linked list implementation

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 396 insertions, 0 deletions

diff --git a/src/libmdsserver/linked-list.c b/src/libmdsserver/linked-list.c
new file mode 100644
index 0000000..b8cb35b
--- /dev/null
+++ b/src/libmdsserver/linked-list.c
@@ -0,0 +1,396 @@
+/**
+ * mds — A micro-display server
+ * Copyright © 2014  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * This program 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 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include "linked-list.h"
+
+#include <string.h>
+
+
+/**
+ * The default initial capacity
+ */
+#ifndef LINKED_LIST_DEFAULT_INITIAL_CAPACITY
+#define LINKED_LIST_DEFAULT_INITIAL_CAPACITY  128
+#endif
+
+
+/**
+ * Computes the nearest, but higher, power of two,
+ * but only if the current value is not a power of two
+ * 
+ * @param   value  The value to be rounded up to a power of two
+ * @return         The nearest, but not smaller, power of two
+ */
+static size_t to_power_of_two(size_t value)
+{
+  value -= 1;
+  value |= value >> 1;
+  value |= value >> 2;
+  value |= value >> 4;
+  value |= value >> 8;
+  value |= value >> 16;
+#if __WORDSIZE == 64
+  value |= value >> 32;
+#endif
+  return value + 1;
+}
+
+
+/**
+ * Create a linked list
+ * 
+ * @param   this      Memory slot in which to store the new linked list
+ * @param   capacity  The minimum initial capacity of the linked list, 0 for default
+ * @return            Non-zero on error, `errno` will have been set accordingly
+ */
+int linked_list_create(linked_list_t* this, size_t capacity)
+{
+  /* Use default capacity of zero is specified. */
+  if (capacity == 0)
+    capacity = LINKED_LIST_DEFAULT_INITIAL_CAPACITY;
+  
+  /* Initialise the linked list. */
+  capacity = to_power_of_two(capacity);
+  this->capacity = capacity;
+  this->edge = 0;
+  this->end = 1;
+  this->reuse_head = 0;
+  this->reusable = NULL;
+  this->values = NULL;
+  this->next = NULL;
+  this->previous = NULL;
+  if ((this->reusable = malloc(capacity * sizeof(ssize_t))) == NULL)
+    return -1;
+  if ((this->values = malloc(capacity * sizeof(size_t))) == NULL)
+    return -1;
+  if ((this->next = malloc(capacity * sizeof(ssize_t))) == NULL)
+    return -1;
+  if ((this->previous = malloc(capacity * sizeof(ssize_t))) == NULL)
+    return -1;
+  this->values[this->edge] = 0;
+  this->next[this->edge] = this->edge;
+  this->previous[this->edge] = this->edge;
+  
+  return 0;
+}
+
+
+/**
+ * Release all resources in a linked list, should
+ * be done even if `linked_list_create` fails
+ * 
+ * @param  this  The linked list
+ */
+void linked_list_destroy(linked_list_t* this)
+{
+  if (this->reusable != NULL)  free(this->reusable);
+  if (this->values   != NULL)  free(this->values);
+  if (this->next     != NULL)  free(this->next);
+  if (this->previous != NULL)  free(this->previous);
+  
+  this->reusable = NULL;
+  this->values   = NULL;
+  this->next     = NULL;
+  this->previous = NULL;
+}
+
+
+/**
+ * Clone a linked list
+ * 
+ * @param   this  The linked list to clone
+ * @param   out   Memory slot in which to store the new linked list
+ * @return        Non-zero on error, `errno` will have been set accordingly
+ */
+int linked_list_clone(linked_list_t* this, linked_list_t* out)
+{
+  size_t n = this->capacity * sizeof(ssize_t);
+  size_t*  new_values;
+  ssize_t* new_next;
+  ssize_t* new_previous;
+  ssize_t* new_reusable;
+  
+  out->values = NULL;
+  out->next = NULL;
+  out->previous = NULL;
+  out->reusable = NULL;
+  
+  if ((new_values = malloc(n)) == NULL)
+    return -1;
+  if ((new_next = malloc(n)) == NULL)
+    {
+      free(new_values);
+      return -1;
+    }
+  if ((new_previous = malloc(n)) == NULL)
+    {
+      free(new_values);
+      free(new_previous);
+      return -1;
+    }
+  if ((new_reusable = malloc(n)) == NULL)
+    {
+      free(new_values);
+      free(new_previous);
+      free(new_reusable);
+      return -1;
+    }
+  
+  out->values = new_values;
+  out->next = new_next;
+  out->previous = new_previous;
+  out->reusable = new_reusable;
+  
+  out->capacity = this->capacity;
+  out->end = this->end;
+  out->reuse_head = this->reuse_head;
+  out->edge = this->edge;
+  
+  memcpy(out->values, this->values, n);
+  memcpy(out->next, this->next, n);
+  memcpy(out->previous, this->previous, n);
+  memcpy(out->reusable, this->reusable, n);
+  
+  return 0;
+}
+
+
+/**
+ * Pack the list so that there are no reusable
+ * positions, and reduce the capacity to the
+ * smallest capacity that can be used. Not that
+ * values (nodes) returned by the list's methods
+ * will become invalid. Additionally (to reduce
+ * the complexity) the list will be defragment
+ * so that the nodes' indices are continuous.
+ * This method has linear time complexity and
+ * linear memory complexity.
+ * 
+ * @param   this  The list
+ * @return        Non-zero on error, `errno` will have been set accordingly
+ */
+int linked_list_pack(linked_list_t* this)
+{
+  size_t size = this->end - this->reuse_head;
+  size_t cap = to_power_of_two(size);
+  ssize_t head = 0;
+  size_t i = 0;
+  ssize_t node;
+  size_t* vals;
+  
+  vals = malloc(cap * sizeof(size_t));
+  if (vals == NULL)
+    return -1;
+  while (((size_t)head != this->end) && (this->next[head] == LINKED_LIST_UNUSED))
+    head++;
+  if ((size_t)head != this->end)
+    for (node = head; (node != head) || (i == 0); i++)
+      {
+	vals[i] = this->values[node];
+	node = this->next[node];
+      }
+  
+  if (cap != this->capacity)
+    {
+      ssize_t* new_next;
+      ssize_t* new_previous;
+      ssize_t* new_reusable;
+      
+      new_next = malloc(cap * sizeof(ssize_t));
+      if (new_next == NULL)
+	{
+	  free(vals);
+	  return -1;
+	}
+      new_previous = malloc(cap * sizeof(ssize_t));
+      if (new_previous == NULL)
+	{
+	  free(vals);
+	  free(new_next);
+	  return -1;
+	}
+      new_reusable = malloc(cap * sizeof(ssize_t));
+      if (new_reusable == NULL)
+	{
+	  free(vals);
+	  free(new_next);
+	  free(new_previous);
+	  return -1;
+	}
+      
+      free(this->next);
+      free(this->previous);
+      free(this->reusable);
+      
+      this->next = new_next;
+      this->previous = new_previous;
+      this->reusable = new_reusable;
+    }
+  
+  for (i = 0; i < size; i++)
+    this->next[i] = (ssize_t)(i + 1);
+  this->next[size - 1] = 0;
+  
+  for (i = 1; i < size; i++)
+    this->previous[i] = (ssize_t)(i - 1);
+  this->previous[0] = (ssize_t)(size - 1);
+  
+  this->values = vals;
+  this->end = size;
+  this->reuse_head = 0;
+  
+  return 0;
+}
+
+
+/**
+ * Gets the next free position, and grow the
+ * arrays if necessary. This methods has constant
+ * amortised time complexity.
+ * 
+ * @param   this  The list
+ * @return        The next free position
+ */
+static ssize_t linked_list_get_next(linked_list_t* this)
+{
+  if (this->reuse_head > 0)
+    return this->reusable[--(this->reuse_head)];
+  if (this->end == this->capacity)
+    {
+      this->capacity <<= 1;
+      this->values = realloc(this->values, this->capacity * sizeof(size_t));
+      if (this->values == NULL)
+	return LINKED_LIST_UNUSED;
+      this->next = realloc(this->next, this->capacity * sizeof(ssize_t));
+      if (this->next == NULL)
+	return LINKED_LIST_UNUSED;
+      this->previous = realloc(this->previous, this->capacity * sizeof(ssize_t));
+      if (this->previous == NULL)
+	return LINKED_LIST_UNUSED;
+      this->reusable = realloc(this->reusable, this->capacity * sizeof(ssize_t));
+      if (this->reusable == NULL)
+	return LINKED_LIST_UNUSED;
+    }
+  return (ssize_t)(this->end++);
+}
+
+
+/**
+ * Mark a position as unused
+ * 
+ * @param   this  The list
+ * @param   node  The position
+ * @return        The position
+ */
+static ssize_t linked_list_unuse(linked_list_t* this, ssize_t node)
+{
+  if (node < 0)
+    return node;
+  this->reusable[this->reuse_head++] = node;
+  this->next[node] = LINKED_LIST_UNUSED;
+  this->previous[node] = LINKED_LIST_UNUSED;
+  return node;
+}
+
+
+/**
+ * Insert a value after a specified, reference, node
+ * 
+ * @param   this         The list
+ * @param   value        The value to insert
+ * @param   predecessor  The reference node
+ * @return               The node that has been created and inserted,
+ *                       `LINKED_LIST_UNUSED` on error, `errno` will be set accordingly
+ */
+ssize_t linked_list_insert_after(linked_list_t* this, size_t value, ssize_t predecessor)
+{
+  ssize_t node = linked_list_get_next(this);
+  this->values[node] = value;
+  this->next[node] = this->next[predecessor];
+  this->next[predecessor] = node;
+  this->previous[node] = predecessor;
+  this->previous[this->next[node]] = node;
+  return node;
+}
+
+
+/**
+ * Remove the node after a specified, reference, node
+ * 
+ * @param   this         The list
+ * @param   predecessor  The reference node
+ * @return               The node that has been removed
+ */
+ssize_t linked_list_remove_after(linked_list_t* this, ssize_t predecessor)
+{
+  ssize_t node = this->next[predecessor];
+  this->next[predecessor] = this->next[node];
+  this->previous[this->next[node]] = predecessor;
+  return linked_list_unuse(this, node);
+}
+
+
+/**
+ * Insert a value before a specified, reference, node
+ * 
+ * @param   this       The list
+ * @param   value      The value to insert
+ * @param   successor  The reference node
+ * @return             The node that has been created and inserted,
+ *                     `LINKED_LIST_UNUSED` on error, `errno` will be set accordingly
+ */
+ssize_t linked_list_insert_before(linked_list_t* this, size_t value, ssize_t successor)
+{
+  ssize_t node = linked_list_get_next(this);
+  this->values[node] = value;
+  this->previous[node] = this->next[successor];
+  this->previous[successor] = node;
+  this->next[node] = successor;
+  this->next[this->previous[node]] = node;
+  return node;
+}
+
+
+/**
+ * Remove the node before a specified, reference, node
+ * 
+ * @param   this       The list
+ * @param   successor  The reference node
+ * @return             The node that has been removed
+ */
+ssize_t linked_list_remove_before(linked_list_t* this, ssize_t successor)
+{
+  ssize_t node = this->previous[successor];
+  this->previous[successor] = this->previous[node];
+  this->next[this->previous[node]] = successor;
+  return linked_list_unuse(this, node);
+}
+
+
+/**
+ * Remove the node from the list
+ * 
+ * @param  this  The list
+ * @param  node  The node to remove
+ */
+void linked_list_remove(linked_list_t* this, ssize_t node)
+{
+  this->next[this->previous[node]] = this->next[node];
+  this->previous[this->next[node]] = this->previous[node];
+  linked_list_unuse(this, node);
+}
+