/* String pool for GCC.
   Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010,
   2012 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 3, 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 COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

/* String text, identifier text and identifier node allocator.
   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 "ggc.h"
#include "ggc-internal.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.  */
static const char digit_vector[] = {
  '0', 0, '1', 0, '2', 0, '3', 0, '4', 0,
  '5', 0, '6', 0, '7', 0, '8', 0, '9', 0
};

#define digit_string(d) (digit_vector + ((d) * 2))

struct ht *ident_hash;

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

static void *
stringpool_ggc_alloc (size_t x)
{
  return ggc_alloc_atomic (x);
}

/* 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;
  ident_hash->alloc_subobject = stringpool_ggc_alloc;
}

/* Allocate a hash node.  */
static hashnode
alloc_node (cpp_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.  */

const char *
ggc_alloc_string_stat (const char *contents, int length MEM_STAT_DECL)
{
  char *result;

  if (length == -1)
    length = strlen (contents);

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

  result = (char *) ggc_alloc_atomic_stat (length + 1 PASS_MEM_STAT);
  memcpy (result, contents, length);
  result[length] = '\0';
  return (const char *) result;
}

/* 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;
}

/* Return true if an identifier should be removed from the table.  */

static int
maybe_delete_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
		    const void *v ATTRIBUTE_UNUSED)
{
  return !ggc_marked_p (HT_IDENT_TO_GCC_IDENT (h));
}

/* Mark the trees hanging off the identifier node for GGC.  These are
   handled specially (not using gengtype) because identifiers are only
   roots during one part of compilation.  */

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

/* Purge the identifier hash of identifiers which are no longer
   referenced.  */

void
ggc_purge_stringpool (void)
{
  ht_purge (ident_hash, maybe_delete_ident, NULL);
}

/* 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 (CONST_CAST (void *, x), CONST_CAST (void *, x),
		      &gt_pch_p_S, gt_types_enum_last);
}


/* User-callable entry point for marking string X.  */

void
gt_pch_nx (const char *& x)
{
  gt_pch_n_S (x);
}

void
gt_pch_nx (unsigned char *& x)
{
  gt_pch_n_S (x);
}

void
gt_pch_nx (unsigned char& x ATTRIBUTE_UNUSED)
{
}

void
gt_pch_nx (unsigned char *x, gt_pointer_operator op, void *cookie)
{
  op (x, cookie);
}

/* 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 GTY(()) string_pool_data {
  ht_identifier_ptr *
    GTY((length ("%h.nslots"),
	 nested_ptr (union tree_node, "%h ? GCC_IDENT_TO_HT_IDENT (%h) : NULL",
		     "%h ? HT_IDENT_TO_GCC_IDENT (%h) : NULL")))
    entries;
  unsigned int nslots;
  unsigned int nelements;
};

static GTY(()) struct string_pool_data * spd;

/* Save the stringpool data in SPD.  */

void
gt_pch_save_stringpool (void)
{
  spd = ggc_alloc_string_pool_data ();
  spd->nslots = ident_hash->nslots;
  spd->nelements = ident_hash->nelements;
  spd->entries = ggc_alloc_vec_ht_identifier_ptr (spd->nslots);
  memcpy (spd->entries, ident_hash->entries,
	  spd->nslots * sizeof (spd->entries[0]));
}

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

void
gt_pch_fixup_stringpool (void)
{
}

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

void
gt_pch_restore_stringpool (void)
{
  ht_load (ident_hash, spd->entries, spd->nslots, spd->nelements, false);
  spd = NULL;
}

#include "gt-stringpool.h"