1 files changed, 37 insertions, 0 deletions

diff --git a/src/lzss/matchring.nim b/src/lzss/matchring.nim
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+++ b/src/lzss/matchring.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/>.
+
+const matchLimit* = 4
+
+type MatchRing* = object
+  offset, size: int
+  indices: array[matchLimit, int]
+
+proc initMatchRing*(): MatchRing =
+  MatchRing()
+
+proc addMatch*(ring: var MatchRing, index: int) =
+  if ring.size < matchLimit:
+    ring.indices[ring.size] = index
+    ring.size += 1
+  else:
+    let ringIndex = (ring.offset + ring.size) mod matchLimit
+    ring.indices[ringIndex] = index
+    ring.offset = (ring.offset + 1) mod ring.indices.len
+
+iterator items*(ring: MatchRing): int {.closure.} =
+  for i in countdown(ring.size - 1, 0):
+    yield ring.indices[(ring.offset + i) mod ring.indices.len]