mpeg4descriptor.cpp

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#include "./mpeg4descriptor.h"
#include "./mp4container.h"
#include "./mp4ids.h"
 
#include <c++utilities/conversion/stringbuilder.h>
#include <c++utilities/conversion/stringconversion.h>
#include <c++utilities/io/binaryreader.h>
 
using namespace std;
using namespace CppUtilities;
 
namespace TagParser {


Mpeg4Descriptor::Mpeg4Descriptor(ContainerType &container, std::uint64_t startOffset, std::uint64_t maxSize)
    : GenericFileElement<Mpeg4Descriptor>(container, startOffset, maxSize)
{
}

Mpeg4Descriptor::Mpeg4Descriptor(Mpeg4Descriptor &parent, std::uint64_t startOffset)
    : GenericFileElement<Mpeg4Descriptor>(parent, startOffset)
{
}

string Mpeg4Descriptor::parsingContext() const
{
    return "parsing " % idToString() % " descriptor at " + startOffset();
}

std::string Mpeg4Descriptor::idToString() const
{
    return "0x" + numberToString(id(), static_cast<std::uint8_t>(16));
}

void Mpeg4Descriptor::internalParse(Diagnostics &diag)
{
    if (maxTotalSize() < minimumElementSize()) {
        diag.emplace_back(DiagLevel::Critical,
            "Descriptor is smaller than 2 byte and hence invalid. The maximum size within the encloding element is " % numberToString(maxTotalSize())
                + '.',
            "parsing MPEG-4 descriptor");
        throw TruncatedDataException();
    }
    stream().seekg(static_cast<streamoff>(startOffset()));
    // read ID
    m_idLength = m_sizeLength = 1;
    m_id = reader().readByte();
    // read data size
    std::uint8_t tmp = reader().readByte();
    m_dataSize = tmp & 0x7F;
    while (tmp & 0x80) {
        m_dataSize = (m_dataSize << 7) | ((tmp = reader().readByte()) & 0x7F);
        ++m_sizeLength;
    }
    // check whether the denoted data size exceeds the available data size
    if (maxTotalSize() < totalSize()) {
        diag.emplace_back(DiagLevel::Warning, "The descriptor seems to be truncated; unable to parse siblings of that ", parsingContext());
        m_dataSize = static_cast<std::uint32_t>(maxTotalSize()); // using max size instead
    }
    m_firstChild.reset();
 
    // check for siblings
    if (totalSize() >= maxTotalSize()) {
        m_nextSibling.reset();
        return;
    }
    if (parent()) {
        m_nextSibling.reset(new Mpeg4Descriptor(*(parent()), startOffset() + totalSize()));
    } else {
        m_nextSibling.reset(new Mpeg4Descriptor(container(), startOffset() + totalSize(), maxTotalSize() - totalSize()));
    }
}
 
} // namespace TagParser