Re: No declaration for --no-strlen

[Bruno Haible]

Hello Behdad,

> In my case, I have a table of all two-byte strings.  ...
> So, in my case storing the length is useless 
> because of the nature of the data.  Here is the file:
> 
>   http://svn.gnome.org/viewvc/vte/trunk/src/vteseq-2.gperf?view=markup

Ah, I see. You are entirely right that the length being == 2 for all
keywords, there is no point in including it in the hash code computation.
I'm changing gperf so that it recognizes this situation automatically:


2009-01-19  Bruno Haible  <address@hidden>

        Don't include the length in the hash function if all keywords have the
        same length.
        * src/search.h (Search): Add _hash_includes_len field.
        * src/search.cc (Search::prepare): Initialize it.
        (Search::count_duplicates_tuple, Search::count_duplicates_multiset,
        Search::prepare_asso_values, Search::find_asso_values,
        Search::compute_hash): Use it instead of !option[NOLENGTH].
        * src/output.h (Output): New field _hash_includes_len. Add it as
        constructor argument.
        * src/output.cc (Output::Output): Add hash_includes_len argument.
        (Output::output_hash_function): Use _hash_includes_len instead of
        !option[NOLENGTH].
        * src/main.cc (main): Pass _hash_includes_len from Search to Output.
        * tests/permut2.exp: Updated expected test result.
        * tests/permut3.exp: Likewise.
        * tests/permutc2.exp: Likewise.
        Reported by Behdad Esfahbod <address@hidden>.

Index: src/main.cc
===================================================================
RCS file: /cvsroot/gperf/gperf/src/main.cc,v
retrieving revision 1.24
diff -u -r1.24 main.cc
--- src/main.cc 23 Aug 2008 18:52:48 -0000      1.24
+++ src/main.cc 19 Jan 2009 09:48:41 -0000
@@ -1,5 +1,5 @@
 /* Driver program for the hash function generator
-   Copyright (C) 1989-1998, 2000, 2002-2003 Free Software Foundation, Inc.
+   Copyright (C) 1989-1998, 2000, 2002-2003, 2009 Free Software Foundation, 
Inc.
    Written by Douglas C. Schmidt <address@hidden>
    and Bruno Haible <address@hidden>.
 
@@ -104,6 +104,7 @@
                           searcher._total_keys,
                           searcher._max_key_len,
                           searcher._min_key_len,
+                          searcher._hash_includes_len,
                           searcher._key_positions,
                           searcher._alpha_inc,
                           searcher._total_duplicates,
Index: src/output.cc
===================================================================
RCS file: /cvsroot/gperf/gperf/src/output.cc,v
retrieving revision 1.39
diff -u -r1.39 output.cc
--- src/output.cc       23 Aug 2008 18:52:48 -0000      1.39
+++ src/output.cc       19 Jan 2009 09:48:42 -0000
@@ -1,5 +1,5 @@
 /* Output routines.
-   Copyright (C) 1989-1998, 2000, 2002-2004, 2006-2007 Free Software 
Foundation, Inc.
+   Copyright (C) 1989-1998, 2000, 2002-2004, 2006-2007, 2009 Free Software 
Foundation, Inc.
    Written by Douglas C. Schmidt <address@hidden>
    and Bruno Haible <address@hidden>.
 
@@ -82,9 +82,9 @@
                 const char *verbatim_code, const char *verbatim_code_end,
                 unsigned int verbatim_code_lineno, bool charset_dependent,
                 int total_keys, int max_key_len, int min_key_len,
-                const Positions& positions, const unsigned int *alpha_inc,
-                int total_duplicates, unsigned int alpha_size,
-                const int *asso_values)
+                bool hash_includes_len, const Positions& positions,
+                const unsigned int *alpha_inc, int total_duplicates,
+                unsigned int alpha_size, const int *asso_values)
   : _head (head), _struct_decl (struct_decl),
     _struct_decl_lineno (struct_decl_lineno), _return_type (return_type),
     _struct_tag (struct_tag),
@@ -97,6 +97,7 @@
     _charset_dependent (charset_dependent),
     _total_keys (total_keys),
     _max_key_len (max_key_len), _min_key_len (min_key_len),
+    _hash_includes_len (hash_includes_len),
     _key_positions (positions), _alpha_inc (alpha_inc),
     _total_duplicates (total_duplicates), _alpha_size (alpha_size),
     _asso_values (asso_values)
@@ -755,7 +756,7 @@
   if (/* The function does not use the 'str' argument?  */
       _key_positions.get_size() == 0
       || /* The function uses 'str', but not the 'len' argument?  */
-         (option[NOLENGTH]
+         (!_hash_includes_len
           && _key_positions[0] < _min_key_len
           && _key_positions[_key_positions.get_size() - 1] != 
Positions::LASTCHAR))
     /* Pacify lint.  */
@@ -817,7 +818,7 @@
     {
       /* Trivial case: No key positions at all.  */
       printf ("  return %s;\n",
-              option[NOLENGTH] ? "0" : "len");
+              _hash_includes_len ? "len" : "0");
     }
   else
     {
@@ -838,7 +839,7 @@
              contain 'unsigned char's or 'unsigned short's.  */
 
           printf ("  return %s",
-                  option[NOLENGTH] ? "" : "len + ");
+                  _hash_includes_len ? "len + " : "");
 
           if (_key_positions.get_size() == 2
               && _key_positions[0] == 0
@@ -873,8 +874,8 @@
                   "  switch (%s)\n"
                   "    {\n"
                   "      default:\n",
-                  option[NOLENGTH] ? "0" : "len",
-                  option[NOLENGTH] ? "len" : "hval");
+                  _hash_includes_len ? "len" : "0",
+                  _hash_includes_len ? "hval" : "len");
 
           while (key_pos != Positions::LASTCHAR && key_pos >= _max_key_len)
             if ((key_pos = iter.next ()) == PositionIterator::EOS)
Index: src/output.h
===================================================================
RCS file: /cvsroot/gperf/gperf/src/output.h,v
retrieving revision 1.23
diff -u -r1.23 output.h
--- src/output.h        23 Aug 2008 18:52:48 -0000      1.23
+++ src/output.h        19 Jan 2009 09:48:42 -0000
@@ -2,7 +2,7 @@
 
 /* Output routines.
 
-   Copyright (C) 1989-1998, 2000, 2002-2003 Free Software Foundation, Inc.
+   Copyright (C) 1989-1998, 2000, 2002-2003, 2009 Free Software Foundation, 
Inc.
    Written by Douglas C. Schmidt <address@hidden>
    and Bruno Haible <address@hidden>.
 
@@ -49,6 +49,7 @@
                                 bool charset_dependent,
                                 int total_keys,
                                 int max_key_len, int min_key_len,
+                                bool hash_includes_len,
                                 const Positions& positions,
                                 const unsigned int *alpha_inc,
                                 int total_duplicates,
@@ -133,6 +134,8 @@
   int const             _max_key_len;
   /* Minimum length of the shortest keyword. */
   int const             _min_key_len;
+  /* Whether the hash function includes the length.  */
+  bool                  _hash_includes_len;
   /* Key positions.  */
   Positions const       _key_positions;
   /* Adjustments to add to bytes add specific key positions.  */
Index: src/search.cc
===================================================================
RCS file: /cvsroot/gperf/gperf/src/search.cc,v
retrieving revision 1.41
diff -u -r1.41 search.cc
--- src/search.cc       23 Aug 2008 18:52:48 -0000      1.41
+++ src/search.cc       19 Jan 2009 09:48:43 -0000
@@ -1,5 +1,5 @@
 /* Search algorithm.
-   Copyright (C) 1989-1998, 2000, 2002 Free Software Foundation, Inc.
+   Copyright (C) 1989-1998, 2000, 2002, 2009 Free Software Foundation, Inc.
    Written by Douglas C. Schmidt <address@hidden>
    and Bruno Haible <address@hidden>.
 
@@ -64,7 +64,7 @@
    where Pos is a set of byte positions,
    each alpha_inc[i] is a nonnegative integer,
    each asso_values[c] is a nonnegative integer,
-   len (keyword) is the keyword's length if !option[NOLENGTH], or 0 otherwise.
+   len (keyword) is the keyword's length if _hash_includes_len, or 0 otherwise.
 
    Theorem 1: If all keywords are different, there is a set Pos such that
    all tuples (keyword[i] : i in Pos) are different.
@@ -103,7 +103,7 @@
      Map (A --> B) := Hom_Set (A, B) is the set of maps from A to B, and
      S(Pos) is the symmetric group over Pos.
 
-   This was the theory for option[NOLENGTH]; if !option[NOLENGTH], slight
+   This was the theory for !_hash_includes_len; if _hash_includes_len, slight
    modifications apply:
      proj1 : String --> Map (Pos --> N) x N
      proj2 : Map (Pos --> N) x N --> Map (Pos --> N) / S(Pos) x N
@@ -175,6 +175,9 @@
               exit (1);
             }
       }
+
+  /* Determine whether the hash function shall include the length.  */
+  _hash_includes_len = !(option[NOLENGTH] || (_min_key_len == _max_key_len));
 }
 
 /* ====================== Finding good byte positions ====================== */
@@ -238,7 +241,7 @@
 
   unsigned int count = 0;
   {
-    Hash_Table representatives (_total_keys, option[NOLENGTH]);
+    Hash_Table representatives (_total_keys, !_hash_includes_len);
     for (KeywordExt_List *temp = _head; temp; temp = temp->rest())
       {
         KeywordExt *keyword = temp->first();
@@ -590,7 +593,7 @@
 
   unsigned int count = 0;
   {
-    Hash_Table representatives (_total_keys, option[NOLENGTH]);
+    Hash_Table representatives (_total_keys, !_hash_includes_len);
     for (KeywordExt_List *temp = _head; temp; temp = temp->rest())
       {
         KeywordExt *keyword = temp->first();
@@ -736,7 +739,7 @@
   _max_selchars_length = _key_positions.iterator(_max_key_len).remaining();
 
   /* Check for duplicates, i.e. keywords with the same _selchars array
-     (and - if !option[NOLENGTH] - also the same length).
+     (and - if _hash_includes_len - also the same length).
      We deal with these by building an equivalence class, so that only
      1 keyword is representative of the entire collection.  Only this
      representative remains in the keyword list; the others are accessible
@@ -747,7 +750,7 @@
     _list_len = _total_keys;
     _total_duplicates = 0;
     /* Make hash table for efficiency.  */
-    Hash_Table representatives (_list_len, option[NOLENGTH]);
+    Hash_Table representatives (_list_len, !_hash_includes_len);
 
     KeywordExt_List *prev = NULL; /* list node before temp */
     for (temp = _head; temp; )
@@ -847,7 +850,7 @@
 
   /* Given the bound for _asso_values[c], we have a bound for the possible
      hash values, as computed in compute_hash().  */
-  _max_hash_value = (option[NOLENGTH] ? 0 : _max_key_len)
+  _max_hash_value = (_hash_includes_len ? _max_key_len : 0)
                     + (_asso_value_max - 1) * _max_selchars_length;
   /* Allocate a sparse bit vector for detection of collisions of hash
      values.  */
@@ -1307,7 +1310,7 @@
                      the yet undetermined asso_values[].  */
                   int hashcode;
                   {
-                    int sum = option[NOLENGTH] ? 0 : keyword->_allchars_length;
+                    int sum = _hash_includes_len ? keyword->_allchars_length : 
0;
                     const unsigned int *p = keyword->_selchars;
                     int i = keyword->_selchars_length;
                     for (; i > 0; p++, i--)
@@ -1407,7 +1410,7 @@
                           _asso_value_max = step->_asso_value_max;
                           /* Reinitialize _max_hash_value.  */
                           _max_hash_value =
-                            (option[NOLENGTH] ? 0 : _max_key_len)
+                            (_hash_includes_len ? _max_key_len : 0)
                             + (_asso_value_max - 1) * _max_selchars_length;
                           /* Reinitialize _collision_detector.  */
                           delete _collision_detector;
@@ -1470,7 +1473,7 @@
 inline int
 Search::compute_hash (KeywordExt *keyword) const
 {
-  int sum = option[NOLENGTH] ? 0 : keyword->_allchars_length;
+  int sum = _hash_includes_len ? keyword->_allchars_length : 0;
 
   const unsigned int *p = keyword->_selchars;
   int i = keyword->_selchars_length;
Index: src/search.h
===================================================================
RCS file: /cvsroot/gperf/gperf/src/search.h,v
retrieving revision 1.27
diff -u -r1.27 search.h
--- src/search.h        23 Aug 2008 18:52:48 -0000      1.27
+++ src/search.h        19 Jan 2009 09:48:43 -0000
@@ -2,7 +2,7 @@
 
 /* Search algorithm.
 
-   Copyright (C) 1989-1998, 2000, 2002 Free Software Foundation, Inc.
+   Copyright (C) 1989-1998, 2000, 2002, 2009 Free Software Foundation, Inc.
    Written by Douglas C. Schmidt <address@hidden>
    and Bruno Haible <address@hidden>.
 
@@ -113,6 +113,9 @@
   /* Minimum length of the shortest keyword.  */
   int                   _min_key_len;
 
+  /* Whether the hash function includes the length.  */
+  bool                  _hash_includes_len;
+
   /* User-specified or computed key positions.  */
   Positions             _key_positions;