Add external multimodal processors to the Rust frontend (#39329)

rust/sglang-mm/src/pipeline.rs

@@ -13,6 +13,22 @@
 pub enum TensorData {
     F32(Vec<f32>),
     I64(Vec<i64>),
+    /// Raw BF16 bits, exposed to numpy as u16 without copying the allocation.
+    Bf16(Vec<u16>),
+}
+
+impl TensorData {
+    pub fn len(&self) -> usize {
+        match self {
+            Self::F32(data) => data.len(),
+            Self::I64(data) => data.len(),
+            Self::Bf16(data) => data.len(),
+        }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
 }
 
 pub struct Tensor {