## Copyright (C) 2016 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/>.

# :start 0
E0002D2B0200    # LOADUI R11 0x200 ; Where we are putting our address pointers
0D00003C        # TRUE R12 ; Our toggle
0D00002D        # FALSE R13 ; Our PC counter
E0002D2E0050    # LOADUI R14 $getLables_2 ; our first iterator
# ;; We will be using R15 for holding our processed nybbles

# ;; Prep TAPE_01
E0002D201100    # LOADUI R0 0x1100
42100000        # FOPEN_READ

# ;; Prep TAPE_02
E0002D201101    # LOADUI R0 0x1101
42100001        # FOPEN_WRITE

E0002D211100    # LOADUI R1 0x1100 ; Read from tape_01

# ;; Function for collecting the address of all labels
# :getLables 2e
42100100        # FGETC ; Read a Char

# ;; Check for EOF
E0002CC00052    # JUMP.NP R0 @stage2

# ;; Check for Label
E000A030003a    # CMPSKIPI.NE R0 58 ; If the Char is : the next char is the label
3C000036        # JUMP @storeLabel

# ;; Check for pointer to label
E000A0300040    # CMPSKIPI.NE R0 64 ; If the Char is @ the next char is the pointer to a label
3C00001e        # JUMP @ignorePointer

# ;; Otherwise attempt to process
3C000100        # JUMP @hex ; Convert it

# :getLables_2 50
E0002CC0ffd8    # JUMP.NP R0 @getLables ; Don't record, nonhex values
090006CC        # NOT R12 R12 ; Flip the toggle
E0002C9Cffce    # JUMP.Z R12 @getLables ; First half doesn't need anything

# ;; Deal with case of second half of byte
E1000FDD0001    # ADDUI R13 R13 1 ; increment PC now that we have a full byte
3C00ffc4        # JUMP @getLables

# :ignorePointer 6a
# ;; Ignore the pointer for now
42100100        # FGETC ; Read a Char
E1000FDD0002    # ADDUI R13 R13 2 ; The pointer will end up taking 2 bytes
3C00ffb6        # JUMP @getLables

# ;; Function for storing the address of the label
# :storeLabel 78
# ;; Get the char of the Label
42100100        # FGETC ; Read a Char

# ;; We require 2 bytes to store the pointer values
E0002D500001    # SL0I R0 1 ; Thus we multiply our label by 2

# ;; Store the current Program counter
0504ADB0        # STOREX16 R13 R11 R0

# ;; Label is safely stored, return
3C00ffa4        # JUMP @getLables

# ;; Now that we have all of the label addresses,
# ;; We can process input to produce our output
# :stage2 8a
# ;; We first need to rewind tape_01 to perform our second pass
E0002D201100    # LOADUI R0 0x1100
42100003        # REWIND

# ;; Reset our toggle and counter
E0002D291101    # LOADUI R9 0x1101 ; Where to write the combined byte
0D00003C        # TRUE R12 ; Our toggle
0D00002D        # FALSE R13 ; Our PC counter
E0002D2E00ca    # LOADUI R14 $loop_hex ; The hex return target

# :loop a8
42100100        # FGETC ; Read a Char

# ;; Check for EOF
E0002CC0010e    # JUMP.NP R0 @finish

# ;; Check for Label
E000A030003a    # CMPSKIPI.NE R0 58 ; Make sure we jump over the label
3C00004e        # JUMP @ignoreLabel

# ;; Check for Pointer
E000A0300040    # CMPSKIPI.NE R0 64 ; If it is a pointer Deal with it
3C00004c        # JUMP @storePointer

# ;; Process Char
3C000086        # JUMP @hex ; Convert it

# :loop_hex ca
E0002CC0ffd8    # JUMP.NP R0 @loop ; Don't use nonhex chars
090006CC        # NOT R12 R12 ; Flip the toggle
E0002CAC000a    # JUMP.NZ R12 @loop_second_nybble ; Jump if toggled

# ;; Process first byte of pair
E100B0F0000f    # ANDI R15 R0 0xF ; Store First nibble
3C00ffc4        # JUMP @loop

# :loop_second_nybble e4
E0002D5F0004    # SL0I R15 4 ; Shift our first nibble
E100B000000f    # ANDI R0 R0 0xF ; Mask out top
0500000F        # ADD R0 R0 R15 ; Combine nibbles
09000319        # SWAP R1 R9 ; Set to write to tape_2
42100200        # FPUTC ; To TAPE_02
09000319        # SWAP R1 R9 ; Restore from tape_1
E1000FDD0001    # ADDUI R13 R13 1 ; increment PC now that we have a full byte
3C00ff9e        # JUMP @loop ; Try to get more bytes

# :ignoreLabel 10a
# ;; Consume next char
42100100        # FGETC ; Read a Char
3C00ff96        # JUMP @loop

# :storePointer 112
# ;; Correct the PC to reflect the size of the pointer
E1000FDD0002    # ADDUI R13 R13 2 ; Exactly 2 bytes

# ;; Get the char of the Label
42100100        # FGETC ; Read a Char

# ;; Since we stored a short pointer taking up 2 bytes
E0002D500001    # SL0I R0 1 ; Thus we multiply our label by 2 to get where it is stored
0503C3B0        # LOADXU16 R3 R11 R0 ; Load the address of the label

# ;; We now have to calculate the distance and store the 2 bytes
0500233D        # SUB R3 R3 R13 ; First determine the difference between the current PC and the stored PC of the label

# ;; Store Upper byte
E100B003ff00    # ANDI R0 R3 0xFF00 ; Mask out everything but top byte
E0002D400008    # SARI R0 8 ; Drop the bottom 8 bits
09000319        # SWAP R1 R9 ; Write the byte
42100200        # FPUTC ; To TAPE_02

# ;; Store Lower byte
E100B00300ff    # ANDI R0 R3 0xFF ; Preserve bottom half for later
42100200        # FPUTC ; Write the byte to TAPE_02
09000319        # SWAP R1 R9 ; Restore Read
3C00ff58        # JUMP @loop

# ;; Hex function
# ;; Returns hex value of ascii char
# ;; Or -1 if not a hex char
# :hex 150
# ;; Deal with line comments starting with #
E000A0300023    # CMPSKIPI.NE R0 35
3C000050        # JUMP @ascii_comment

# ;; Deal with line comments starting with ;
E000A030003b    # CMPSKIPI.NE R0 59
3C000046        # JUMP @ascii_comment

# ;; Deal with all ascii less than '0'
E000A0100030    # CMPSKIPI.GE R0 48
3C00004a        # JUMP @ascii_other

# ;; Deal with '0'-'9'
E000A0000039    # CMPSKIPI.G R0 57
3C00001e        # JUMP @ascii_num

# ;; Deal with all ascii less than 'A'
E000A0100041    # CMPSKIPI.GE R0 65
3C000036        # JUMP @ascii_other

# ;; Unset high bit to set everything into uppercase
E100B00000df    # ANDI R0 R0 0xDF

# ;; Deal with 'A'-'F'
E000A0000046    # CMPSKIPI.G R0 70
3C00000e        # JUMP @ascii_high

# ;; Ignore the rest
3C000022        # JUMP @ascii_other

# :ascii_num 196
E10011000030    # SUBUI R0 R0 48
0D01000E        # JSR_COROUTINE R14
# :ascii_high 1a0
E10011000037    # SUBUI R0 R0 55
0D01000E        # JSR_COROUTINE R14
# :ascii_comment 1aa
42100100        # FGETC ; Read another char
E000A020000a    # CMPSKIPI.E R0 10 ; Stop at the end of line
3C00fff2        # JUMP @ascii_comment ; Otherwise keep looping
# :ascii_other 1b8
0D000030        # TRUE R0
0D01000E        # JSR_COROUTINE R14

# :finish 1c0
E0002D201100    # LOADUI R0 0x1100 ; Close TAPE_01
42100002        # FCLOSE
E0002D201101    # LOADUI R0 0x1101 ; Close TAPE_02
42100002        # FCLOSE
FFFFFFFF        # HALT

# ;; Where all of our pointers will be stored for our locations
# :table 1d8