170 lines
5.0 KiB
Plaintext
170 lines
5.0 KiB
Plaintext
## Copyright (C) 2016 Jeremiah Orians
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## This file is part of stage0.
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##
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## stage0 is free software: you can redistribute it and/or modify
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## it under the terms of the GNU General Public License as published by
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## the Free Software Foundation, either version 3 of the License, or
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## (at your option) any later version.
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##
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## stage0 is distributed in the hope that it will be useful,
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## but WITHOUT ANY WARRANTY; without even the implied warranty of
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## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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## GNU General Public License for more details.
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##
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## You should have received a copy of the GNU General Public License
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## along with stage0. If not, see <http://www.gnu.org/licenses/>.
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# ;; R14 will be storing our condition
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# ;;
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# ;; R13 will be a stack pointer. It will be zero
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# ;; on the start, and the stack grows up.
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# ;; This means that when stack is used, the
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# ;; first instructions of this program will be
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# ;; overwritten. But because this is initialization
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# ;; code, it is already not used at the time.
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# ;; And the stack usage is fixed - there is only one CALL
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# ;; instruction in this file
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# ;;
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# ;; R2 Is our holder.
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# ;; It holds the first nybble of the byte till the second iteration
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# ;;
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# ;; R12 Is our toggle. It is initialized to zero on start.
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# ;; When non-zero, it means that we are processing the second nybble
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# ;;
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# ;; R8 will hold zero. It is initialized to zero on start.
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# :start ; offset = 0
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# ;; Prepare often-used values that will be held in registers
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E0002D2F000f # LOADUI R15 0xF ; Set R15 to 0xF
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E0002D2B1101 # LOADUI R11 0x1101 ; R11 will hold 0x1101
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# ;; Prep TAPE_01
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01100FB8 # MUX R0 R15 R11 R8 ; 0x1100 = ((0x1101 & ~0xF) | (0 | 0xF))
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42100001 # FOPEN_WRITE
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# ;; Prep TAPE_02
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0900040B # COPY R0 R11 ; 0x1101
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42100001 # FOPEN_WRITE
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# :loop ; offset = 1c
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0D000021 # FALSE R1 ; Read from tty
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42100100 # FGETC ; Read a Char
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E000A030000d # CMPSKIPI.NE R0 13 ; Replace all CR
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E0002D20000a # LOADUI R0 10 ; WIth LF
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42100200 # FPUTC
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# ; Display the Char to User
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# ;; Check for Ctrl-D
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E000A0300004 # CMPSKIPI.NE R0 4
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3C000104 # JUMP @finish
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# ;; Check for EOF
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E0002CC000fe # JUMP.NP R0 @finish
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# ;; Write out unprocessed byte
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0900041B # COPY R1 R11 ; Write to TAPE_02
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42100200 # FPUTC ; Print the Char
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# ;; Convert byte to nybble
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E0002D0D0036 # CALLI R13 @hex ; Convert it
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# ;; Get another byte if nonhex
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E0002CC0ffc4 # JUMP.NP R0 @loop ; Don't use nonhex chars
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# ;; Deal with the case of second nybble
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E0002CAC000c # JUMP.NZ R12 @second_nybble ; Jump if toggled
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# ;; Process first byte of pair
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0502020F # AND R2 R0 R15 ; Store First nibble
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0D00003C # TRUE R12 ; Flip the toggle
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3C00ffb2 # JUMP @loop
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# ;; Combined second nybble in pair with first
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# :second_nybble ; offset = 6a
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E0002D520004 # SL0I R2 4 ; Shift our first nibble
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0502000F # AND R0 R0 R15 ; Mask out top
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05000002 # ADD R0 R0 R2 ; Combine nibbles
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# ;; Writeout and prepare for next cycle
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0D00002C # FALSE R12 ; Flip the toggle
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# ; Write the combined byte
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01101FB8 # MUX R1 R15 R11 R8 ; To TAPE_01
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42100200 # FPUTC
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3C00ff94 # JUMP @loop ; Try to get more bytes
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# :hex ; offset = 88
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# ;; Deal with line comments starting with #
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E1001FE00023 # CMPUI R14 R0 35
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E0002C5E007e # JUMP.E R14 @ascii_comment
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# ;; Deal with line comments starting with ;
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E1001FE0003b # CMPUI R14 R0 59
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E0002C5E0072 # JUMP.E R14 @ascii_comment
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# ;; Deal with all ascii less than '0'
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E1001FE00030 # CMPUI R14 R0 48
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E0002C8E005e # JUMP.L R14 @ascii_other
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# ;; Deal with '0'-'9'
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E1001FE00039 # CMPUI R14 R0 57
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E0002C7E0034 # JUMP.LE R14 @ascii_num
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# ;; Deal with all ascii less than 'A'
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E1001FE00041 # CMPUI R14 R0 65
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E0002C8E0046 # JUMP.L R14 @ascii_other
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# ;; Deal with 'A'-'F'
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E1001FE00046 # CMPUI R14 R0 70
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E0002C7E0030 # JUMP.LE R14 @ascii_high
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# ;; Deal with all ascii less than 'a'
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E1001FE00061 # CMPUI R14 R0 97
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E0002C8E002e # JUMP.L R14 @ascii_other
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# ;; Deal with 'a'-'f'
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E1001FE00066 # CMPUI R14 R0 102
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E0002C7E000e # JUMP.LE R14 @ascii_low
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# ;; Ignore the rest
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3C00001e # JUMP @ascii_other
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# :ascii_num ; offset = ec
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E10011000030 # SUBUI R0 R0 48
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0D01001D # RET R13
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# :ascii_low ; offset = f6
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E10011000057 # SUBUI R0 R0 87
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0D01001D # RET R13
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# :ascii_high ; offset = 100
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E10011000037 # SUBUI R0 R0 55
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0D01001D # RET R13
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# :ascii_other ; offset = 10a
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0D000030 # TRUE R0
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0D01001D # RET R13
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# :ascii_comment ; offset = 112
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0D000021 # FALSE R1 ; Read from tty
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42100100 # FGETC ; Read another char
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E000A030000d # CMPSKIPI.NE R0 13 ; Replace all CR
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E0002D20000a # LOADUI R0 10 ; WIth LF
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42100200 # FPUTC ; Let the user see it
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E1001FE0000a # CMPUI R14 R0 10 ; Stop at the end of line
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0900041B # COPY R1 R11 ; Write to TAPE_02
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42100200 # FPUTC ; The char we just read
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E0002C6Effd4 # JUMP.NE R14 @ascii_comment ; Otherwise keep looping
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3C00ffc8 # JUMP @ascii_other
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# :finish ; offset = 142
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01100FB8 # MUX R0 R15 R11 R8 ; Close TAPE_01
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42100002 # FCLOSE
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0900040B # COPY R0 R11 ; Close TAPE_02
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42100002 # FCLOSE
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FFFFFFFF # HALT
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