import struct
from fileformat import *

CPU_TYPE_X86 = 7
CPU_SUBTYPE_LITTLE_ENDIAN = 0

MH_EXECUTE = 2
MH_DYLIB   = 6

class MachO(FileFormat):
	capabilities = (FILEFORMAT_WRITE, )
	
	def write(self, fp):
		"""
		Write file to given file pointer
   
		@param	fp:		File pointer to output file
		@type	fp:		C{file}
		"""
	
		cputype = CPU_TYPE_X86
		cpusubtype = CPU_SUBTYPE_LITTLE_ENDIAN

		if self.is_shared:
			filetype = MH_DYLIB
		else:
			filetype = MH_EXECUTE

		flags = 0x20000

		ncmds = len(self.sections)
		cmds = self.commands()
		sizeofcmds = len(cmds)
		reserved = 0

		fp.write(struct.pack('<LLL', 0xfeedfaceL, cputype, cpusubtype))
		fp.write(struct.pack('<LLLL', filetype, ncmds, sizeofcmds, flags))
		fp.write(cmds)

		for section in self.sections:
			fp.write(section.data)
	
	def commands(self):
		data = ''
		fileoff = 7*4 # Size of the Mach-O header we use
		
		for sec in self.sections:
			fileoff += 56 + 68
		
		for sec in self.sections:
			datatemp = self.writeSegment(sec, fileoff)
			data    += datatemp
			fileoff += len(datatemp)
		
		return data
	
	def writeSegment(self, sec, fileoff):
		cmd, cmdsize = 0x1, 56 + 68

		segname = sec.name
		
		if segname == '.':
			segname = segname[1:]
		elif segname[0] == '_':
			segname = segname[1:]
			if segname[0] == '_':
				segname = segname[1:]
		
		segname = segname.upper()
		segname = segname.replace('alky', '')
				
		data = struct.pack(
			'<LL16sLLLLLLLL', cmd, cmdsize,
			segname, sec.addr, sec.size,
			fileoff, len(sec.data), 7,
			sec.prot, 1, 0
		)
		
		data += self.writeSection(segname, sec, fileoff)
		
		return data
	
	def writeSection(self, segname, sec, fileoff):
		align = 2
		reloff = nreloc = flags = 0
		reserved1 = reserved2 = 0
		return struct.pack(
			'<16s16sLLLLLLLLL', segname, sec.name,
			sec.addr, sec.size, fileoff, align,
			reloff, nreloc, flags, reserved1,
			reserved2
		)