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

@@ -75,22 +75,49 @@ /* returns dest bits 0b00000ddd
  */
 static bool parse_c_type_dest(const char *dest_line, uint8_t *dest)
 {
-	DEBUG("dest_line: %s\n", dest_line);
+	size_t len;
 
-	/* if 'A'
-	 *     if 'D'
-	 *         if 'M'
-	 *     else if '='
-	 * if 'D'
-	 *     if 'M'
-	 *     else if '='
-	 * if 'M'
-	 *     if '='
-	 * default:
-	 *     "syntax error"
-	 */
+	for (len = 0; dest_line[len] != '='; ++len) {}  // read until '='
 
-	*dest = 0x03;  // 0b00000011
+	if (len == 3) {
+		if (dest_line[0] == 'A' && dest_line[1] == 'D' &&
+		    dest_line[2] == 'M') {
+			*dest = 0x7;
+		} else {
+			alert("syntax error: destination format incorrect\n");
+			return false;
+		}
+	} else if (len == 2) {
+		if (dest_line[0] == 'D' && dest_line[1] == 'M') {
+			*dest = 0x3;
+		} else if (dest_line[0] == 'A' && dest_line[1] == 'M') {
+			*dest = 0x5;
+		} else if (dest_line[0] == 'A' && dest_line[1] == 'D') {
+			*dest = 0x6;
+		} else {
+			alert("syntax error: destination format incorrect\n");
+			return false;
+		}
+	} else if (len == 1) {
+		switch (dest_line[0]) {
+		case 'M':
+			*dest = 0x1;
+			break;
+		case 'D':
+			*dest = 0x2;
+			break;
+		case 'A':
+			*dest = 0x4;
+			break;
+		default:
+			alert("syntax error: destination format incorrect\n");
+			return false;
+		}
+	} else {
+		alert("syntax error: dest field incorrect length %lu\n", len);
+		return false;
+	}
+
 	return true;
 }
 
@@ -98,8 +125,10 @@ /* returns comp bits 0b0acccccc
  */
 static bool parse_c_type_comp(const char *comp_line, uint8_t *comp)
 {
+	size_t len;
 	DEBUG("comp_line: %s\n", comp_line);
-	*comp = 0x53;  // 0b01010011
+
+	*comp = 0x53;  // STUB: 0b01010011
 	return true;
 }
 
@@ -108,13 +137,10 @@ */
 static bool parse_c_type_jump(const char *jump_line, uint8_t *jump)
 {
 	size_t len;
-	char j0, j1, j2;
 	char *err_1st_char = "syntax error: jump field doesn't start with 'J'\n";
 	char *err_2nd_char = "syntax error: 2nd letter in jump field incorrect\n";
 	char *err_3rd_char = "syntax error: 3rd letter in jump field incorrect\n";
 
-	DEBUG("jump_line: %s\n", jump_line);
-
 	for (len = 0; jump_line[len] == 'J' || jump_line[len] == 'G' ||
 	              jump_line[len] == 'T' || jump_line[len] == 'E' ||
 	              jump_line[len] == 'Q' || jump_line[len] == 'L' ||
@@ -125,46 +151,42 @@ alert("syntax error: jump field incorrect length %lu\n", len);
 		return false;
 	}
 
-	j0 = jump_line[0];
-	j1 = jump_line[1];
-	j2 = jump_line[2];
-
-	if (j0 == 'J') {                         // if "J__"
-		switch (j1) {
-		case 'G':                        // if "JG_"
-			if (j2 == 'T') {         // if "JGT"
+	if (jump_line[0] == 'J') {                         // if "J__"
+		switch (jump_line[1]) {
+		case 'G':                                  // if "JG_"
+			if (jump_line[2] == 'T') {         // if "JGT"
 				*jump = 0x1;
-			} else if (j2 == 'E') {  // if "JGE"
+			} else if (jump_line[2] == 'E') {  // if "JGE"
 				*jump = 0x3;
 			} else {
 				alert(err_3rd_char); return false;
 			}
 			break;
-		case 'E':                        // if "JE_"
-			if (j2 == 'Q') {         // if "JEQ"
+		case 'E':                                  // if "JE_"
+			if (jump_line[2] == 'Q') {         // if "JEQ"
 				*jump = 0x2;
 			} else {
 				alert(err_3rd_char); return false;
 			}
 			break;
-		case 'L':                        // if "JL_"
-			if (j2 == 'T') {         // if "JLT"
+		case 'L':                                  // if "JL_"
+			if (jump_line[2] == 'T') {         // if "JLT"
 				*jump = 0x4;
-			} else if (j2 == 'E') {  // if "JLE"
+			} else if (jump_line[2] == 'E') {  // if "JLE"
 				*jump = 0x6;
 			} else {
 				alert(err_3rd_char); return false;
 			}
 			break;
-		case 'N':                        // if "JN_"
-			if (j2 == 'E') {         // if "JNE"
+		case 'N':                                  // if "JN_"
+			if (jump_line[2] == 'E') {         // if "JNE"
 				*jump = 0x5;
 			} else {
 				alert(err_3rd_char); return false;
 			}
 			break;
-		case 'M':                        // if "JM_"
-			if (j2 == 'P') {         // if "JMP"
+		case 'M':                                  // if "JM_"
+			if (jump_line[2] == 'P') {         // if "JMP"
 				*jump = 0x7;
 			} else {
 				alert(err_3rd_char); return false;
@@ -189,9 +211,9 @@ 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;
+	const char *dest_start = NULL;
+	const char *comp_start = NULL;
+	const char *jump_start = NULL;
 	size_t i = 0;
 	uint8_t dest = 0;  // default value when not present
 	uint8_t comp = 0;
@@ -208,9 +230,8 @@ dest_start = &line[0];   // start of line
 				// this 'i+1' might be dangerous!
 				comp_start = &line[i+1]; // after "[dest]="
 			} else {
-				//syntax error
-				alert("syntax error: destination field in line"
-				      " incorrectly formatted\n");
+				alert("syntax error: destination field"
+				      " incorrect length\n");
 				return false;
 			}
 		} else if (c == ';') {
@@ -218,9 +239,8 @@ if (1 <= i && i <= 7) {
 				// this 'i+1' might be dangerous!
 				jump_start = &line[i+1]; // after "[comp];"
 			} else {
-				//syntax error
-				alert("syntax error: jump field in line"
-				      " incorrectly formatted\n");
+				alert("syntax error: jump field incorrect"
+				      " length\n");
 				return false;
 			}
 		}
@@ -251,7 +271,6 @@ return false;
 		}
 	}
 
-	// STUB: DM=D-M;JGT  // 0b111 1010011 011 001
 	*instruction = 0xe000 | ((uint16_t)comp << 6)
 	                      | ((uint16_t)dest << 3)
 	                      | ((uint16_t)jump);