1 files changed, 55 insertions, 0 deletions
diff --git a/dnglib/queue.lua b/dnglib/queue.lua
new file mode 100644
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--- /dev/null
+++ b/dnglib/queue.lua
@@ -0,0 +1,55 @@
+-- -----------------------------------------------------------------------
+-- dng
+-- ------------------------------------------------------------------------
+-- Copyright (c) 2022 Steph Enders <steph@senders.io>
+--
+-- This software is provided 'as-is', without any express or implied
+-- warranty. In no event will the authors be held liable for any damages
+-- arising from the use of this software.
+--
+-- Permission is granted to anyone to use this software for any purpose,
+-- including commercial applications, and to alter it and redistribute it
+-- freely, subject to the following restrictions:
+--
+-- 1. The origin of this software must not be misrepresented; you must not
+--    claim that you wrote the original software. If you use this software
+--    in a product, an acknowledgment in the product documentation would
+--    be appreciated but is not required.
+--
+-- 2. Altered source versions must be plainly marked as such, and must not
+--    be misrepresented as being the original software.
+--
+-- 3. This notice may not be removed or altered from any source
+--    distribution.
+--
+-- -----------------------------------------------------------------------
+
+Queue = {}
+
+function Queue:new()
+    o = { first = 1, top = 0, data = {} }
+    self.__index = self
+    return setmetatable(o, self)
+end
+
+function Queue:push(val)
+    local top = self.top + 1
+    self.top = top
+    self.data[top] = val
+end
+
+function Queue:pop()
+    if self:empty() then
+        return nil
+    end
+    local val = self.data[self.first]
+    self.data[self.first] = nil
+    self.first = self.first + 1
+    return val
+end
+
+function Queue:empty()
+    return self.top < self.first
+end
+
+return Queue