Check if invoked as FastCGI

src/lib.rs

@@ -32,6 +32,7 @@
 //!     use std::io::Write;
 //!
 //!     fn main() {
+//!         if !fastcgi::is_fastcgi() { return }
 //!         fastcgi::run(|mut req| {
 //!             write!(&mut req.stdout(), "Content-Type: text/plain\n\nHello, world!")
 //!             .unwrap_or(());
@@ -630,3 +631,10 @@ pub fn run_tcp<F>(handler: F, listener: &TcpListener) where
         F: Fn(Request) + Send + Sync + 'static {
     run_transport(handler, &mut Transport::from_tcp(&listener))
 }
+
+#[cfg(unix)]
+/// Check if the program is running as FastCGI. This check is not necessary if
+/// you use `run_tcp`.
+pub fn is_fastcgi() -> bool {
+    Transport::new().is_fastcgi()
+}

src/unix.rs

@@ -28,6 +28,7 @@ use std::io::{self, Read, Write};
 use std::mem;
 use std::net::{Ipv4Addr, Ipv6Addr};
 use std::os::unix::io::RawFd;
+use std::ptr::{null_mut};
 
 const LISTENSOCK_FILENO: c::c_int = 0;
 
@@ -44,6 +45,11 @@ impl Transport {
         Transport { inner: raw_fd }
     }
 
+    pub fn is_fastcgi(&self) -> bool {
+        let res = unsafe { c::getpeername(self.inner, null_mut(), null_mut()) };
+        res == -1 && io::Error::last_os_error().raw_os_error() == Some(c::ENOTCONN)
+    }
+
     pub fn accept(&mut self) -> io::Result<Socket> {
         let res = unsafe {
             c::accept(self.inner, 0 as *mut _, 0 as *mut _)