/* String pool for GCC.
   Copyright (C) 2000, 2001, 2002, 2003 Free Software Foundation, Inc.

This file is part of GCC.

GCC 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.

GCC 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 GCC; see the file COPYING.  If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.  */

/* String text, identifier text and identifier node allocator.  Strings
   allocated by ggc_alloc_string are stored in an obstack which is
   never shrunk.  Identifiers are uniquely stored in a hash table.

   We use cpplib's hash table implementation.  libiberty's
   hashtab.c is not used because it requires 100% average space
   overhead per string, which is unacceptable.  Also, this algorithm
   is faster.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "ggc.h"
#include "tree.h"
#include "symtab.h"
#include "cpplib.h"

/* The "" allocated string.  */
const char empty_string[] = "";

/* Character strings, each containing a single decimal digit.
   Written this way to save space.  */
const char digit_vector[] = {
  '0', 0, '1', 0, '2', 0, '3', 0, '4', 0,
  '5', 0, '6', 0, '7', 0, '8', 0, '9', 0
};

struct ht *ident_hash;
static struct obstack string_stack;

static hashnode alloc_node (hash_table *);
static int mark_ident (struct cpp_reader *, hashnode, const void *);
static int ht_copy_and_clear (struct cpp_reader *, hashnode, const void *);

/* Initialize the string pool.  */
void
init_stringpool (void)
{
  /* Create with 16K (2^14) entries.  */
  ident_hash = ht_create (14);
  ident_hash->alloc_node = alloc_node;
  gcc_obstack_init (&string_stack);
}

/* Allocate a hash node.  */
static hashnode
alloc_node (hash_table *table ATTRIBUTE_UNUSED)
{
  return GCC_IDENT_TO_HT_IDENT (make_node (IDENTIFIER_NODE));
}

/* Allocate and return a string constant of length LENGTH, containing
   CONTENTS.  If LENGTH is -1, CONTENTS is assumed to be a
   nul-terminated string, and the length is calculated using strlen.
   If the same string constant has been allocated before, that copy is
   returned this time too.  */

const char *
ggc_alloc_string (const char *contents, int length)
{
  if (length == -1)
    length = strlen (contents);

  if (length == 0)
    return empty_string;
  if (length == 1 && ISDIGIT (contents[0]))
    return digit_string (contents[0] - '0');

  obstack_grow0 (&string_stack, contents, length);
  return obstack_finish (&string_stack);
}

/* Return an IDENTIFIER_NODE whose name is TEXT (a null-terminated string).
   If an identifier with that name has previously been referred to,
   the same node is returned this time.  */

#undef get_identifier

tree
get_identifier (const char *text)
{
  hashnode ht_node = ht_lookup (ident_hash,
				(const unsigned char *) text,
				strlen (text), HT_ALLOC);

  /* ht_node can't be NULL here.  */
  return HT_IDENT_TO_GCC_IDENT (ht_node);
}

/* Identical to get_identifier, except that the length is assumed
   known.  */

tree
get_identifier_with_length (const char *text, size_t length)
{
  hashnode ht_node = ht_lookup (ident_hash,
				(const unsigned char *) text,
				length, HT_ALLOC);

  /* ht_node can't be NULL here.  */
  return HT_IDENT_TO_GCC_IDENT (ht_node);
}

/* If an identifier with the name TEXT (a null-terminated string) has
   previously been referred to, return that node; otherwise return
   NULL_TREE.  */

tree
maybe_get_identifier (const char *text)
{
  hashnode ht_node;

  ht_node = ht_lookup (ident_hash, (const unsigned char *) text,
		       strlen (text), HT_NO_INSERT);
  if (ht_node)
    return HT_IDENT_TO_GCC_IDENT (ht_node);

  return NULL_TREE;
}

/* Report some basic statistics about the string pool.  */

void
stringpool_statistics (void)
{
  ht_dump_statistics (ident_hash);
}

/* Mark an identifier for GC.  */

static int
mark_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
	    const void *v ATTRIBUTE_UNUSED)
{
  gt_ggc_m_9tree_node (HT_IDENT_TO_GCC_IDENT (h));
  return 1;
}

/* Mark the trees hanging off the identifier node for GGC.  These are
   handled specially (not using gengtype) because of the special
   treatment for strings.  */

void
ggc_mark_stringpool (void)
{
  ht_forall (ident_hash, mark_ident, NULL);
}

/* Strings are _not_ GCed, but this routine exists so that a separate
   roots table isn't needed for the few global variables that refer
   to strings.  */

void
gt_ggc_m_S (void *x ATTRIBUTE_UNUSED)
{
}

/* Pointer-walking routine for strings (not very interesting, since
   strings don't contain pointers).  */

void
gt_pch_p_S (void *obj ATTRIBUTE_UNUSED, void *x ATTRIBUTE_UNUSED,
	    gt_pointer_operator op ATTRIBUTE_UNUSED,
	    void *cookie ATTRIBUTE_UNUSED)
{
}

/* PCH pointer-walking routine for strings.  */

void
gt_pch_n_S (const void *x)
{
  gt_pch_note_object ((void *)x, (void *)x, &gt_pch_p_S);
}

/* Handle saving and restoring the string pool for PCH.  */

/* SPD is saved in the PCH file and holds the information needed
   to restore the string pool.  */

struct string_pool_data GTY(())
{
  tree * GTY((length ("%h.nslots"))) entries;
  unsigned int nslots;
  unsigned int nelements;
};

static GTY(()) struct string_pool_data * spd;

/* Copy HP into the corresponding entry in HT2, and then clear
   the cpplib parts of HP.  */

static int
ht_copy_and_clear (cpp_reader *r ATTRIBUTE_UNUSED, hashnode hp, const void *ht2_p)
{
  cpp_hashnode *h = CPP_HASHNODE (hp);
  struct ht *ht2 = (struct ht *) ht2_p;

  if (h->type != NT_VOID
      && (h->flags & NODE_BUILTIN) == 0)
    {
      cpp_hashnode *h2 = CPP_HASHNODE (ht_lookup (ht2,
						  NODE_NAME (h),
						  NODE_LEN (h),
						  HT_ALLOC));
      h2->type = h->type;
      memcpy (&h2->value, &h->value, sizeof (h->value));

      h->type = NT_VOID;
      memset (&h->value, 0, sizeof (h->value));
    }
  return 1;
}

/* The hash table as it was before gt_pch_save_stringpool was called.  */

static struct ht *saved_ident_hash;

/* The hash table contains pointers to the cpp_hashnode inside the
   lang_identifier.  The PCH machinery can't handle pointers that refer
   to the inside of an object, so to save the hash table for PCH the
   pointers are adjusted and stored in the variable SPD.  */

void
gt_pch_save_stringpool (void)
{
  unsigned int i;

  spd = ggc_alloc (sizeof (*spd));
  spd->nslots = ident_hash->nslots;
  spd->nelements = ident_hash->nelements;
  spd->entries = ggc_alloc (sizeof (tree *) * spd->nslots);
  for (i = 0; i < spd->nslots; i++)
    if (ident_hash->entries[i] != NULL)
      spd->entries[i] = HT_IDENT_TO_GCC_IDENT (ident_hash->entries[i]);
    else
      spd->entries[i] = NULL;

  saved_ident_hash = ht_create (14);
  saved_ident_hash->alloc_node = alloc_node;
  ht_forall (ident_hash, ht_copy_and_clear, saved_ident_hash);
}

/* Return the stringpool to its state before gt_pch_save_stringpool
   was called.  */

void
gt_pch_fixup_stringpool (void)
{
  ht_forall (saved_ident_hash, ht_copy_and_clear, ident_hash);
  ht_destroy (saved_ident_hash);
  saved_ident_hash = 0;
}

/* A PCH file has been restored, which loaded SPD; fill the real hash table
   with adjusted pointers from SPD.  */

void
gt_pch_restore_stringpool (void)
{
  unsigned int i;

  ident_hash->nslots = spd->nslots;
  ident_hash->nelements = spd->nelements;
  ident_hash->entries = xrealloc (ident_hash->entries,
				  sizeof (hashnode) * spd->nslots);
  for (i = 0; i < spd->nslots; i++)
    if (spd->entries[i] != NULL)
      ident_hash->entries[i] = GCC_IDENT_TO_HT_IDENT (spd->entries[i]);
    else
      ident_hash->entries[i] = NULL;

  spd = NULL;
}

#include "gt-stringpool.h"