Re: gzip --force bug

[Mark Adler]

bug-gzip,

Below is a patch fix the bug.  (Note: the patch is against 1.4, except that the 
source files were expanded to eliminate tabs.)

Mark


--- gzip-1.4.c  2010-01-03 09:26:02.000000000 -0800
+++ gzip.c      2010-02-02 23:11:45.000000000 -0800
@@ -1239,6 +1239,7 @@
 {
     uch flags;     /* compression flags */
     char magic[2]; /* magic header */
+    int imagic0;   /* first magic byte or EOF */
     int imagic1;   /* like magic[1], but can represent EOF */
     ulg stamp;     /* time stamp */
 
@@ -1246,12 +1247,14 @@
      * premature end of file: use try_byte instead of get_byte.
      */
     if (force && to_stdout) {
-        magic[0] = (char)try_byte();
+        imagic0 = try_byte();
+        magic[0] = (char) imagic0;
         imagic1 = try_byte ();
         magic[1] = (char) imagic1;
         /* If try_byte returned EOF, magic[1] == (char) EOF.  */
     } else {
         magic[0] = (char)get_byte();
+        imagic0 = 0;
         if (magic[0]) {
             magic[1] = (char)get_byte();
             imagic1 = 0; /* avoid lint warning */
@@ -1395,8 +1398,13 @@
     } else if (force && to_stdout && !list) { /* pass input unchanged */
         method = STORED;
         work = copy;
-        inptr = 0;
+        inptr--;
         last_member = 1;
+        if (imagic0 != EOF) {
+            write_buf(fileno(stdout), magic, 1);
+            bytes_in++;
+            bytes_out++;
+        }
     }
     if (method >= 0) return method;
 
--- util-1.4.c  2010-01-03 09:26:02.000000000 -0800
+++ util.c      2010-02-02 23:25:31.000000000 -0800
@@ -44,21 +44,23 @@
 
 /* ===========================================================================
  * Copy input to output unchanged: zcat == cat with --force.
- * IN assertion: insize bytes have already been read in inbuf.
+ * IN assertion: insize bytes have already been read in inbuf and inptr bytes
+ * already processed or copied.
  */
 int copy(in, out)
     int in, out;   /* input and output file descriptors */
 {
     errno = 0;
-    while (insize != 0 && (int)insize != -1) {
-        write_buf(out, (char*)inbuf, insize);
-        bytes_out += insize;
+    while (insize > inptr && (int)insize != -1) {
+        write_buf(out, (char*)inbuf + inptr, insize - inptr);
+        bytes_in += insize - inptr;
+        bytes_out += insize - inptr;
         insize = read_buffer (in, (char *) inbuf, INBUFSIZ);
+        inptr = 0;
     }
     if ((int)insize == -1) {
         read_error();
     }
-    bytes_in = bytes_out;
     return OK;
 }
 
gromit%