M projects/06/assembler1/assembler1.c → projects/06/assembler1/assembler1.c

@@ -13,7 +13,7 @@ 
 #define MAX_LINE_LEN            256
 
 
-uint32_t myatoi(const char *a_field_str)
+static uint32_t myatoi(const char *a_field_str)
 {
 	size_t i;
 	uint32_t ret = 0;
@@ -25,7 +25,7 @@ 
 	return ret;
 }
 
-bool parse_a_type(const char *line, uint16_t *instruction)
+static bool parse_a_type(const char *line, uint16_t *instruction)
 {
 	char c, a_field_str[6];  // TODO: eventually factor out use of array
 	uint32_t a_field = 0;
@@ -71,17 +71,143 @@ *instruction = 0x0000 | (uint16_t) a_field;
 	return true; // STUB, A-type MSB == 0 anyway
 }
 
-bool parse_c_type(const char *line, uint16_t *instruction)
+/* returns dest bits 0b00000ddd
+ */
+static bool parse_c_type_dest(const char *dest_line, uint8_t *dest)
 {
-	// Note: could do 'jump' fields via lookup tables once
-	// they're extracted from the line
-	*instruction = 0x8888; // STUB, TODO implement
+	DEBUG("dest_line: %s\n", dest_line);
+
+	/* if 'A'
+	 *     if 'D'
+	 *         if 'M'
+	 *     else if '='
+	 * if 'D'
+	 *     if 'M'
+	 *     else if '='
+	 * if 'M'
+	 *     if '='
+	 * default:
+	 *     "syntax error"
+	 */
+
+	*dest = 0x03;  // 0b00000011
+	return true;
+}
+
+/* returns comp bits 0b0acccccc
+ */
+static bool parse_c_type_comp(const char *comp_line, uint8_t *comp)
+{
+	DEBUG("comp_line: %s\n", comp_line);
+	*comp = 0x53;  // 0b01010011
+	return true;
+}
+
+/* returns jump bits 0b00000jjj
+ */
+static bool parse_c_type_jump(const char *jump_line, uint8_t *jump)
+{
+	// Note: can do 'jump' fields via lookup tables once extracted from line
+	DEBUG("jump_line: %s\n", jump_line);
+	
+	/* if 'J'
+	 *     if 'G'
+	 *         if 'T'
+	 *         if 'E'
+	 *     if 'E'
+	 *         if 'Q'
+	 *     if 'L'
+	 *         if 'T'
+	 *         if 'E'
+	 *     if 'N'
+	 *         if 'E'
+	 *     if 'M'
+	 *         if 'P'
+	 * default:
+	 *     "syntax error"
+	 */
+
+	*jump = 0x01;  // 0b00000001
+	return true;
+}
+
+/* Instruction format: 0b111accccccdddjjj
+ * Assumes line begins with actual instruction (prepended whitespace stripped)
+ */
+static bool parse_c_type(const char *line, uint16_t *instruction)
+{
+	bool ret;
+	char c;
+	char *dest_start = NULL;
+	char *comp_start = NULL;
+	char *jump_start = NULL;
+	size_t i = 0;
+	uint8_t dest = 0;
+	uint8_t comp = 0;
+	uint8_t jump = 0;
+
+	c = line[0];
+	for (i = 0; c != ' ' && c != '\t' &&
+	            c != '\n' && c != '\0'; ++i) {
+		c = line[i];
+
+		if (c == '=') {
+			if (1 <= i && i <= 3) {
+				dest_start = &line[0];   // start of line
+				comp_start = &line[i+1]; // after "[dest]="
+			} else {
+				//syntax error
+				alert("syntax error: destination field in line"
+				      " incorrectly formatted\n");
+				return false;
+			}
+		} else if (c == ';') {
+			if (1 <= i && i <= 7) {
+				jump_start = &line[i+1]; // after "[comp];"
+			} else {
+				//syntax error
+				alert("syntax error: jump field in line"
+				      " incorrectly formatted\n");
+				return false;
+			}
+		}
+	}
+
+	// Only the comp field is mandatory for assembly instructions;
+	// dest and jump fields are optional, and may/may not be present
+	if (comp_start == NULL) {
+		comp_start = &line[0];  // start of line (no dest field)
+	}
+
+	ret = parse_c_type_comp(comp_start, &comp);
+	if (!ret) {
+		return false;
+	}
+
+	if (dest_start != NULL) {
+		ret = parse_c_type_dest(dest_start, &dest);
+		if (!ret) {
+			return false;
+		}
+	}
+
+	if (jump_start != NULL) {
+		ret = parse_c_type_jump(jump_start, &jump);
+		if (!ret) {
+			return false;
+		}
+	}
+
+	// STUB: DM=D-M;JGT  // 0b111 1010011 011 001
+	*instruction = 0xe000 | ((uint16_t)comp << 6)
+	                      | ((uint16_t)dest << 3)
+	                      | ((uint16_t)jump);
 	return true;
 }
 
 // does not care about line line length; exits at first newline or after
 // relevant portion parsed (allows for syntactically-incorrect lines, I know)
-bool parse_next_instruction(const char *line, uint16_t *instruction)
+static bool parse_next_instruction(const char *line, uint16_t *instruction)
 {
 	bool ret;
 	char c;