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from sys import stderr
from argparse import ArgumentParser
EXIT_CODES = {
"file_error": 1,
"illegal_char": 2,
"size_exceeded": 3,
"syntax_error": 4,
"addr_error": 5,
"symbol_error": 6,
}
PREDEFINED_SYMBOL_CNT = 23
MAX_INST_LEN = 32768
MAX_ADDR = 32767
PREDEFINED_SYMBOLS = {
"SP": 0,
"LCL": 1,
"ARG": 2,
"THIS": 3,
"THAT": 4,
"R0": 0,
"R1": 1,
"R2": 2,
"R3": 3,
"R4": 4,
"R5": 5,
"R6": 6,
"R7": 7,
"R8": 8,
"R9": 9,
"R10": 10,
"R11": 11,
"R12": 12,
"R13": 13,
"R14": 14,
"R15": 15,
"SCREEN": 16384,
"KBD": 24576,
}
DEST = {
"": 0b000 << 3,
"M": 0b001 << 3,
"D": 0b010 << 3,
"MD": 0b011 << 3,
"A": 0b100 << 3,
"AM": 0b101 << 3,
"AD": 0b110 << 3,
"AMD": 0b111 << 3,
}
JMP = {
"": 0b000,
"JGT": 0b001,
"JEQ": 0b010,
"JGE": 0b011,
"JLT": 0b100,
"JNE": 0b101,
"JLE": 0b110,
"JMP": 0b111,
}
COMP = {
"0": 0b0101010 << 6,
"1": 0b0111111 << 6,
"-1": 0b0111010 << 6,
"D": 0b0001100 << 6,
"A": 0b0110000 << 6,
"M": 0b1110000 << 6,
"!D": 0b0001101 << 6,
"!A": 0b0110001 << 6,
"!M": 0b1110001 << 6,
"-D": 0b0001111 << 6,
"-A": 0b0110011 << 6,
"-M": 0b1110011 << 6,
"D+1": 0b0011111 << 6,
"A+1": 0b0110111 << 6,
"M+1": 0b1110111 << 6,
"D-1": 0b0001110 << 6,
"A-1": 0b0110010 << 6,
"M-1": 0b1110010 << 6,
"D+A": 0b0000010 << 6,
"A+D": 0b0000010 << 6,
"D+M": 0b1000010 << 6,
"M+D": 0b1000010 << 6,
"D-A": 0b0010011 << 6,
"D-M": 0b1010011 << 6,
"A-D": 0b0000111 << 6,
"M-D": 0b1000111 << 6,
"D&A": 0b0000000 << 6,
"A&D": 0b0000000 << 6,
"D&M": 0b1000000 << 6,
"M&D": 0b1000000 << 6,
"D|A": 0b0010101 << 6,
"A|D": 0b0010101 << 6,
"D|M": 0b1010101 << 6,
"M|D": 0b1010101 << 6,
}
def find_illegal_symbol_char(symbol):
for c in symbol:
if (not c.isascii()) or (not (c.isalnum() or c in "_.$:")):
return c
return None
def print_symbols(symbols):
print("====== SYMBOLS =====")
print("label\taddr")
for label, addr in symbols.items():
print(f"{label}\t{addr}")
def print_binary_and_asm(binary, asm_lines):
# binary and asm_lines are assumed to be of the same length
print("====== RESULTS =====")
print("addr\tbinary \tinst")
for line_no, bin, asm in zip(range(len(binary)), binary, asm_lines):
print(f"{line_no}\t{bin:016b}\t{asm}")
def write_binary(file, binary):
for inst in binary:
file.write(f"{inst:016b}\n")
def assemble_inst(asm_line):
if asm_line.startswith("@"):
# A instruction
addr_str = asm_line[1:]
addr = int(addr_str)
if addr > MAX_ADDR:
print(f"Address out of range: {addr}", file=stderr)
exit(EXIT_CODES["addr_error"])
return addr
else:
# dest=comp;jmp
inst = 0xE000
dest, _, rhs = asm_line.partition("=")
if not rhs:
rhs = dest
dest = ""
comp, _, jmp = rhs.partition(";")
if dest not in DEST:
print(f"Invalid destination: {dest}", file=stderr)
exit(EXIT_CODES["syntax_error"])
inst |= DEST[dest]
if jmp not in JMP:
print(f"Invalid jump instruction: {jmp}", file=stderr)
exit(EXIT_CODES["syntax_error"])
inst |= JMP[jmp]
if comp not in COMP:
print(f"Invalid computation: {comp}", file=stderr)
exit(EXIT_CODES["syntax_error"])
inst |= COMP[comp]
return inst
def assembler(input_fn, verbose):
try:
input_file = open(input_fn, "r")
except FileNotFoundError:
print(f"Cannot open input file: {input_fn}", file=stderr)
exit(EXIT_CODES["file_error"])
asm_lines = []
line = input_file.readline()
asm_line_cnt = 0
user_symbols = {}
while line:
line = line.rstrip("\n")
# throw away comment and whitespace
asm_line = line.partition("//")[0].replace(" ", "").replace("\t", "")
if not asm_line:
# skip blank or comment line
line = input_file.readline()
continue
if asm_line.startswith("(") and asm_line.endswith(")"):
# asm_line may be a label
label = asm_line[1:-1]
illegal_char = find_illegal_symbol_char(label)
if illegal_char is not None:
print(f"Illegal character: {illegal_char}", file=stderr)
exit(EXIT_CODES["illegal_char"])
if label in user_symbols or label in PREDEFINED_SYMBOLS:
print(f"Symbol {label} already exists", file=stderr)
exit(EXIT_CODES["symbol_error"])
user_symbols[label] = asm_line_cnt
else:
# asm_line may be an instruction
asm_lines.append(asm_line)
asm_line_cnt += 1
if asm_line_cnt > MAX_INST_LEN:
print(
f"Max number of instruction ({MAX_INST_LEN}) exceeded", file=stderr
)
exit(EXIT_CODE_SIZE_EXCEEDED)
line = input_file.readline()
input_file.close()
# find and assign address to variables on the fly
addr = 16 # variable addresses start at 16
for line_no, asm_line in enumerate(asm_lines):
if not asm_line.startswith("@"):
continue
addr_str = asm_line[1:] # whatever comes after the @
if not addr_str:
print("Address cannot be empty", file=stderr)
exit(EXIT_CODES["addr_error"])
if addr_str.isascii() and addr_str.isdecimal():
# address is decimal constant
continue
if addr_str in PREDEFINED_SYMBOLS:
asm_lines[line_no] = f"@{PREDEFINED_SYMBOLS[addr_str]}"
elif addr_str in user_symbols:
asm_lines[line_no] = f"@{user_symbols[addr_str]}"
else:
user_symbols[addr_str] = addr
asm_lines[line_no] = f"@{addr}"
addr += 1
binary = []
for asm_line in asm_lines:
binary.append(assemble_inst(asm_line))
if verbose:
print_symbols(user_symbols)
print_binary_and_asm(binary, asm_lines)
output_fn = (
input_fn[:-4] + ".hack" if input_fn.endswith(".asm") else input_fn + ".hack"
)
try:
output_file = open(output_fn, "w")
except:
print(f"Cannot open output file: {output_fn}", file=stderr)
write_binary(output_file, binary)
output_file.close()
print(f"Binary written to {output_fn}")
if __name__ == "__main__":
parser = ArgumentParser()
parser.add_argument("-v", "--verbose", action="store_true", help="verbose mode")
parser.add_argument("input_fn", help="input file in assembly")
args = parser.parse_args()
assembler(args.input_fn, args.verbose)
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