unprotbas: replace some magic numbers with constants.

1 files changed, 23 insertions, 12 deletions

diff --git a/unprotbas.c b/unprotbas.c
index bf8fc76..acfd528 100644
--- a/unprotbas.c
+++ b/unprotbas.c
@@ -15,7 +15,9 @@
 	   or whatever), we "fix" that by making up new variable names.
 */
 
-#define STM_OFFSET 0xf2
+/* the difference between the VVTP and VNTP values in the file, and the
+	actual file positions of the variable names and values. */
+#define TBL_OFFSET 0xf2
 
 /* minimum program size, for a program that has no variables and
 	only one line of code (the immediate line 32768, consisting only of
@@ -23,14 +25,22 @@
 	can't process. */
 #define MIN_PROG_SIZE 21
 
-#define MAP_FILE "varnames.txt"
+/* maximum size of the program in memory. 64KB is actually way overkill. */
+#define BUFSIZE 65536
+
+/* maximum number of variables in the variable name and value tables. this
+	could be 128, but "ERROR- 4" still expands the tables. Entries >128
+	don't have tokens, can't be referred to in code, but we'll preserve
+	them anyway. */
+#define MAXVARS 256
 
 /* entire file gets read into memory (for now) */
-unsigned char data[65536];
+unsigned char data[BUFSIZE];
 
 /* for the -r option */
-unsigned char varnames[65536];
-unsigned char *varmap[256];
+#define MAP_FILE "varnames.txt"
+unsigned char varnames[BUFSIZE];
+unsigned char *varmap[MAXVARS];
 int varmap_count;
 
 /* BASIC 14-byte header values */
@@ -108,9 +118,9 @@ void read_header(void) {
 	stmtab = getword(8);
 	stmcur = getword(10);
 	starp = getword(12);
-	codestart = stmtab - STM_OFFSET - (vntp - 256);
-	vnstart = vntp - 256 + 14;
-	vvstart = vvtp - 256 + 14;
+	codestart = stmtab - TBL_OFFSET - (vntp - 256);
+	vnstart = vntp - TBL_OFFSET;
+	vvstart = vvtp - TBL_OFFSET;
 	if(verbose) dump_header_vars();
 }
 
@@ -294,6 +304,7 @@ void move_code(int offset) {
 	or letter+number or one-letter string/array names).
 */
 
+/* return true if the variable name table is OK */
 int vntable_ok(void) {
 	int vp, bad;
 
@@ -355,8 +366,8 @@ int rebuild_vntable(int write) {
 		unsigned char type = data[vv] >> 6;
 		/* fprintf(stderr, "%04x: %04x, %d\n", vv, data[vv], type); */
 
-		if(varnum == 256) {
-			fprintf(stderr, "Warning: skipping variable numbers >=256 in value table.\n");
+		if(varnum == MAXVARS) {
+			fprintf(stderr, "Warning: skipping variable numbers >=%d in value table.\n", MAXVARS);
 			break;
 		}
 
@@ -396,7 +407,7 @@ int rebuild_vntable(int write) {
 	}
 
 	/* there's supposed to be a null byte at the end of the table, unless
-		all 128 table slots are used... except really, there can be 129
+		all 128 table slots are used... except really, there can be >=129
 		entries, and there's always a null byte. */
 	if(write) data[vp] = 0;
 	size++;
@@ -560,7 +571,7 @@ void read_var_map(void) {
 }
 
 void apply_var_map(void) {
-	unsigned char new_vntable[65536];
+	unsigned char new_vntable[BUFSIZE];
 	int i, newp = 0;
 	unsigned char *v;