base64Layer.H

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/*---------------------------------------------------------------------------*\
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-------------------------------------------------------------------------------
    Copyright (C) 2016-2025 OpenCFD Ltd.
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.
 
    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
 
    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    for more details.
 
    You should have received a copy of the GNU General Public License
    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
 
Class
    Foam::base64Layer
 
Description
    An output filter layer to write base-64 encoded content.
 
    Base64 encoding according to RFC 4648 specification
    (https://tools.ietf.org/html/rfc4648#page-5).
    It is the obligation of the caller to avoid using normal output
    while the base-64 encoding layer is actively used.
 
SourceFiles
    base64Layer.C
 
\*---------------------------------------------------------------------------*/
 
#ifndef Foam_base64Layer_H
#define Foam_base64Layer_H
 
#include <iostream>
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
 
/*---------------------------------------------------------------------------*\
                         Class base64Layer Declaration
\*---------------------------------------------------------------------------*/
 
class base64Layer
{
    // Private Data
 
        //- The output stream for the layer
        std::ostream& os_;
 
        //- Buffer of characters to encode
        unsigned char group_[3];
 
        //- Current length of the encode buffer
        unsigned char groupLen_;
 
 
    // Private Member Functions
 
        inline unsigned char encode0() const noexcept;
        inline unsigned char encode1() const noexcept;
        inline unsigned char encode2() const noexcept;
        inline unsigned char encode3() const noexcept;
 
        //- Add a character to the group, outputting when the group is full.
        inline void add_char(char c);
 
protected:
 
    // Protected Member Functions
 
        //- Add a character to the group, outputting when the group is full.
        void add(char c);
 
public:
 
    // Constructors
 
        //- Attach to an output stream
        explicit base64Layer(std::ostream& os) noexcept;
 
        //- No copy construct
        base64Layer(const base64Layer&) = delete;
 
        //- No copy assignment
        void operator=(const base64Layer&) = delete;
 
 
    //- Destructor. Performs close()
    ~base64Layer();
 
 
    // Static Functions
 
        //- The encoded length has 4 bytes out for every 3 bytes and
        //- any trailing bytes are padded with '='.
        //
        //  The output length is (4*ceil(len / 3.0))
        static constexpr std::size_t encodedLength(std::size_t len) noexcept
        {
            return (4*((len+2)/3));
        }
 
 
    // Member Functions
 
        //- Encode the character sequence, writing when possible.
        void write(const char* s, std::streamsize n);
 
        //- Restart a new encoding sequence.
        void reset() noexcept;
 
        //- End the encoding sequence, padding the final characters with '='.
        //  \return false if no encoding was actually performed.
        bool close();
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //