query drivers and dsn with an immutable reference

odbc-api/src/environment.rs

@@ -172,7 +172,7 @@ impl Environment {
     ///
     /// # Ok::<_, odbc_api::Error>(())
     /// ```
-    pub fn drivers(&mut self) -> Result<Vec<DriverInfo>, Error> {
+    pub fn drivers(&self) -> Result<Vec<DriverInfo>, Error> {
         // Find required buffer size to avoid truncation.
 
         // Start with first so we are independent of state
@@ -235,7 +235,7 @@ impl Environment {
     ///
     /// # Ok::<_, odbc_api::Error>(())
     /// ```
-    pub fn data_sources(&mut self) -> Result<Vec<DataSourceInfo>, Error> {
+    pub fn data_sources(&self) -> Result<Vec<DataSourceInfo>, Error> {
         self.data_sources_impl(FetchOrientation::First)
     }
 
@@ -276,7 +276,7 @@ impl Environment {
     }
 
     fn data_sources_impl(
-        &mut self,
+        &self,
         direction: FetchOrientation,
     ) -> Result<Vec<DataSourceInfo>, Error> {
         // Find required buffer size to avoid truncation.

odbc-api/src/handles/environment.rs

@@ -128,7 +128,7 @@ impl Environment {
     ///
     /// [1]: https://docs.microsoft.com/sql/odbc/reference/syntax/sqldrivers-function
     pub fn drivers_buffer_fill(
-        &mut self,
+        &self,
         direction: FetchOrientation,
         buffer_description: &mut Vec<u16>,
         buffer_attributes: &mut Vec<u16>,
@@ -175,7 +175,7 @@ impl Environment {
     ///
     /// [1]: https://docs.microsoft.com/sql/odbc/reference/syntax/sqldrivers-function
     pub fn drivers_buffer_len(
-        &mut self,
+        &self,
         direction: FetchOrientation,
     ) -> Result<Option<(i16, i16)>, Error> {
         // Lengths in characters minus terminating zero
@@ -214,7 +214,7 @@ impl Environment {
     ///
     /// `(server name length,  description length)`. Length is in characters minus terminating zero.
     pub fn data_source_buffer_len(
-        &mut self,
+        &self,
         direction: FetchOrientation,
     ) -> Result<Option<(i16, i16)>, Error> {
         // Lengths in characters minus terminating zero
@@ -254,7 +254,7 @@ impl Environment {
     ///
     ///  Use [`Environment::data_source_buffer_len`] to determine buffer lengths.
     pub fn data_source_buffer_fill(
-        &mut self,
+        &self,
         direction: FetchOrientation,
         buffer_name: &mut Vec<u16>,
         buffer_description: &mut Vec<u16>,

odbc-api/tests/integration.rs

@@ -2091,6 +2091,28 @@ fn arbitrary_input_parameters(profile: &Profile) {
     assert_eq!("Hello, World!,42", actual)
 }
 
+#[test]
+fn synchronized_access_to_driver_and_data_source_info() {
+    let expected_drivers = ENV.drivers().unwrap();
+    let expected_data_sources = ENV.data_sources().unwrap();
+
+    const NUM_THREADS: usize = 100;
+    let handles = (0..NUM_THREADS).map(|_| {
+        let expected_drivers = expected_drivers.clone();
+        let expected_data_sources = expected_data_sources.clone();
+        thread::spawn(move || {
+            let drivers = ENV.drivers().unwrap();
+            assert_eq!(expected_drivers, drivers);
+            let data_sources_for_thread = ENV.data_sources().unwrap();
+            assert_eq!(expected_data_sources, data_sources_for_thread);
+        })
+    });
+
+    for handle in handles {
+        handle.join().unwrap();
+    }
+}
+
 /// This test is inspired by a bug caused from a fetch statement generating a lot of diagnostic
 /// messages.
 #[test]

odbcsv/src/main.rs

@@ -123,7 +123,7 @@ fn main() -> Result<(), Error> {
         .init()?;
 
     // We know this is going to be the only ODBC environment in the entire process, so this is safe.
-    let mut environment = unsafe { Environment::new() }?;
+    let environment = unsafe { Environment::new() }?;
 
     match opt.command {
         Command::Query { query_opt } => {