diff --git a/build/src/lib.rs b/build/src/lib.rs
index f24578f3..66a0ac86 100644
--- a/build/src/lib.rs
+++ b/build/src/lib.rs
@@ -1,116 +1,19 @@
-extern crate cfg_if;
+cfg_if::cfg_if! {
+    if #[cfg(windows)] {
+      mod windows;
+      pub use windows::setup;
+    } else if #[cfg(target_os = "macos")] {
+      mod macos;
+      pub use macos::setup;
+    } else {
+      pub fn setup() {
+        setup_napi_feature();
+      }
+    }
+}
 
 use std::process::Command;
 
-use cfg_if::cfg_if;
-
-cfg_if! {
-  if #[cfg(windows)] {
-    use std::fs::{create_dir, metadata, write};
-    use std::path::PathBuf;
-    use std::io::Read;
-
-    fn get_node_version() -> std::io::Result<String> {
-        let output = Command::new("node").arg("-v").output()?;
-        let stdout_str = String::from_utf8_lossy(&output.stdout);
-
-        // version should not have a leading "v" or trailing whitespace
-        Ok(stdout_str.trim().trim_start_matches('v').to_string())
-    }
-
-    fn download_node_lib(dist_url: &str, version: &str, arch: &str) -> Vec<u8> {
-      // Assume windows since we know we are building on windows.
-      let url = format!("{dist_url}/v{version}/win-{arch}/node.lib", dist_url = dist_url, version = version, arch = arch);
-
-      let response = ureq::get(&url).call();
-      if let Some(error) = response.synthetic_error() {
-        panic!("Failed to download node.lib: {:#?}", error);
-      }
-
-      let mut reader = response.into_reader();
-      let mut bytes = vec![];
-      reader.read_to_end(&mut bytes).unwrap();
-
-      bytes
-    }
-
-    pub fn setup() {
-      // Assume nodejs if not specified.
-      let dist_url = std::env::var("NPM_CONFIG_DISTURL")
-        .unwrap_or("https://nodejs.org/dist".into());
-
-      // Try to get local nodejs version if not specified.
-      let node_version = std::env::var("NPM_CONFIG_TARGET")
-        .or_else(|_| get_node_version())
-        .expect("Failed to determine nodejs version");
-
-      // NPM also gives us an arch var, but let's trust cargo more.
-      // We translate from cargo's arch env format into npm/gyps's.
-      // See https://doc.rust-lang.org/reference/conditional-compilation.html#target_arch for rust env values.
-      // Nodejs appears to follow `process.arch`.
-      // See https://nodejs.org/docs/latest/api/process.html#process_process_arch for npm env values.
-      let arch = std::env::var("CARGO_CFG_TARGET_ARCH")
-        .map(|arch| match arch.as_str() {
-          "x86" => "x86", // TODO: x86 appears to also be called ia32 in npm_config_arch sometimes. What is the right value?
-          "x86_64" => "x64",
-          "mips" => "mips",
-          "powerpc" => "ppc",
-          "powerpc64" => "ppc64",
-          "arm" => "arm",
-          "aarch64" => "arm64",
-          arch => panic!("Unknown Architecture: {}", arch),
-        })
-        .expect("Failed to determine target arch");
-
-      println!("cargo:rerun-if-env-changed=NPM_CONFIG_DISTURL");
-      println!("cargo:rerun-if-env-changed=NPM_CONFIG_TARGET");
-
-      let mut node_lib_file_dir =
-        PathBuf::from(String::from_utf8(Command::new("node").arg("-e").arg("console.log(require('os').homedir())").output().unwrap().stdout).unwrap().trim_end().to_owned());
-
-      node_lib_file_dir.push(".napi-rs");
-
-      match create_dir(&node_lib_file_dir) {
-        Ok(_) => {},
-        Err(err) => {
-          if err.kind() != std::io::ErrorKind::AlreadyExists {
-            panic!("create {} folder failed: {}", node_lib_file_dir.to_str().unwrap(), err)
-          }
-        },
-      }
-
-      let link_search_dir = node_lib_file_dir.clone();
-
-      node_lib_file_dir.push(format!("node-{}.lib", node_version));
-
-      if let Err(_) = metadata(&node_lib_file_dir) {
-        let node_lib = download_node_lib(&dist_url, &node_version, &arch);
-        write(&node_lib_file_dir, &node_lib).expect(&format!("Could not save file to {}", node_lib_file_dir.to_str().unwrap()));
-      }
-      println!(
-        "cargo:rustc-link-lib={}",
-        &node_lib_file_dir.file_stem().unwrap().to_str().unwrap()
-      );
-      println!("cargo:rustc-link-search=native={}", link_search_dir.to_str().unwrap());
-      println!("cargo:rustc-cdylib-link-arg=delayimp.lib");
-      println!("cargo:rustc-cdylib-link-arg=/DELAYLOAD:node.exe");
-      setup_napi_feature();
-    }
-  } else if #[cfg(target_os = "macos")] {
-    /// Set up the build environment by setting Cargo configuration variables.
-    pub fn setup() {
-      println!("cargo:rustc-cdylib-link-arg=-Wl");
-      println!("cargo:rustc-cdylib-link-arg=-undefined");
-      println!("cargo:rustc-cdylib-link-arg=dynamic_lookup");
-      setup_napi_feature();
-    }
-  } else {
-    pub fn setup() {
-      setup_napi_feature();
-    }
-  }
-}
-
 pub fn setup_napi_feature() {
   let napi_version = String::from_utf8(
     Command::new("node")
diff --git a/build/src/macos.rs b/build/src/macos.rs
new file mode 100644
index 00000000..49ecd4c2
--- /dev/null
+++ b/build/src/macos.rs
@@ -0,0 +1,8 @@
+use crate::*;
+
+pub fn setup() {
+  println!("cargo:rustc-cdylib-link-arg=-Wl");
+  println!("cargo:rustc-cdylib-link-arg=-undefined");
+  println!("cargo:rustc-cdylib-link-arg=dynamic_lookup");
+  setup_napi_feature();
+}
diff --git a/build/src/windows.rs b/build/src/windows.rs
new file mode 100644
index 00000000..1deb581a
--- /dev/null
+++ b/build/src/windows.rs
@@ -0,0 +1,116 @@
+use crate::*;
+use std::fs::{create_dir, metadata, write};
+use std::io::Read;
+use std::path::PathBuf;
+
+fn get_node_version() -> std::io::Result<String> {
+  let output = Command::new("node").arg("-v").output()?;
+  let stdout_str = String::from_utf8_lossy(&output.stdout);
+
+  // version should not have a leading "v" or trailing whitespace
+  Ok(stdout_str.trim().trim_start_matches('v').to_string())
+}
+
+fn download_node_lib(dist_url: &str, version: &str, arch: &str) -> Vec<u8> {
+  // Assume windows since we know we are building on windows.
+  let url = format!(
+    "{dist_url}/v{version}/win-{arch}/node.lib",
+    dist_url = dist_url,
+    version = version,
+    arch = arch
+  );
+
+  let response = ureq::get(&url).call();
+  if let Some(error) = response.synthetic_error() {
+    panic!("Failed to download node.lib: {:#?}", error);
+  }
+
+  let mut reader = response.into_reader();
+  let mut bytes = vec![];
+  reader.read_to_end(&mut bytes).unwrap();
+
+  bytes
+}
+
+pub fn setup() {
+  // Assume nodejs if not specified.
+  let dist_url = std::env::var("NPM_CONFIG_DISTURL").unwrap_or("https://nodejs.org/dist".into());
+
+  // Try to get local nodejs version if not specified.
+  let node_version = std::env::var("NPM_CONFIG_TARGET")
+    .or_else(|_| get_node_version())
+    .expect("Failed to determine nodejs version");
+
+  // NPM also gives us an arch var, but let's trust cargo more.
+  // We translate from cargo's arch env format into npm/gyps's.
+  // See https://doc.rust-lang.org/reference/conditional-compilation.html#target_arch for rust env values.
+  // Nodejs appears to follow `process.arch`.
+  // See https://nodejs.org/docs/latest/api/process.html#process_process_arch for npm env values.
+  let arch = std::env::var("CARGO_CFG_TARGET_ARCH")
+    .map(|arch| match arch.as_str() {
+      "x86" => "x86", // TODO: x86 appears to also be called ia32 in npm_config_arch sometimes. What is the right value?
+      "x86_64" => "x64",
+      "mips" => "mips",
+      "powerpc" => "ppc",
+      "powerpc64" => "ppc64",
+      "arm" => "arm",
+      "aarch64" => "arm64",
+      arch => panic!("Unknown Architecture: {}", arch),
+    })
+    .expect("Failed to determine target arch");
+
+  println!("cargo:rerun-if-env-changed=NPM_CONFIG_DISTURL");
+  println!("cargo:rerun-if-env-changed=NPM_CONFIG_TARGET");
+
+  let mut node_lib_file_dir = PathBuf::from(
+    String::from_utf8(
+      Command::new("node")
+        .arg("-e")
+        .arg("console.log(require('os').homedir())")
+        .output()
+        .unwrap()
+        .stdout,
+    )
+    .unwrap()
+    .trim_end()
+    .to_owned(),
+  );
+
+  node_lib_file_dir.push(".napi-rs");
+
+  match create_dir(&node_lib_file_dir) {
+    Ok(_) => {}
+    Err(err) => {
+      if err.kind() != std::io::ErrorKind::AlreadyExists {
+        panic!(
+          "create {} folder failed: {}",
+          node_lib_file_dir.to_str().unwrap(),
+          err
+        )
+      }
+    }
+  }
+
+  let link_search_dir = node_lib_file_dir.clone();
+
+  node_lib_file_dir.push(format!("node-{}.lib", node_version));
+
+  if let Err(_) = metadata(&node_lib_file_dir) {
+    let node_lib = download_node_lib(&dist_url, &node_version, &arch);
+    write(&node_lib_file_dir, &node_lib).expect(&format!(
+      "Could not save file to {}",
+      node_lib_file_dir.to_str().unwrap()
+    ));
+  }
+  println!(
+    "cargo:rustc-link-lib={}",
+    &node_lib_file_dir.file_stem().unwrap().to_str().unwrap()
+  );
+  println!(
+    "cargo:rustc-link-search=native={}",
+    link_search_dir.to_str().unwrap()
+  );
+  println!("cargo:rustc-cdylib-link-arg=delayimp.lib");
+  println!("cargo:rustc-cdylib-link-arg=/DELAYLOAD:node.exe");
+  setup_napi_feature();
+}