Use a callback to select which elements should be written

This is more flexible than a flag that applies to all the elements inside a Master.
It can now be filtered by element, based on their ID, position, profile, etc.

A EBML_WRITE_FILTER define is added to be able to check libmatroska 2.0
with this feature or not.

ebml/EbmlBinary.h

@@ -32,9 +32,9 @@ class EBML_DLL_API EbmlBinary : public EbmlElement {
 
     bool ValidateSize() const override {return IsFiniteSize() && GetSize() < 0x7FFFFFFF;} // we don't mind about what's inside
 
-    filepos_t RenderData(IOCallback & output, bool bForceRender, bool bWithDefault = false) override;
+    filepos_t RenderData(IOCallback & output, bool bForceRender, ShouldWrite writeFilter = WriteSkipDefault) override;
     filepos_t ReadData(IOCallback & input, ScopeMode ReadFully = SCOPE_ALL_DATA) override;
-    filepos_t UpdateSize(bool bWithDefault = false, bool bForceRender = false) override;
+    filepos_t UpdateSize(ShouldWrite writeFilter = WriteSkipDefault, bool bForceRender = false) override;
 
     void SetBuffer(const binary *Buffer, const std::uint32_t BufferSize) {
       Data = const_cast<binary *>(Buffer);

ebml/EbmlCrc32.h

@@ -20,9 +20,9 @@ namespace libebml {
 DECLARE_EBML_BINARY(EbmlCrc32)
   public:
     bool ValidateSize() const override {return IsFiniteSize() && (GetSize() == 4);}
-    filepos_t RenderData(IOCallback & output, bool bForceRender, bool bWithDefault = false) override;
+    filepos_t RenderData(IOCallback & output, bool bForceRender, ShouldWrite writeFilter = WriteSkipDefault) override;
     filepos_t ReadData(IOCallback & input, ScopeMode ReadFully = SCOPE_ALL_DATA) override;
-//    filepos_t UpdateSize(bool bWithDefault = false);
+//    filepos_t UpdateSize(ShouldWrite writeFilter = WriteSkipDefault);
 
     bool IsDefaultValue() const override {
       return false;

ebml/EbmlDate.h

@@ -40,7 +40,7 @@ class EBML_DLL_API EbmlDate : public EbmlElement {
     /*!
       \note no Default date handled
     */
-    filepos_t UpdateSize(bool /* bWithDefault = false */, bool /* bForceRender = false */) override {
+    filepos_t UpdateSize(ShouldWrite /* writeFilter */, bool /* bForceRender = false */) override {
       if(!ValueIsSet())
         SetSize_(0);
       else
@@ -57,7 +57,7 @@ class EBML_DLL_API EbmlDate : public EbmlElement {
     }
 
     private:
-    filepos_t RenderData(IOCallback & output, bool bForceRender, bool bWithDefault = false) override;
+    filepos_t RenderData(IOCallback & output, bool bForceRender, ShouldWrite writeFilter = WriteSkipDefault) override;
 
     std::int64_t myDate{0}; ///< internal format of the date
 

ebml/EbmlElement.h

@@ -280,6 +280,21 @@ class EBML_DLL_API EbmlSemanticContext {
 */
 class EBML_DLL_API EbmlElement {
   public:
+    // callback to tell if the element should be written or not
+    // \return true if the element should be written
+    using ShouldWrite = bool (*)(const EbmlElement &);
+
+    // write only elements that don't have their default value set
+    static bool WriteSkipDefault(const EbmlElement &elt) {
+      if (elt.IsDefaultValue())
+        return false;
+      return true;
+    }
+
+    static bool WriteAll(const EbmlElement &elt) {
+      return true;
+    }
+
     explicit EbmlElement(std::uint64_t aDefaultSize, bool bValueSet = false);
     virtual ~EbmlElement() = default;
     EbmlElement& operator=(const EbmlElement&) = delete;
@@ -319,11 +334,11 @@ class EBML_DLL_API EbmlElement {
       return ElementPosition;
     }
 
-    std::uint64_t ElementSize(bool bWithDefault = false) const; /// return the size of the header+data, before writing
+    std::uint64_t ElementSize(ShouldWrite writeFilter = WriteSkipDefault) const; /// return the size of the header+data, before writing
 
-    filepos_t Render(IOCallback & output, bool bWithDefault = false, bool bKeepPosition = false, bool bForceRender = false);
+    filepos_t Render(IOCallback & output, ShouldWrite writeFilter = WriteSkipDefault, bool bKeepPosition = false, bool bForceRender = false);
 
-    virtual filepos_t UpdateSize(bool bWithDefault = false, bool bForceRender = false) = 0; /// update the Size of the Data stored
+    virtual filepos_t UpdateSize(ShouldWrite writeFilter = WriteSkipDefault, bool bForceRender = false) = 0; /// update the Size of the Data stored
     virtual filepos_t GetSize() const {return Size;} /// return the size of the data stored in the element, on reading
 
     virtual filepos_t ReadData(IOCallback & input, ScopeMode ReadFully = SCOPE_ALL_DATA) = 0;
@@ -354,7 +369,7 @@ class EBML_DLL_API EbmlElement {
     /*!
       \brief void the content of the element (replace by EbmlVoid)
     */
-    std::uint64_t VoidMe(IOCallback & output, bool bWithDefault = false) const;
+    std::uint64_t VoidMe(IOCallback & output, ShouldWrite writeFilter = WriteSkipDefault) const;
 
     bool DefaultISset() const {return DefaultIsSet;}
     void ForceNoDefault() {SetDefaultIsSet(false);}
@@ -380,13 +395,13 @@ class EBML_DLL_API EbmlElement {
     */
     static EbmlElement *CreateElementUsingContext(const EbmlId & aID, const EbmlSemanticContext & Context, int & LowLevel, bool IsGlobalContext, bool bAllowDummy = false, unsigned int MaxLowerLevel = 1);
 
-    filepos_t RenderHead(IOCallback & output, bool bForceRender, bool bWithDefault = false, bool bKeepPosition = false);
+    filepos_t RenderHead(IOCallback & output, bool bForceRender, ShouldWrite writeFilter = WriteSkipDefault, bool bKeepPosition = false);
     filepos_t MakeRenderHead(IOCallback & output, bool bKeepPosition);
 
     /*!
       \brief prepare the data before writing them (in case it's not already done by default)
     */
-    virtual filepos_t RenderData(IOCallback & output, bool bForceRender, bool bWithDefault = false) = 0;
+    virtual filepos_t RenderData(IOCallback & output, bool bForceRender, ShouldWrite writeFilter = WriteSkipDefault) = 0;
 
     /*!
       \brief special constructor for cloning
@@ -413,4 +428,6 @@ class EBML_DLL_API EbmlElement {
 
 } // namespace libebml
 
+#define EBML_WRITE_FILTER 1
+
 #endif // LIBEBML_ELEMENT_H

ebml/EbmlFloat.h

@@ -32,9 +32,9 @@ class EBML_DLL_API EbmlFloat : public EbmlElement {
       return (GetSize() == 4 || GetSize() == 8);
     }
 
-    filepos_t RenderData(IOCallback & output, bool bForceRender, bool bWithDefault = false) override;
+    filepos_t RenderData(IOCallback & output, bool bForceRender, ShouldWrite writeFilter = WriteSkipDefault) override;
     filepos_t ReadData(IOCallback & input, ScopeMode ReadFully = SCOPE_ALL_DATA) override;
-    filepos_t UpdateSize(bool bWithDefault = false, bool bForceRender = false) override;
+    filepos_t UpdateSize(ShouldWrite writeFilter = WriteSkipDefault, bool bForceRender = false) override;
 
     void SetPrecision(const EbmlFloat::Precision prec = FLOAT_32)
     {

ebml/EbmlMaster.h

@@ -39,9 +39,9 @@ class EBML_DLL_API EbmlMaster : public EbmlElement {
     */
     ~EbmlMaster() override;
 
-    filepos_t RenderData(IOCallback & output, bool bForceRender, bool bWithDefault = false) override;
+    filepos_t RenderData(IOCallback & output, bool bForceRender, ShouldWrite writeFilter = WriteSkipDefault) override;
     filepos_t ReadData(IOCallback & input, ScopeMode ReadFully) override;
-    filepos_t UpdateSize(bool bWithDefault = false, bool bForceRender = false) override;
+    filepos_t UpdateSize(ShouldWrite writeFilter = WriteSkipDefault, bool bForceRender = false) override;
 
     /*!
       \brief Set wether the size is finite (size is known in advance when writing, or infinite size is not known on writing)
@@ -134,7 +134,7 @@ class EBML_DLL_API EbmlMaster : public EbmlElement {
     /*!
       \brief facility for Master elements to write only the head and force the size later
     */
-    filepos_t WriteHead(IOCallback & output, int SizeLength, bool bWithDefault = false);
+    filepos_t WriteHead(IOCallback & output, int SizeLength, ShouldWrite writeFilter = WriteSkipDefault);
 
     void EnableChecksum(bool bIsEnabled = true) { bChecksumUsed = bIsEnabled; }
     bool HasChecksum() const {return bChecksumUsed;}

ebml/EbmlSInteger.h

@@ -36,9 +36,9 @@ class EBML_DLL_API EbmlSInteger : public EbmlElement {
         void SetDefaultSize(std::uint64_t nDefaultSize = DEFAULT_INT_SIZE) override {EbmlElement::SetDefaultSize(nDefaultSize); SetSize_(nDefaultSize);}
 
     bool ValidateSize() const override {return IsFiniteSize() && (GetSize() <= 8);}
-    filepos_t RenderData(IOCallback & output, bool bForceRender, bool bWithDefault = false) override;
+    filepos_t RenderData(IOCallback & output, bool bForceRender, ShouldWrite writeFilter = WriteSkipDefault) override;
     filepos_t ReadData(IOCallback & input, ScopeMode ReadFully = SCOPE_ALL_DATA) override;
-    filepos_t UpdateSize(bool bWithDefault = false, bool bForceRender = false) override;
+    filepos_t UpdateSize(ShouldWrite writeFilter = WriteSkipDefault, bool bForceRender = false) override;
 
     bool IsSmallerThan(const EbmlElement *Cmp) const override;
 

ebml/EbmlString.h

@@ -25,9 +25,9 @@ class EBML_DLL_API EbmlString : public EbmlElement {
     explicit EbmlString(const std::string & aDefaultValue);
 
     bool ValidateSize() const override {return IsFiniteSize() && GetSize() < 0x7FFFFFFF;} // any size is possible
-    filepos_t RenderData(IOCallback & output, bool bForceRender, bool bWithDefault = false) override;
+    filepos_t RenderData(IOCallback & output, bool bForceRender, ShouldWrite writeFilter = WriteSkipDefault) override;
     filepos_t ReadData(IOCallback & input, ScopeMode ReadFully = SCOPE_ALL_DATA) override;
-    filepos_t UpdateSize(bool bWithDefault = false, bool bForceRender = false) override;
+    filepos_t UpdateSize(ShouldWrite writeFilter = WriteSkipDefault, bool bForceRender = false) override;
 
     EbmlString & operator=(const std::string &);
     using EbmlElement::operator const EbmlId &;

ebml/EbmlUInteger.h

@@ -34,9 +34,9 @@ class EBML_DLL_API EbmlUInteger : public EbmlElement {
     void SetDefaultSize(std::uint64_t nDefaultSize = DEFAULT_UINT_SIZE) override {EbmlElement::SetDefaultSize(nDefaultSize); SetSize_(nDefaultSize);}
 
     bool ValidateSize() const override {return IsFiniteSize() && (GetSize() <= 8);}
-    filepos_t RenderData(IOCallback & output, bool bForceRender, bool bWithDefault = false) override;
+    filepos_t RenderData(IOCallback & output, bool bForceRender, ShouldWrite writeFilter = WriteSkipDefault) override;
     filepos_t ReadData(IOCallback & input, ScopeMode ReadFully = SCOPE_ALL_DATA) override;
-    filepos_t UpdateSize(bool bWithDefault = false, bool bForceRender = false) override;
+    filepos_t UpdateSize(ShouldWrite writeFilter = WriteSkipDefault, bool bForceRender = false) override;
 
     bool IsSmallerThan(const EbmlElement *Cmp) const override;
 

ebml/EbmlUnicodeString.h

@@ -71,9 +71,9 @@ class EBML_DLL_API EbmlUnicodeString : public EbmlElement {
     explicit EbmlUnicodeString(const UTFstring & DefaultValue);
 
     bool ValidateSize() const override {return IsFiniteSize();} // any size is possible
-    filepos_t RenderData(IOCallback & output, bool bForceRender, bool bWithDefault = false) override;
+    filepos_t RenderData(IOCallback & output, bool bForceRender, ShouldWrite writeFilter = WriteSkipDefault) override;
     filepos_t ReadData(IOCallback & input, ScopeMode ReadFully = SCOPE_ALL_DATA) override;
-    filepos_t UpdateSize(bool bWithDefault = false, bool bForceRender = false) override;
+    filepos_t UpdateSize(ShouldWrite writeFilter = WriteSkipDefault, bool bForceRender = false) override;
 
     EbmlUnicodeString & operator=(const UTFstring &); ///< platform dependant code
     using EbmlElement::operator const EbmlId &;

ebml/EbmlVoid.h

@@ -23,17 +23,17 @@ DECLARE_EBML_BINARY(EbmlVoid)
     /*!
       \note overwrite to write fake data
     */
-    filepos_t RenderData(IOCallback & output, bool bForceRender, bool bWithDefault = false) override;
+    filepos_t RenderData(IOCallback & output, bool bForceRender, ShouldWrite writeFilter = WriteSkipDefault) override;
 
     /*!
       \brief Replace the void element content (written) with this one
     */
-    std::uint64_t ReplaceWith(EbmlElement & EltToReplaceWith, IOCallback & output, bool ComeBackAfterward = true, bool bWithDefault = false);
+    std::uint64_t ReplaceWith(EbmlElement & EltToReplaceWith, IOCallback & output, bool ComeBackAfterward = true, ShouldWrite writeFilter = WriteSkipDefault);
 
     /*!
       \brief Void the content of an element
     */
-    std::uint64_t Overwrite(const EbmlElement & EltToVoid, IOCallback & output, bool ComeBackAfterward = true, bool bWithDefault = false);
+    std::uint64_t Overwrite(const EbmlElement & EltToVoid, IOCallback & output, bool ComeBackAfterward = true, ShouldWrite writeFilter = WriteSkipDefault);
 
         EBML_CONCRETE_CLASS(EbmlVoid)
 };

src/EbmlBinary.cpp

@@ -50,7 +50,7 @@ EbmlBinary::~EbmlBinary() {
 EbmlBinary::operator const binary &() const {return *Data;}
 
 
-filepos_t EbmlBinary::RenderData(IOCallback & output, bool /* bForceRender */, bool /* bWithDefault */)
+filepos_t EbmlBinary::RenderData(IOCallback & output, bool /* bForceRender */, ShouldWrite /* writeFilter */)
 {
   output.writeFully(Data,GetSize());
 
@@ -60,7 +60,7 @@ filepos_t EbmlBinary::RenderData(IOCallback & output, bool /* bForceRender */, b
 /*!
   \note no Default binary value handled
 */
-std::uint64_t EbmlBinary::UpdateSize(bool /* bWithDefault */, bool /* bForceRender */)
+std::uint64_t EbmlBinary::UpdateSize(ShouldWrite /* writeFilter */, bool /* bForceRender */)
 {
   return GetSize();
 }

src/EbmlCrc32.cpp

@@ -159,7 +159,7 @@ void EbmlCrc32::AddElementCRC32(EbmlElement &ElementToCRC)
 {
   // Use a special IOCallback class that Render's to memory instead of to disk
   MemIOCallback memoryBuffer;
-  ElementToCRC.Render(memoryBuffer, true, true);
+  ElementToCRC.Render(memoryBuffer, WriteAll, true);
 
   const std::uint64_t memSize = memoryBuffer.GetDataBufferSize();
   if (memSize > std::numeric_limits<std::uint32_t>::max())
@@ -181,7 +181,7 @@ bool EbmlCrc32::CheckElementCRC32(EbmlElement &ElementToCRC) const
   return CheckCRC(m_crc_final, memoryBuffer.GetDataBuffer(), static_cast<std::uint32_t>(memSize));
 }
 
-filepos_t EbmlCrc32::RenderData(IOCallback & output, bool /* bForceRender */, bool /* bWithDefault */)
+filepos_t EbmlCrc32::RenderData(IOCallback & output, bool /* bForceRender */, ShouldWrite /* writeFilter */)
 {
   filepos_t Result = 4;
 

src/EbmlDate.cpp

@@ -31,7 +31,7 @@ filepos_t EbmlDate::ReadData(IOCallback & input, ScopeMode ReadFully)
   return GetSize();
 }
 
-filepos_t EbmlDate::RenderData(IOCallback & output, bool /* bForceRender */, bool  /* bWithDefault */)
+filepos_t EbmlDate::RenderData(IOCallback & output, bool /* bForceRender */, ShouldWrite /* writeFilter */)
 {
   assert(GetSize() == 8 || GetSize() == 0);
   if (GetSize() == 8) {

src/EbmlElement.cpp

@@ -474,18 +474,18 @@ EbmlElement *EbmlElement::CreateElementUsingContext(const EbmlId & aID, const Eb
 /*!
   \todo verify that the size written is the same as the data written
 */
-filepos_t EbmlElement::Render(IOCallback & output, bool bWithDefault, bool bKeepPosition, bool bForceRender)
+filepos_t EbmlElement::Render(IOCallback & output, ShouldWrite writeFilter, bool bKeepPosition, bool bForceRender)
 {
-  assert(bValueIsSet || (bWithDefault && DefaultISset())); // an element is been rendered without a value set !!!
+  assert(bValueIsSet || writeFilter(*this)); // an element is been rendered without a value set !!!
   // it may be a mandatory element without a default value
-  if (!bWithDefault && IsDefaultValue()) {
+  if (!writeFilter(*this)) {
     return 0;
   }
 #if !defined(NDEBUG)
-  std::uint64_t SupposedSize = UpdateSize(bWithDefault, bForceRender);
+  std::uint64_t SupposedSize = UpdateSize(writeFilter, bForceRender);
 #endif // !NDEBUG
-  filepos_t result = RenderHead(output, bForceRender, bWithDefault, bKeepPosition);
-  const std::uint64_t WrittenSize = RenderData(output, bForceRender, bWithDefault);
+  filepos_t result = RenderHead(output, bForceRender, writeFilter, bKeepPosition);
+  const std::uint64_t WrittenSize = RenderData(output, bForceRender, writeFilter);
 #if !defined(NDEBUG)
   if (static_cast<std::int64_t>(SupposedSize) != (0-1))
     assert(WrittenSize == SupposedSize);
@@ -499,12 +499,12 @@ filepos_t EbmlElement::Render(IOCallback & output, bool bWithDefault, bool bKeep
   \todo handle exceptions on errors
   \todo handle CodeSize bigger than 5 bytes
 */
-filepos_t EbmlElement::RenderHead(IOCallback & output, bool bForceRender, bool bWithDefault, bool bKeepPosition)
+filepos_t EbmlElement::RenderHead(IOCallback & output, bool bForceRender, ShouldWrite writeFilter, bool bKeepPosition)
 {
   if (EBML_ID_LENGTH((const EbmlId&)*this) <= 0 || EBML_ID_LENGTH((const EbmlId&)*this) > 4)
     return 0;
 
-  UpdateSize(bWithDefault, bForceRender);
+  UpdateSize(writeFilter, bForceRender);
 
   return MakeRenderHead(output, bKeepPosition);
 }
@@ -530,9 +530,9 @@ filepos_t EbmlElement::MakeRenderHead(IOCallback & output, bool bKeepPosition)
   return FinalHeadSize;
 }
 
-std::uint64_t EbmlElement::ElementSize(bool bWithDefault) const
+std::uint64_t EbmlElement::ElementSize(ShouldWrite writeFilter) const
 {
-  if (!bWithDefault && IsDefaultValue())
+  if (!writeFilter(*this))
     return 0; // won't be saved
   return Size + EBML_ID_LENGTH((const EbmlId&)*this) + CodedSizeLength(Size, SizeLength, bSizeIsFinite);
 }
@@ -601,21 +601,21 @@ filepos_t EbmlElement::OverwriteData(IOCallback & output, bool bKeepPosition)
 
   auto CurrentPosition = output.getFilePointer();
   output.setFilePointer(GetElementPosition() + HeaderSize);
-  auto Result = RenderData(output, true, bKeepPosition);
+  auto Result = RenderData(output, true, bKeepPosition ? WriteAll : WriteSkipDefault);
   output.setFilePointer(CurrentPosition);
   assert(Result == DataSize);
   return Result;
 }
 
 
-std::uint64_t EbmlElement::VoidMe(IOCallback & output, bool bWithDefault) const
+std::uint64_t EbmlElement::VoidMe(IOCallback & output, ShouldWrite writeFilter) const
 {
   if (ElementPosition == 0) {
     return 0; // the element has not been written
   }
 
   EbmlVoid Dummy;
-  return Dummy.Overwrite(*this, output, true, bWithDefault);
+  return Dummy.Overwrite(*this, output, true, writeFilter);
 }
 
 } // namespace libebml

src/EbmlFloat.cpp

@@ -51,7 +51,7 @@ EbmlFloat & EbmlFloat::SetValue(double NewValue) {
   \todo handle exception on errors
   \todo handle 10 bits precision
 */
-filepos_t EbmlFloat::RenderData(IOCallback & output, bool /* bForceRender */, bool /* bWithDefault */)
+filepos_t EbmlFloat::RenderData(IOCallback & output, bool /* bForceRender */, ShouldWrite /* writeFilter */)
 {
   assert(GetSize() == 4 || GetSize() == 8);
 
@@ -74,9 +74,9 @@ filepos_t EbmlFloat::RenderData(IOCallback & output, bool /* bForceRender */, bo
   return GetSize();
 }
 
-std::uint64_t EbmlFloat::UpdateSize(bool bWithDefault, bool  /* bForceRender */)
+std::uint64_t EbmlFloat::UpdateSize(ShouldWrite writeFilter, bool /* bForceRender */)
 {
-  if (!bWithDefault && IsDefaultValue())
+  if (!writeFilter(*this))
     return 0;
   return GetSize();
 }