From b7661fd2bb461e68493014c1406ace0281d899d0 Mon Sep 17 00:00:00 2001
From: "B. Watson" <urchlay@slackware.uk>
Date: Fri, 31 May 2024 17:51:52 -0400
Subject: unprotbas: detect truncated files, count invalid offsets.

---
 unprotbas.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

(limited to 'unprotbas.c')

diff --git a/unprotbas.c b/unprotbas.c
index 2961f1c..2290f47 100644
--- a/unprotbas.c
+++ b/unprotbas.c
@@ -79,6 +79,7 @@ unsigned short starp;
 /* positions where various parts of the file start,
 	derived from the header vars above. */
 unsigned short codestart;
+unsigned short code_end;
 unsigned short vnstart;
 unsigned short vvstart;
 int filelen;
@@ -131,7 +132,7 @@ void setword(int addr, int value) {
 void dump_header_vars(void) {
 	fprintf(stderr, "LOMEM  $%04x    VNTP $%04x   VNTD $%04x  VVTP $%04x\n", lomem, vntp, vntd, vvtp);
 	fprintf(stderr, "STMTAB $%04x  STMCUR $%04x  STARP $%04x\n", stmtab, stmcur, starp);
-	fprintf(stderr, "vnstart $%04x, vvstart $%04x, codestart $%04x\n", vnstart, vvstart, codestart);
+	fprintf(stderr, "vnstart $%04x, vvstart $%04x, codestart $%04x, code_end $%04x\n", vnstart, vvstart, codestart, code_end);
 }
 
 void read_header(void) {
@@ -145,6 +146,12 @@ void read_header(void) {
 	codestart = stmtab - TBL_OFFSET - (vntp - 256);
 	vnstart = vntp - TBL_OFFSET;
 	vvstart = vvtp - TBL_OFFSET;
+	code_end = starp - TBL_OFFSET;
+
+	if(filelen < code_end) {
+		fprintf(stderr, "Warning: file is truncated: %d bytes, should be %d.\n", filelen, code_end);
+	}
+
 	if(verbose) dump_header_vars();
 }
 
@@ -248,6 +255,9 @@ int fixcode(void) {
 			fprintf(stderr, ", %s.\n", (keepgarbage ? "keeping" : "removing"));
 		}
 		if(!keepgarbage) filelen = pos;
+	} else {
+		if(verbose)
+			fprintf(stderr, "No trailing garbage at EOF.\n");
 	}
 	return result;
 }
@@ -835,7 +845,7 @@ void parse_args(int argc, char **argv) {
 }
 
 int main(int argc, char **argv) {
-	int outbytes;
+	int outbytes, invoffs = 0;
 	parse_args(argc, argv);
 
 	filelen = readfile();
@@ -872,8 +882,11 @@ int main(int argc, char **argv) {
 			}
 		}
 
-		if(fixcode()) {
-			if(verbose) fprintf(stderr, "Fixed invalid offset in code.\n");
+		invoffs = fixcode();
+		if(invoffs) {
+			if(verbose)
+				fprintf(stderr, "Fixed %d invalid offset%s in code.\n",
+						invoffs, (invoffs == 1 ? "" : "s"));
 			was_protected = 1;
 		} else {
 			if(verbose) fprintf(stderr, "No invalid offsets.\n");
-- 
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