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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_RAX_R14 4C01F0
DEFINE CMP_RAX_Immediate8 4883F8
DEFINE CMP_R15_Immediate8 4983FF
DEFINE JE8 74
DEFINE JNE8 75
DEFINE JGE8 7D
DEFINE JE32 0F84
DEFINE JL8 7C
DEFINE JMP8 EB
DEFINE JMP32 E9
DEFINE LOAD32I_RDX 48C7C2
DEFINE LOAD32I_RSI 48C7C6
DEFINE LOAD32I_RDI 48C7C7
DEFINE LOAD32I_RAX 48C7C0
DEFINE LOAD32I_R14 49C7C6
DEFINE LOAD32I_R15 49C7C7
DEFINE LOAD8_al_Absolute32 8A0425
DEFINE STORE8_al_Absolute32 880425
DEFINE SYSCALL 0F05
DEFINE SHL_R14_Immediate8 49C1E6
DEFINE TEST_RAX_RAX 4885C0
DEFINE MOVE_R14_RAX 4989C6
DEFINE MOVZBQ_RAX_AL 480FB6C0
DEFINE RETQ C3
DEFINE SUB_RAX_Immediate8 4883E8
DEFINE CALLI32 E8
DEFINE NULL 00000000
# Where the ELF Header is going to hit is :_start
:hex
# Purge Comment Lines (#)
CMP_RAX_Immediate8 !35
JE8 !purge_comment
# Purge Comment Lines (;)
CMP_RAX_Immediate8 !59
JE8 !purge_comment
# deal all ascii less than '0'
CMP_RAX_Immediate8 !48
JL8 !ascii_other
# deal with 0-9
CMP_RAX_Immediate8 !58
JL8 !ascii_num
# deal with all ascii less than 'A'
CMP_RAX_Immediate8 !65
JL8 !ascii_other
# deal with 'A'-'F'
CMP_RAX_Immediate8 !71
JL8 !ascii_high
# deal with all ascii less than 'a'
CMP_RAX_Immediate8 !97
JL8 !ascii_other
#deal with 'a'-'f'
CMP_RAX_Immediate8 !103
JL8 !ascii_low
# The rest that remains needs to be ignored
JMP8 !ascii_other
:purge_comment
# Attempt to read 1 byte from STDIN
LOAD32I_RDX %1 # set the size of chars we want
LOAD32I_RSI &input # Where to put it
LOAD32I_RDI %0 # Where are we reading from
LOAD32I_RAX %0 # the syscall number for read
SYSCALL # call the Kernel
TEST_RAX_RAX # check what we got
JE32 %Done # Got EOF call it done
# load byte
LOAD8_al_Absolute32 &input # load char
MOVZBQ_RAX_AL # We have to zero extend it to use it
# Loop if not LF
CMP_RAX_Immediate8 !10
JNE8 !purge_comment
# Otherwise return -1
LOAD32I_RAX %-1
RETQ
:ascii_num
SUB_RAX_Immediate8 !48
RETQ
:ascii_low
SUB_RAX_Immediate8 !87
RETQ
:ascii_high
SUB_RAX_Immediate8 !55
RETQ
:ascii_other
LOAD32I_RAX %-1
RETQ
# Our main function
:_start
# Our flag for byte processing
LOAD32I_R15 %-1
# temp storage for the sum
LOAD32I_R14 %0
:loop
# Attempt to read 1 byte from STDIN
LOAD32I_RDX %1 # set the size of chars we want
LOAD32I_RSI &input # Where to put it
LOAD32I_RDI %0 # Where are we reading from
LOAD32I_RAX %0 # the syscall number for read
SYSCALL # call the Kernel
TEST_RAX_RAX # check what we got
JE8 !Done # Got EOF call it done
# load byte
LOAD8_al_Absolute32 &input # load char
MOVZBQ_RAX_AL # We have to zero extend it to use it
# process byte
CALLI32 %hex
# deal with -1 values
CMP_RAX_Immediate8 !0
JL8 !loop
# deal with toggle
CMP_R15_Immediate8 !0
JGE8 !print
# process first byte of pair
MOVE_R14_RAX
LOAD32I_R15 %0
JMP8 !loop
# process second byte of pair
:print
# update the sum and store in output
SHL_R14_Immediate8 !4
ADD_RAX_R14
STORE8_al_Absolute32 &output
# flip the toggle
LOAD32I_R15 %-1
# Print our Hex
LOAD32I_RDX %1 # set the size of chars we want
LOAD32I_RSI &output # What we are writing
LOAD32I_RDI %1 # Stdout File Descriptor
LOAD32I_RAX %1 # the syscall number for write
SYSCALL # call the Kernel
JMP8 !loop
:Done
# program completed Successfully
LOAD32I_RDI %0 # All is well
LOAD32I_RAX %60 # put the exit syscall number in rax
SYSCALL # Call it a good day
# Where we are putting our output
:output
# Reserve 4bytes of Zeros
NULL
# Where we get our input
:input
# Reserve 4bytes of Zeros
NULL
:ELF_end
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