Initial work on pipelines

faststreams/multisync.nim

@@ -0,0 +1,32 @@
+import
+  stew/shims/macros,
+  async_backend, input_stream, output_stream
+
+macro fsMultiSync*(body: untyped) =
+  # We will produce an identical copy of the annotated proc,
+  # but taking async parameters and having the async pragma.
+  var
+    asyncProcBody = copy body
+    asyncProcParams = asyncBody[3]
+
+  asyncProcBody.addPragma(bindSym"async")
+
+  # The return types becomes Future[T]
+  if asyncProcParams[0].kind == nnkEmpty
+    asyncProcParams[0] = newBracketExpr(ident"Future", ident"void")
+  else:
+    asyncProcParams[0] = newBracketExpr(ident"Future", asyncProcParams[0])
+
+  # We replace all stream inputs with their async counterparts
+  for i in 1 ..< asyncProcParams.len:
+    let paramsDef = asyncProcParams[i]
+    let typ = paramsDef[^2]
+    if sameType(typ, bindSym"InputStream"):
+      paramsDef[^2] = bindSym "AsyncInputStream"
+    elif sameType(typ, bindSym"OutputStream"):
+      paramsDef[^2] = bindSym "AsyncOutputStream"
+
+  result = newStmtList(body, asyncBody)
+  if defined(debugSupportAsync):
+    echo result.repr
+