svgtiny_list.c

   1 /*
   2  * This file is part of Libsvgtiny
   3  * Licensed under the MIT License,
   4  *                http://opensource.org/licenses/mit-license.php
   5  * Copyright 2008 James Bursa <james@semichrome.net>
   6  */
   7
   8 /**
   9  * A svgtiny_list is a managed array of objects. It grows in chunks to reduce
  10  * calls to realloc(), but keeps wasted space low.
  11  */
  12
  13 #include <assert.h>
  14 #include "svgtiny.h"
  15 #include "svgtiny_internal.h"
  16
  17
  18 struct svgtiny_list {
  19         unsigned int size;      /* number of slots used */
  20         unsigned int allocated; /* number of slots allocated (>= size) */
  21         size_t item_size;       /* size of each slot / bytes */
  22         char *items;            /* array of slots */
  23 };
  24
  25
  26 /**
  27  * Create an empty svgtiny_list.
  28  */
  29
  30 struct svgtiny_list *svgtiny_list_create(size_t item_size)
  31 {
  32         struct svgtiny_list *list = malloc(sizeof *list);
  33         if (!list)
  34                 return 0;
  35         list->size = 0;
  36         list->allocated = 0;
  37         list->item_size = item_size;
  38         list->items = 0;
  39         return list;
  40 }
  41
  42
  43 /**
  44  * Return the number of objects in a list.
  45  */
  46
  47 unsigned int svgtiny_list_size(struct svgtiny_list *list)
  48 {
  49         return list->size;
  50 }
  51
  52
  53 /**
  54  * Set the number of objects in a list. If the size is increased, the new
  55  * objects are not initialized in any way.
  56  *
  57  * The allocation size formula is taken from Python's list:
  58  * http://svn.python.org/view/python/trunk/Objects/listobject.c?view=markup
  59  *
  60  * Objects may have moved after this call. Use svgtiny_list_get() to get new
  61  * pointers.
  62  */
  63
  64 svgtiny_code svgtiny_list_resize(struct svgtiny_list *list,
  65                 unsigned int new_size)
  66 {
  67         unsigned int new_allocated;
  68         void *new_items;
  69
  70         if (new_size <= list->allocated) {
  71                 list->size = new_size;
  72                 return svgtiny_OK;
  73         }
  74
  75         new_allocated = (new_size >> 3) + (new_size < 9 ? 3 : 6) + new_size;
  76         if (new_size == 0)
  77                 new_allocated = 0;
  78         new_items = realloc(list->items, new_allocated * list->item_size);
  79         if (!new_items)
  80                 return svgtiny_OUT_OF_MEMORY;
  81
  82         list->size = new_size;
  83         list->allocated = new_allocated;
  84         list->items = new_items;
  85
  86         return svgtiny_OK;
  87 }
  88
  89
  90 /**
  91  * Return a pointer to an object in a list.
  92  */
  93
  94 void *svgtiny_list_get(struct svgtiny_list *list,
  95                 unsigned int i)
  96 {
  97         assert(i < list->size);
  98         return (void *) (list->items + i * list->item_size);
  99 }
 100
 101
 102 /**
 103  * Add space for one object to a list and return a pointer to it.
 104  */
 105
 106 void *svgtiny_list_push(struct svgtiny_list *list)
 107 {
 108         svgtiny_code code;
 109         code = svgtiny_list_resize(list, list->size + 1);
 110         if (code != svgtiny_OK)
 111                 return 0;
 112         return svgtiny_list_get(list, list->size - 1);
 113 }
 114
 115
 116 /**
 117  * Free an entire list.
 118  */
 119
 120 void svgtiny_list_free(struct svgtiny_list *list)
 121 {
 122         free(list->items);
 123         free(list);
 124 }
 125