Sanity-check and warn for bad Atari filenames. Needs refinement.

1 files changed, 42 insertions, 0 deletions

diff --git a/src/extract.c b/src/extract.c
index 515d2dd..dc6a4f1 100644
--- a/src/extract.c
+++ b/src/extract.c
@@ -52,6 +52,47 @@ void make_backup(void) {
 	rename(out_filename, backup);
 }
 
+static void bad_atari_filename(const char *msg) {
+	fprintf(stderr, "%s: bad Atari filename: %s\n", self, msg);
+}
+
+/* note to self: it's tempting to use isalpha(), isprint(), etc
+	from ctype.h... but those are locale-aware. we want ASCII-only
+	versions. */
+static void sanity_check_filename(void) {
+	u8 c;
+	unsigned int i, bad = 0, dots = 0;
+
+	c = out_filename[0];
+	if(!c) {
+		bad_atari_filename("empty! corrupt ALF file?");
+		return;
+	} else if(c < 'A' || c > 'Z') {
+		bad_atari_filename("does not begin with A-Z");
+	}
+
+	for(i = 0; (c = out_filename[i]) && i < 12; i++) {
+		if(c >= 'A' && c <= 'Z')
+			continue;
+		if(c >= '0' && c <= '9')
+			continue;
+		if(c == '.') {
+			dots++;
+			continue;
+		}
+		bad++;
+	}
+
+	if(!dots) {
+		bad_atari_filename("no \".\"");
+	} else if(dots > 1) {
+		bad_atari_filename("more than one \".\"");
+	}
+
+	if(bad)
+		bad_atari_filename("invalid characters. corrupt ALF file?");
+}
+
 void extract_alf(void) {
 	/* get ready to call fake 6502 stuff. set up memory like the Atari. */
 	dpoke(MEMTOP, 0xbc1f);
@@ -59,6 +100,7 @@ void extract_alf(void) {
 	while(read_alf_header()) {
 		out_filename = (char *)(mem + alf_hdr_filename);
 
+		sanity_check_filename();
 		fix_filename();
 
 		if(!file_wanted(out_filename)) {