mp4atom.cpp

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#include "./mp4atom.h"
#include "./mp4container.h"
#include "./mp4ids.h"
#include "./mp4tag.h"
#include "./mp4track.h"
 
#include "../exceptions.h"
#include "../mediafileinfo.h"
 
#include <c++utilities/conversion/stringbuilder.h>
#include <c++utilities/io/binaryreader.h>
#include <c++utilities/io/binarywriter.h>
 
#include <sstream>
 
using namespace std;
using namespace CppUtilities;
 
namespace TagParser {


Mp4Atom::Mp4Atom(GenericFileElement::ContainerType &container, std::uint64_t startOffset)
    : GenericFileElement<Mp4Atom>(container, startOffset)
{
}

Mp4Atom::Mp4Atom(GenericFileElement::ContainerType &container, std::uint64_t startOffset, std::uint64_t maxSize)
    : GenericFileElement<Mp4Atom>(container, startOffset, maxSize)
{
}

Mp4Atom::Mp4Atom(Mp4Atom &parent, std::uint64_t startOffset)
    : GenericFileElement<Mp4Atom>(parent, startOffset)
{
}

string Mp4Atom::parsingContext() const
{
    return "parsing " % idToString() % " atom at " + startOffset();
}

void Mp4Atom::internalParse(Diagnostics &diag)
{
    static const string context("parsing MP4 atom");
    if (maxTotalSize() < minimumElementSize()) {
        diag.emplace_back(DiagLevel::Critical,
            argsToString("Atom is smaller than 8 byte and hence invalid. The remaining size within the parent atom is ", maxTotalSize(), '.'),
            context);
        throw TruncatedDataException();
    }
    stream().seekg(static_cast<streamoff>(startOffset()));
    m_dataSize = reader().readUInt32BE();
    if (m_dataSize == 0) {
        // atom size extends to rest of the file/enclosing container
        m_dataSize = maxTotalSize();
    }
    if (!m_dataSize) {
        diag.emplace_back(DiagLevel::Critical, "No data found (only null bytes).", context);
        throw NoDataFoundException();
    }
    if (m_dataSize < 8 && m_dataSize != 1) {
        diag.emplace_back(DiagLevel::Critical, "Atom is smaller than 8 byte and hence invalid.", context);
        throw TruncatedDataException();
    }
    m_id = reader().readUInt32BE();
    m_idLength = 4;
    if (m_dataSize == 1) { // atom denotes 64-bit size
        m_dataSize = reader().readUInt64BE();
        m_sizeLength = 12; // 4 bytes indicate long size denotation + 8 bytes for actual size denotation
        if (dataSize() < 16 && m_dataSize != 1) {
            diag.emplace_back(DiagLevel::Critical, "Atom denoting 64-bit size is smaller than 16 byte and hence invalid.", parsingContext());
            throw TruncatedDataException();
        }
    } else {
        m_sizeLength = 4;
    }
    if (maxTotalSize() < m_dataSize) { // currently m_dataSize holds data size plus header size!
        diag.emplace_back(DiagLevel::Warning, "The atom seems to be truncated; unable to parse siblings of that ", parsingContext());
        m_dataSize = maxTotalSize(); // using max size instead
    }
    // currently m_dataSize holds data size plus header size!
    m_dataSize -= headerSize();
    Mp4Atom *child = nullptr;
    if (std::uint64_t firstChildOffset = this->firstChildOffset()) {
        if (firstChildOffset + minimumElementSize() <= totalSize()) {
            child = new Mp4Atom(static_cast<Mp4Atom &>(*this), startOffset() + firstChildOffset);
        }
    }
    m_firstChild.reset(child);
    Mp4Atom *sibling = nullptr;
    if (totalSize() < maxTotalSize()) {
        if (parent()) {
            sibling = new Mp4Atom(*(parent()), startOffset() + totalSize());
        } else {
            sibling = new Mp4Atom(container(), startOffset() + totalSize(), maxTotalSize() - totalSize());
        }
    }
    m_nextSibling.reset(sibling);
}

void Mp4Atom::seekBackAndWriteAtomSize(std::ostream &stream, const std::ostream::pos_type &startOffset, Diagnostics &diag)
{
    ostream::pos_type currentOffset = stream.tellp();
    const auto atomSize(currentOffset - startOffset);
    if (atomSize > numeric_limits<std::uint32_t>::max()) {
        diag.emplace_back(DiagLevel::Fatal, argsToString(atomSize, " exceeds maximum."), "write 32-bit atom size");
        throw Failure();
    }
    stream.seekp(startOffset);
    BinaryWriter writer(&stream);
    writer.writeUInt32BE(static_cast<std::uint32_t>(atomSize));
    stream.seekp(currentOffset);
}

void Mp4Atom::seekBackAndWriteAtomSize64(std::ostream &stream, const ostream::pos_type &startOffset)
{
    ostream::pos_type currentOffset = stream.tellp();
    stream.seekp(startOffset);
    BinaryWriter writer(&stream);
    writer.writeUInt32BE(1);
    stream.seekp(4, ios_base::cur);
    writer.writeUInt64BE(static_cast<std::uint64_t>(currentOffset - startOffset));
    stream.seekp(currentOffset);
}

void Mp4Atom::makeHeader(std::uint64_t size, std::uint32_t id, BinaryWriter &writer)
{
    if (size < numeric_limits<std::uint32_t>::max()) {
        writer.writeUInt32BE(static_cast<std::uint32_t>(size));
        writer.writeUInt32BE(id);
    } else {
        writer.writeUInt32BE(1);
        writer.writeUInt32BE(id);
        writer.writeUInt64BE(size);
    }
}

bool Mp4Atom::isParent() const
{
    using namespace Mp4AtomIds;
    // some atom ids are known to be parents
    switch (id()) {
    case Movie:
    case Track:
    case Edit:
    case Media:
    case MediaInformation:
    case MediaInformationHeader:
    case DataInformation:
    case SampleTable:
    case UserData:
    case Meta:
    case ItunesList:
    case MovieFragment:
    case TrackFragment:
    case TrackReference:
    case MovieExtends:
    case DataReference:
    case Mp4AtomIds::AvcConfiguration:
    case FourccIds::Mpeg4Audio:
    case FourccIds::AmrNarrowband:
    case FourccIds::Amr:
    case FourccIds::Drms:
    case FourccIds::Alac:
    case FourccIds::WindowsMediaAudio:
    case FourccIds::Ac3:
    case FourccIds::EAc3:
    case FourccIds::DolbyMpl:
    case FourccIds::Dts:
    case FourccIds::DtsH:
    case FourccIds::DtsE:
        return true;
    default:
        if (parent()) {
            // some atom ids are known to contain parents
            switch (parent()->id()) {
            case ItunesList:
                return true;
            default:;
            }
        }
    }
    return false;
}

bool Mp4Atom::isPadding() const
{
    using namespace Mp4AtomIds;
    switch (id()) {
    case Free:
    case Skip:
        return true;
    default:
        return false;
    }
}

std::uint64_t Mp4Atom::firstChildOffset() const
{
    using namespace Mp4AtomIds;
    using namespace FourccIds;
    if (isParent()) {
        switch (id()) {
        case Meta:
            if (parent() && parent()->id() == Mp4AtomIds::UserData) {
                return headerSize() + 0x4u;
            }
            return headerSize();
        case DataReference:
            return headerSize() + 0x8u;
        default:
            return headerSize();
        }
    } else {
        switch (id()) {
        case SampleDescription:
            return headerSize() + 0x08u;
        default:
            return 0x00u;
        }
    }
}
 
} // namespace TagParser