Add svgtiny_list and convert gradient plotting to use it.

[libsvgtiny.git] / svgtiny_list.c

diff --git a/svgtiny_list.c b/svgtiny_list.c
new file mode 100644 (file)
index 0000000..53cfb34
--- /dev/null
+++ b/svgtiny_list.c
@@ -0,0 +1,125 @@
+/*
+ * This file is part of Libsvgtiny
+ * Licensed under the MIT License,
+ *                http://opensource.org/licenses/mit-license.php
+ * Copyright 2008 James Bursa <james@semichrome.net>
+ */
+
+/**
+ * A svgtiny_list is a managed array of objects. It grows in chunks to reduce
+ * calls to realloc(), but keeps wasted space low.
+ */
+
+#include <assert.h>
+#include "svgtiny.h"
+#include "svgtiny_internal.h"
+
+
+struct svgtiny_list {
+       unsigned int size;      /* number of slots used */
+       unsigned int allocated; /* number of slots allocated (>= size) */
+       size_t item_size;       /* size of each slot / bytes */
+       char *items;            /* array of slots */
+};
+
+
+/**
+ * Create an empty svgtiny_list.
+ */
+
+struct svgtiny_list *svgtiny_list_create(size_t item_size)
+{
+       struct svgtiny_list *list = malloc(sizeof *list);
+       if (!list)
+               return 0;
+       list->size = 0;
+       list->allocated = 0;
+       list->item_size = item_size;
+       list->items = 0;
+       return list;
+}
+
+
+/**
+ * Return the number of objects in a list.
+ */
+
+unsigned int svgtiny_list_size(struct svgtiny_list *list)
+{
+       return list->size;
+}
+
+
+/**
+ * Set the number of objects in a list. If the size is increased, the new
+ * objects are not initialized in any way.
+ *
+ * The allocation size formula is taken from Python's list:
+ * http://svn.python.org/view/python/trunk/Objects/listobject.c?view=markup
+ *
+ * Objects may have moved after this call. Use svgtiny_list_get() to get new
+ * pointers.
+ */
+
+svgtiny_code svgtiny_list_resize(struct svgtiny_list *list,
+               unsigned int new_size)
+{
+       unsigned int new_allocated;
+       void *new_items;
+
+       if (new_size <= list->allocated) {
+               list->size = new_size;
+               return svgtiny_OK;
+       }
+
+       new_allocated = (new_size >> 3) + (new_size < 9 ? 3 : 6) + new_size;
+       if (new_size == 0)
+               new_allocated = 0;
+       new_items = realloc(list->items, new_allocated * list->item_size);
+       if (!new_items)
+               return svgtiny_OUT_OF_MEMORY;
+
+       list->size = new_size;
+       list->allocated = new_allocated;
+       list->items = new_items;
+
+       return svgtiny_OK;
+}
+
+
+/**
+ * Return a pointer to an object in a list.
+ */
+
+void *svgtiny_list_get(struct svgtiny_list *list,
+               unsigned int i)
+{
+       assert(i < list->size);
+       return (void *) (list->items + i * list->item_size);
+}
+
+
+/**
+ * Add space for one object to a list and return a pointer to it.
+ */
+
+void *svgtiny_list_push(struct svgtiny_list *list)
+{
+       svgtiny_code code;
+       code = svgtiny_list_resize(list, list->size + 1);
+       if (code != svgtiny_OK)
+               return 0;
+       return svgtiny_list_get(list, list->size - 1);
+}
+
+
+/**
+ * Free an entire list.
+ */
+
+void svgtiny_list_free(struct svgtiny_list *list)
+{
+       free(list->items);
+       free(list);
+}
+