From ef7848921174412d68e70190eb58b9ce1687ff12 Mon Sep 17 00:00:00 2001
From: ubq323 <ubq323@ubq323.website>
Date: Mon, 13 Feb 2023 16:36:09 +0000
Subject: run length encoding for chunk data, more reasonable player speeds,
 controls help menu

---
 common/chunk.lua |  5 +++--
 common/rle.lua   | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+), 2 deletions(-)
 create mode 100644 common/rle.lua

(limited to 'common')

diff --git a/common/chunk.lua b/common/chunk.lua
index 39fcaaf..563723e 100644
--- a/common/chunk.lua
+++ b/common/chunk.lua
@@ -1,6 +1,7 @@
 local json = require"common.dkjson"
 local class = require"common.class"
 local coords = require"common.coords"
+local rle = require"common.rle"
 
 local CHUNK_SIZE = require"common.constants".CHUNK_SIZE
 
@@ -32,14 +33,14 @@ function Chunk.set_at(self,hoffs,tile)
 end
 
 function Chunk.data_packet(self)
-	return json.encode{t="chunk",tiles=self.tiles,u=self.cp.u,v=self.cp.v}
+	return json.encode{t="chunk",tiles=rle.encode(self.tiles),u=self.cp.u,v=self.cp.v}
 end
 function Chunk.from_packet_data(cls,packet)
 	-- assuming packet has already been json.decoded
 	-- since otherwise how would we know it's a chunk packet
 
 	local cp = coords.ChunkPos:make(packet.u,packet.v)
-	return cls:make(cp,packet.tiles)
+	return cls:make(cp,rle.decode(packet.tiles))
 end
 
 return {
diff --git a/common/rle.lua b/common/rle.lua
new file mode 100644
index 0000000..2944c4c
--- /dev/null
+++ b/common/rle.lua
@@ -0,0 +1,50 @@
+-- run length encoding
+
+local function encode(l)
+	local out = {}
+
+	local last = l[1]
+	local count = 1
+
+	local function ap()
+		if count == 1 then
+			table.insert(out,last)
+		elseif count == 2 then
+			table.insert(out,last)
+			table.insert(out,last)
+		else
+			table.insert(out,{count,last})
+		end
+	end
+
+	for ix=2,#l do
+		local val = l[ix]
+		if val == last then
+			count = count + 1
+		else
+			ap()
+			last = val
+			count = 1
+		end
+	end
+
+	ap()
+
+	return out
+end
+
+local function decode(l)
+	local out = {}
+	for _,r in ipairs(l) do
+		if type(r) == "table" and #r == 2 then
+			for i = 1,r[1] do
+				table.insert(out,r[2])
+			end
+		else
+			table.insert(out,r)
+		end
+	end
+	return out
+end
+
+return {encode=encode,decode=decode}
-- 
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