move implementation to internal/ directory (#828)

internal/zfs/zfs_pipe.go

@@ -0,0 +1,23 @@
+//go:build !linux
+// +build !linux
+
+package zfs
+
+import (
+	"os"
+	"sync"
+)
+
+func getPipeCapacityHint(envvar string) int {
+	return 0 // not supported
+}
+
+var zfsPipeCapacityNotSupported sync.Once
+
+func trySetPipeCapacity(p *os.File, capacity int) {
+	if debugEnabled && capacity != 0 {
+		zfsPipeCapacityNotSupported.Do(func() {
+			debug("trySetPipeCapacity error: OS does not support setting pipe capacity")
+		})
+	}
+}