Implement bounded XML LLSD codec

crates/libremetaverse-structured-data/src/lib.rs

@@ -7,16 +7,44 @@ mod dispatch;
 mod generated;
 mod model;
 mod notation;
+mod xml_codec;
 
 pub mod xml {
+    use std::sync::{Arc, Mutex};
+
     /// Project-owned XML element boundary; external XML APIs are not copied.
     pub struct Element;
 
     /// Native XML reader boundary; external XML APIs are not copied.
-    pub struct Reader;
+    #[derive(Clone, Debug, Default, Eq, PartialEq)]
+    pub struct Reader(pub String);
 
     /// Native XML writer boundary; external XML APIs are not copied.
-    pub struct Writer;
+    #[derive(Clone, Debug, Default)]
+    pub struct Writer(pub Arc<Mutex<String>>);
+
+    impl Writer {
+        #[must_use]
+        pub fn contents(&self) -> String {
+            self.0
+                .lock()
+                .unwrap_or_else(std::sync::PoisonError::into_inner)
+                .clone()
+        }
+
+        pub(crate) fn append(&self, value: &str) -> Result<(), crate::Error> {
+            let mut output = self.0.lock().map_err(|_| crate::Error::InvalidOperation)?;
+            let length = output
+                .len()
+                .checked_add(value.len())
+                .ok_or(crate::Error::Argument)?;
+            if length > crate::OSD::DEFAULT_MAX_BINARY_BYTES {
+                return Err(crate::Error::Argument);
+            }
+            output.push_str(value);
+            Ok(())
+        }
+    }
 }
 
 pub use generated::*;