PT_NULL = 0
PT_LOAD = 1
PT_DYNAMIC = 2
PT_INTERP = 3
PT_NOTE = 4
PT_SHLIB = 5
PT_PHDR = 6
PT_LOOS = 0x60000000
PT_HIOS = 0x6fffffff
PT_LOPROC = 0x70000000
PT_HIPROC = 0x7fffffff
PT_GNU_EH_FRAME	= 0x6474e550

ET_NONE = 0
ET_REL = 1
ET_EXEC = 2
ET_DYN = 3
ET_CORE = 4
ET_LOPROC = 0xff00
ET_HIPROC = 0xffff

EM_NONE = 0
EM_M32 = 1
EM_SPARC = 2
EM_386 = 3
EM_68K = 4
EM_88K = 5
EM_486 = 6
EM_860 = 7

import struct

class section:
    def __init__(self, name=0, addr=0, data=''):
        self.name = name
        self.addr = addr
        self.size = len(data)
        self.data = data

    def writePhdr(self, fileOff=0):
        type = PT_LOAD
        return struct.pack('<LLLLLLLL',
                          type, fileOff, self.addr,
                          0, self.size, self.size,
                          0x7, 2
                          )
    def writeShdr(self, fileOff=0, nameOff=0):
        return struct.pack('<LLLLLLLLLL',
                           nameOff, 1, 0x7,
                           self.addr, fileOff, self.size,
                           0, 0, 2, 0)

class ELF:
    def __init__(self, entry=None, isSO=False):
        self.sections = []
        self.entry = entry
        self.isSO = isSO

    def addSection(self, sec):
        self.sections.append(sec)

    def write(self, fp):
        type = (ET_EXEC, ET_DYN)[int(self.isSO)]
        machine = EM_386
        version = 1
        entry = self.entry
        flags = 0
        ehsize = 52 # sizeof(Elf32'Ehdr)
        phentsize = 32 # sizeof(Elf32.Phdr)
        phnum = len(self.sections)
        shentsize = 40 # sizeof(Elf32.Shdr)
        shnum = len(self.sections) + 2
        phoff = ehsize
        shoff = phoff + (phentsize * phnum)
        shstrndx = shnum - 1

        # phnum = shnum = shstrndx = 0
        # phoff = shoff = 0
        
        fp.write('\x7FELF')
        fp.write('\x01\x01\x01' + ('\x00' * 9)) # Rest of e'ident
        fp.write(struct.pack('<HHLLLLLHHHHHH',
                             type, machine, version,
                             entry, phoff, shoff,
                             flags, ehsize, phentsize,
                             phnum, shentsize, shnum,
                             shstrndx))

        # return

        shstr = '\0'
        fileOff = shoff + (shentsize * shnum)

        for sec in self.sections:
            fp.write(sec.writePhdr(fileOff=fileOff))
            fileOff += sec.size

        fileOff = shoff + (shentsize * shnum)

        fp.write(struct.pack('<LLLLLLLLLL',
                             0, 0, 0, 0, 0,
                             0, 0, 0, 0, 0))

        for sec in self.sections:
            fp.write(sec.writeShdr(fileOff=fileOff, nameOff=len(shstr)))
            fileOff += sec.size
            shstr += '%s\0' % sec.name
        
        fp.write(struct.pack('<LLLLLLLLLL',
                           0, 3, 0x7,
                           0, fileOff, len(shstr),
                           0, 0, 0, 0))

        for sec in self.sections:
            fp.write(sec.data)

        fp.write(shstr)