/* GLIB - Library of useful routines for C programming

 * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * This library 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, see <http://www.gnu.org/licenses/>.

 */

/*

 * Modified by the GLib Team and others 1997-2000.  See the AUTHORS

 * file for a list of people on the GLib Team.  See the ChangeLog

 * files for a list of changes.  These files are distributed with

 * GLib at ftp://ftp.gtk.org/pub/gtk/.

 */

/*

 * MT safe

 */

#include "config.h"

#include <string.h>

#include "gstringchunk.h"

#include "ghash.h"

#include "gslist.h"

#include "gmessages.h"

#include "gutils.h"

/**

 * SECTION:string_chunks

 * @title: String Chunks

 * @short_description: efficient storage of groups of strings

 *

 * String chunks are used to store groups of strings. Memory is

 * allocated in blocks, and as strings are added to the #GStringChunk

 * they are copied into the next free position in a block. When a block

 * is full a new block is allocated.

 *

 * When storing a large number of strings, string chunks are more

 * efficient than using g_strdup() since fewer calls to malloc() are

 * needed, and less memory is wasted in memory allocation overheads.

 *

 * By adding strings with g_string_chunk_insert_const() it is also

 * possible to remove duplicates.

 *

 * To create a new #GStringChunk use g_string_chunk_new().

 *

 * To add strings to a #GStringChunk use g_string_chunk_insert().

 *

 * To add strings to a #GStringChunk, but without duplicating strings

 * which are already in the #GStringChunk, use

 * g_string_chunk_insert_const().

 *

 * To free the entire #GStringChunk use g_string_chunk_free(). It is

 * not possible to free individual strings.

 */

/**

 * GStringChunk:

 *

 * An opaque data structure representing String Chunks.

 * It should only be accessed by using the following functions.

 */

struct _GStringChunk

{

  GHashTable *const_table;

  GSList     *storage_list;

  gsize       storage_next;

  gsize       this_size;

  gsize       default_size;

};

#define MY_MAXSIZE ((gsize)-1)

static inline gsize

nearest_power (gsize base,

               gsize num)

{

  if (num > MY_MAXSIZE / 2)

    {

      return MY_MAXSIZE;

    }

  else

    {

      gsize n = base;

      while (n < num)

        n <<= 1;

      return n;

    }

}

/**

 * g_string_chunk_new:

 * @size: the default size of the blocks of memory which are

 *     allocated to store the strings. If a particular string

 *     is larger than this default size, a larger block of

 *     memory will be allocated for it.

 *

 * Creates a new #GStringChunk.

 *

 * Returns: a new #GStringChunk

 */

GStringChunk *

g_string_chunk_new (gsize size)

{

  GStringChunk *new_chunk = g_new (GStringChunk, 1);

  gsize actual_size = 1;

  actual_size = nearest_power (1, size);

  new_chunk->const_table  = NULL;

  new_chunk->storage_list = NULL;

  new_chunk->storage_next = actual_size;

  new_chunk->default_size = actual_size;

  new_chunk->this_size    = actual_size;

  return new_chunk;

}

/**

 * g_string_chunk_free:

 * @chunk: a #GStringChunk

 *

 * Frees all memory allocated by the #GStringChunk.

 * After calling g_string_chunk_free() it is not safe to

 * access any of the strings which were contained within it.

 */

void

g_string_chunk_free (GStringChunk *chunk)

{

  g_return_if_fail (chunk != NULL);

  if (chunk->storage_list)

    g_slist_free_full (chunk->storage_list, g_free);

  if (chunk->const_table)

    g_hash_table_destroy (chunk->const_table);

  g_free (chunk);

}

/**

 * g_string_chunk_clear:

 * @chunk: a #GStringChunk

 *

 * Frees all strings contained within the #GStringChunk.

 * After calling g_string_chunk_clear() it is not safe to

 * access any of the strings which were contained within it.

 *

 * Since: 2.14

 */

void

g_string_chunk_clear (GStringChunk *chunk)

{

  g_return_if_fail (chunk != NULL);

  if (chunk->storage_list)

    {

      g_slist_free_full (chunk->storage_list, g_free);

      chunk->storage_list = NULL;

      chunk->storage_next = chunk->default_size;

      chunk->this_size    = chunk->default_size;

    }

  if (chunk->const_table)

      g_hash_table_remove_all (chunk->const_table);

}

/**

 * g_string_chunk_insert:

 * @chunk: a #GStringChunk

 * @string: the string to add

 *

 * Adds a copy of @string to the #GStringChunk.

 * It returns a pointer to the new copy of the string

 * in the #GStringChunk. The characters in the string

 * can be changed, if necessary, though you should not

 * change anything after the end of the string.

 *

 * Unlike g_string_chunk_insert_const(), this function

 * does not check for duplicates. Also strings added

 * with g_string_chunk_insert() will not be searched

 * by g_string_chunk_insert_const() when looking for

 * duplicates.

 *

 * Returns: a pointer to the copy of @string within

 *     the #GStringChunk

 */

gchar*

g_string_chunk_insert (GStringChunk *chunk,

                       const gchar  *string)

{

  g_return_val_if_fail (chunk != NULL, NULL);

  return g_string_chunk_insert_len (chunk, string, -1);

}

/**

 * g_string_chunk_insert_const:

 * @chunk: a #GStringChunk

 * @string: the string to add

 *

 * Adds a copy of @string to the #GStringChunk, unless the same

 * string has already been added to the #GStringChunk with

 * g_string_chunk_insert_const().

 *

 * This function is useful if you need to copy a large number

 * of strings but do not want to waste space storing duplicates.

 * But you must remember that there may be several pointers to

 * the same string, and so any changes made to the strings

 * should be done very carefully.

 *

 * Note that g_string_chunk_insert_const() will not return a

 * pointer to a string added with g_string_chunk_insert(), even

 * if they do match.

 *

 * Returns: a pointer to the new or existing copy of @string

 *     within the #GStringChunk

 */

gchar*

g_string_chunk_insert_const (GStringChunk *chunk,

                             const gchar  *string)

{

  char* lookup;

  g_return_val_if_fail (chunk != NULL, NULL);

  if (!chunk->const_table)

    chunk->const_table = g_hash_table_new (g_str_hash, g_str_equal);

  lookup = (char*) g_hash_table_lookup (chunk->const_table, (gchar *)string);

  if (!lookup)

    {

      lookup = g_string_chunk_insert (chunk, string);

      g_hash_table_add (chunk->const_table, lookup);

    }

  return lookup;

}

/**

 * g_string_chunk_insert_len:

 * @chunk: a #GStringChunk

 * @string: bytes to insert

 * @len: number of bytes of @string to insert, or -1 to insert a

 *     nul-terminated string

 *

 * Adds a copy of the first @len bytes of @string to the #GStringChunk.

 * The copy is nul-terminated.

 *

 * Since this function does not stop at nul bytes, it is the caller's

 * responsibility to ensure that @string has at least @len addressable

 * bytes.

 *

 * The characters in the returned string can be changed, if necessary,

 * though you should not change anything after the end of the string.

 *

 * Returns: a pointer to the copy of @string within the #GStringChunk

 *

 * Since: 2.4

 */

gchar*

g_string_chunk_insert_len (GStringChunk *chunk,

                           const gchar  *string,

                           gssize        len)

{

  gssize size;

  gchar* pos;

  g_return_val_if_fail (chunk != NULL, NULL);

  if (len < 0)

    size = strlen (string);

  else

    size = len;

  if ((chunk->storage_next + size + 1) > chunk->this_size)

    {

      gsize new_size = nearest_power (chunk->default_size, size + 1);

      chunk->storage_list = g_slist_prepend (chunk->storage_list,

                                             g_new (gchar, new_size));

      chunk->this_size = new_size;

      chunk->storage_next = 0;

    }

  pos = ((gchar *) chunk->storage_list->data) + chunk->storage_next;

  *(pos + size) = '\0';

  memcpy (pos, string, size);

  chunk->storage_next += size + 1;

  return pos;

}