1 files changed, 55 insertions, 0 deletions
diff --git a/third_party/rust/cargo-platform/examples/matches.rs b/third_party/rust/cargo-platform/examples/matches.rs
new file mode 100644
index 0000000000..9ad5d10dd5
--- /dev/null
+++ b/third_party/rust/cargo-platform/examples/matches.rs
@@ -0,0 +1,55 @@
+//! This example demonstrates how to filter a Platform based on the current
+//! host target.
+
+use cargo_platform::{Cfg, Platform};
+use std::process::Command;
+use std::str::FromStr;
+
+static EXAMPLES: &[&str] = &[
+    "cfg(windows)",
+    "cfg(unix)",
+    "cfg(target_os=\"macos\")",
+    "cfg(target_os=\"linux\")",
+    "cfg(any(target_arch=\"x86\", target_arch=\"x86_64\"))",
+];
+
+fn main() {
+    let target = get_target();
+    let cfgs = get_cfgs();
+    println!("host target={} cfgs:", target);
+    for cfg in &cfgs {
+        println!("  {}", cfg);
+    }
+    let mut examples: Vec<&str> = EXAMPLES.iter().copied().collect();
+    examples.push(target.as_str());
+    for example in examples {
+        let p = Platform::from_str(example).unwrap();
+        println!("{:?} matches: {:?}", example, p.matches(&target, &cfgs));
+    }
+}
+
+fn get_target() -> String {
+    let output = Command::new("rustc")
+        .arg("-Vv")
+        .output()
+        .expect("rustc failed to run");
+    let stdout = String::from_utf8(output.stdout).unwrap();
+    for line in stdout.lines() {
+        if line.starts_with("host: ") {
+            return String::from(&line[6..]);
+        }
+    }
+    panic!("Failed to find host: {}", stdout);
+}
+
+fn get_cfgs() -> Vec<Cfg> {
+    let output = Command::new("rustc")
+        .arg("--print=cfg")
+        .output()
+        .expect("rustc failed to run");
+    let stdout = String::from_utf8(output.stdout).unwrap();
+    stdout
+        .lines()
+        .map(|line| Cfg::from_str(line).unwrap())
+        .collect()
+}