feat: add network nbt to serializer

fastnbt/src/lib.rs

@@ -253,9 +253,20 @@ pub fn to_writer<T: Serialize, W: Write>(writer: W, v: &T) -> Result<()> {
 }
 
 /// Options for customizing serialization.
-#[derive(Default, Clone)]
+#[derive(Clone)]
 pub struct SerOpts {
     root_name: String,
+    /// Whether to include the root compound name.
+    serialize_root_name: bool,
+}
+
+impl Default for SerOpts {
+    fn default() -> Self {
+        Self {
+            root_name: Default::default(),
+            serialize_root_name: true,
+        }
+    }
 }
 
 impl SerOpts {
@@ -264,11 +275,21 @@ impl SerOpts {
         Default::default()
     }
 
+    pub fn network_nbt() -> Self {
+        Self::new().serialize_root_compound_name(false)
+    }
+
+    pub fn serialize_root_compound_name(mut self, serialize_root_name: bool) -> Self {
+        self.serialize_root_name = serialize_root_name;
+        self
+    }
+
     /// Set the root name (top level) of the compound. In most Minecraft data
     /// structures this is the empty string. The [`ser`][`crate::ser`] module
     /// contains an example.
     pub fn root_name(mut self, root_name: impl Into<String>) -> Self {
         self.root_name = root_name.into();
+        self.serialize_root_name = true;
         self
     }
 }
@@ -281,6 +302,7 @@ pub fn to_bytes_with_opts<T: Serialize>(v: &T, opts: SerOpts) -> Result<Vec<u8>>
     let mut serializer = Serializer {
         writer: &mut result,
         root_name: opts.root_name,
+        serialize_root_name: opts.serialize_root_name,
     };
     v.serialize(&mut serializer)?;
     Ok(result)
@@ -293,6 +315,7 @@ pub fn to_writer_with_opts<T: Serialize, W: Write>(writer: W, v: &T, opts: SerOp
     let mut serializer = Serializer {
         writer,
         root_name: opts.root_name,
+        serialize_root_name: opts.serialize_root_name,
     };
     v.serialize(&mut serializer)?;
     Ok(())

fastnbt/src/ser/serializer.rs

@@ -18,7 +18,7 @@ use super::{
 enum DelayedHeader {
     List { len: usize }, // header for a list, so element tag and list size.
     MapEntry { outer_name: Vec<u8> }, // header for a compound, so tag, name of compound.
-    Root { root_name: String }, // root compound, special because it isn't allowed to be an array type. Must be compound.
+    Root { root_name: Option<String> }, // root compound, special because it isn't allowed to be an array type. Must be compound.
 }
 
 pub struct Serializer<W: Write> {
@@ -27,6 +27,7 @@ pub struct Serializer<W: Write> {
     // Desired name of the root compound, typically an empty string.
     // NOTE: This is `mem:take`en, so is only valid at the start of serialization!
     pub(crate) root_name: String,
+    pub(crate) serialize_root_name: bool,
 }
 
 macro_rules! no_root {
@@ -69,10 +70,13 @@ impl<'a, W: 'a + Write> serde::ser::Serializer for &'a mut Serializer<W> {
         // Take the root name to avoid a clone. Need to be careful not to use
         // self.root_name elsewhere.
         let root_name = mem::take(&mut self.root_name);
+        let serialize_root_name = mem::take(&mut self.serialize_root_name);
         Ok(SerializerMap {
             ser: self,
             key: None,
-            header: Some(DelayedHeader::Root { root_name }),
+            header: Some(DelayedHeader::Root {
+                root_name: serialize_root_name.then_some(root_name),
+            }),
             trailer: Some(Tag::End),
         })
     }
@@ -143,7 +147,9 @@ fn write_header(writer: &mut impl Write, header: DelayedHeader, actual_tag: Tag)
                 return Err(Error::no_root_compound());
             }
             writer.write_tag(Tag::Compound)?;
-            writer.write_size_prefixed_str(&outer_name)?;
+            if let Some(outer_name) = &outer_name {
+                writer.write_size_prefixed_str(&outer_name)?;
+            }
         }
         DelayedHeader::MapEntry { ref outer_name } => {
             writer.write_tag(actual_tag)?;

fastnbt/src/test/ser.rs

@@ -1,10 +1,10 @@
 use std::{collections::HashMap, io::Cursor, iter::FromIterator};
 
 use crate::{
-    borrow, from_bytes,
+    borrow, from_bytes, from_bytes_with_opts,
     test::{resources::CHUNK_RAW_WITH_ENTITIES, Single, Wrap},
-    to_bytes, to_bytes_with_opts, to_writer_with_opts, ByteArray, IntArray, LongArray, SerOpts,
-    Tag, Value,
+    to_bytes, to_bytes_with_opts, to_writer_with_opts, ByteArray, DeOpts, IntArray, LongArray,
+    SerOpts, Tag, Value,
 };
 use serde::{ser::SerializeMap, Deserialize, Serialize};
 use serde_bytes::{ByteBuf, Bytes};
@@ -936,3 +936,26 @@ fn serialize_root_with_name() {
     assert_eq!(actual_via_writer.into_inner(), expected);
     assert_eq!(actual_value, expected);
 }
+
+#[test]
+fn serialize_networked_compound() {
+    #[derive(Serialize)]
+    struct Example {
+        networked: String,
+    }
+
+    let data = Example {
+        networked: "compound".to_string(),
+    };
+    let bytes: Vec<u8> = to_bytes_with_opts(&data, SerOpts::network_nbt()).unwrap();
+
+    assert_eq!(
+        bytes,
+        b"\
+        \x0a\
+            \x08\
+                \x00\x09networked\
+                \x00\x08compound\
+        \x00"
+    );
+}