add docs

datastore/threadbackend.nim

@@ -17,12 +17,30 @@ export key, query, smartptrs, databuffer
 push: {.upraises: [].}
 
 type
-  ThreadSafeTypes* = DataBuffer | void | bool | ThreadDatastorePtr | QueryResponseBuffer
+  ThreadSafeTypes* = DataBuffer | void | bool | ThreadDatastorePtr | QueryResponseBuffer ##\
+    ## This is a whitelisting of types that can be used with ThreadResult below
+    ## These types need to be thread safe with refc. That means no
+    ## GC types.
+
   ThreadResult*[T: ThreadSafeTypes] = object
+    ## Encapsulates both the results from a thread but also the cross
+    ## thread signaling mechanism. This makes it easier to keep them 
+    ## together.
     signal*: ThreadSignalPtr
     results*: Result[T, CatchableErrorBuffer]
 
-  TResult*[T] = SharedPtr[ThreadResult[T]]
+  TResult*[T] = SharedPtr[ThreadResult[T]] ##\
+    ## SharedPtr that allocates a shared buffer and keeps the 
+    ## memory allocated until all references to it are gone.
+    ## 
+    ## Since ThreadResult is a plain object, and if its lifetime is
+    ## tied to that of an async proc or the thread-backend request
+    ## it could be freed before the other thread is finished.
+    ## 
+    ## For example, `myFuture.cancel()` can end an async proc early. 
+    ## If the ThreadResult was stored in the async's memory then it'd
+    ## be free'ed along with the rest of the async env. This would
+    ## result in likely memory corruption (use-after-free).
 
   ThreadDatastore* = object
     tp*: Taskpool
@@ -37,6 +55,11 @@ type
 proc newThreadResult*[T](
     tp: typedesc[T]
 ): Result[TResult[T], ref CatchableError] =
+  ## Creates a new TResult including allocating
+  ## a new ThreadSignalPtr.
+  ## 
+  ## Since allocating the TSP can fail, this returns 
+  ## a Result.
   let res = newSharedPtr(ThreadResult[T])
   let signal = ThreadSignalPtr.new()
   if signal.isErr:
@@ -46,15 +69,25 @@ proc newThreadResult*[T](
   ok res
 
 proc success*[T](ret: TResult[T], value: T) =
+  ## convenience wrapper for `TResult` to make
+  ## "returning" results easier
   ret[].results.ok(value)
 
 proc success*[T: void](ret: TResult[T]) =
+  ## convenience wrapper for `TResult` to make
+  ## "returning" results easier
   ret[].results.ok()
 
 proc failure*[T](ret: TResult[T], exc: ref Exception) =
+  ## convenience wrapper for `TResult` to make
+  ## "returning" results easier
   ret[].results.err(exc.toBuffer())
 
-proc convert*[T, S](ret: TResult[T], tp: typedesc[S]): Result[S, ref CatchableError] =
+proc convert*[T, S](ret: TResult[T],
+                    tp: typedesc[S]
+                    ): Result[S, ref CatchableError] =
+  ## convenience wrapper for `TResult` to make
+  ## fetching results from `TResult` easier.
   if ret[].results.isOk():
     when S is seq[byte]:
       result.ok(ret[].results.get().toSeq(byte))