Add PORT_env().

Author: mleonhard

Readme.md

@@ -147,6 +147,8 @@ Functions  Expressions  Impls  Traits  Methods  Dependency
                                                        │   [build-dependencies]
 0/0        0/0          0/0    0/0     0/0      ❓  │   └── autocfg 1.1.0
 0/0        2/4          0/0    0/0     0/0      ☢️  │   ├── async-io 1.13.0
+                                                       │   │   [build-dependencies]
+0/0        0/0          0/0    0/0     0/0      ❓  │   │   └── autocfg 1.1.0
 4/4        91/91        16/16  0/0     1/1      ☢️  │   │   ├── async-lock 2.7.0
 0/0        0/0          0/0    0/0     0/0      ❓  │   │   ├── cfg-if 1.0.0
 0/0        168/168      2/2    0/0     1/1      ☢️  │   │   ├── concurrent-queue 2.2.0
@@ -172,13 +174,11 @@ Functions  Expressions  Impls  Traits  Methods  Dependency
                                                        │   │   │   [build-dependencies]
 0/1        0/201        0/2    0/0     0/4      ❓  │   │   │   └── cc 1.0.79
 0/0        24/24        0/0    0/0     3/3      ☢️  │   │   ├── slab 0.4.8
-0/0        5/5          0/0    0/0     0/0      ☢️  │   │   │   └── serde 1.0.159
                                                        │   │   │   [build-dependencies]
 0/0        0/0          0/0    0/0     0/0      ❓  │   │   │   └── autocfg 1.1.0
+0/0        5/5          0/0    0/0     0/0      ☢️  │   │   │   └── serde 1.0.159
 3/6        540/673      2/4    0/0     3/4      ☢️  │   │   ├── socket2 0.4.9
 0/0        21/21        0/0    0/0     4/4      ☢️  │   │   └── waker-fn 1.1.0
-                                                       │   │   [build-dependencies]
-0/0        0/0          0/0    0/0     0/0      ❓  │   │   └── autocfg 1.1.0
 0/0        28/28        4/4    0/0     0/0      ☢️  │   ├── blocking 1.3.1
 0/0        0/0          0/0    0/0     0/0      ❓  │   └── futures-lite 1.13.0
 0/0        0/0          0/0    0/0     0/0      🔒  ├── fixed-buffer 0.5.0
@@ -244,6 +244,7 @@ See [rust-webserver-comparison.md](https://github.com/mleonhard/servlin/blob/mai
    - `Response::not_implemented_501()`
    - `Response::service_unavailable_503()`
    - `EventSender::is_connected()`
+   - `PORT_env()`
 - v0.1.1 - Add `EventSender::unconnected`.
 - v0.1.0 - Rename library to Servlin.
 

src/accept.rs

@@ -21,6 +21,24 @@ pub fn socket_addr_all_interfaces(port: u16) -> SocketAddr {
     SocketAddr::new(IpAddr::V6(Ipv6Addr::UNSPECIFIED), port)
 }
 
+/// Reads and parses the `PORT` environment variable.
+///
+/// # Panics
+/// Panics with a useful error message when the PORT env var is not an integer in 1..65536.
+#[allow(non_snake_case)]
+#[must_use]
+pub fn PORT_env() -> u16 {
+    let port: u16 = std::env::var("PORT")
+        .expect("PORT env var")
+        .parse()
+        .expect("failed parsing PORT env var");
+    if (1..=65535).contains(&port) {
+        port
+    } else {
+        panic!("PORT env var is out of range 1-65535: {port}")
+    }
+}
+
 /// # Errors
 /// Returns an error when we fail to bind to the address.
 pub async fn listen_127_0_0_1_any_port() -> Result<async_net::TcpListener, std::io::Error> {

src/lib.rs

@@ -110,6 +110,7 @@
 //!    - `Response::not_implemented_501()`
 //!    - `Response::service_unavailable_503()`
 //!    - `EventSender::is_connected()`
+//!    - `PORT_env()`
 //! - v0.1.1 - Add `EventSender::unconnected`.
 //! - v0.1.0 - Rename library to Servlin.
 //!
@@ -143,7 +144,7 @@ mod token_set;
 mod util;
 
 pub use crate::accept::{
-    socket_addr_127_0_0_1, socket_addr_127_0_0_1_any_port, socket_addr_all_interfaces,
+    socket_addr_127_0_0_1, socket_addr_127_0_0_1_any_port, socket_addr_all_interfaces, PORT_env,
 };
 pub use crate::ascii_string::AsciiString;
 pub use crate::body_async_reader::BodyAsyncReader;