Start reading the CnC file

Cargo.toml

@@ -13,6 +13,7 @@ maintenance = { status = "actively-developed" }
 
 [dependencies]
 aeron_driver-sys = { path = "./aeron_driver-sys" }
+memmap = "0.7"
 
 [dev-dependencies]
 clap = "2.33"

src/client/cnc_descriptor.rs

@@ -0,0 +1,92 @@
+//! Description of the command and control file used to communicate between the Media Driver
+//! and its clients.
+//!
+//! File layout:
+//!
+//! ```text
+//! +-----------------------------+
+//! |          Meta Data          |
+//! +-----------------------------+
+//! |      to-driver Buffer       |
+//! +-----------------------------+
+//! |      to-clients Buffer      |
+//! +-----------------------------+
+//! |   Counters Metadata Buffer  |
+//! +-----------------------------+
+//! |    Counters Values Buffer   |
+//! +-----------------------------+
+//! |          Error Log          |
+//! +-----------------------------+
+//! ```
+
+/// The CnC file metadata header. Layout:
+///
+/// ```text
+///  0                   1                   2                   3
+///  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+/// |                      Aeron CnC Version                        |
+/// +---------------------------------------------------------------+
+/// |                   to-driver buffer length                     |
+/// +---------------------------------------------------------------+
+/// |                  to-clients buffer length                     |
+/// +---------------------------------------------------------------+
+/// |               Counters Metadata buffer length                 |
+/// +---------------------------------------------------------------+
+/// |                Counters Values buffer length                  |
+/// +---------------------------------------------------------------+
+/// |                   Error Log buffer length                     |
+/// +---------------------------------------------------------------+
+/// |                   Client Liveness Timeout                     |
+/// |                                                               |
+/// +---------------------------------------------------------------+
+/// |                    Driver Start Timestamp                     |
+/// |                                                               |
+/// +---------------------------------------------------------------+
+/// |                         Driver PID                            |
+/// |                                                               |
+/// +---------------------------------------------------------------+
+/// ```
+#[repr(C, align(4))]
+pub struct MetaDataDefinition {
+    cnc_version: i32,
+    _to_driver_buffer_length: i32,
+    _to_client_buffer_length: i32,
+    _counter_metadata_buffer_length: i32,
+    _counter_values_buffer_length: i32,
+    _error_log_buffer_length: i32,
+    _client_liveness_timeout: i64,
+    _start_timestamp: i64,
+    _pid: i64,
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::client::cnc_descriptor::MetaDataDefinition;
+    use crate::driver::{DriverContext, MediaDriver};
+    use memmap::MmapOptions;
+    use std::fs::File;
+    use tempfile::tempdir;
+
+    #[test]
+    fn read_cnc_version() {
+        let dir = tempdir().unwrap();
+        let dir_path = dir.as_ref().to_path_buf();
+        dir.close().unwrap();
+
+        let context = DriverContext::default().set_aeron_dir(&dir_path);
+        let _driver = MediaDriver::with_context(context).unwrap();
+
+        // Open the CnC location
+        let cnc_path = dir_path.join("cnc.dat");
+        let cnc_file = File::open(&cnc_path).expect("Unable to open CnC file");
+        let mmap = unsafe {
+            MmapOptions::default()
+                .map(&cnc_file)
+                .expect("Unable to memory map CnC file")
+        };
+
+        let metadata: &MetaDataDefinition = unsafe { &*(mmap.as_ptr().cast()) };
+        assert_eq!(metadata.cnc_version, 16);
+    }
+}

src/client/context.rs

@@ -5,7 +5,7 @@ use std::path::PathBuf;
 
 /// Context used to initialize the Aeron client
 pub struct ClientContext {
-    aeron_dir: PathBuf,
+    _aeron_dir: PathBuf,
 }
 
 impl ClientContext {
@@ -31,7 +31,7 @@ impl ClientContext {
 impl Default for ClientContext {
     fn default() -> Self {
         ClientContext {
-            aeron_dir: ClientContext::default_aeron_path(),
+            _aeron_dir: ClientContext::default_aeron_path(),
         }
     }
 }

src/client/mod.rs

@@ -0,0 +1,5 @@
+//! Aeron client
+//!
+//! These are the modules necessary to construct a functioning Aeron client
+pub mod cnc_descriptor;
+pub mod context;