unalf: Fix -F for small input files.

1 files changed, 17 insertions, 5 deletions

diff --git a/src/io.c b/src/io.c
index 294751a..cc50b8b 100644
--- a/src/io.c
+++ b/src/io.c
@@ -73,14 +73,26 @@ static void sanity_check_header(long pos) {
 
 	if(compsize > (s.st_size - pos)) {
 		fatal = !(opts.force || opts.listonly);
-		fprintf(stderr, "%s: %s: compressed size for header #%d is bigger than the rest of the file (truncated?), use -F to override.\n", fatal ? "fatal" : "warning", self, headers_read);
-		if(fatal) exit(1);
+		fprintf(stderr, "%s: %s: compressed size for header #%d is bigger than the rest of the file (truncated?)", self, fatal ? "fatal" : "warning", headers_read);
+		if(fatal) {
+			fputs(", use -F to override.\n", stderr);
+			exit(1);
+		}
+		fputs("\n", stderr);
 	}
 
-	if(compsize > origsize * 2) {
+	/* 0 byte input gives a 2-byte output, 1 byte input gives 4,
+	   2 bytes gives 5.
+	   don't complain about these. starting with any 3 byte input,
+	   the compressed size will always be under 2x the input size. */
+	if(origsize > 2 && compsize > 5 && compsize > origsize * 2) {
 		fatal = !(opts.force || opts.listonly);
-		fprintf(stderr, "%s: %s: compressed size for header #%d is over twice the uncompressed size (corrupt?), use -F to override.\n", fatal ? "fatal": "warning", self, headers_read);
-		if(fatal) exit(1);
+		fprintf(stderr, "%s: %s: compressed size for header #%d is over twice the uncompressed size (corrupt?)", self, fatal ? "fatal": "warning", headers_read);
+		if(fatal) {
+			fputs(", use -F to override.\n", stderr);
+			exit(1);
+		}
+		fputs("\n", stderr);
 	}
 }