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Chapter 7 - Virtual Machine I: Stack Arithmetic
Python3 for Virtual Machine Translator. Python3 for VMT modules CodeWriter, Parser, and Command.
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‎07/vmt.py

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#!/usr/bin/env python3
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"""Virtual Machine Translator
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Translates the VM code (either a single .vm file
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or a directory of .vm files) into its Hack ASM
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equivalent, which can then be assembled and run
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on Hack.
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"""
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import sys
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from pathlib import Path
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from vmt_modules.parser import Parser
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from vmt_modules.command import Command
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from vmt_modules.code_writer import CodeWriter
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def main():
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vm_path = Path(sys.argv[-1])
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vm_glob = []
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asm_path = str(vm_path.parent) + '\\' + (vm_path.name[:vm_path.name.find('.')] + '.asm')
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if vm_path.name == 'vmt.py':
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raise IOError('Please supply a .vm source file, or a directory of .vm source files.')
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if vm_path.is_dir():
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vm_glob = list(vm_path.glob('*.vm'))
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if not vm_glob:
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raise RuntimeError('No *.vm files found in supplied directory.')
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asm_path = str(vm_path.parent) + '\\' + vm_path.name + '\\' + vm_path.name + '.asm'
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elif vm_path.is_file():
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if vm_path.suffix != '.vm':
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raise IOError('Valid VM source file not supplied.')
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vm_glob.append(vm_path)
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code_writer = CodeWriter(asm_path)
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for vm_file in vm_glob:
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vm_parser = Parser(vm_file)
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while vm_parser.has_more_commands():
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if vm_parser.command_type() is Command.C_ARITHMETIC:
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code_writer.write_arithmetic(vm_parser.arg1())
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elif vm_parser.command_type() is Command.C_PUSH:
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code_writer.write_push_pop(Command.C_PUSH, vm_parser.arg1(), vm_parser.arg2())
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elif vm_parser.command_type() is Command.C_POP:
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code_writer.write_push_pop(Command.C_POP, vm_parser.arg1(), vm_parser.arg2())
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else:
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raise NotImplementedError()
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code_writer.close()
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print('[=>] IN .vm file(s):')
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print(*vm_glob, sep='\n')
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print('[<=] OUT .asm file:\n' + asm_path)
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if __name__ == "__main__":
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main()

‎07/vmt_modules/code_writer.py

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#!/usr/bin/env python3
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"""The CodeWriter Module
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Translates given VM commands into Hack ASM code.
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"""
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from .command import Command
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class CodeWriter:
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def __init__(self, out_path):
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self.out_path = out_path
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self._dynamic_labels = {'lt':0, 'eq':0, 'gt':0}
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self._bool_jmp_logic_symbol = ''
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self._asm_file = open(out_path, 'w+')
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def set_file_name(self, file_name):
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"""Informs the code writer that the
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translation of a new VM file has started.
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(Possibly for dynamic label making)?
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"""
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def write_arithmetic(self, command):
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"""Writes the assembly code that is the
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translation of the given arithmetic
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command.
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"""
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self._asm_file.write('@SP\n')
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if command in ['neg', 'not']:
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self._asm_file.write('A=M-1\n')
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if command == 'neg':
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self._asm_file.write('M=-M\n')
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elif command == 'not':
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self._asm_file.write('M=!M\n')
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else:
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self._asm_file.write('AM=M-1\n')
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self._asm_file.write('D=M\n')
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self._asm_file.write('A=A-1\n')
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if command == 'add':
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self._asm_file.write('M=M+D\n')
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elif command == 'sub':
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self._asm_file.write('M=M-D\n')
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elif command in ['lt', 'eq', 'gt']:
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self._asm_file.write('D=M-D\n')
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self._asm_file.write('M=0\n')
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if command == 'lt':
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self._bool_jmp_logic_symbol = 'LTJGE$' + str(self._dynamic_labels['lt'])
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self._dynamic_labels['lt'] += 1
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self._asm_file.write('@'+self._bool_jmp_logic_symbol+'\n')
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self._asm_file.write('D;JGE\n')
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elif command == 'eq':
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self._bool_jmp_logic_symbol = 'EQJNE$' + str(self._dynamic_labels['eq'])
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self._dynamic_labels['eq'] += 1
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self._asm_file.write('@'+self._bool_jmp_logic_symbol+'\n')
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self._asm_file.write('D;JNE\n')
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elif command == 'gt':
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self._bool_jmp_logic_symbol = 'GTJLE$' + str(self._dynamic_labels['gt'])
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self._dynamic_labels['gt'] += 1
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self._asm_file.write('@'+self._bool_jmp_logic_symbol+'\n')
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self._asm_file.write('D;JLE\n')
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self._asm_file.write('@SP\n')
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self._asm_file.write('A=M-1\n')
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self._asm_file.write('M=-1\n')
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self._asm_file.write('('+self._bool_jmp_logic_symbol+')\n')
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elif command == 'and':
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self._asm_file.write('M=M&D\n')
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elif command == 'or':
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self._asm_file.write('M=M|D\n')
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def write_push_pop(self, command, segment, index):
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"""Writes the assembly code that is the
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translation of the given command, where
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command is either C_PUSH or C_POP.
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"""
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self._asm_file.write('@'+str(index)+'\n')
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self._asm_file.write('D=A\n')
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if command is Command.C_PUSH:
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if segment == 'constant':
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self._asm_file.write('@SP\n')
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self._asm_file.write('AM=M+1\n')
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self._asm_file.write('A=A-1\n')
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self._asm_file.write('M=D\n')
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elif segment in ['local', 'argument', 'this', 'that', 'pointer', 'temp', 'static']:
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if segment == 'local':
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self._asm_file.write('@LCL\n')
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self._asm_file.write('A=D+M\n')
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elif segment == 'argument':
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self._asm_file.write('@ARG\n')
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self._asm_file.write('A=D+M\n')
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elif segment == 'this':
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self._asm_file.write('@THIS\n')
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self._asm_file.write('A=D+M\n')
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elif segment == 'that':
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self._asm_file.write('@THAT\n')
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self._asm_file.write('A=D+M\n')
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elif segment == 'pointer':
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self._asm_file.write('@THIS\n')
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self._asm_file.write('A=D+A\n')
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elif segment == 'temp':
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self._asm_file.write('@5\n')
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self._asm_file.write('A=D+A\n')
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elif segment == 'static':
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self._asm_file.write('@16\n')
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self._asm_file.write('A=D+A\n')
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self._asm_file.write('D=M\n')
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self._asm_file.write('@SP\n')
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self._asm_file.write('AM=M+1\n')
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self._asm_file.write('A=A-1\n')
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self._asm_file.write('M=D\n')
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else:
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raise ValueError('Invalid segment ', segment)
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self.close()
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elif command is Command.C_POP:
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if segment in ['local', 'argument', 'this', 'that', 'pointer', 'temp', 'static']:
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if segment == 'local':
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self._asm_file.write('@LCL\n')
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self._asm_file.write('D=D+M\n')
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elif segment == 'argument':
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self._asm_file.write('@ARG\n')
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self._asm_file.write('D=D+M\n')
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elif segment == 'this':
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self._asm_file.write('@THIS\n')
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self._asm_file.write('D=D+M\n')
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elif segment == 'that':
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self._asm_file.write('@THAT\n')
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self._asm_file.write('D=D+M\n')
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elif segment == 'pointer':
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self._asm_file.write('@THIS\n')
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self._asm_file.write('D=D+A\n')
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elif segment == 'temp':
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self._asm_file.write('@5\n')
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self._asm_file.write('D=D+A\n')
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elif segment == 'static':
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self._asm_file.write('@16\n')
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self._asm_file.write('D=D+A\n')
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self._asm_file.write('@R13\n')
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self._asm_file.write('M=D\n')
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self._asm_file.write('@SP\n')
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self._asm_file.write('AM=M-1\n')
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self._asm_file.write('D=M\n')
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self._asm_file.write('@R13\n')
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self._asm_file.write('A=M\n')
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self._asm_file.write('M=D\n')
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else:
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raise ValueError('Invalid segment ', segment)
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self.close()
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else:
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raise ValueError('Invalid command ', command)
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self.close()
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def close(self):
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"""Closes the output Hack ASM file.
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"""
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self._asm_file.close()

‎07/vmt_modules/command.py

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#!/usr/bin/env python3
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"""Command Enum
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Provides an enum for the command types associated with
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the VM language.
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"""
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import enum
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__author__ = "Merrick Ryman"
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__version__ = "1.0"
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class Command(enum.Enum):
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C_ARITHMETIC = 1
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C_PUSH = 2
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C_POP = 3
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C_LABEL = 4
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C_GOTO = 5
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C_IF = 6
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C_FUNCTION = 7
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C_RETURN = 8
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C_CALL = 9

‎07/vmt_modules/parser.py

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#!/usr/bin/env python3
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"""The Parser Module
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Handles the parsing of a single .vm file, and encapsulates
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access to the input code. Overall: reads VM commands, parses them,
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and provides convenient access to their components. In addition,
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remove all white space and comments.
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"""
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from .command import Command
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class Parser:
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def __init__(self, in_path):
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self.in_path = in_path
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self._vm_commands = None
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self._vm_command_current = None
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self._vm_commands_iter = None
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self._parse_vm_file()
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self._reset_iter()
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def _parse_vm_file(self):
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"""Parse the Hack ASM file into memory so it
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is easier to work with. Remove comments, spaces,
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empty lines, etc, so all that remains are commands
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(and pseudo-commands). Also, create an iterable
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to get the next command.
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"""
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with open(self.in_path, 'r') as vm_file:
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lines = vm_file.readlines()
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lines = list(map(lambda x: x[:x.find('//')], lines))
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lines = list(filter(None, lines))
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self._vm_commands = self._format_vm_commands(lines)
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def _format_vm_commands(self, commands):
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"""Format a list of VM commands; in other words,
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break up the input arguments. Returns the
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commands in the form of a list of dictionaries.
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Each dictionary pertains to its particular
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command.
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"""
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formatted_list = []
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for command in commands:
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args_dict = {'name': None, 'arg1': None, 'arg2': None}
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args = command.split()
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args_dict['name'] = args[0]
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if len(args) == 2 or len(args) == 3:
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args_dict['arg1'] = args[1]
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if len(args) == 3:
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args_dict['arg2'] = args[2]
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formatted_list.append(args_dict)
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return formatted_list
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def _reset_iter(self):
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"""Resets (or sets) the iterator object that
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iterates over the vm commands. Useful for
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re-parsing the file as necessary.
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"""
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self._vm_commands_iter = iter(self._vm_commands)
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def has_more_commands(self):
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"""Are there any more commands in the file?
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Returns True if command iterable successfully
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gets the next command. Otherwise, return False.
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"""
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try:
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self._vm_command_current = next(self._vm_commands_iter)
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return True
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except StopIteration:
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return False
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def command_type(self):
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"""Returns the type of the current VM command.
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C_ARITHMETIC is returned for all the arithmetic
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commands.
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"""
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return {
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'push': Command.C_PUSH,
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'pop': Command.C_POP,
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'label': Command.C_LABEL,
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'goto': Command.C_GOTO,
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'if-goto': Command.C_IF,
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'function': Command.C_FUNCTION,
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'call': Command.C_CALL,
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'return': Command.C_RETURN
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}.get(self._vm_command_current['name'], Command.C_ARITHMETIC)
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def arg1(self):
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"""Returns the first argument of the current
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command. In the case of C_ARITHMETIC, the
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command itself (add, sub, etc.) is returned.
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Should not be called if the current command is
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C_RETURN.
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"""
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if self.command_type() is Command.C_ARITHMETIC:
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return self._vm_command_current['name']
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else:
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return self._vm_command_current['arg1']
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def arg2(self):
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"""Returns the second argument of the current
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command. Should only be called if the current
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command is C_PUSH, C_POP, C_FUNCTION, or
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C_CALL.
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"""
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return int(self._vm_command_current['arg2'])

‎README.md

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### Chapter 06 - Assembler
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Python3 for Hack Assembler and Hack Assembler(No Symbols).\
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Python3 for Assembler Modules Code, Command, Parser, and SymbolTable.
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Python3 for Assembler modules Code, Command, Parser, and SymbolTable.
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* **UPDATE 3/18/19:** Assembler module Parser v2.0 is now out! This adds support for macro-commands.
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* *For an example of this*, take a look at Max_no_macros.asm, Max_macros.asm, and their respective Hack files in the 06 project directory.
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* *Note that the Hack machine code is equivalent*, while the asm file with macro-commands has essentially halved.
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Of course, this also works for symbols: 'M=D[foo]' is equivalent to '@foo' followed by 'M=D'.
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### Chapter 07 - VM I: Stack Arithmetic
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#### In Progress (soon...)
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Python3 for Virtual Machine Translator.\
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Python3 for VMT modules CodeWriter, Parser, and Command.
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### Chapter 08 - VM II: Program Control
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#### In Progress.

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