pdf: move encrypt code into emitEncrypt, add PDFStructureWriter

Move the encryption code into emitEncrypt and rewrite that with
the newly introduced PDFStructureWriter, which is now responsible
to write the PDF basic structure elements into a string buffer.

The PDFStructureWriter will be extended with new features when
there is demand.

Change-Id: I4f4099886860b72b4f1866b19a8afb7cc8fb4ea4
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/176024
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
Tested-by: Tomaž Vajngerl <quikee@gmail.com>

2 files changed, 97 insertions, 27 deletions

diff --git a/vcl/inc/pdf/pdfwriter_impl.hxx b/vcl/inc/pdf/pdfwriter_impl.hxx
index df86ea640e96..24a2858ec994 100644
--- a/vcl/inc/pdf/pdfwriter_impl.hxx
+++ b/vcl/inc/pdf/pdfwriter_impl.hxx
@@ -1025,6 +1025,8 @@ i12626
     // creates a PKCS7 object using the ByteRange and overwrite /Contents
     // of the signature dictionary
     bool finalizeSignature();
+    //writes encrypt
+    sal_Int32 emitEncrypt();
     // writes xref and trailer
     bool emitTrailer();
     // emits info dict (if applicable)
diff --git a/vcl/source/gdi/pdfwriter_impl.cxx b/vcl/source/gdi/pdfwriter_impl.cxx
index ce3d102d5c55..b5d7ad31cf08 100644
--- a/vcl/source/gdi/pdfwriter_impl.cxx
+++ b/vcl/source/gdi/pdfwriter_impl.cxx
@@ -276,6 +276,67 @@ void appendDestinationName( const OUString& rString, OStringBuffer& rBuffer )
     }
 }
 
+/** Writes the PDF structure to the string buffer.
+ *
+ * Structure elements like: objects, IDs, dictionaries, key/values, ...
+ *
+ */
+class PDFStructureWriter
+{
+    OStringBuffer maLine;
+public:
+    PDFStructureWriter()
+        : maLine(1024)
+    {
+    }
+
+    void startObject(sal_Int32 nID)
+    {
+        appendObjectID(nID, maLine);
+    }
+
+    void endObject()
+    {
+        maLine.append("endobj\n\n");
+    }
+
+    OStringBuffer& getLine()
+    {
+        return maLine;
+    }
+
+    void startDict()
+    {
+        maLine.append("<<");
+    }
+
+    void endDict()
+    {
+        maLine.append(">>\n");
+    }
+
+    void write(std::string_view key, std::string_view value)
+    {
+        maLine.append(key);
+        maLine.append(value);
+    }
+
+    void write(std::string_view key, sal_Int32 value)
+    {
+        maLine.append(key);
+        maLine.append(" ");
+        maLine.append(value);
+    }
+
+    void writeString(std::string_view key, char* pString, sal_Int32 nSize)
+    {
+        maLine.append(key);
+        maLine.append(" (");
+        appendLiteralString(pString, nSize, maLine);
+        maLine.append(")");
+    }
+};
+
 } // end anonymous namespace
 
 namespace vcl
@@ -6085,6 +6146,39 @@ sal_Int32 PDFWriterImpl::emitDocumentMetadata()
     return nObject;
 }
 
+sal_Int32 PDFWriterImpl::emitEncrypt()
+{
+    //emit the security information
+    //must be emitted as indirect dictionary object, since
+    //Acrobat Reader 5 works only with this kind of implementation
+
+    sal_Int32 nObject = createObject();
+
+    if (updateObject(nObject))
+    {
+        PDFStructureWriter aWriter;
+        aWriter.startObject(nObject);
+        aWriter.startDict();
+        aWriter.write("/Filter", "/Standard");
+        aWriter.write("/V", 2);
+        aWriter.write("/Length", 128);
+        aWriter.write("/R", 3);
+        // emit the owner password, must not be encrypted
+        aWriter.writeString("/O", reinterpret_cast<char*>(m_aContext.Encryption.OValue.data()), sal_Int32(m_aContext.Encryption.OValue.size()));
+        aWriter.writeString("/U", reinterpret_cast<char*>(m_aContext.Encryption.UValue.data()), sal_Int32(m_aContext.Encryption.UValue.size()));
+        aWriter.write("/P", m_nAccessPermissions);
+        aWriter.endDict();
+        aWriter.endObject();
+
+        if (!writeBuffer(aWriter.getLine()))
+            nObject = 0;
+    }
+    else
+        nObject = 0;
+
+    return nObject;
+}
+
 bool PDFWriterImpl::emitTrailer()
 {
     // emit doc info
@@ -6094,33 +6188,7 @@ bool PDFWriterImpl::emitTrailer()
 
     if( m_aContext.Encryption.Encrypt() )
     {
-        //emit the security information
-        //must be emitted as indirect dictionary object, since
-        //Acrobat Reader 5 works only with this kind of implementation
-        nSecObject = createObject();
-
-        if( updateObject( nSecObject ) )
-        {
-            OStringBuffer aLineS( 1024 );
-            aLineS.append( nSecObject );
-            aLineS.append( " 0 obj\n"
-                           "<</Filter/Standard/V " );
-            // check the version
-            aLineS.append( "2/Length 128/R 3" );
-
-            // emit the owner password, must not be encrypted
-            aLineS.append( "/O(" );
-            appendLiteralString( reinterpret_cast<char*>(m_aContext.Encryption.OValue.data()), sal_Int32(m_aContext.Encryption.OValue.size()), aLineS );
-            aLineS.append( ")/U(" );
-            appendLiteralString( reinterpret_cast<char*>(m_aContext.Encryption.UValue.data()), sal_Int32(m_aContext.Encryption.UValue.size()), aLineS );
-            aLineS.append( ")/P " );// the permission set
-            aLineS.append( m_nAccessPermissions );
-            aLineS.append( ">>\nendobj\n\n" );
-            if( !writeBuffer( aLineS ) )
-                nSecObject = 0;
-        }
-        else
-            nSecObject = 0;
+        nSecObject = emitEncrypt();
     }
     // emit xref table
     // remember start