/*
Copyright (C) 2001-present by Serge Lamikhov-Center

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/

#ifndef ELF_HEADER_HPP
#define ELF_HEADER_HPP

#include <iostream>

namespace ELFIO {

/**
 * @class elf_header
 * @brief Abstract base class for ELF header.
 */
class elf_header
{
  public:
    /**
     * @brief Virtual destructor.
     */
    virtual ~elf_header() = default;

    /**
     * @brief Load ELF header from stream.
     * @param stream Input stream.
     * @return True if successful, false otherwise.
     */
    virtual bool load( std::istream& stream ) = 0;

    /**
     * @brief Save ELF header to stream.
     * @param stream Output stream.
     * @return True if successful, false otherwise.
     */
    virtual bool save( std::ostream& stream ) const = 0;

    // ELF header functions
    ELFIO_GET_ACCESS_DECL( unsigned char, class );
    ELFIO_GET_ACCESS_DECL( unsigned char, elf_version );
    ELFIO_GET_ACCESS_DECL( unsigned char, encoding );
    ELFIO_GET_ACCESS_DECL( Elf_Half, header_size );
    ELFIO_GET_ACCESS_DECL( Elf_Half, section_entry_size );
    ELFIO_GET_ACCESS_DECL( Elf_Half, segment_entry_size );

    ELFIO_GET_SET_ACCESS_DECL( Elf_Word, version );
    ELFIO_GET_SET_ACCESS_DECL( unsigned char, os_abi );
    ELFIO_GET_SET_ACCESS_DECL( unsigned char, abi_version );
    ELFIO_GET_SET_ACCESS_DECL( Elf_Half, type );
    ELFIO_GET_SET_ACCESS_DECL( Elf_Half, machine );
    ELFIO_GET_SET_ACCESS_DECL( Elf_Word, flags );
    ELFIO_GET_SET_ACCESS_DECL( Elf64_Addr, entry );
    ELFIO_GET_SET_ACCESS_DECL( Elf_Half, sections_num );
    ELFIO_GET_SET_ACCESS_DECL( Elf64_Off, sections_offset );
    ELFIO_GET_SET_ACCESS_DECL( Elf_Half, segments_num );
    ELFIO_GET_SET_ACCESS_DECL( Elf64_Off, segments_offset );
    ELFIO_GET_SET_ACCESS_DECL( Elf_Half, section_name_str_index );
};

/**
 * @struct elf_header_impl_types
 * @brief Template specialization for ELF header implementation types.
 */
template <class T> struct elf_header_impl_types;
template <> struct elf_header_impl_types<Elf32_Ehdr>
{
    using Phdr_type                       = Elf32_Phdr;
    using Shdr_type                       = Elf32_Shdr;
    static const unsigned char file_class = ELFCLASS32;
};
template <> struct elf_header_impl_types<Elf64_Ehdr>
{
    using Phdr_type                       = Elf64_Phdr;
    using Shdr_type                       = Elf64_Shdr;
    static const unsigned char file_class = ELFCLASS64;
};

/**
 * @class elf_header_impl
 * @brief Template class for ELF header implementation.
 */
template <class T> class elf_header_impl : public elf_header
{
  public:
    /**
     * @brief Constructor.
     * @param convertor Endianness convertor.
     * @param encoding Encoding type.
     * @param translator Address translator.
     */
    elf_header_impl( std::shared_ptr<endianness_convertor> convertor,
                     unsigned char                         encoding,
                     std::shared_ptr<address_translator>   translator )
        : convertor( convertor ), translator( translator )
    {
        header.e_ident[EI_MAG0]    = ELFMAG0;
        header.e_ident[EI_MAG1]    = ELFMAG1;
        header.e_ident[EI_MAG2]    = ELFMAG2;
        header.e_ident[EI_MAG3]    = ELFMAG3;
        header.e_ident[EI_CLASS]   = elf_header_impl_types<T>::file_class;
        header.e_ident[EI_DATA]    = encoding;
        header.e_ident[EI_VERSION] = EV_CURRENT;
        header.e_version           = ( *convertor )( (Elf_Word)EV_CURRENT );
        header.e_ehsize            = ( sizeof( header ) );
        header.e_ehsize            = ( *convertor )( header.e_ehsize );
        header.e_shstrndx          = ( *convertor )( (Elf_Half)1 );
        header.e_phentsize =
            sizeof( typename elf_header_impl_types<T>::Phdr_type );
        header.e_shentsize =
            sizeof( typename elf_header_impl_types<T>::Shdr_type );
        header.e_phentsize = ( *convertor )( header.e_phentsize );
        header.e_shentsize = ( *convertor )( header.e_shentsize );
    }

    /**
     * @brief Load ELF header from stream.
     * @param stream Input stream.
     * @return True if successful, false otherwise.
     */
    bool load( std::istream& stream ) override
    {
        stream.seekg( ( *translator )[0] );
        stream.read( reinterpret_cast<char*>( &header ), sizeof( header ) );

        return ( stream.gcount() == sizeof( header ) );
    }

    /**
     * @brief Save ELF header to stream.
     * @param stream Output stream.
     * @return True if successful, false otherwise.
     */
    bool save( std::ostream& stream ) const override
    {
        stream.seekp( ( *translator )[0] );
        stream.write( reinterpret_cast<const char*>( &header ),
                      sizeof( header ) );

        return stream.good();
    }

    //------------------------------------------------------------------------------
    // ELF header functions
    ELFIO_GET_ACCESS( unsigned char, class, header.e_ident[EI_CLASS] );
    ELFIO_GET_ACCESS( unsigned char, elf_version, header.e_ident[EI_VERSION] );
    ELFIO_GET_ACCESS( unsigned char, encoding, header.e_ident[EI_DATA] );
    ELFIO_GET_ACCESS( Elf_Half, header_size, header.e_ehsize );
    ELFIO_GET_ACCESS( Elf_Half, section_entry_size, header.e_shentsize );
    ELFIO_GET_ACCESS( Elf_Half, segment_entry_size, header.e_phentsize );

    ELFIO_GET_SET_ACCESS( Elf_Word, version, header.e_version );
    ELFIO_GET_SET_ACCESS( unsigned char, os_abi, header.e_ident[EI_OSABI] );
    ELFIO_GET_SET_ACCESS( unsigned char,
                          abi_version,
                          header.e_ident[EI_ABIVERSION] );
    ELFIO_GET_SET_ACCESS( Elf_Half, type, header.e_type );
    ELFIO_GET_SET_ACCESS( Elf_Half, machine, header.e_machine );
    ELFIO_GET_SET_ACCESS( Elf_Word, flags, header.e_flags );
    ELFIO_GET_SET_ACCESS( Elf_Half, section_name_str_index, header.e_shstrndx );
    ELFIO_GET_SET_ACCESS( Elf64_Addr, entry, header.e_entry );
    ELFIO_GET_SET_ACCESS( Elf_Half, sections_num, header.e_shnum );
    ELFIO_GET_SET_ACCESS( Elf64_Off, sections_offset, header.e_shoff );
    ELFIO_GET_SET_ACCESS( Elf_Half, segments_num, header.e_phnum );
    ELFIO_GET_SET_ACCESS( Elf64_Off, segments_offset, header.e_phoff );

  private:
    T                                     header     = {};
    std::shared_ptr<endianness_convertor> convertor  = nullptr;
    std::shared_ptr<address_translator>   translator = nullptr;
};

} // namespace ELFIO

#endif // ELF_HEADER_HPP