1 files changed, 83 insertions, 0 deletions
diff --git a/stockton-levels/src/q3/header.rs b/stockton-levels/src/q3/header.rs
new file mode 100644
index 0000000..d4e4f2f
--- /dev/null
+++ b/stockton-levels/src/q3/header.rs
@@ -0,0 +1,83 @@
+// Copyright (C) Oscar Shrimpton 2019  
+
+// This program is free software: you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by the Free
+// Software Foundation, either version 3 of the License, or (at your option)
+// any later version.
+
+// This program is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+// more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+use std::convert::TryInto;
+use crate::types::{ParseError, Result};
+
+const MAGIC_HEADER: &[u8] = &[0x49, 0x42, 0x53, 0x50];
+const HEADER_LEN: usize = 4 + 4 + (17 * 4 * 2);
+
+/// The header found at the start of a (Q3) bsp file
+#[derive(Clone, Copy, Debug)]
+pub struct Header {
+    pub version: u32,
+    pub dir_entries: [DirEntry; 17],
+}
+
+/// A directory entry, pointing to a lump in the file
+#[derive(Clone, Copy, Debug)]
+pub struct DirEntry {
+    /// Offset from beginning of file to start of lump
+    pub offset: u32,
+
+    /// Length of lump, multiple of 4.
+    pub length: u32,
+}
+
+impl Header {
+    /// Deserialise from buffer.
+    /// # Format
+    /// string[4] magic             Magic number. Always "IBSP".
+    /// int version                 Version number. 0x2e for the BSP files distributed with Quake 3.
+    /// direntry[17] direntries     Lump directory, seventeen entries.
+    pub fn from(v: &[u8]) -> Result<Header> {
+        if v.len() < HEADER_LEN {
+            return Err(ParseError::Invalid);
+        }
+        let magic = &v[0..4];
+
+        if magic != MAGIC_HEADER {
+            return Err(ParseError::Invalid);
+        }
+
+        let version: &[u8; 4] = v[4..8].try_into().unwrap();
+
+        let entries: &[u8] = &v[8..144];
+        let mut dir_entries: [DirEntry; 17] = [DirEntry {
+            offset: 0,
+            length: 0,
+        }; 17];
+
+        for n in 0..17 {
+            let base = &entries[(n * 8)..(n * 8) + 8];
+            dir_entries[n] = DirEntry {
+                offset: u32::from_le_bytes(base[0..4].try_into().unwrap()),
+                length: u32::from_le_bytes(base[4..8].try_into().unwrap()),
+            }
+        }
+
+        Ok(Header {
+            version: u32::from_le_bytes(*version),
+            dir_entries,
+        })
+    }
+
+    /// Get the lump at given index from the buffer, with offset & length based on this directory.
+    pub fn get_lump<'l>(&self, buf: &'l [u8], index: usize) -> &'l [u8] {
+        let entry = self.dir_entries[index];
+
+        &buf[entry.offset as usize..entry.offset as usize + entry.length as usize]
+    }
+}
+\ No newline at end of file