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Brainfuck Assembler
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| *----------------------------------------------------------- | |
| * Title : Brainfuck Assembler | |
| * Written by : Stuart Haidon | |
| * Date : 2015-06-16 | |
| * Versions: | |
| * 1.0: Release | |
| * 1.1: Changed JMP instruction in assembled program to RTS. | |
| * 1.2: Now handles mis-matched brackets. | |
| *----------------------------------------------------------- | |
| ORG $1000 | |
| readlen EQU $100 | |
| *------------------------ | |
| * Subroutines | |
| * Input | |
| * D6 : Character to test. | |
| * Output | |
| * D7 : 0 if invalid. | |
| is_valid: | |
| move.l #1,d7 | |
| cmp.b #'>', d6 | |
| beq is_valid_exit | |
| cmp.b #'<', d6 | |
| beq is_valid_exit | |
| cmp.b #'-', d6 | |
| beq is_valid_exit | |
| cmp.b #'+', d6 | |
| beq is_valid_exit | |
| cmp.b #'.', d6 | |
| beq is_valid_exit | |
| cmp.b #',', d6 | |
| beq is_valid_exit | |
| cmp.b #'[', d6 | |
| beq is_valid_exit | |
| cmp.b #']', d6 | |
| beq is_valid_exit | |
| move.l #0,d7 | |
| is_valid_exit: | |
| rts | |
| * Zeroes the first 128kb of program memory. Memory pointer in A6. | |
| zero_mem: | |
| move.l #$8000, d0 | |
| zero_mem_start: | |
| move.l #0,-4(a6,d0.l) | |
| sub.l #4, d0 | |
| tst d0 | |
| bne zero_mem_start | |
| rts | |
| START: ; first instruction of program | |
| *------------------------ | |
| * Put program code here | |
| * Close existing handles. Just in case. | |
| move.l #50, d0 | |
| trap #15 | |
| * Get filename. | |
| move.l #0, a1 | |
| lea extensions, a2 | |
| lea fname_buffer, a3 | |
| move.l #58, d0 ; Open/save file dialog. | |
| move.l #0, d1 ; Open file | |
| trap #15 | |
| tst d1 | |
| beq end * User clicked cancel or closed the dialog. Exit. | |
| * Start assembling the program. | |
| * Open file | |
| lea fname_buffer, a1 | |
| move.l #51, d0 | |
| trap #15 * D1 = File ID. | |
| program_assemble: | |
| lea program, a5 * A5 = Program output address. | |
| lea read_buffer, a1 * A1 = Buffer address. | |
| REPEAT | |
| * Read 256 bytes into buffer. | |
| move.l #53, d0 * Read file. | |
| move.l #readlen, d2 | |
| trap #15 * D2 = Number of bytes read. | |
| * Read and assemble brainfuck. | |
| move.l #0, d3 * D3 = Buffer read offset pointer. | |
| REPEAT | |
| move.b (a1,d3.l), d6 * D6 = Read character. | |
| jsr is_valid | |
| tst d7 | |
| beq next_iter * Invalid character. Skip to next. | |
| IF.b d6 <EQ> #'>' THEN.s | |
| move.w #$528E, (a5)+ * add.l #1, A6 | |
| ENDI | |
| IF.b d6 <EQ> #'<' THEN.s | |
| move.w #$538E, (a5)+ * sub.l #1, A6 | |
| ENDI | |
| IF.b d6 <EQ> #'+' THEN.s | |
| move.w #$5216, (a5)+ * add.b #1, (A6) | |
| ENDI | |
| IF.b d6 <EQ> #'-' THEN.s | |
| move.w #$5316, (a5)+ * sub.b #1, (A6) | |
| ENDI | |
| IF.b d6 <EQ> #'.' THEN.s | |
| move.w #$7006, (a5)+ * move.l #6, d0 | |
| move.w #$1216, (a5)+ * move.b (a6), d1 | |
| move.w #$4E4F, (a5)+ * trap #15 | |
| ENDI | |
| IF.b d6 <EQ> #',' THEN.s | |
| move.w #$7005, (a5)+ * move.l #5, d0 | |
| move.w #$4E4F, (a5)+ * trap #15 | |
| move.w #$1C81, (a5)+ * move.b d1, (a6) | |
| ENDI | |
| IF.b d6 <EQ> #'[' THEN.s | |
| move.w #$4A16, (a5)+ * tst (a6) | |
| move.w #$6600, (a5)+ * bne | |
| move.w #$0008, (a5)+ * Address for bne | |
| move.w #$4ED5, (a5)+ * Jump to (a5) Is for handling mismatched bracket, and will be corrected to 4EF9 later. | |
| *move.w #$4EF9, (a5)+ * jmp to following address. | |
| * Push address to destination of current [. | |
| move.l a5, -(a7) | |
| move.w #$0000, (a5)+ | |
| move.w #$0000, (a5)+ * Address to matching ] | |
| ENDI | |
| IF.b d6 <EQ> #']' THEN.s | |
| move.l a5,d5 * D5 = Address of current ] before writing the instruction. | |
| * Write current instruction. | |
| move.w #$4A16, (a5)+ * tst (a6) | |
| move.w #$6700, (a5)+ * beq | |
| move.w #$0008, (a5)+ * Address for beq | |
| * Test for mis-matched bracket. | |
| IF.l a7 <NE> #$1000000 THEN.s | |
| move.l (a7)+, a3 * A3 = Address to matching [ | |
| move.w d5, 2(a3) | |
| swap d5 | |
| move.w d5, 0(a3) | |
| * Correct the jump opcode | |
| move.w #$4EF9, -2(a3) | |
| * Write jump opcode for current bracket. | |
| move.w #$4EF9, (a5)+ * jmp | |
| * Write matching return address. | |
| move.l a3, d5 | |
| sub.l #8, d5 | |
| swap d5 | |
| move.w d5, (a5)+ | |
| swap d5 | |
| move.w d5, (a5)+ | |
| ELSE.s | |
| * Write return error opcode. | |
| move.w #$4ED5, (a5)+ | |
| ENDI | |
| ENDI | |
| next_iter: | |
| add.w #1, d3 | |
| UNTIL.w d3 <EQ> d2 DO.l * Read untill reached the end of read data. | |
| UNTIL.l d2 <NE> #readlen DO.l * Reached end of file. | |
| * Exit program. | |
| move.w #$4E75, (a5)+ * rts | |
| * Close file. | |
| move.l #56, d0 | |
| trap #15 | |
| * Zero memory, setup memory pointer, and jump to program. | |
| lea program_memory, a6 | |
| * Write message. | |
| move.l #13, d0 | |
| lea zero_mem_message, a1 | |
| trap #15 | |
| jsr zero_mem | |
| * Clear screen. | |
| move.l #11, d0 | |
| move.l #$ff00, d1 | |
| trap #15 | |
| * Set error pointer address. | |
| lea program_error, a5 | |
| jsr program | |
| * Program will jump here when finished. | |
| prog_finish: | |
| move.l #13, d0 | |
| lea finish_text, a1 | |
| trap #15 * Display string. | |
| prog_finish_input_loop: | |
| move.l #5, d0 | |
| trap #15 | |
| cmp.b #'y',d1 | |
| beq prog_finish_clear_restart | |
| cmp.b #'n',d1 | |
| beq end | |
| move.l #13,d0 | |
| lea finish_text_invalid, a1 | |
| trap #15 | |
| jmp prog_finish_input_loop | |
| prog_finish_clear_restart: | |
| move.l #11, d0 | |
| move.l #$ff00, d1 | |
| trap #15 * Clear screen. | |
| jmp start | |
| end: | |
| SIMHALT ; halt simulator | |
| program_error: | |
| move.l #13,d0 | |
| lea mismatch_bracket, a1 | |
| trap #15 | |
| rts | |
| *------------------------ | |
| * Put variables and constants here | |
| zero_mem_message: dc.b 'Zeroing Memory',0 | |
| finish_text: dc.b $d,$a,'Program finished. Load another? (y or n)',0 | |
| finish_text_invalid: dc.b $d,$a,'Invalid Input',$d,$a,0 | |
| mismatch_bracket: dc.b $d,$a,'Encountered a program error. Exiting.',0 | |
| extensions: dc.b '*.b;*.bf',0 | |
| fname_buffer: dcb.b $100,0 | |
| read_buffer: dcb.b readlen,0 | |
| ORG $10000 | |
| program: | |
| ORG $100000 | |
| program_memory: | |
| END START ; last line of source | |
Thank you. I did originally intend to write an interpreter, hence the title in the file, but changed my mind when I realised I would have to search along the brainfuck code for the matching bracket. I figured it would be easier to assemble it to raw opcodes and just jump to it.
I used the Easy68k assembler/emulator to compile and run it, so it uses some emulator-specific functions, such as the open file dialog and file reading (Lines 66 to 96).
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I would update the first block comment to say "Assembler" instead of "Interpreter". It looks like it really is assembling the code and then running it as bare metal opcodes.
BTW, I haven't done any assembly in a long time and this is still pretty readable to me. Nice work! Do you think you could include a comment with the command-line you use to assemble this?