~AbstractFifo();
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//==============================================================================
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/** Returns the total size of the buffer being managed. */
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int getTotalSize() const noexcept;
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/** Returns the number of items that can currently be added to the buffer without it overflowing. */
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int getFreeSpace() const noexcept;
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/** Returns the number of items that can currently be read from the buffer. */
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int getNumReady() const noexcept;
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/** Clears the buffer positions, so that it appears empty. */
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void reset() noexcept;
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/** Changes the buffer's total size.
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Note that this isn't thread-safe, so don't call it if there's any danger that it
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might overlap with a call to any other method in this class!
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*/
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void setTotalSize (int newSize) noexcept;
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//==============================================================================
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/** Returns the location within the buffer at which an incoming block of data should be written.
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Because the section of data that you want to add to the buffer may overlap the end
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and wrap around to the start, two blocks within your buffer are returned, and you
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should copy your data into the first one, with any remaining data spilling over into
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the second.
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If the number of items you ask for is too large to fit within the buffer's free space, then
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blockSize1 + blockSize2 may add up to a lower value than numToWrite. If this happens, you
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may decide to keep waiting and re-trying the method until there's enough space available.
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After calling this method, if you choose to write your data into the blocks returned, you
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must call finishedWrite() to tell the FIFO how much data you actually added.
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e.g.
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@code
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void addToFifo (const int* someData, int numItems)
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{
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int start1, size1, start2, size2;
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prepareToWrite (numItems, start1, size1, start2, size2);
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if (size1 > 0)
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copySomeData (myBuffer + start1, someData, size1);
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if (size2 > 0)
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copySomeData (myBuffer + start2, someData + size1, size2);
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finishedWrite (size1 + size2);
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}
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@endcode
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@param numToWrite indicates how many items you'd like to add to the buffer
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@param startIndex1 on exit, this will contain the start index in your buffer at which your data should be written
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@param blockSize1 on exit, this indicates how many items can be written to the block starting at startIndex1
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@param startIndex2 on exit, this will contain the start index in your buffer at which any data that didn't fit into
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the first block should be written
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@param blockSize2 on exit, this indicates how many items can be written to the block starting at startIndex2
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@see finishedWrite
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*/
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void prepareToWrite (int numToWrite, int& startIndex1, int& blockSize1, int& startIndex2, int& blockSize2) const noexcept;
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/** Called after writing from the FIFO, to indicate that this many items have been added.
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@see prepareToWrite
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*/
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void finishedWrite (int numWritten) noexcept;
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/** Returns the location within the buffer from which the next block of data should be read.
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Because the section of data that you want to read from the buffer may overlap the end
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and wrap around to the start, two blocks within your buffer are returned, and you
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should read from both of them.
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If the number of items you ask for is greater than the amount of data available, then
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blockSize1 + blockSize2 may add up to a lower value than numWanted. If this happens, you
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may decide to keep waiting and re-trying the method until there's enough data available.
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After calling this method, if you choose to read the data, you must call finishedRead() to
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tell the FIFO how much data you have consumed.
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e.g.
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@code
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void readFromFifo (int* someData, int numItems)
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{
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int start1, size1, start2, size2;
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prepareToRead (numSamples, start1, size1, start2, size2);
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if (size1 > 0)
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copySomeData (someData, myBuffer + start1, size1);
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if (size2 > 0)
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copySomeData (someData + size1, myBuffer + start2, size2);
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finishedRead (size1 + size2);
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}
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@endcode
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@param numWanted indicates how many items you'd like to add to the buffer
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@param startIndex1 on exit, this will contain the start index in your buffer at which your data should be written
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@param blockSize1 on exit, this indicates how many items can be written to the block starting at startIndex1
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@param startIndex2 on exit, this will contain the start index in your buffer at which any data that didn't fit into
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the first block should be written
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@param blockSize2 on exit, this indicates how many items can be written to the block starting at startIndex2
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@see finishedRead
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*/
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void prepareToRead (int numWanted, int& startIndex1, int& blockSize1, int& startIndex2, int& blockSize2) const noexcept;
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/** Called after reading from the FIFO, to indicate that this many items have now been consumed.
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@see prepareToRead
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*/
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void finishedRead (int numRead) noexcept;
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//==============================================================================
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private:
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enum class ReadOrWrite
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{
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read,
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write
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};
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public:
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/** Class for a scoped reader/writer */
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template <ReadOrWrite mode>
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class ScopedReadWrite final
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{
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public:
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/** Construct an unassigned reader/writer. Doesn't do anything upon destruction. */
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ScopedReadWrite() = default;
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/** Construct a reader/writer and immediately call prepareRead/prepareWrite
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on the abstractFifo which was passed in.
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This object will hold a pointer back to the fifo, so make sure that
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the fifo outlives this object.
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*/
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ScopedReadWrite (AbstractFifo&, int num) noexcept;
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ScopedReadWrite (const ScopedReadWrite&) = delete;
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ScopedReadWrite (ScopedReadWrite&&) noexcept;
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ScopedReadWrite& operator= (const ScopedReadWrite&) = delete;
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ScopedReadWrite& operator= (ScopedReadWrite&&) noexcept;
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/** Calls finishedRead or finishedWrite if this is a non-null scoped
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reader/writer.
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*/
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~ScopedReadWrite() noexcept;
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/** Calls the passed function with each index that was deemed valid
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for the current read/write operation.
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*/
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template <typename FunctionToApply>
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void forEach (FunctionToApply&& func) const
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{
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for (auto i = startIndex1, e = startIndex1 + blockSize1; i != e; ++i) func (i);
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for (auto i = startIndex2, e = startIndex2 + blockSize2; i != e; ++i) func (i);
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}
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int startIndex1, blockSize1, startIndex2, blockSize2;
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private:
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void prepare (AbstractFifo&, int) noexcept;
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static void finish (AbstractFifo&, int) noexcept;
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void swap (ScopedReadWrite&) noexcept;
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AbstractFifo* fifo = nullptr;
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};
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using ScopedRead = ScopedReadWrite<ReadOrWrite::read>;
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using ScopedWrite = ScopedReadWrite<ReadOrWrite::write>;
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/** Replaces prepareToRead/finishedRead with a single function.
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This function returns an object which contains the start indices and
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block sizes, and also automatically finishes the read operation when
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it goes out of scope.
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@code
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{
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auto readHandle = fifo.read (4);
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for (auto i = 0; i != readHandle.blockSize1; ++i)
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{
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// read the item at index readHandle.startIndex1 + i
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}
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for (auto i = 0; i != readHandle.blockSize2; ++i)
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{
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// read the item at index readHandle.startIndex2 + i
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}
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} // readHandle goes out of scope here, finishing the read operation
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@endcode
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*/
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ScopedRead read (int numToRead) noexcept { return { *this, numToRead }; }
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/** Replaces prepareToWrite/finishedWrite with a single function.
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This function returns an object which contains the start indices and
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block sizes, and also automatically finishes the write operation when
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it goes out of scope.
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@code
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{
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auto writeHandle = fifo.write (5);
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for (auto i = 0; i != writeHandle.blockSize1; ++i)
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{
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// write the item at index writeHandle.startIndex1 + i
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}
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for (auto i = 0; i != writeHandle.blockSize2; ++i)
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{
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// write the item at index writeHandle.startIndex2 + i
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}
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} // writeHandle goes out of scope here, finishing the write operation
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@endcode
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*/
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ScopedWrite write (int numToWrite) noexcept { return { *this, numToWrite }; }
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private:
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//==============================================================================
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int bufferSize;
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Atomic<int> validStart, validEnd;
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JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AbstractFifo)
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};
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} // namespace juce
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