xmp_exiv2.hpp

// SPDX-License-Identifier: GPL-2.0-or-later

#ifndef XMP_HPP_
#define XMP_HPP_

// *****************************************************************************
#include "exiv2lib_export.h"

// included header files
#include "metadatum.hpp"
#include "properties.hpp"

// *****************************************************************************
// namespace extensions
namespace Exiv2 {
// *****************************************************************************
// class declarations
class ExifData;

// *****************************************************************************
// class definitions

/*!
  @brief Information related to an XMP property. An XMP metadatum consists
         of an XmpKey and a Value and provides methods to manipulate these.
 */
class EXIV2API Xmpdatum : public Metadatum {
 public:
  //! @name Creators
  //@{
  /*!
    @brief Constructor for new tags created by an application. The
           %Xmpdatum is created from a key / value pair. %Xmpdatum
           copies (clones) the value if one is provided. Alternatively, a
           program can create an 'empty' %Xmpdatum with only a key and
           set the value using setValue().

    @param key The key of the %Xmpdatum.
    @param pValue Pointer to a %Xmpdatum value.
    @throw Error if the key cannot be parsed and converted
           to a known schema namespace prefix and property name.
   */
  explicit Xmpdatum(const XmpKey& key, const Value* pValue = nullptr);
  //! Copy constructor
  Xmpdatum(const Xmpdatum& rhs);
  //! Destructor
  ~Xmpdatum() override;
  //@}

  //! @name Manipulators
  //@{
  //! Assignment operator
  Xmpdatum& operator=(const Xmpdatum& rhs);
  /*!
    @brief Assign std::string \em value to the %Xmpdatum.
           Calls setValue(const std::string&).
   */
  Xmpdatum& operator=(const std::string& value);
  /*!
    @brief Assign a \em value of any type with an output operator
           to the %Xmpdatum. Calls operator=(const std::string&).
   */
  template <typename T>
  Xmpdatum& operator=(const T& value);
  /*!
    @brief Assign Value \em value to the %Xmpdatum.
           Calls setValue(const Value*).
   */
  Xmpdatum& operator=(const Value& value);
  void setValue(const Value* pValue) override;
  /*!
    @brief Set the value to the string \em value. Uses Value::read(const
           std::string&).  If the %Xmpdatum does not have a Value yet,
           then a %Value of the correct type for this %Xmpdatum is
           created. If the key is unknown, a XmpTextValue is used as
           default. Return 0 if the value was read successfully.
   */
  int setValue(const std::string& value) override;
  //@}

  //! @name Accessors
  //@{
  //! Not implemented. Calling this method will raise an exception.
  size_t copy(byte* buf, ByteOrder byteOrder) const override;
  std::ostream& write(std::ostream& os, const ExifData* pMetadata = nullptr) const override;
  /*!
    @brief Return the key of the Xmpdatum. The key is of the form
           '<b>Xmp</b>.prefix.property'. Note however that the
           key is not necessarily unique, i.e., an XmpData object may
           contain multiple metadata with the same key.
   */
  [[nodiscard]] std::string key() const override;
  [[nodiscard]] const char* familyName() const override;
  //! Return the (preferred) schema namespace prefix.
  [[nodiscard]] std::string groupName() const override;
  //! Return the property name.
  [[nodiscard]] std::string tagName() const override;
  [[nodiscard]] std::string tagLabel() const override;
  [[nodiscard]] std::string tagDesc() const override;
  //! Properties don't have a tag number. Return 0.
  [[nodiscard]] uint16_t tag() const override;
  [[nodiscard]] TypeId typeId() const override;
  [[nodiscard]] const char* typeName() const override;
  // Todo: Remove this method from the baseclass
  //! The Exif typeSize doesn't make sense here. Return 0.
  [[nodiscard]] size_t typeSize() const override;
  [[nodiscard]] size_t count() const override;
  [[nodiscard]] size_t size() const override;
  [[nodiscard]] std::string toString() const override;
  [[nodiscard]] std::string toString(size_t n) const override;
  [[nodiscard]] int64_t toInt64(size_t n = 0) const override;
  [[nodiscard]] float toFloat(size_t n = 0) const override;
  [[nodiscard]] Rational toRational(size_t n = 0) const override;
  [[nodiscard]] Value::UniquePtr getValue() const override;
  [[nodiscard]] const Value& value() const override;
  //@}

 private:
  // Pimpl idiom
  struct Impl;
  std::unique_ptr<Impl> p_;

};  // class Xmpdatum

//! Container type to hold all metadata
using XmpMetadata = std::vector<Xmpdatum>;

/*!
  @brief A container for XMP data. This is a top-level class of
         the %Exiv2 library.

  Provide high-level access to the XMP data of an image:
  - read XMP information from an XML block
  - access metadata through keys and standard C++ iterators
  - add, modify and delete metadata
  - serialize XMP data to an XML block
*/
class EXIV2API XmpData {
 public:
  //! Default constructor
  XmpData() = default;

  //! XmpMetadata iterator type
  using iterator = XmpMetadata::iterator;
  //! XmpMetadata const iterator type
  using const_iterator = XmpMetadata::const_iterator;

  //! @name Manipulators
  //@{
  /*!
    @brief Returns a reference to the %Xmpdatum that is associated with a
           particular \em key. If %XmpData does not already contain such
           an %Xmpdatum, operator[] adds object \em Xmpdatum(key).

    @note  Since operator[] might insert a new element, it can't be a const
           member function.
   */
  Xmpdatum& operator[](const std::string& key);
  /*!
    @brief Add an %Xmpdatum from the supplied key and value pair. This
           method copies (clones) the value.
    @return 0 if successful.
   */
  int add(const XmpKey& key, const Value* value);
  /*!
    @brief Add a copy of the Xmpdatum to the XMP metadata.
    @return 0 if successful.
   */
  int add(const Xmpdatum& xmpdatum);
  /*
  @brief Delete the Xmpdatum at iterator position pos, return the
          position of the next Xmpdatum.

  @note  Iterators into the metadata, including pos, are potentially
          invalidated by this call.
  @brief Delete the Xmpdatum at iterator position pos and update pos
  */
  iterator erase(XmpData::iterator pos);
  /*!
    @brief Delete the Xmpdatum at iterator position pos and update pos
           erases all following keys from the same family
           See: https://github.com/Exiv2/exiv2/issues/521
   */
  void eraseFamily(XmpData::iterator& pos);
  //! Delete all Xmpdatum instances resulting in an empty container.
  void clear();
  //! Sort metadata by key
  void sortByKey();
  //! Begin of the metadata
  iterator begin();
  //! End of the metadata
  iterator end();
  /*!
    @brief Find the first Xmpdatum with the given key, return an iterator
           to it.
   */
  iterator findKey(const XmpKey& key);
  //@}

  //! @name Accessors
  //@{
  //! Begin of the metadata
  [[nodiscard]] const_iterator begin() const;
  //! End of the metadata
  [[nodiscard]] const_iterator end() const;
  /*!
    @brief Find the first Xmpdatum with the given key, return a const
           iterator to it.
   */
  [[nodiscard]] const_iterator findKey(const XmpKey& key) const;
  //! Return true if there is no XMP metadata
  [[nodiscard]] bool empty() const;
  //! Get the number of metadata entries
  [[nodiscard]] long count() const;

  //! are we to use the packet?
  [[nodiscard]] bool usePacket() const {
    return usePacket_;
  }

  //! set usePacket_
  bool usePacket(bool b) {
    bool r = usePacket_;
    usePacket_ = b;
    return r;
  }
  //! setPacket
  void setPacket(std::string xmpPacket) {
    xmpPacket_ = std::move(xmpPacket);
    usePacket(false);
  }
  // ! getPacket
  [[nodiscard]] const std::string& xmpPacket() const {
    return xmpPacket_;
  }

  //@}

 private:
  // DATA
  XmpMetadata xmpMetadata_;
  std::string xmpPacket_;
  bool usePacket_{};
};  // class XmpData

/*!
  @brief Stateless parser class for XMP packets. Images use this
         class to parse and serialize XMP packets. The parser uses
         the XMP toolkit to do the job.
 */
class EXIV2API XmpParser {
 public:
  //! Options to control the format of the serialized XMP packet.
  enum XmpFormatFlags {
    omitPacketWrapper = 0x0010UL,    //!< Omit the XML packet wrapper.
    readOnlyPacket = 0x0020UL,       //!< Default is a writeable packet.
    useCompactFormat = 0x0040UL,     //!< Use a compact form of RDF.
    includeThumbnailPad = 0x0100UL,  //!< Include a padding allowance for a thumbnail image.
    exactPacketLength = 0x0200UL,    //!< The padding parameter is the overall packet length.
    writeAliasComments = 0x0400UL,   //!< Show aliases as XML comments.
    omitAllFormatting = 0x0800UL     //!< Omit all formatting whitespace.
  };
  /*!
    @brief Decode XMP metadata from an XMP packet \em xmpPacket into
           \em xmpData. The format of the XMP packet must follow the
           XMP specification. This method clears any previous contents
           of \em xmpData.

    @param xmpData   Container for the decoded XMP properties
    @param xmpPacket The raw XMP packet to decode
    @return 0 if successful;<BR>
            1 if XMP support has not been compiled-in;<BR>
            2 if the XMP toolkit failed to initialize;<BR>
            3 if the XMP toolkit failed and raised an XMP_Error
  */
  static int decode(XmpData& xmpData, const std::string& xmpPacket);
  /*!
    @brief Encode (serialize) XMP metadata from \em xmpData into a
           string xmpPacket. The XMP packet returned in the string
           follows the XMP specification. This method only modifies
           \em xmpPacket if the operations succeeds (return code 0).

    @param xmpPacket   Reference to a string to hold the encoded XMP
                       packet.
    @param xmpData     XMP properties to encode.
    @param formatFlags Flags that control the format of the XMP packet,
                       see enum XmpFormatFlags.
    @param padding     Padding length.
    @return 0 if successful;<BR>
            1 if XMP support has not been compiled-in;<BR>
            2 if the XMP toolkit failed to initialize;<BR>
            3 if the XMP toolkit failed and raised an XMP_Error
  */
  static int encode(std::string& xmpPacket, const XmpData& xmpData, uint16_t formatFlags = useCompactFormat,
                    uint32_t padding = 0);
  /*!
    @brief Lock/unlock function type

    A function of this type can be passed to initialize() to
    make subsequent registration of XMP namespaces thread-safe.
    See the initialize() function for more information.

    @param pLockData Pointer to the pLockData passed to initialize()
    @param lockUnlock Indicates whether to lock (true) or unlock (false)
   */
  using XmpLockFct = void (*)(void* pLockData, bool lockUnlock);

  /*!
    @brief Initialize the XMP Toolkit.

    Calling this method is usually not needed, as encode() and
    decode() will initialize the XMP Toolkit if necessary.

    The function takes optional pointers to a callback function
    \em xmpLockFct and related data \em pLockData that the parser
    uses when XMP namespaces are subsequently registered.

    The initialize() function itself still is not thread-safe and
    needs to be called in a thread-safe manner (e.g., on program
    startup), but if used with suitable additional locking
    parameters, any subsequent registration of namespaces will be
    thread-safe.

    Example usage on Windows using a critical section:

    @code
    void main()
    {
        struct XmpLock
        {
            CRITICAL_SECTION cs;
            XmpLock()  { InitializeCriticalSection(&cs); }
            ~XmpLock() { DeleteCriticalSection(&cs); }

            static void LockUnlock(void* pData, bool fLock)
            {
                XmpLock* pThis = reinterpret_cast<XmpLock*>(pData);
                if (pThis)
                {
                    (fLock) ? EnterCriticalSection(&pThis->cs)
                            : LeaveCriticalSection(&pThis->cs);
                }
            }
        } xmpLock;

        // Pass the locking mechanism to the XMP parser on initialization.
        // Note however that this call itself is still not thread-safe.
        Exiv2::XmpParser::initialize(XmpLock::LockUnlock, &xmpLock);

        // Program continues here, subsequent registrations of XMP
        // namespaces are serialized using xmpLock.

    }
    @endcode

    @return True if the initialization was successful, else false.
   */
  static bool initialize(XmpParser::XmpLockFct xmpLockFct = nullptr, void* pLockData = nullptr);
  /*!
    @brief Terminate the XMP Toolkit and unregister custom namespaces.

    Call this method when the XmpParser is no longer needed to
    allow the XMP Toolkit to cleanly shutdown.
   */
  static void terminate();

 private:
  /*!
    @brief Register a namespace with the XMP Toolkit.
   */
  static void registerNs(const std::string& ns, const std::string& prefix);
  /*!
    @brief Delete a namespace from the XMP Toolkit.

    XmpProperties::unregisterNs calls this to synchronize namespaces.
  */
  static void unregisterNs(const std::string& ns);

  /*!
    @brief Get namespaces registered with XMPsdk
   */
  static void registeredNamespaces(Exiv2::Dictionary&);

  // DATA
  static bool initialized_;  //! Indicates if the XMP Toolkit has been initialized
  static XmpLockFct xmpLockFct_;
  static void* pLockData_;

  friend class XmpProperties;  // permit XmpProperties -> registerNs() and registeredNamespaces()

};  // class XmpParser

// *****************************************************************************
// free functions, template and inline definitions

template <typename T>
Xmpdatum& Xmpdatum::operator=(const T& value) {
#ifdef __cpp_if_constexpr
  if constexpr (std::is_same_v<T, bool>) {
#else
  if (std::is_same<T, bool>::value) {
#endif
    setValue(Exiv2::toString(value ? "True" : "False"));
    return *this;
  } else {
    setValue(Exiv2::toString(value));
    return *this;
  }
}

}  // namespace Exiv2

#endif  // #ifndef XMP_HPP_