first commit

httpdl/alloc_other.go

@@ -0,0 +1,14 @@
+//go:build !linux
+
+package httpdl
+
+import "os"
+
+// allocate is the portable fallback: fallocate is Linux-specific, so on other
+// platforms prealloc/falloc degrade to a plain truncate.
+func allocate(f *os.File, mode string, size int64) error {
+	if mode == "none" {
+		return nil
+	}
+	return f.Truncate(size)
+}