--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/semicongine/background_loader.nim	Mon Nov 04 00:06:30 2024 +0700
@@ -0,0 +1,67 @@
+import std/syncio
+import std/tables
+
+type
+  LoaderThreadArgs[T] =
+    (ptr Channel[string], ptr Channel[LoaderResponse[T]], proc(f: string): T {.gcsafe.})
+  LoaderResponse[T] = object
+    file: string
+    data: T
+    error: string
+
+  BackgroundLoader[T] = object
+    loadRequestCn: Channel[string] # used for sending load requests
+    responseCn: Channel[LoaderResponse[T]] # used for sending back loaded data
+    worker: Thread[LoaderThreadArgs[T]] # does the actual loading from the disk
+    responseTable: Table[string, LoaderResponse[T]] # stores results
+
+proc loader[T](args: LoaderThreadArgs[T]) {.thread.} =
+  while true:
+    let file = args[0][].recv()
+    try:
+      args[1][].send(LoaderResponse[T](file: file, data: args[2](file)))
+    except Exception as e:
+      args[1][].send(LoaderResponse[T](file: file, error: e.msg))
+
+proc fetchAll*(ld: var BackgroundLoader) =
+  var (hasData, response) = ld.responseCn.tryRecv()
+  while hasData:
+    ld.responseTable[response.file] = response
+    (hasData, response) = ld.responseCn.tryRecv()
+
+proc requestLoading*(ld: var BackgroundLoader, file: string) =
+  ld.loadRequestCn.send(file)
+
+proc isLoaded*(ld: var BackgroundLoader, file: string): bool =
+  ld.fetchAll * ()
+  file in ld.responseTable
+
+proc getLoaded*[T](ld: var BackgroundLoader[T], file: string): T =
+  var item: LoaderResponse[T]
+  doAssert ld.responseTable.pop(file, item)
+  if item.error != "":
+    raise newException(Exception, item.error)
+  result = item.data
+
+proc initBackgroundLoader*[T](
+    loadFn: proc(f: string): T {.gcsafe.}
+): ptr BackgroundLoader[T] =
+  result = cast[ptr BackgroundLoader[T]](allocShared0(sizeof(BackgroundLoader[T])))
+  open(result.loadRequestCn)
+  open(result.responseCn)
+  createThread[LoaderThreadArgs[T]](
+    result.worker,
+    loader[T],
+    (addr result.loadRequestCn, addr result.responseCn, loadFn),
+  )
+
+# threaded background loaders
+
+proc rawLoaderFunc(f: string): seq[byte] {.gcsafe.} =
+  cast[seq[byte]](toSeq(f.readFile()))
+
+proc audioLoaderFunc(f: string): seq[byte] {.gcsafe.} =
+  cast[seq[byte]](toSeq(f.readFile()))
+
+var rawLoader = initBackgroundLoader(rawLoaderFunc)
+var rawLoader = initBackgroundLoader(rawLoaderFunc)