diff --git a/external/libdxfrw/intern/dwgbuffer.cpp b/external/libdxfrw/intern/dwgbuffer.cpp
index 2b19c8d1709..c1b98ebe03d 100644
--- a/external/libdxfrw/intern/dwgbuffer.cpp
+++ b/external/libdxfrw/intern/dwgbuffer.cpp
@@ -151,34 +151,29 @@ bool dwgCharStream::read( duint8 *s, duint64 n )
   return true;
 }
 
-dwgBuffer::dwgBuffer( duint8 *buf, int size, DRW_TextCodec *dc )
-{
-  filestr = new dwgCharStream( buf, size );
-  decoder = dc;
-  maxSize = size;
-  bitPos = 0;
-}
+dwgBuffer::dwgBuffer(duint8 *buf, duint64 size, DRW_TextCodec *dc)
+    :decoder{dc}
+    ,filestr{new dwgCharStream(buf, size)}
+    ,maxSize{size}
+{}
 
-dwgBuffer::dwgBuffer( std::ifstream *stream, DRW_TextCodec *dc )
-{
-  filestr = new dwgFileStream( stream );
-  decoder = dc;
-  maxSize = filestr->size();
-  bitPos = 0;
-}
+dwgBuffer::dwgBuffer(std::ifstream *stream, DRW_TextCodec *dc)
+    :decoder{dc}
+    ,filestr{new dwgFileStream(stream)}
+    ,maxSize{filestr->size()}
+{}
 
-dwgBuffer::dwgBuffer( const dwgBuffer &org )
-{
-  filestr = org.filestr->clone();
-  decoder = org.decoder;
-  maxSize = filestr->size();
-  currByte = org.currByte;
-  bitPos = org.bitPos;
-}
+dwgBuffer::dwgBuffer( const dwgBuffer& org )
+    :decoder{org.decoder}
+    ,filestr{org.filestr->clone()}
+    ,maxSize{filestr->size()}
+    ,currByte{org.currByte}
+    ,bitPos{org.bitPos}
+{}
 
 dwgBuffer &dwgBuffer::operator=( const dwgBuffer &org )
 {
-  filestr = org.filestr->clone();
+  filestr.reset(org.filestr->clone());
   decoder = org.decoder;
   maxSize = filestr->size();
   currByte = org.currByte;
@@ -186,10 +181,7 @@ dwgBuffer &dwgBuffer::operator=( const dwgBuffer &org )
   return *this;
 }
 
-dwgBuffer::~dwgBuffer()
-{
-  delete filestr;
-}
+dwgBuffer::~dwgBuffer() = default;
 
 //! Gets the current byte position in buffer
 duint64 dwgBuffer::getPosition()
@@ -349,9 +341,9 @@ dint16 dwgBuffer::getSBitShort()
 {
   duint8 b = get2Bits();
   if ( b == 0 )
-    return ( dint16 )getRawShort16();
+    return static_cast<dint16>(getRawShort16());
   else if ( b == 1 )
-    return ( dint16 )getRawChar8();
+    return static_cast<dint16>(getRawChar8());
   else if ( b == 2 )
     return 0;
   else
@@ -880,16 +872,12 @@ duint32 dwgBuffer::getCmColor( DRW::Version v )
   {
     case 0xC0:
       return 256;//ByLayer
-      break;
     case 0xC1:
       return 0;//ByBlock
-      break;
     case 0xC2:
       return 256;//RGB RLZ TODO
-      break;
     case 0xC3:
       return rgb & 0xFF; //ACIS
-      break;
     default:
       break;
   }
@@ -978,7 +966,7 @@ bool dwgBuffer::getBytes( unsigned char *buf, int size )
 
 duint16 dwgBuffer::crc8( duint16 dx, dint32 start, dint32 end )
 {
-  int pos = filestr->getPos();
+  duint64 pos = filestr->getPos();
   filestr->setPos( start );
   int n = end - start;
   duint8 *tmpBuf = new duint8[n];
@@ -1003,7 +991,7 @@ duint16 dwgBuffer::crc8( duint16 dx, dint32 start, dint32 end )
 
 duint32 dwgBuffer::crc32( duint32 seed, dint32 start, dint32 end )
 {
-  int pos = filestr->getPos();
+  duint64 pos = filestr->getPos();
   filestr->setPos( start );
   int n = end - start;
   duint8 *tmpBuf = new duint8[n];
diff --git a/external/libdxfrw/intern/dwgbuffer.h b/external/libdxfrw/intern/dwgbuffer.h
index 37dd386c464..9b4fcdaea56 100644
--- a/external/libdxfrw/intern/dwgbuffer.h
+++ b/external/libdxfrw/intern/dwgbuffer.h
@@ -15,6 +15,7 @@
 
 #include <fstream>
 #include <sstream>
+#include <memory>
 #include "../drw_base.h"
 
 class DRW_Coord;
@@ -51,20 +52,17 @@ class dwgFileStream: public dwgBasicStream
     virtual bool good() {return stream->good();}
     virtual dwgBasicStream *clone() {return new dwgFileStream( stream );}
   private:
-    std::ifstream *stream = nullptr;
-    duint64 sz;
+    std::ifstream *stream{nullptr};
+    duint64 sz{0};
 };
 
 class dwgCharStream: public dwgBasicStream
 {
   public:
-    dwgCharStream( duint8 *buf, int s )
-    {
-      stream = buf;
-      sz = s;
-      pos = 0;
-      isOk = true;
-    }
+    dwgCharStream( duint8 *buf, duint64 s )
+        :stream{buf}
+        ,sz{s}
+    {}
     virtual bool read( duint8 *s, duint64 n );
     virtual duint64 size() {return sz;}
     virtual duint64 getPos() {return pos;}
@@ -72,17 +70,17 @@ class dwgCharStream: public dwgBasicStream
     virtual bool good() {return isOk;}
     virtual dwgBasicStream *clone() {return new dwgCharStream( stream, sz );}
   private:
-    duint8 *stream = nullptr;
-    duint64 sz;
-    duint64 pos;
-    bool isOk;
+    duint8 *stream{nullptr};
+    duint64 sz{0};
+    duint64 pos{0};
+    bool isOk{true};
 };
 
 class dwgBuffer
 {
   public:
     dwgBuffer( std::ifstream *stream, DRW_TextCodec *decoder = nullptr );
-    dwgBuffer( duint8 *buf, int size, DRW_TextCodec *decoder = nullptr );
+    dwgBuffer( duint8 *buf, duint64 size, DRW_TextCodec *decoder = nullptr );
     dwgBuffer( const dwgBuffer &org );
     dwgBuffer &operator=( const dwgBuffer &org );
     ~dwgBuffer();
@@ -144,13 +142,13 @@ class dwgBuffer
     duint32 crc32( duint32 seed, dint32 start, dint32 end );
 
 //    duint8 getCurrByte(){return currByte;}
-    DRW_TextCodec *decoder = nullptr;
+    DRW_TextCodec *decoder{nullptr};
 
   private:
-    dwgBasicStream *filestr = nullptr;
-    int maxSize;
-    duint8 currByte;
-    duint8 bitPos;
+    std::unique_ptr<dwgBasicStream> filestr;
+    duint64 maxSize{0};
+    duint8 currByte{0};
+    duint8 bitPos{0};
 
     UTF8STRING get8bitStr();
     UTF8STRING get16bitStr( duint16 textSize, bool nullTerm = true );