Merged.

diff --cc io.c
index 8f5e09b,c399353..d8c9562
--- 1/io.c
--- 2/io.c
+++ b/io.c
@@@ -25,55 -25,47 +25,50 @@@ make_crctable(void
      }
  }
  
- /*
- 
-     shift bitbuf n bits left, read n bits
- 
-                       <---- n bits shift |
- 
-          7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
-          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- bitbuf   |                               |
-          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-                             <-----n----->
- 
- 
- 
-                            read from file
-                           <------------->
-                           7 6 5 4 3 2 1 0
-                          +-+-+-+-+-+-+-+-+
-                 subbitbuf|          1 1 1|
-                          +-+-+-+-+-+-+-+-+
-                             <-----n----->
-                                     <--->
-                                      bitcount (size of subbitbuf data)
- 
- */
- 
- const char *
+ static const char *
 -bitstring(unsigned int bitbuf, int n, char *ptr)
 +bitstring(unsigned int bitbuf, int n, char *ptr, size_t sz)
  {
      static char str[256];
 +    size_t size = sz;
  
 -    if (ptr == NULL)
 -        ptr = str;
 +    if (ptr == NULL) {
 +      ptr = str;
 +      size = sizeof(str);
 +    }
  
 -    if (n+1 > sizeof(str))
 +    if (n+1 > size)
          return "bit size is too big";
  
-     str[n] = '\0';
+     ptr[n] = '\0';
  
      while (n > 0) {
-       str[--n] = (bitbuf & 1) ? '1' : '0';
+       ptr[--n] = (bitbuf & 1) ? '1' : '0';
        bitbuf >>= 1;
      }
-     return str;
+     return ptr;
  }
  
+ /*
+   fill bitbuf for reading.
+ 
+     o shift bitbuf n bits left.
+     o read 8 bits from file and put it to subbitbuf.
+     o get n bits from subbitbuf and fill into bitbuf.
+ 
+          7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
+          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ bitbuf   |                      a b c d e|
+          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ 
+                                 already filled at last time.
+                                <--------->
+                                 7 6 5 4 3 2 1 0
+                                +-+-+-+-+-+-+-+-+
+                     subbitbuf  |a b c d e 1 1 1|
+                                +-+-+-+-+-+-+-+-+
+                                          <----->
+                                           bitcount (size of subbitbuf data)
+ */
  void
  fillbuf(struct lzh_istream *rp, int n)
  {