#-------------------------------------------------------------------------------
# readelf.py
#
# A clone of 'readelf' in Python, based on the pyelftools library
#
# Eli Bendersky (eliben@gmail.com)
# This code is in the public domain
#-------------------------------------------------------------------------------
import sys
from optparse import OptionParser

# If elftools is not installed, maybe we're running from the root or scripts
# dir of the source distribution
#
try:
    import elftools
except ImportError:
    sys.path.extend(['.', '..'])

from elftools.common.exceptions import ELFError
from elftools.elf.elffile import ELFFile
from elftools.elf.descriptions import (
    describe_ei_class, describe_ei_data, describe_ei_version,
    describe_ei_osabi, describe_e_type, describe_e_machine,
    describe_e_version_numeric,
    )


class ReadElf(object):
    """ display_* methods are used to emit output into the output stream
    """
    def __init__(self, file, output):
        """ file: 
                stream object with the ELF file to read
            
            output:
                output stream to write to
        """
        self.elffile = ELFFile(file)
        self.output = output

    def display_file_header(self):
        """ Display the ELF file header
        """
        self._emitline('ELF Header:')
        self._emit('  Magic:   ')
        self._emitline(' '.join('%2.2x' % ord(b) 
                                    for b in self.elffile.e_ident_raw))
        header = self.elffile.header
        e_ident = header['e_ident']
        self._emitline('  Class:                             %s' % 
                describe_ei_class(e_ident['EI_CLASS']))
        self._emitline('  Data:                              %s' % 
                describe_ei_data(e_ident['EI_DATA']))
        self._emitline('  Version:                           %s' % 
                describe_ei_version(e_ident['EI_VERSION']))
        self._emitline('  OS/ABI:                            %s' %
                describe_ei_osabi(e_ident['EI_OSABI']))
        self._emitline('  ABI Version:                       %d' % 
                e_ident['EI_ABIVERSION'])
        self._emitline('  Type:                              %s' %
                describe_e_type(header['e_type']))
        self._emitline('  Machine:                           %s' % 
                describe_e_machine(header['e_machine']))
        self._emitline('  Version:                           %s' %
                describe_e_version_numeric(header['e_version']))
        self._emitline('  Entry point address:               %s' % 
                self._format_addr(header['e_entry']))
        self._emit('  Start of program headers           %s' % 
                header['e_phoff'])
        self._emitline(' (bytes into file)')
        self._emit('  Start of section headers           %s' % 
                header['e_shoff'])
        self._emitline(' (bytes into file)')
        self._emitline('  Flags:                             %s' % 
                self._format_addr(header['e_flags']))
        self._emitline('  Size of this header:               %s (bytes)' %
                header['e_ehsize'])
        self._emitline('  Size of program headers:           %s (bytes)' %
                header['e_phentsize'])
        self._emitline('  Number of program headers:         %s' %
                header['e_phnum'])
        self._emitline('  Size of section headers:           %s (bytes)' %
                header['e_shentsize'])
        self._emitline('  Number of section headers:         %s' %
                header['e_shnum'])
        self._emitline('  Section header string table index: %s' %
                header['e_shstrndx'])


    def _format_addr(self, addr):
        """ Format an address into a string
        """
        return '0x%x' % addr
        
    def _emit(self, s):
        """ Emit an object to output
        """
        self.output.write(str(s))

    def _emitline(self, s):
        """ Emit an object to output, followed by a newline
        """
        self.output.write(str(s) + '\n')


def main():
    optparser = OptionParser()
    options, args = optparser.parse_args()

    with open(args[0], 'rb') as file:
        try:
            readelf = ReadElf(file, sys.stdout)
            readelf.display_file_header()
        except ELFError as ex:
            sys.stderr.write('ELF read error: %s\n' % ex)
            sys.exit(1)


#-------------------------------------------------------------------------------
if __name__ == '__main__':
    main()