Add an example to print trust anchors.

Cargo.toml

@@ -19,6 +19,7 @@ webpki-roots = "0.22"
 ring = "0.16.5"
 untrusted = "0.7.0"
 rustls = "0.20"
+x509-parser = "0.9.2"
 
 [target.'cfg(windows)'.dependencies]
 schannel = "0.1.15"

examples/print-trust-anchors.rs

@@ -0,0 +1,15 @@
+//! Print the Subject of all extracted trust anchors.
+
+use rustls_native_certs;
+use std::error::Error;
+use x509_parser::prelude::*;
+
+fn main() -> Result<(), Box<dyn Error>> {
+    for cert in rustls_native_certs::load_native_certs()? {
+        match parse_x509_certificate(&cert.0) {
+                Ok((_, cert)) => println!("{}", cert.tbs_certificate.subject),
+                Err(e) => eprintln!("error parsing certificate: {}", e),
+        };
+    }
+    Ok(())
+}