feat: configure DEFAULT_BUF_SIZE from env variable

Author: AsakuraMizu

build.rs

@@ -1,3 +1,5 @@
+use std::{env, fs, path::PathBuf};
+
 fn main() {
     autocfg::emit_possibility("borrowedbuf_init");
     autocfg::rerun_path("build.rs");
@@ -13,4 +15,16 @@ fn main() {
     if ac.probe_raw(code).is_ok() {
         autocfg::emit("borrowedbuf_init");
     }
+
+    let buf_size = env::var("AXIO_DEFAULT_BUF_SIZE")
+        .map(|v| v.parse::<usize>().expect("Invalid AXIO_DEFAULT_BUF_SIZE"))
+        .unwrap_or(1024 * 2);
+    fs::write(
+        PathBuf::from(env::var_os("OUT_DIR").unwrap()).join("config.rs"),
+        format!(
+            "/// Default buffer size for I/O operations.\npub const DEFAULT_BUF_SIZE: usize = {};",
+            buf_size
+        ),
+    )
+    .expect("Failed to write config file");
 }

src/lib.rs

@@ -11,8 +11,7 @@ extern crate alloc;
 #[doc(no_inline)]
 pub use axerrno::{AxError as Error, AxErrorKind as ErrorKind, AxResult as Result};
 
-/// Default buffer size for I/O operations.
-pub const DEFAULT_BUF_SIZE: usize = 1024 * 2;
+include!(concat!(env!("OUT_DIR"), "/config.rs"));
 
 mod buffered;
 pub mod prelude;