M projects/08/src/codewriter.h → projects/08/src/codewriter.h

@@ -33,11 +33,11 @@ #define STATIC   (16)  // start of static variables segment (240 words, 16-255)
 
 char *static_sym_name;
 
-// static segment index indexes into map, retrieves hack assembly symbol offset
+// retrieve hack assembly RAM offset given static "symbol" number
 #define MAX_STATIC_SYMBOLS  (240)  // for whatever.
-uint16_t static_symbol_map[MAX_STATIC_SYMBOLS];
-uint8_t g_symbol_offset_bump = 0;  // holds current largest symbol offset, bumps
-
+uint16_t static_symbol_map[MAX_STATIC_SYMBOLS];  // 0..239 maps to 16..255
+uint8_t g_symbol_offset_start = 0;  // set to g_symbol_offset_stop on new file
+uint8_t g_symbol_offset_stop = 0;   // bump when new static number (sym) found
 
 char comp_vm_funcs[] = "@__comp_funcs_end\n"
                        "0;JMP\n"
@@ -97,13 +97,17 @@ "0;JMP\n"              // return
                        "\n"
                        "(__comp_funcs_end)\n";
 
-char vm_init[] = "@256\n"       // start address of stack (nothing pushed yet)
-                 "D=A\n"        // D = 256
+char vm_init[] = "@261\n"       // start address of stack (nothing pushed yet)
+                 "D=A\n"        // D = 261 (why? because we are simulating a
+				// "call", and a call would add 5 to SP, which
+				// is expected to be initialized to 256.
+				// TODO: verify if I also need to init LCL, ARG
+				// THIS/THAT etc... (I probably don't)
                  "@SP\n"        // A = <constant representing address of SP>
                  "M=D\n"        // <memory pointed to by SP> = 256
                  "@Sys.init\n"  // jump to Sys.init function (not call since
                  "0;JMP\n\n";   // we don't need to set up the stack)
-// TODO: add initializers for argument, local, static, constant, this, that
+// TODO: add initializers for argument, local, static, this, that
 
 // TODO only output vm_stop when Main.main
 char vm_stop[] = "(END)\n"   // starting address of stack (nothing pushed yet)
@@ -197,30 +201,35 @@ 
 	return true;
 }
 
+// attempt to either 1) resolve an existing static variable, or 2) associate
+// the static variable with a new slot in the static section (which can later
+// be resolved)
 static bool resolve_static_address(struct vm_instruction_t *vm_instr,
                                    uint16_t *addr)
 {
-	uint16_t symbol_offset;
-	if (vm_instr->arg2 >= MAX_STATIC_SYMBOLS) {
-		err("error: arg2 too large, >= %u\n", MAX_STATIC_SYMBOLS);
+	uint16_t sym_offset;
+	// Basically, g_symbol_offset_start "indexes" into the VM files', and
+	// g_symbol_offset_stop indexes the last added static var per file.
+	// These variables serve as a window into static_symbol_map
+	if (g_symbol_offset_stop >= MAX_STATIC_SYMBOLS) {
+		err("error: symbol offset grew too large (>= %u), too many "
+		    "static variables\n", MAX_STATIC_SYMBOLS);
 		return false;
 	}
 
-	symbol_offset = static_symbol_map[vm_instr->arg2];
-	if (symbol_offset == 0xffff) {  // new offset not in map (-1 special)
-		if (g_symbol_offset_bump >= MAX_STATIC_SYMBOLS) {
-			err("error: symbol offset grew too large (>= %u), "
-			    "too many static variables\n", MAX_STATIC_SYMBOLS);
-			return false;
+	for (sym_offset = g_symbol_offset_start;
+	     sym_offset <= g_symbol_offset_stop; ++sym_offset) {
+		// found static "symbol" (number after push/pop static ...)
+		if (static_symbol_map[sym_offset] == vm_instr->arg2) {
+			*addr = sym_offset + 16;
+			return true;
 		}
-		static_symbol_map[vm_instr->arg2] = g_symbol_offset_bump;
-		*addr = g_symbol_offset_bump;
-		++g_symbol_offset_bump;  // bump global symbol offset
-	} else {
-		// offset found in map, return symbol value/index
-		*addr = symbol_offset;
 	}
 
+	// insert vm_instr->arg2 into next static_symbol_map slot
+	static_symbol_map[g_symbol_offset_stop] = vm_instr->arg2;
+	++g_symbol_offset_stop;                   // bump stop offset
+	*addr = (g_symbol_offset_stop - 1) + 16;  // add 16 to map to RAM
 	return true;
 }
 
@@ -491,6 +500,8 @@ "A=M\n"      // A = retAddr
 	                         "0;JMP\n"    // return
 	                         "\n";
 
+	// idea: make global function, "call" this function when doing 'return'
+	// similar to conditional branch (TODO)
 	fprintf(fp, "%s", ret_boilerplate);
 	return true;
 }

M projects/08/src/util.h → projects/08/src/util.h

@@ -21,6 +21,9 @@ 
 extern char  *file_line;     // reference to currently-read line (for convenience)
 extern size_t file_line_no;  // line number, regardless of line content
 
+extern uint8_t g_symbol_offset_start;
+extern uint8_t g_symbol_offset_stop;
+
 #define err(...) (fprintf(stdout, __VA_ARGS__), \
                   fprintf(stdout, "%lu | %s\n", file_line_no, file_line))
 #define die(...)   do { fprintf(stderr, __VA_ARGS__); exit(-1); } while (0)

M projects/08/src/vmtranslator.c → projects/08/src/vmtranslator.c

@@ -102,6 +102,7 @@ size_t i, line_len;
 
 	if (add_init)
 		write_vm_init(out_file);
+	//g_symbol_offset_bump = 0;  // reset symbol map pointer (might be bug/unnecessary)
 	for (i = 0; i < MAX_STATIC_SYMBOLS; ++i)
 		static_symbol_map[i] = -1;  // initialize symbol map table
 
@@ -148,6 +149,7 @@ FILE *in_file = fopen(vm_file_path, "r"); // read input file
 	if (in_file == NULL)
 		die("failed to open %s for reading\n", vm_file_path);
 
+	g_symbol_offset_start = g_symbol_offset_stop;  // bump on new file
 	if (!set_static_symbol_name(vm_file_path))
 		die("error reading file name %s\n", vm_file_path);
 	fprintf(out_file, "// path: %s\n", vm_file_path);  // for debugging