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-rw-r--r--Server/Plugins/APIDump/UsingChunkStays.html43
1 files changed, 30 insertions, 13 deletions
diff --git a/Server/Plugins/APIDump/UsingChunkStays.html b/Server/Plugins/APIDump/UsingChunkStays.html
index a7cb5302a..faedfdfaa 100644
--- a/Server/Plugins/APIDump/UsingChunkStays.html
+++ b/Server/Plugins/APIDump/UsingChunkStays.html
@@ -14,7 +14,7 @@
<p>
A plugin may need to manipulate data in arbitrary chunks, and it needs a way to make the server
guarantee that the chunks are available in memory.</p>
-
+
<h2>The problem</h2>
<p>
Usually when plugins want to manipulate larger areas of world data, they need to make sure that the
@@ -27,7 +27,7 @@
either the block area has incomplete data (Read() failed) or incomplete data has been written to the
world (Write() failed). Recovery from this is near impossible - you can't simply read or write again
later, because the world may have changed in the meantime.</p>
-
+
<h2>The solution</h2>
<p>
The naive solution would be to monitor chunk loads and unloads, and postpone the operations until all
@@ -47,7 +47,7 @@
despawned. So the callback must use the longer way to access such objects, such as calling
<a href="cWorld.html">cWorld:DoWithEntityByID()</a> or
<a href="cWorld.html">cWorld:DoWithPlayer()</a>.</p>
-
+
<h2>The example</h2>
<p>
As a simple example, consider a theoretical plugin that allows a player to save the immediate
@@ -66,13 +66,13 @@ function HandleCommandSaveSpawn(a_Split, a_Player)
local SpawnZ = a_Player:GetWorld():GetSpawnZ()
local Bounds = cCuboid(SpawnX - 25, SpawnY - 25, SpawnZ - 25, SpawnX + 25, SpawnY + 25, SpawnZ + 25)
Bounds:ClampY(0, 255)
-
+
-- Read the area around spawn into a cBlockArea, save to file:
local Area = cBlockArea()
local FileName = a_Player:GetName() .. "_spawn.schematic"
Area:Read(a_Player:GetWorld(), Bounds, cBlockArea.baTypes + cBlockArea.baMetas)
Area:SaveToSchematicFile(FileName)
-
+
-- Notify the player:
a_Player:SendMessage(cCompositeChat("The spawn has been saved", mtInfo))
return true
@@ -96,7 +96,7 @@ function HandleCommandSaveSpawn(a_Split, a_Player)
local SpawnZ = a_Player:GetWorld():GetSpawnZ()
local Bounds = cCuboid(SpawnX - 25, SpawnY - 25, SpawnZ - 25, SpawnX + 25, SpawnY + 25, SpawnZ + 25)
Bounds:ClampY(0, 255)
-
+
-- Get a list of chunks that we need loaded:
local MinChunkX = math.floor((SpawnX - 25) / 16)
local MaxChunkX = math.ceil ((SpawnX + 25) / 16)
@@ -108,11 +108,11 @@ function HandleCommandSaveSpawn(a_Split, a_Player)
table.insert(Chunks, {x, z})
end
end -- for x
-
+
-- Store the player's name and world to use in the callback, because the a_Player object may no longer be valid:
local PlayerName = a_Player:GetName()
local World = a_Player:GetWorld()
-
+
-- This is the callback that is executed once all the chunks are loaded:
local OnAllChunksAvailable = function()
-- Read the area around spawn into a cBlockArea, save to file:
@@ -124,7 +124,7 @@ function HandleCommandSaveSpawn(a_Split, a_Player)
else
Msg = cCompositeChat("Cannot save the spawn", mtFailure)
end
-
+
-- Notify the player:
-- Note that we cannot use a_Player here, because it may no longer be valid (if the player disconnected before the command completes)
World:DoWithPlayer(PlayerName,
@@ -133,14 +133,14 @@ function HandleCommandSaveSpawn(a_Split, a_Player)
end
)
end
-
+
-- Ask the server to load our chunks and notify us once it's done:
World:ChunkStay(Chunks, nil, OnAllChunksAvailable)
-
+
-- Note that code here may get executed before the callback is called!
-- The ChunkStay says "once you have the chunks", not "wait until you have the chunks"
-- So you can't notify the player here, because the saving needn't have occurred yet.
-
+
return true
end
</pre>
@@ -150,7 +150,7 @@ end
when we've got the chunks loaded, there's still the issue of free RAM - if the memory for the area
cannot be allocated, it cannot be read even with all the chunks present. So we still do need that
check.</p>
-
+
<h2>The conclusion</h2>
<p>
Although it makes the code a little bit longer and is a bit more difficult to grasp at first, the
@@ -163,5 +163,22 @@ end
prettyPrint();
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