add lightwave parser

rust/lightwave/src/lwo2/mod.rs

@@ -0,0 +1,24 @@
+use binrw::{BinReaderExt, BinResult, Endian};
+use std::io::{Read, Seek};
+
+pub mod sub_tags;
+pub mod tags;
+
+/// This is an index into an array of items (points or polygons), or a collection of items
+/// each uniquely identified by an integer (clips or envelopes). A VX is written as a variable
+/// length 2- or 4-byte element. If the index value is less than 65,280 (0xFF00), then the
+/// index is written as an unsigned two-byte integer. Otherwise the index is written as an
+/// unsigned four byte integer with bits 24-31 set. When reading an index, if the first byte
+/// encountered is 255 (0xFF), then the four-byte form is being used and the first byte should
+/// be discarded or masked out.
+pub fn vx<R>(reader: &mut R, endian: Endian, _args: ()) -> BinResult<u32>
+where
+    R: Read + Seek,
+{
+    let kind: u16 = reader.read_type(endian)?;
+    Ok(if (kind & 0xff) != 0xff {
+        kind as u32
+    } else {
+        (((kind as u32) & 0xff) << 16) | (reader.read_type::<u16>(endian)? as u32)
+    })
+}