unprotbas: grow variable name table, if needed.

1 files changed, 88 insertions, 25 deletions

diff --git a/unprotbas.c b/unprotbas.c
index 9c45fbb..70741e3 100644
--- a/unprotbas.c
+++ b/unprotbas.c
@@ -8,6 +8,7 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <stdlib.h>
+#include <string.h>
 
 /* attempt to fix a "list-protected" Atari 8-bit BASIC program.
 	we don't fully detokenize, so this won't fix truly corrupted
@@ -71,6 +72,46 @@ unsigned short getword(int addr) {
 	return data[addr] | (data[addr + 1] << 8);
 }
 
+void setword(int addr, int value) {
+	data[addr] = value & 0xff;
+	data[addr + 1] = value >> 8;
+}
+
+void dump_header_vars(void) {
+	fprintf(stderr, "LOMEM %04x\n", lomem);
+	fprintf(stderr, "VNTP %04x\n", vntp);
+	fprintf(stderr, "VNTD %04x\n", vntd);
+	fprintf(stderr, "VVTP %04x\n", vvtp);
+	fprintf(stderr, "STMTAB %04x, codestart %04x\n", stmtab, codestart);
+	fprintf(stderr, "STMCUR %04x\n", stmcur);
+	fprintf(stderr, "STARP %04x\n", starp);
+	fprintf(stderr, "vvstart %04x\n", vvstart);
+}
+
+void read_header(void) {
+	lomem = getword(0);
+	vntp = getword(2);
+	vntd = getword(4);
+	vvtp = getword(6);
+	stmtab = getword(8);
+	stmcur = getword(10);
+	starp = getword(12);
+	codestart = stmtab - STM_OFFSET - (vntp - 256);
+	vnstart = vntp - 256 + 14;
+	vvstart = vvtp - 256 + 14;
+	dump_header_vars();
+}
+
+void set_header_vars(void) {
+	setword(0, lomem);
+	setword(2, vntp);
+	setword(4, vntd);
+	setword(6, vvtp);
+	setword(8, stmtab);
+	setword(10, stmcur);
+	setword(12, starp);
+}
+
 /* fixline() calculates & sets correct line length, by iterating
 	over the statement(s) within the line. the last statement's
 	offset will be the same as the line offset should have been,
@@ -157,6 +198,21 @@ int fixcode(void) {
 	return result;
 }
 
+/* sometimes the variable name table isn't large enough to hold
+	the generated variable names. move_code_up() makes more space,
+	by moving the rest of the program (including the variable value
+	table) up in memory. */
+void move_code_up(int offset) {
+	memmove(data + vvstart + offset, data + vvstart, filelen);
+	vvtp += offset;
+	stmtab += offset;
+	stmcur += offset;
+	starp += offset;
+	set_header_vars();
+	read_header();
+	filelen += offset;
+}
+
 /* Fixing the variables is a bit more work than it seems like
 	it might be, because the last byte of the name has to match
 	the type (inverse video "(" for numeric array, inverse "$" for
@@ -171,9 +227,10 @@ int fixcode(void) {
 	the file.
 
 	We can find the actual table size in the file by subtracting VNTP
-	(start of variable name table) from VNTD (end of variable name table),
-	and if we run out of space for the generated names, something is
-	seriously off...
+	(start of variable name table) from VNTD (end of variable name table).
+	It's possible that the table size is too small for the generated
+	variable names, in which case we have to call move_code_up() to
+	make more room.
 
 	The maximum number of variable names is 128. If all 128 vars are in
 	use, the minimum table size is 230 (26 one-letter names, 102 2-letter
@@ -214,7 +271,9 @@ int fixvars(void) {
 	vp = vnstart;
 	while(vp < vvstart) {
 		unsigned char c = data[vp];
+		/*
 		fprintf(stderr, "%04x/%04x: %04x\n", vp, vvstart, c);
+		*/
 
 		/* allow a null byte only at the end of the table! */
 		/* if(c == 0 && vp == vvstart - 1) break; */
@@ -237,7 +296,26 @@ int fixvars(void) {
 	}
 	if(!forcevars && !bad) return 0;
 
+	/* decide whether we have enough room. pretend every new variable name
+		is 3 bytes (really only true for the 10th and later strings and
+		arrays, but a little wasted space won't hurt anything). */
+	{
+		int vntblsize = vvstart - vnstart;
+		int varcount = (codestart - vvstart) / 8;
+		int neededsize = varcount * 3 + 1;
+		int move_up_by;
+
+		fprintf(stderr, "%d variables according to value table\n", varcount);
+		if(neededsize > vntblsize) {
+			move_up_by = neededsize - vntblsize;
+			fprintf(stderr, "need %d bytes for vntable, only have %d, moving up by %d to %04x\n",
+					neededsize, vntblsize, move_up_by, vvtp + move_up_by);
+			move_code_up(move_up_by);
+		}
+	}
+
 	vp = vnstart;
+	vv = vvstart;
 	while(vv < codestart) {
 		unsigned char sigil = 0;
 		/* type: scalar = 0, array = 1, string = 2 */
@@ -259,8 +337,8 @@ int fixvars(void) {
 			data[vp] = ('A' + varname);
 		} else {
 			varname -= 26;
-			data[vp++] = 'A' + (varname / 9);
-			data[vp] = ('1' + (varname % 9));
+			data[vp++] = 'A' + ((varname - 26) / 9);
+			data[vp] = ('1' + ((varname - 26) % 9));
 		}
 
 		if(sigil) {
@@ -327,6 +405,10 @@ void open_input(const char *name) {
 
 void open_output(const char *name) {
 	if(!name) {
+		if(isatty(fileno(stdout))) {
+			fprintf(stderr, "%s: refusing to write binary data to standard output\n", self);
+			exit(1);
+		}
 		if(freopen(NULL, "wb", stdout)) {
 			output_file = stdout;
 			return;
@@ -381,29 +463,10 @@ int main(int argc, char **argv) {
 	parse_args(argc, argv);
 
 	filelen = readfile();
-
-	lomem = getword(0);
-	vntp = getword(2);
-	vntd = getword(4);
-	vvtp = getword(6);
-	stmtab = getword(8);
-	stmcur = getword(10);
-	starp = getword(12);
-	codestart = stmtab - STM_OFFSET - (vntp - 256);
-	vnstart = vntp - 256 + 14;
-	vvstart = vvtp - 256 + 14;
+	read_header();
 
 	if(lomem) die("This doesn't look like an Atari BASIC program (no $0000 signature)");
 
-	fprintf(stderr, "LOMEM %04x\n", lomem);
-	fprintf(stderr, "VNTP %04x\n", vntp);
-	fprintf(stderr, "VNTD %04x\n", vntd);
-	fprintf(stderr, "VVTP %04x\n", vvtp);
-	fprintf(stderr, "STMTAB %04x, codestart %04x\n", stmtab, codestart);
-	fprintf(stderr, "STMCUR %04x\n", stmcur);
-	fprintf(stderr, "STARP %04x\n", starp);
-	fprintf(stderr, "vvstart %04x\n", vvstart);
-
 	/*
 	fprintf(stderr, "data at STMTAB (we hope):\n");
 	for(int i=codestart; i<filelen; i++) {