Expand staining template read support

Nothing is exposed in the API, but I think it's reading properly now.

src/stm.rs

@@ -1,31 +1,156 @@
 // SPDX-FileCopyrightText: 2024 Joshua Goins <josh@redstrate.com>
 // SPDX-License-Identifier: GPL-3.0-or-later
 
-use std::io::Cursor;
+use std::io::{Cursor, Read, Seek, SeekFrom};
 
 use crate::ByteSpan;
-use binrw::binrw;
+use binrw::{binread, BinReaderExt, binrw};
+use binrw::__private::assert;
 use binrw::BinRead;
+use half::f16;
+use crate::model_vertex_declarations::VertexType::Half2;
+
+/// Maximum number of elements in one row
+const MAX_ELEMENTS: usize = 128;
 
 #[binrw]
 #[derive(Debug)]
 #[brw(little)]
 struct StmHeader {
-    #[br(pad_before = 1)] // TODO: what is this byte?
-    entry_count: i32
+    #[br(pad_before = 4)] // TODO: what is this byte?
+    entry_count: i32,
+
+    #[br(count = entry_count)]
+    keys: Vec<u16>,
+
+    #[br(count = entry_count)]
+    offsets: Vec<u16>
 }
 
 #[derive(Debug)]
-pub struct Stm {
+pub struct DyePack {
+    diffuse: [f32; 3],
+    specular: [f32; 3],
+    emissive: [f32; 3],
+    gloss: f32,
+    specular_power: f32
+}
+
+pub(crate) fn read_half3(data: [u16; 3]) -> Half3 {
+    Half3 {
+        r: f16::from_bits(data[0]),
+        g: f16::from_bits(data[0]),
+        b: f16::from_bits(data[0])
+    }
+}
+
+#[binread]
+#[derive(Debug, Default, Clone, Copy)]
+#[br(map = read_half3)]
+struct Half3 {
+    r: f16,
+    g: f16,
+    b: f16
+}
+
+pub(crate) fn read_half1(data: [u16; 1]) -> Half1 {
+    Half1 {
+        value: f16::from_bits(data[0])
+    }
+}
+
+#[binread]
+#[derive(Debug, Default, Clone, Copy)]
+#[br(map = read_half1)]
+struct Half1 {
+    value: f16,
+}
+
+#[derive(Debug)]
+pub struct StainingTemplate {
 
 }
 
-impl Stm {
+impl StainingTemplate {
     /// Reads an existing ULD file
     pub fn from_existing(buffer: ByteSpan) -> Option<Self> {
         let mut cursor = Cursor::new(buffer);
-        let header = StmHeader::read(&mut cursor).ok()?;
+        let header = StmHeader::read(&mut cursor).unwrap();
 
-        Some(Stm{})
+        for entry_offset in header.offsets {
+            let offset = entry_offset as i32 * 2 + 8 + 4 * header.entry_count;
+
+            // read the stm entry
+            cursor.seek(SeekFrom::Start(offset as u64));
+
+            // read the value offsets
+            let mut ends = [0u16; 5];
+            for end in &mut ends {
+                *end = cursor.read_le::<u16>().unwrap() * 2;
+            }
+
+            let new_offset = (offset + 10) as u64;
+
+            assert_eq!(std::mem::size_of::<Half1>(), std::mem::size_of::<f16>());
+            assert_eq!(std::mem::size_of::<Half3>(), std::mem::size_of::<f16>() * 3);
+
+            let diffuse_entries = StainingTemplate::read_array::<Half3>(&mut cursor, new_offset, ends[0] as usize);
+            let specular_entries = StainingTemplate::read_array::<Half3>(&mut cursor, new_offset + ends[0] as u64, ends[1] as usize - ends[0] as usize);
+            let emissive_entries = StainingTemplate::read_array::<Half3>(&mut cursor, new_offset + ends[1] as u64, ends[2] as usize - ends[1] as usize);
+            let gloss_entries = StainingTemplate::read_array::<Half1>(&mut cursor, new_offset + ends[2] as u64, ends[3] as usize - ends[2] as usize);
+            let specular_power_entries = StainingTemplate::read_array::<Half1>(&mut cursor, new_offset + ends[3] as u64, ends[4] as usize - ends[3] as usize);
+
+            break;
+        }
+
+        Some(StainingTemplate{})
+    }
+
+    fn read_array<T: binrw::BinRead<Args<'static> = ()> + Default + Clone + Copy>(cursor: &mut Cursor<ByteSpan>, offset: u64, size: usize) -> Vec<T> {
+        cursor.seek(SeekFrom::Start(offset));
+
+        let array_size = size / std::mem::size_of::<T>();
+        if array_size == 0 {
+            return vec![T::default(); MAX_ELEMENTS];
+        } else if array_size == 1 {
+            let element = cursor.read_le::<T>().unwrap();
+            return vec![element; MAX_ELEMENTS];
+        } else if array_size < MAX_ELEMENTS {
+            let real_count = array_size - MAX_ELEMENTS / std::mem::size_of::<T>();
+            let mut values = vec![];
+            let mut indices = vec![];
+            values.push(T::default());
+            for _ in 0..real_count {
+                values.push(cursor.read_le::<T>().unwrap());
+            }
+
+            println!("{:#?}", cursor.position());
+
+            let eof_marker = cursor.read_le::<u8>().unwrap();
+            assert_eq!(eof_marker, 0xFF);
+
+            for i in 0..MAX_ELEMENTS {
+                indices.push(cursor.read_le::<u8>().unwrap());
+            }
+
+            let mut vec = vec![];
+            for index in indices {
+                if index >= 0 && (index as usize) < values.len() {
+                    vec.push(values[index as usize]);
+                } else {
+                    vec.push(T::default());
+                }
+            }
+
+            vec
+        } else if array_size == MAX_ELEMENTS {
+            let mut vec = vec![];
+            for _ in 0..size {
+                vec.push(cursor.read_le::<T>().unwrap());
+            }
+            vec
+        } else {
+            panic!("Too many elements");
+        }
     }
 }