--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/conv.rs	Tue Apr 15 00:50:23 2025 -0400
@@ -0,0 +1,94 @@
+use libc::{c_char, c_int};
+use std::ffi::{CStr, CString};
+use std::ptr;
+
+use constants::PamMessageStyle;
+use constants::PamResultCode;
+use items::Item;
+use module::PamResult;
+
+#[repr(C)]
+struct PamMessage {
+    msg_style: PamMessageStyle,
+    msg: *const c_char,
+}
+
+#[repr(C)]
+struct PamResponse {
+    resp: *const c_char,
+    resp_retcode: libc::c_int, // Unused - always zero
+}
+
+/// `PamConv` acts as a channel for communicating with user.
+///
+/// Communication is mediated by the pam client (the application that invoked
+/// pam).  Messages sent will be relayed to the user by the client, and response
+/// will be relayed back.
+#[repr(C)]
+pub struct Inner {
+    conv: extern "C" fn(
+        num_msg: c_int,
+        pam_message: &&PamMessage,
+        pam_response: &mut *const PamResponse,
+        appdata_ptr: *const libc::c_void,
+    ) -> PamResultCode,
+    appdata_ptr: *const libc::c_void,
+}
+
+pub struct Conv<'a>(&'a Inner);
+
+impl Conv<'_> {
+    /// Sends a message to the pam client.
+    ///
+    /// This will typically result in the user seeing a message or a prompt.
+    /// There are several message styles available:
+    ///
+    /// - PAM_PROMPT_ECHO_OFF
+    /// - PAM_PROMPT_ECHO_ON
+    /// - PAM_ERROR_MSG
+    /// - PAM_TEXT_INFO
+    /// - PAM_RADIO_TYPE
+    /// - PAM_BINARY_PROMPT
+    ///
+    /// Note that the user experience will depend on how the client implements
+    /// these message styles - and not all applications implement all message
+    /// styles.
+    pub fn send(&self, style: PamMessageStyle, msg: &str) -> PamResult<Option<&CStr>> {
+        let mut resp_ptr: *const PamResponse = ptr::null();
+        let msg_cstr = CString::new(msg).unwrap();
+        let msg = PamMessage {
+            msg_style: style,
+            msg: msg_cstr.as_ptr(),
+        };
+
+        let ret = (self.0.conv)(1, &&msg, &mut resp_ptr, self.0.appdata_ptr);
+
+        if PamResultCode::PAM_SUCCESS == ret {
+            // PamResponse.resp is null for styles that don't return user input like PAM_TEXT_INFO
+            let response = unsafe { (*resp_ptr).resp };
+            if response.is_null() {
+                Ok(None)
+            } else {
+                Ok(Some(unsafe { CStr::from_ptr(response) }))
+            }
+        } else {
+            Err(ret)
+        }
+    }
+}
+
+impl Item for Conv<'_> {
+    type Raw = Inner;
+
+    fn type_id() -> crate::items::ItemType {
+        crate::items::ItemType::Conv
+    }
+
+    unsafe fn from_raw(raw: *const Self::Raw) -> Self {
+        Self(&*raw)
+    }
+
+    fn into_raw(self) -> *const Self::Raw {
+        self.0 as _
+    }
+}