1 files changed, 269 insertions, 0 deletions
diff --git a/projects/hack-as/hack-as.py b/projects/hack-as/hack-as.py
new file mode 100644
index 0000000..bb70abc
--- /dev/null
+++ b/projects/hack-as/hack-as.py
@@ -0,0 +1,269 @@
+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)