alf: Handle 0-byte input files.

3 files changed, 9 insertions, 13 deletions

diff --git a/src/alf.1 b/src/alf.1
index e87b333..569e980 100644
--- a/src/alf.1
+++ b/src/alf.1
@@ -169,6 +169,9 @@ must be given as command\-line arguments.
 overwrites (making a backup) by default, and can append with the \fB\-a\fP
 option.
 .IP \(bu 2
+\fBLZ.COM\fP doesn\(aqt handle 0\-byte (empty) files correctly, but \fBalf\fP
+does. Not that this is very useful.
+.IP \(bu 2
 Turning the screen off for speed makes no sense on modern operating
 systems, so there\(aqs no option for that.
 .UNINDENT
@@ -190,9 +193,6 @@ actually can\(aqt handle files above about 15MB, if you compress one with
 a pathological case. A real Atari would take hours or even days to
 compress/decompress such files, and you\(aqd have to have a hard disk and
 a DOS capable of handling multi\-megabyte files...
-.sp
-It\(aqs also impossible to compress empty (0\-byte) files. \fBalf\fP will
-skip them, if any are found.
 .SS Performance
 .sp
 Performance is \fIhorrible\fP\&. This shouldn\(aqt be a real problem on
diff --git a/src/alf.c b/src/alf.c
index 7559eae..a366a5c 100644
--- a/src/alf.c
+++ b/src/alf.c
@@ -285,13 +285,14 @@ void crunch(void) {
 
 	out_bitpos = 0;
 
-	store_token(TOK_RESET);
+	/* 0-byte input files don't get a TOK_RESET */
+	if(input_len)
+		store_token(TOK_RESET);
 
 	while(in_pos < input_len) {
 		token = match_token(in_pos);
 		store_token(token);
 		new_pos = in_pos + tokentab[token].length;
-		// printf("   in_pos %d, new_pos %d\n", in_pos, new_pos);
 		if(new_pos < input_len)
 			make_token(in_pos, new_pos);
 		in_pos = new_pos;
@@ -332,11 +333,6 @@ void crunch_file(const char *filename) {
 		fprintf(stderr, "%s: %s: this file is too large; only compressing the first 16MB.\n", self, filename);
 	}
 
-	if(!input_len) {
-		fprintf(stderr, "%s: %s: can't compress a 0-byte (empty) file, skipping.\n", self, filename);
-		return;
-	}
-
 	if(opt_txtconv)
 		convert_eols();
 
diff --git a/src/alf.rst b/src/alf.rst
index 4bf2c6c..4d48afc 100644
--- a/src/alf.rst
+++ b/src/alf.rst
@@ -141,6 +141,9 @@ Atari **LZ.COM** aka **ALF.COM**, with the following differences:
   overwrites (making a backup) by default, and can append with the **-a**
   option.
 
+- **LZ.COM** doesn't handle 0-byte (empty) files correctly, but **alf**
+  does. Not that this is very useful.
+
 - Turning the screen off for speed makes no sense on modern operating
   systems, so there's no option for that.
 
@@ -164,9 +167,6 @@ a pathological case. A real Atari would take hours or even days to
 compress/decompress such files, and you'd have to have a hard disk and
 a DOS capable of handling multi-megabyte files...
 
-It's also impossible to compress empty (0-byte) files. **alf** will
-skip them, if any are found.
-
 Performance
 -----------