implement lzss encoding

1 files changed, 42 insertions, 0 deletions

diff --git a/src/polyfill.nim b/src/polyfill.nim
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+# gzip-like LZSS compressor
+# Copyright (C) 2018  Pacien TRAN-GIRARD
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero 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 Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+import lists
+
+# https://github.com/nim-lang/Nim/pull/9805
+
+proc prepend*[T](L: var SinglyLinkedList[T], n: SinglyLinkedNode[T]) =
+  ## prepends a node to `L`. Efficiency: O(1).
+  n.next = L.head
+  L.head = n
+  if L.tail == nil: L.tail = n
+
+proc prepend*[T](L: var SinglyLinkedList[T], value: T) =
+  ## prepends a node to `L`. Efficiency: O(1).
+  polyfill.prepend(L, newSinglyLinkedNode(value))
+
+proc append*[T](L: var SinglyLinkedList[T], n: SinglyLinkedNode[T]) =
+  ## appends a node `n` to `L`. Efficiency: O(1).
+  n.next = nil
+  if L.tail != nil:
+    assert(L.tail.next == nil)
+    L.tail.next = n
+  L.tail = n
+  if L.head == nil: L.head = n
+
+proc append*[T](L: var SinglyLinkedList[T], value: T) =
+  ## appends a value to `L`. Efficiency: O(1).
+  append(L, newSinglyLinkedNode(value))