feat(rust): first pass at v2 implementation - don't merge

mkdocs.yml

@@ -64,6 +64,7 @@ nav:
   - Implementation Status: implementation-status.md
   - Encoding Algorithms: encodings.md
   - Specification: specification.md
+  - Migrating to v2: migrating-to-v2.md
 
 extra:
   social:

rust/mlt-core/src/decoder/layer.rs

@@ -1,6 +1,7 @@
 use crate::codecs::varint::parse_varint;
 use crate::decoder::{Layer01, Unknown};
 use crate::utils::{parse_u8, take};
+use crate::v2::decode_v2_layer;
 use crate::{DecodeState, Decoder, Layer, MltError, MltRefResult, MltResult, ParsedLayer, Parser};
 
 impl<'a, S: DecodeState> Layer<'a, S> {
@@ -9,7 +10,7 @@ impl<'a, S: DecodeState> Layer<'a, S> {
     pub fn as_layer01(&self) -> Option<&Layer01<'a, S>> {
         match self {
             Self::Tag01(l) => Some(l),
-            Self::Unknown(_) => None,
+            _ => None,
         }
     }
 
@@ -18,7 +19,7 @@ impl<'a, S: DecodeState> Layer<'a, S> {
     pub fn into_layer01(self) -> Option<Layer01<'a, S>> {
         match self {
             Self::Tag01(l) => Some(l),
-            Self::Unknown(_) => None,
+            _ => None,
         }
     }
 }
@@ -38,6 +39,7 @@ impl<'a> Layer<'a> {
 
         let layer = match tag {
             1 => Layer::Tag01(Layer01::from_bytes(value, parser)?),
+            2 => Layer::Tag02(decode_v2_layer(value)?),
             tag => Layer::Unknown(Unknown { tag, value }),
         };
 
@@ -51,6 +53,7 @@ impl<'a> Layer<'a> {
     pub fn decode_all(self, dec: &mut Decoder) -> MltResult<ParsedLayer<'a>> {
         match self {
             Layer::Tag01(v) => Ok(Layer::Tag01(v.decode_all(dec)?)),
+            Layer::Tag02(v) => Ok(Layer::Tag02(v)),
             Layer::Unknown(u) => Ok(Layer::Unknown(u)),
         }
     }

rust/mlt-core/src/decoder/model.rs

@@ -41,6 +41,11 @@ impl From<Extent> for NonZeroU32 {
 pub enum Layer<'a, S: DecodeState = Lazy> {
     /// MVT-compatible layer (tag = 1)
     Tag01(Layer01<'a, S>),
+    /// Experimental v2 layer (tag = 2), decoded eagerly to owned row-oriented form.
+    ///
+    /// Unlike `Tag01`, this variant is always fully decoded when parsed: the
+    /// `S` type parameter is ignored and the data is stored as a [`TileLayer01`].
+    Tag02(TileLayer01),
     /// Unknown layer with tag, size, and value
     Unknown(Unknown<'a>),
 }
@@ -53,6 +58,7 @@ where
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Self::Tag01(l) => f.debug_tuple("Tag01").field(l).finish(),
+            Self::Tag02(t) => f.debug_tuple("Tag02").field(t).finish(),
             Self::Unknown(u) => f.debug_tuple("Unknown").field(u).finish(),
         }
     }

rust/mlt-core/src/lib.rs

@@ -23,6 +23,7 @@ pub(crate) mod decoder;
 pub mod encoder;
 pub(crate) mod errors;
 pub(crate) mod utils;
+pub mod v2;
 
 pub use convert::{geojson, mvt};
 pub use decoder::{

rust/mlt-core/src/utils/test_helpers.rs

@@ -27,6 +27,7 @@ pub fn assert_empty<T>(result: MltRefResult<T>) -> T {
 pub fn into_layer01(layer: Layer) -> Layer01 {
     match layer {
         Layer::Tag01(v) => v,
+        Layer::Tag02(_) => panic!("expected Tag01 layer, got Tag02"),
         Layer::Unknown(v) => panic!("expected Tag01 layer, got Tag{:02x}", v.tag),
     }
 }