1 files changed, 125 insertions, 0 deletions
diff --git a/projects/hack-vm/function.py b/projects/hack-vm/function.py
new file mode 100644
index 0000000..596c9cf
--- /dev/null
+++ b/projects/hack-vm/function.py
@@ -0,0 +1,125 @@
+CALL_ASM = """@{return_address}
+D=A
+@SP
+A=M
+M=D
+@LCL
+D=A
+@SP
+AM=M+1
+M=D
+@ARG
+D=A
+@SP
+AM=M+1
+M=D
+@THIS
+D=A
+@SP
+AM=M+1
+M=D
+@THAT
+D=A
+@SP
+AM=M+1
+M=D
+@SP
+DM=M+1
+@LCL
+M=D
+@{arg_lcl_offset}
+D=D-A
+@ARG
+M=D
+@{function_label}
+0;JMP
+({return_address})
+"""
+
+FUNCTION_ASM = """({function_label})
+@SP
+A=M
+M=0
+{init_vars}@SP
+M=M+1
+"""
+
+# repeated for each local variable of function
+INIT_VAR_ASM = """@SP
+AM=M+1
+M=0
+"""
+
+RETURN_ASM = """@ARG
+A=M
+D=M
+@{tmp}
+M=D
+@SP
+A=M-1
+D=M
+@ARG
+A=M
+M=D
+@ARG
+D=M+1
+@SP
+M=D
+@LCL
+AM=M-1
+D=M
+@THAT
+M=D
+@LCL
+AM=M-1
+D=M
+@THIS
+M=D
+@LCL
+AM=M-1
+D=M
+@ARG
+M=D
+@LCL
+AM=M-1
+D=M
+@LCL
+M=D
+@{tmp}
+A=M
+0;JMP
+"""
+
+ret_idx = {}
+
+
+def translate_function(action, function, n, prog, verbose=False):
+    global ret_idx
+    try:
+        n = int(n)
+    except ValueError:
+        exit_on_error(f"Syntax error: not an integer: {n}", EXIT_CODE_SYNTAX_ERROR)
+
+    asm = f"// {action} {function} {n}\n" if verbose else ""
+    if action == "call":
+        if prog not in ret_idx:
+            ret_idx[prog] = 0
+        else:
+            ret_idx[prog] += 1
+        asm += CALL_ASM.format(
+            return_address=f"{prog}$ret.{ret_idx[prog]}",
+            arg_lcl_offset=(5 + n),
+            function_label=f"{function}",
+        )
+    else:
+        asm += FUNCTION_ASM.format(
+            function_label=f"{function}", init_vars=INIT_VAR_ASM * (n - 1)
+        )
+
+    return asm
+
+
+def translate_return(verbose=False):
+    asm = "// return\n" if verbose else ""
+    asm += RETURN_ASM.format(tmp="R13")
+    return asm