factor out ega loader

2016-09-19 03:00:54 -07:00
parent fd9d1cca13
commit 067e8906be
3 changed files with 75 additions and 35 deletions
--- a/src/ega.rs
+++ b/src/ega.rs
@@ -0,0 +1,61 @@
+static EGA_PALETTE: [[u8; 4]; 16] = [[0x00, 0x00, 0x00, 0x00],
+                                     [0x00, 0x00, 0xAA, 0x00],
+                                     [0x00, 0xAA, 0x00, 0x00],
+                                     [0x00, 0xAA, 0xAA, 0x00],
+                                     [0xAA, 0x00, 0x00, 0x00],
+                                     [0xAA, 0x00, 0xAA, 0x00],
+                                     [0xAA, 0x55, 0x00, 0x00],
+                                     [0xAA, 0xAA, 0xAA, 0x00],
+                                     [0x55, 0x55, 0x55, 0x00],
+                                     [0x55, 0x55, 0xFF, 0x00],
+                                     [0x55, 0xFF, 0x55, 0x00],
+                                     [0x55, 0xFF, 0xFF, 0x00],
+                                     [0xFF, 0x55, 0x55, 0x00],
+                                     [0xFF, 0x55, 0xFF, 0x00],
+                                     [0xFF, 0xFF, 0x55, 0x00],
+                                     [0xFF, 0xFF, 0xFF, 0x00]];
+
+pub enum Compression {
+  UNCOMPRESSED,
+  RLE,
+  LZW
+}
+
+pub enum Tiling {
+  UNTILED,
+  TILED(u16)
+}
+
+pub struct EgaPage {
+  pub data: Vec<u8>,
+  pub tilesize: u16,
+}
+
+impl EgaPage {
+  pub fn iter<'a>(&'a self) -> impl Iterator<Item=&'a [u8]> {
+    self.data.chunks(self.tilesize as usize)
+  }
+}
+
+pub fn decode<'a>(buf: &[u8], compression: Compression, tiling: Tiling)
+                  -> EgaPage {
+  let out: Vec<u8>;
+
+  out = match compression {
+    Compression::UNCOMPRESSED => buf.iter()
+                                    .flat_map(|tile_byte| {
+                                      EGA_PALETTE[(tile_byte >> 4u8 & 0xF) as usize]
+                                        .into_iter()
+                                        .chain(EGA_PALETTE[(tile_byte & 0xF) as usize]
+                                               .into_iter())
+                                    })
+                                    .map(|x| *x)
+                                    .collect(),
+    _ => unimplemented!()
+  };
+  let tilesize = match tiling {
+    Tiling::TILED(tiledim) => 4 * tiledim * tiledim,
+    Tiling::UNTILED => out.len() as u16
+  };
+  EgaPage { data: out, tilesize: tilesize}
+}