uncachedbuffer.cpp

来自「C++封装的视频采集代码」· C++ 代码 · 共 59 行

#include "UnCachedBuffer.h"

namespace oxsemi
{
    UnCachedBuffer::UnCachedBuffer(
        unsigned long bufferSizeBytes,
        unsigned char alignmentPowerOf2) :
        uncachedAlignedMemory_(0),
        rawMemory_(0),
        rawSize_(0),
        requestedSize_(bufferSizeBytes)
    {
        // Calculate the alignment step size
        int alignmentBoundary = 1 << alignmentPowerOf2;

        // Create a mask for the l.s. bits of the address which correspond to
        // the alignment boundary
        unsigned long alignmentBoundaryMask = ~0UL << alignmentPowerOf2;

        // Allocate sufficient memory to allow for adjustment to an alignment
        // boundary
        rawSize_ = bufferSizeBytes + alignmentBoundary - 1;
        rawMemory_ = new unsigned char[rawSize_];
        if (rawMemory_)
        {
            // Pointer to memory area which satisfies the alignment requirements
            unsigned char* alignedMemory;

            // Check the alignment of the allocated memory
            if ((reinterpret_cast<unsigned long>(rawMemory_) & ~alignmentBoundaryMask) == 0)
            {
                // Base of allocated memory is already on an alignment boundary
                alignedMemory = rawMemory_;
            }
            else
            {
                // Adjust memory base to an alignment boundary
                alignedMemory =
                    reinterpret_cast<unsigned char*>((reinterpret_cast<unsigned long>(rawMemory_) & alignmentBoundaryMask)) +
                    alignmentBoundary;
            }

            // Convert pointer to aligned cached memory to an uncached pointer
#ifdef NO_UNCACHED_BUFFERS
            uncachedAlignedMemory_ = alignedMemory;
#else
            uncachedAlignedMemory_ = TranslateCachedToUncached(alignedMemory);
#endif
        }

        SetIsComplete(rawMemory_);
    }

    UnCachedBuffer::~UnCachedBuffer()
    {
        delete[] rawMemory_;
    }
}