1 files changed, 32 insertions, 0 deletions
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..5c01557
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,32 @@
+use std::fs::read;
+use std::path::Path;
+
+/// Name of tag file.
+pub const CACHEDIR_TAG: &str = "CACHEDIR.TAG";
+
+/// Prefix of contents of tag file.
+pub const TAG: &str = "Signature: 8a477f597d28d172789f06886806bc55";
+
+/// Is a given file a cache directory tag?
+pub fn is_cachedir_tag(filename: &Path) -> Result<bool, std::io::Error> {
+    // Is the filename OK?
+    if let Some(basename) = filename.file_name() {
+        if basename != CACHEDIR_TAG {
+            return Ok(false);
+        }
+    }
+
+    // Does the file exist? It's OK if it doesn't, but we don't want
+    // to try to read it if it doesn't.
+    if !filename.exists() {
+        return Ok(false);
+    }
+
+    // Does the file start with the right prefix?
+    let data = read(filename)?;
+    if data.len() >= TAG.len() {
+        Ok(&data[..TAG.len()] == TAG.as_bytes())
+    } else {
+        Ok(false)
+    }
+}