Lazy load stackless functions (#1656)

- I noticed that fasthttp was taking up 1.8MB of heap memory, even
though it wasn't being used. This turned out to be the stackless
function: 1.80MB  github.com/valyala/fasthttp/stackless.NewFunc
- Lazy load the stackless functions with sync.Once, given this a simple
atomic read, it shouldn't affect performance for the fast-path (I
haven't seen benchmarks with compression enabled).

1 files changed, 11 insertions, 1 deletions

diff --git a/brotli.go b/brotli.go
index c829c39..032bd95 100644
--- a/brotli.go
+++ b/brotli.go
@@ -132,7 +132,17 @@ func WriteBrotliLevel(w io.Writer, p []byte, level int) (int, error) {
 	}
 }
 
-var stacklessWriteBrotli = stackless.NewFunc(nonblockingWriteBrotli)
+var (
+	stacklessWriteBrotliOnce sync.Once
+	stacklessWriteBrotliFunc func(ctx interface{}) bool
+)
+
+func stacklessWriteBrotli(ctx interface{}) {
+	stacklessWriteBrotliOnce.Do(func() {
+		stacklessWriteBrotliFunc = stackless.NewFunc(nonblockingWriteBrotli)
+	})
+	stacklessWriteBrotliFunc(ctx)
+}
 
 func nonblockingWriteBrotli(ctxv interface{}) {
 	ctx := ctxv.(*compressCtx)