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- ## Copyright (C) 2017 Jeremiah Orians
- ## This file is part of stage0.
- ##
- ## stage0 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.
- ##
- ## stage0 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 stage0. If not, see <http://www.gnu.org/licenses/>.
- DEFINE ADD_ebp_TO_eax 01E8
- DEFINE CALLI32 E8
- DEFINE CMP_eax_Immediate8 83F8
- DEFINE CMP_edi_Immediate8 83FF
- DEFINE INT_80 CD80
- DEFINE JE32 0F84
- DEFINE JE8 74
- DEFINE JGE8 7D
- DEFINE JL8 7C
- DEFINE JMP32 E9
- DEFINE JMP8 EB
- DEFINE LOAD32I_eax B8
- DEFINE LOAD32I_ebp BD
- DEFINE LOAD32I_ebx BB
- DEFINE LOAD32I_ecx B9
- DEFINE LOAD32I_edi BF
- DEFINE LOAD32I_edx BA
- DEFINE LOAD8_al_Absolute32 A0
- DEFINE MOVE_eax_TO_ebp 89C5
- DEFINE MOVZBL_eax_al 0FB6C0
- DEFINE NULL 00000000
- DEFINE RET C3
- DEFINE SHL_ebp_Immediate8 C1E5
- DEFINE STORE8_al_Absolute32 A2
- DEFINE SUB_eax_Immediate8 83E8
- DEFINE TEST_eax_eax 85C0
- # Where the ELF Header is going to hit :_start first
- :read_byte
- # Attempt to read 1 byte from STDIN
- LOAD32I_edx %1 # set the size of chars we want
- LOAD32I_ecx &input # Where to put it
- LOAD32I_ebx %0 # Where are we reading from
- LOAD32I_eax %3 # the syscall number for read
- INT_80 # call the Kernel
- TEST_eax_eax # check what we got
- JE32 %Done # Got EOF call it done
- # load byte
- LOAD8_al_Absolute32 &input # load char
- MOVZBL_eax_al # We have to zero extend it to use it
- RET
- :print_byte
- # Print our first Hex
- LOAD32I_edx %1 # set the size of chars we want
- LOAD32I_ecx &output # What we are writing
- LOAD32I_ebx %1 # Stdout File Descriptor
- LOAD32I_eax %4 # the syscall number for write
- INT_80 # call the Kernel
- :hex
- # Deal with #
- CMP_eax_Immediate8 !35
- JE8 !ascii_comment
- # deal with ;
- CMP_eax_Immediate8 !59
- JE8 !ascii_comment
- # deal all ascii less than 0
- CMP_eax_Immediate8 !48
- JL8 !ascii_other
- # deal with 0-9
- CMP_eax_Immediate8 !58
- JL8 !ascii_num
- # deal with all ascii less than A
- CMP_eax_Immediate8 !65
- JL8 !ascii_other
- # deal with A-F
- CMP_eax_Immediate8 !71
- JL8 !ascii_high
- #deal with all ascii less than a
- CMP_eax_Immediate8 !97
- JL8 !ascii_other
- #deal with a-f
- CMP_eax_Immediate8 !103
- JL8 !ascii_low
- # The rest that remains needs to be ignored
- JMP8 !ascii_other
- :ascii_num
- SUB_eax_Immediate8 !48
- RET
- :ascii_low
- SUB_eax_Immediate8 !87
- RET
- :ascii_high
- SUB_eax_Immediate8 !55
- RET
- :ascii_other
- LOAD32I_eax %-1
- RET
- :ascii_comment
- CALLI32 %read_byte
- CMP_eax_Immediate8 !10
- JE8 !ascii_other
- JMP8 !ascii_comment
- :_start
- # Our flag for byte processing
- LOAD32I_edi %-1
- # temp storage for the sum
- LOAD32I_ebp %0
- :loop
- # Read in a byte
- CALLI32 %read_byte
- # process byte
- CALLI32 %hex
- # deal with -1 values
- CMP_eax_Immediate8 !0
- JL8 !loop
- # deal with toggle
- CMP_edi_Immediate8 !0
- JGE8 !print
- # process first byte of pair
- MOVE_eax_TO_ebp
- LOAD32I_edi %0
- JMP8 !loop
- # process second byte of pair
- :print
- # update the sum and store in output
- SHL_ebp_Immediate8 !4
- ADD_ebp_TO_eax
- STORE8_al_Absolute32 &output
- # flip the toggle
- LOAD32I_edi %-1
- CALLI32 %print_byte
- JMP8 !loop
- :Done
- # program completed Successfully
- LOAD32I_ebx %0 # All is well
- LOAD32I_eax %1 # put the exit syscall number in eax
- INT_80 # Call it a good day
- # Our writable space
- :input
- NULL
- :output
- NULL
- :ELF_end
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