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/* Hash tables.

   Copyright (C) 2000, 2001, 2003, 2004 Free Software Foundation, Inc.

This program is free software; you can redistribute it and/or modify it

under the terms of the GNU General Public License as published by the

Free Software Foundation; either version 2, or (at your option) any

later version.

This program is distributed in the hope that it will be useful,

but WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

GNU General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 In other words, you are welcome to use, share and improve this program.

 You are forbidden to forbid anyone else to use, share and improve

 what you give them.   Help stamp out software-hoarding!  */

#include "config.h"

#include "system.h"

#include "symtab.h"

/* The code below is a specialization of Vladimir Makarov's expandable

   hash tables (see libiberty/hashtab.c).  The abstraction penalty was

   too high to continue using the generic form.  This code knows

   intrinsically how to calculate a hash value, and how to compare an

   existing entry with a potential new one.  Also, the ability to

   delete members from the table has been removed.  */

static unsigned int calc_hash (const unsigned char *, size_t);

static void ht_expand (hash_table *);

static double approx_sqrt (double);

/* Calculate the hash of the string STR of length LEN.  */

static unsigned int

calc_hash (const unsigned char *str, size_t len)

{

  size_t n = len;

  unsigned int r = 0;

  while (n--)

    r = HT_HASHSTEP (r, *str++);

  return HT_HASHFINISH (r, len);

}

/* Initialize an identifier hashtable.  */

hash_table *

ht_create (unsigned int order)

{

  unsigned int nslots = 1 << order;

  hash_table *table;

  table = XCNEW (hash_table);

  /* Strings need no alignment.  */

  _obstack_begin (&table->stack, 0, 0,

                  (void *(*) (long)) xmalloc,

                  (void (*) (void *)) free);

  obstack_alignment_mask (&table->stack) = 0;

  table->entries = XCNEWVEC (hashnode, nslots);

  table->entries_owned = true;

  table->nslots = nslots;

  return table;

}

/* Frees all memory associated with a hash table.  */

void

ht_destroy (hash_table *table)

{

  obstack_free (&table->stack, NULL);

  if (table->entries_owned)

    free (table->entries);

  free (table);

}

/* Returns the hash entry for the a STR of length LEN.  If that string

   already exists in the table, returns the existing entry, and, if

   INSERT is CPP_ALLOCED, frees the last obstack object.  If the

   identifier hasn't been seen before, and INSERT is CPP_NO_INSERT,

   returns NULL.  Otherwise insert and returns a new entry.  A new

   string is alloced if INSERT is CPP_ALLOC, otherwise INSERT is

   CPP_ALLOCED and the item is assumed to be at the top of the

   obstack.  */

hashnode

ht_lookup (hash_table *table, const unsigned char *str, size_t len,

           enum ht_lookup_option insert)

{

  return ht_lookup_with_hash (table, str, len, calc_hash (str, len),

                              insert);

}

hashnode

ht_lookup_with_hash (hash_table *table, const unsigned char *str,

                     size_t len, unsigned int hash,

                     enum ht_lookup_option insert)

{

  unsigned int hash2;

  unsigned int index;

  size_t sizemask;

  hashnode node;

  sizemask = table->nslots - 1;

  index = hash & sizemask;

  table->searches++;

  node = table->entries[index];

  if (node != NULL)

    {

      if (node->hash_value == hash

          && HT_LEN (node) == (unsigned int) len

          && !memcmp (HT_STR (node), str, len))

        {

          if (insert == HT_ALLOCED)

            /* The string we search for was placed at the end of the

               obstack.  Release it.  */

            obstack_free (&table->stack, (void *) str);

          return node;

        }

      /* hash2 must be odd, so we're guaranteed to visit every possible

         location in the table during rehashing.  */

      hash2 = ((hash * 17) & sizemask) | 1;

      for (;;)

        {

          table->collisions++;

          index = (index + hash2) & sizemask;

          node = table->entries[index];

          if (node == NULL)

            break;

          if (node->hash_value == hash

              && HT_LEN (node) == (unsigned int) len

              && !memcmp (HT_STR (node), str, len))

            {

              if (insert == HT_ALLOCED)

              /* The string we search for was placed at the end of the

                 obstack.  Release it.  */

                obstack_free (&table->stack, (void *) str);

              return node;

            }

        }

    }

  if (insert == HT_NO_INSERT)

    return NULL;

  node = (*table->alloc_node) (table);

  table->entries[index] = node;

  HT_LEN (node) = (unsigned int) len;

  node->hash_value = hash;

  if (insert == HT_ALLOC)

    HT_STR (node) = (const unsigned char *) obstack_copy0 (&table->stack,

                                                           str, len);

  else

    HT_STR (node) = str;

  if (++table->nelements * 4 >= table->nslots * 3)

    /* Must expand the string table.  */

    ht_expand (table);

  return node;

}

/* Double the size of a hash table, re-hashing existing entries.  */

static void

ht_expand (hash_table *table)

{

  hashnode *nentries, *p, *limit;

  unsigned int size, sizemask;

  size = table->nslots * 2;

  nentries = XCNEWVEC (hashnode, size);

  sizemask = size - 1;

  p = table->entries;

  limit = p + table->nslots;

  do

    if (*p)

      {

        unsigned int index, hash, hash2;

        hash = (*p)->hash_value;

        index = hash & sizemask;

        if (nentries[index])

          {

            hash2 = ((hash * 17) & sizemask) | 1;

            do

              {

                index = (index + hash2) & sizemask;

              }

            while (nentries[index]);

          }

        nentries[index] = *p;

      }

  while (++p < limit);

  if (table->entries_owned)

    free (table->entries);

  table->entries_owned = true;

  table->entries = nentries;

  table->nslots = size;

}

/* For all nodes in TABLE, callback CB with parameters TABLE->PFILE,

   the node, and V.  */

void

ht_forall (hash_table *table, ht_cb cb, const void *v)

{

  hashnode *p, *limit;

  p = table->entries;

  limit = p + table->nslots;

  do

    if (*p)

      {

        if ((*cb) (table->pfile, *p, v) == 0)

          break;

      }

  while (++p < limit);

}

/* Restore the hash table.  */

void

ht_load (hash_table *ht, hashnode *entries,

         unsigned int nslots, unsigned int nelements,

         bool own)

{

  if (ht->entries_owned)

    free (ht->entries);

  ht->entries = entries;

  ht->nslots = nslots;

  ht->nelements = nelements;

  ht->entries_owned = own;

}

/* Dump allocation statistics to stderr.  */

void

ht_dump_statistics (hash_table *table)

{

  size_t nelts, nids, overhead, headers;

  size_t total_bytes, longest;

  double sum_of_squares, exp_len, exp_len2, exp2_len;

  hashnode *p, *limit;

#define SCALE(x) ((unsigned long) ((x) < 1024*10 \

                  ? (x) \

                  : ((x) < 1024*1024*10 \

                     ? (x) / 1024 \

                     : (x) / (1024*1024))))

#define LABEL(x) ((x) < 1024*10 ? ' ' : ((x) < 1024*1024*10 ? 'k' : 'M'))

  total_bytes = longest = sum_of_squares = nids = 0;

  p = table->entries;

  limit = p + table->nslots;

  do

    if (*p)

      {

        size_t n = HT_LEN (*p);

        total_bytes += n;

        sum_of_squares += (double) n * n;

        if (n > longest)

          longest = n;

        nids++;

      }

  while (++p < limit);

  nelts = table->nelements;

  overhead = obstack_memory_used (&table->stack) - total_bytes;

  headers = table->nslots * sizeof (hashnode);

  fprintf (stderr, "\nString pool\nentries\t\t%lu\n",

           (unsigned long) nelts);

  fprintf (stderr, "identifiers\t%lu (%.2f%%)\n",

           (unsigned long) nids, nids * 100.0 / nelts);

  fprintf (stderr, "slots\t\t%lu\n",

           (unsigned long) table->nslots);

  fprintf (stderr, "bytes\t\t%lu%c (%lu%c overhead)\n",

           SCALE (total_bytes), LABEL (total_bytes),

           SCALE (overhead), LABEL (overhead));

  fprintf (stderr, "table size\t%lu%c\n",

           SCALE (headers), LABEL (headers));

  exp_len = (double)total_bytes / (double)nelts;

  exp2_len = exp_len * exp_len;

  exp_len2 = (double) sum_of_squares / (double) nelts;

  fprintf (stderr, "coll/search\t%.4f\n",

           (double) table->collisions / (double) table->searches);

  fprintf (stderr, "ins/search\t%.4f\n",

           (double) nelts / (double) table->searches);

  fprintf (stderr, "avg. entry\t%.2f bytes (+/- %.2f)\n",

           exp_len, approx_sqrt (exp_len2 - exp2_len));

  fprintf (stderr, "longest entry\t%lu\n",

           (unsigned long) longest);

#undef SCALE

#undef LABEL

}

/* Return the approximate positive square root of a number N.  This is for

   statistical reports, not code generation.  */

static double

approx_sqrt (double x)

{

  double s, d;

  if (x < 0)

    abort ();

  if (x == 0)

    return 0;

  s = x;

  do

    {

      d = (s * s - x) / (2 * s);

      s -= d;

    }

  while (d > .0001);

  return s;

}