fix: breakpad use miniz

third_party/tracy/examples/ToyPathTracer/Source/enkiTS/LockLessMultiReadPipe.h

@@ -0,0 +1,240 @@
+// Copyright (c) 2013 Doug Binks
+// 
+// This software is provided 'as-is', without any express or implied
+// warranty. In no event will the authors be held liable for any damages
+// arising from the use of this software.
+// 
+// Permission is granted to anyone to use this software for any purpose,
+// including commercial applications, and to alter it and redistribute it
+// freely, subject to the following restrictions:
+// 
+// 1. The origin of this software must not be misrepresented; you must not
+//    claim that you wrote the original software. If you use this software
+//    in a product, an acknowledgement in the product documentation would be
+//    appreciated but is not required.
+// 2. Altered source versions must be plainly marked as such, and must not be
+//    misrepresented as being the original software.
+// 3. This notice may not be removed or altered from any source distribution.
+
+#pragma once
+
+#include <stdint.h>
+#include <assert.h>
+
+#include "Atomics.h"
+#include <string.h>
+
+
+namespace enki
+{
+    // LockLessMultiReadPipe - Single writer, multiple reader thread safe pipe using (semi) lockless programming
+    // Readers can only read from the back of the pipe
+    // The single writer can write to the front of the pipe, and read from both ends (a writer can be a reader)
+    // for many of the principles used here, see http://msdn.microsoft.com/en-us/library/windows/desktop/ee418650(v=vs.85).aspx
+    // Note: using log2 sizes so we do not need to clamp (multi-operation)
+    // T is the contained type
+    // Note this is not true lockless as the use of flags as a form of lock state.
+    template<uint8_t cSizeLog2, typename T> class LockLessMultiReadPipe
+    {
+    public:
+        LockLessMultiReadPipe();
+        ~LockLessMultiReadPipe() {}
+
+        // ReaderTryReadBack returns false if we were unable to read
+        // This is thread safe for both multiple readers and the writer
+        bool ReaderTryReadBack(   T* pOut );
+
+        // WriterTryReadFront returns false if we were unable to read
+        // This is thread safe for the single writer, but should not be called by readers
+        bool WriterTryReadFront(  T* pOut );
+
+        // WriterTryWriteFront returns false if we were unable to write
+        // This is thread safe for the single writer, but should not be called by readers
+        bool WriterTryWriteFront( const T& in );
+
+        // IsPipeEmpty() is a utility function, not intended for general use
+        // Should only be used very prudently.
+        bool IsPipeEmpty() const
+        {
+            return 0 == m_WriteIndex - m_ReadCount;
+        }
+
+        void Clear()
+        {
+            m_WriteIndex = 0;
+            m_ReadIndex = 0;
+            m_ReadCount = 0;
+            memset( (void*)m_Flags, 0, sizeof( m_Flags ) );
+        }
+
+    private:
+        const static uint32_t           ms_cSize        = ( 1 << cSizeLog2 );
+        const static uint32_t           ms_cIndexMask   = ms_cSize - 1;
+        const static uint32_t           FLAG_INVALID    = 0xFFFFFFFF; // 32bit for CAS
+        const static uint32_t           FLAG_CAN_WRITE  = 0x00000000; // 32bit for CAS
+        const static uint32_t           FLAG_CAN_READ   = 0x11111111; // 32bit for CAS
+
+        T                               m_Buffer[ ms_cSize ];
+
+        // read and write indexes allow fast access to the pipe, but actual access
+        // controlled by the access flags. 
+        volatile uint32_t BASE_ALIGN(4) m_WriteIndex;
+        volatile uint32_t BASE_ALIGN(4) m_ReadCount;
+        volatile uint32_t               m_Flags[  ms_cSize ];
+        volatile uint32_t BASE_ALIGN(4) m_ReadIndex;
+    };
+
+    template<uint8_t cSizeLog2, typename T> inline
+        LockLessMultiReadPipe<cSizeLog2,T>::LockLessMultiReadPipe()
+        : m_WriteIndex(0)
+        , m_ReadIndex(0)
+        , m_ReadCount(0)
+    {
+        assert( cSizeLog2 < 32 );
+        memset( (void*)m_Flags, 0, sizeof( m_Flags ) );
+    }
+
+    template<uint8_t cSizeLog2, typename T> inline
+        bool LockLessMultiReadPipe<cSizeLog2,T>::ReaderTryReadBack(   T* pOut )
+    {
+
+        uint32_t actualReadIndex;
+
+        uint32_t readCount  = m_ReadCount;
+
+        // We get hold of read index for consistency,
+        // and do first pass starting at read count
+        uint32_t readIndexToUse  = readCount;
+
+
+        while(true)
+        {
+
+            uint32_t writeIndex = m_WriteIndex;
+            // power of two sizes ensures we can use a simple calc without modulus
+            uint32_t numInPipe = writeIndex - readCount;
+            if( 0 == numInPipe )
+            {
+                return false;
+            }
+            if( readIndexToUse >= writeIndex )
+            {
+                // move back to start
+                readIndexToUse = m_ReadIndex;
+            }
+
+
+            // power of two sizes ensures we can perform AND for a modulus
+            actualReadIndex    = readIndexToUse & ms_cIndexMask;
+
+            // Multiple potential readers mean we should check if the data is valid,
+            // using an atomic compare exchange
+            uint32_t previous = AtomicCompareAndSwap( &m_Flags[  actualReadIndex ], FLAG_INVALID, FLAG_CAN_READ );
+            if( FLAG_CAN_READ == previous )
+            {
+                break;
+            }
+            ++readIndexToUse;
+
+            //update known readcount
+            readCount  = m_ReadCount;
+        }
+
+        // we update the read index using an atomic add, as we've only read one piece of data.
+        // this ensure consistency of the read index, and the above loop ensures readers
+        // only read from unread data
+        AtomicAdd(  (volatile int32_t*)&m_ReadCount, 1 );
+
+        BASE_MEMORYBARRIER_ACQUIRE();
+        // now read data, ensuring we do so after above reads & CAS
+        *pOut = m_Buffer[ actualReadIndex ];
+
+        m_Flags[  actualReadIndex ] = FLAG_CAN_WRITE;
+
+        return true;
+    }
+
+    template<uint8_t cSizeLog2, typename T> inline
+        bool LockLessMultiReadPipe<cSizeLog2,T>::WriterTryReadFront(  T* pOut )
+    {
+        uint32_t writeIndex = m_WriteIndex;
+        uint32_t frontReadIndex  = writeIndex;
+
+        // Multiple potential readers mean we should check if the data is valid,
+        // using an atomic compare exchange - which acts as a form of lock (so not quite lockless really).
+        uint32_t previous = FLAG_INVALID;
+        uint32_t actualReadIndex = 0;
+        while( true )
+        {
+            // power of two sizes ensures we can use a simple calc without modulus
+            uint32_t readCount = m_ReadCount;
+            uint32_t numInPipe = writeIndex - readCount;
+            if( 0 == numInPipe || 0 == frontReadIndex )
+            {
+                // frontReadIndex can get to 0 here if that item was just being read by another thread.
+                m_ReadIndex = readCount;
+                return false;
+            }
+            --frontReadIndex;
+            actualReadIndex = frontReadIndex & ms_cIndexMask;
+            previous = AtomicCompareAndSwap( &m_Flags[  actualReadIndex ], FLAG_INVALID, FLAG_CAN_READ );
+            if( FLAG_CAN_READ == previous )
+            {
+                break;
+            }
+            else if( m_ReadIndex >= frontReadIndex  )
+            {
+                return false;
+            }
+        }
+
+        // now read data, ensuring we do so after above reads & CAS
+        *pOut = m_Buffer[ actualReadIndex ];
+
+        m_Flags[  actualReadIndex ] = FLAG_CAN_WRITE;
+
+        BASE_MEMORYBARRIER_RELEASE();
+
+        // 32-bit aligned stores are atomic, and writer owns the write index
+        // we only move one back as this is as many as we have read, not where we have read from.
+        --m_WriteIndex;
+        return true;
+    }
+
+
+    template<uint8_t cSizeLog2, typename T> inline
+        bool LockLessMultiReadPipe<cSizeLog2,T>::WriterTryWriteFront( const T& in )
+    {
+        // The writer 'owns' the write index, and readers can only reduce
+        // the amount of data in the pipe.
+        // We get hold of both values for consistency and to reduce false sharing
+        // impacting more than one access
+        uint32_t writeIndex = m_WriteIndex;
+
+
+        // power of two sizes ensures we can perform AND for a modulus
+        uint32_t actualWriteIndex    = writeIndex & ms_cIndexMask;
+
+        // a reader may still be reading this item, as there are multiple readers
+        if( m_Flags[ actualWriteIndex ] != FLAG_CAN_WRITE ) 
+        {
+            return false; // still being read, so have caught up with tail. 
+        }
+
+
+        // as we are the only writer we can update the data without atomics
+        //  whilst the write index has not been updated
+        m_Buffer[ actualWriteIndex ] = in;
+        m_Flags[  actualWriteIndex ] = FLAG_CAN_READ;
+
+        // We need to ensure the above writes occur prior to updating the write index,
+        // otherwise another thread might read before it's finished
+        BASE_MEMORYBARRIER_RELEASE();
+
+        // 32-bit aligned stores are atomic, and the writer controls the write index
+        ++writeIndex;
+        m_WriteIndex = writeIndex;
+        return true;
+    }
+
+}