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use crate::bitstream::BitStream;
use crate::error::{Result, SmkError};
use crate::huff::Huff16;
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
pub enum YScaleMode {
#[default]
None,
Interlace,
Double,
}
pub(crate) struct Video {
pub enable: bool,
pub w: u32,
pub h: u32,
pub y_scale_mode: YScaleMode,
pub version: u8, // b'2' or b'4'
pub tree: [Huff16; 4],
pub palette: [[u8; 3]; 256],
pub frame: Vec<u8>,
}
/// Smacker 6-bit to 8-bit palette expansion table.
const PALMAP: [u8; 64] = [
0x00, 0x04, 0x08, 0x0C, 0x10, 0x14, 0x18, 0x1C, 0x20, 0x24, 0x28, 0x2C, 0x30, 0x34, 0x38, 0x3C,
0x41, 0x45, 0x49, 0x4D, 0x51, 0x55, 0x59, 0x5D, 0x61, 0x65, 0x69, 0x6D, 0x71, 0x75, 0x79, 0x7D,
0x82, 0x86, 0x8A, 0x8E, 0x92, 0x96, 0x9A, 0x9E, 0xA2, 0xA6, 0xAA, 0xAE, 0xB2, 0xB6, 0xBA, 0xBE,
0xC3, 0xC7, 0xCB, 0xCF, 0xD3, 0xD7, 0xDB, 0xDF, 0xE3, 0xE7, 0xEB, 0xEF, 0xF3, 0xF7, 0xFB, 0xFF,
];
impl Video {
/// Decode a palette chunk, updating `self.palette` in place.
///
/// The palette format uses delta-encoding against the previous palette:
/// - `0x80` prefix: skip (preserve) C+1 entries from the old palette
/// - `0x40` prefix: copy C+1 entries from old palette starting at offset S
/// - Otherwise: direct-set 3 bytes (6-bit values expanded via PALMAP)
pub fn render_palette(&mut self, data: &[u8]) -> Result<()> {
let old_palette = self.palette;
let mut i: usize = 0;
let mut pos: usize = 0;
while i < 256 && pos < data.len() {
let b = data[pos];
if b & 0x80 != 0 {
// Skip block: preserve (count) entries from old palette.
let count = (b & 0x7F) as usize + 1;
pos += 1;
if i + count > 256 {
return Err(SmkError::InvalidData("palette skip overflow"));
}
// Entries already match old_palette since we copied it above,
// but we need to restore them in case earlier ops modified them.
self.palette[i..i + count].copy_from_slice(&old_palette[i..i + count]);
i += count;
} else if b & 0x40 != 0 {
// Color-shift block: copy (count) entries from old palette at (src).
let count = (b & 0x3F) as usize + 1;
pos += 1;
if pos >= data.len() {
return Err(SmkError::InvalidData("palette copy: missing src byte"));
}
let src = data[pos] as usize;
pos += 1;
if i + count > 256 || src + count > 256 {
return Err(SmkError::InvalidData("palette copy overflow"));
}
if src < i && src + count > i {
return Err(SmkError::InvalidData("palette copy overlaps destination"));
}
self.palette[i..i + count].copy_from_slice(&old_palette[src..src + count]);
i += count;
} else {
// Set Color block: read 3 bytes (6-bit each), expand to 8-bit.
if pos + 3 > data.len() {
return Err(SmkError::InvalidData("palette set: not enough bytes"));
}
for c in 0..3 {
let val = data[pos] as usize;
if val > 0x3F {
return Err(SmkError::InvalidData("palette index exceeds 0x3F"));
}
self.palette[i][c] = PALMAP[val];
pos += 1;
}
i += 1;
}
}
if i < 256 {
return Err(SmkError::InvalidData("palette incomplete"));
}
Ok(())
}
/// Decode a video frame from the bitstream into `self.frame`.
///
/// The frame is processed as a grid of 4x4 pixel blocks, left-to-right,
/// top-to-bottom. Each block's type is determined by looking up the TYPE
/// tree, which yields the block type (2 bits), a repeat count via the
/// size table (6 bits), and per-type data (8 bits).
pub fn render_video(&mut self, data: &[u8]) -> Result<()> {
// Size table: entries 0-58 are literal (n+1), last 5 are powers of 2.
const SIZETABLE: [u16; 64] = [
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46,
47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 128, 256, 512, 1024, 2048,
];
// Tree indices.
const TREE_MMAP: usize = 0;
const TREE_MCLR: usize = 1;
const TREE_FULL: usize = 2;
const TREE_TYPE: usize = 3;
let w = self.w as usize;
let h = self.h as usize;
let mut bs = BitStream::new(data);
// Reset the MRU cache on all 4 Huff16 trees before each frame.
for tree in &mut self.tree {
tree.reset_cache();
}
let mut row: usize = 0;
let mut col: usize = 0;
while row < h {
let type_val = self.tree[TREE_TYPE].lookup(&mut bs)?;
let mut block_type = (type_val & 0x0003) as u8;
let blocklen = ((type_val & 0x00FC) >> 2) as usize;
let typedata = ((type_val & 0xFF00) >> 8) as u8;
// SMK v4 extends type 1 (full block) with two sub-types.
if block_type == 1 && self.version == b'4' {
if bs.read_bit()? {
block_type = 4; // v4 double block
} else if bs.read_bit()? {
block_type = 5; // v4 half block
}
}
let repeat = SIZETABLE[blocklen] as usize;
for _ in 0..repeat {
if row >= h {
break;
}
let mut skip = row * w + col;
match block_type {
0 => {
// MONO BLOCK: 2-color pattern via MCLR + MMAP trees.
let clr = self.tree[TREE_MCLR].lookup(&mut bs)?;
let s1 = ((clr >> 8) & 0xFF) as u8;
let s2 = (clr & 0xFF) as u8;
let map = self.tree[TREE_MMAP].lookup(&mut bs)?;
let mut mask = 0x0001u16;
for _ in 0..4 {
for i in 0..4 {
self.frame[skip + i] = if map & mask != 0 { s1 } else { s2 };
mask <<= 1;
}
skip += w;
}
}
1 => {
// FULL BLOCK (v2): each row is two 16-bit lookups,
// pixels stored in reverse order within each pair.
for _ in 0..4 {
let val = self.tree[TREE_FULL].lookup(&mut bs)?;
self.frame[skip + 3] = ((val >> 8) & 0xFF) as u8;
self.frame[skip + 2] = (val & 0xFF) as u8;
let val = self.tree[TREE_FULL].lookup(&mut bs)?;
self.frame[skip + 1] = ((val >> 8) & 0xFF) as u8;
self.frame[skip] = (val & 0xFF) as u8;
skip += w;
}
}
2 => {
// VOID BLOCK: no change (preserve previous frame data).
}
3 => {
// SOLID BLOCK: fill 4x4 with typedata color.
for _ in 0..4 {
self.frame[skip..skip + 4].fill(typedata);
skip += w;
}
}
4 => {
// V4 DOUBLE BLOCK: 2x2 pixel sub-blocks, each row
// pair gets the same colors.
for _ in 0..2 {
let val = self.tree[TREE_FULL].lookup(&mut bs)?;
let hi = ((val >> 8) & 0xFF) as u8;
let lo = (val & 0xFF) as u8;
for _ in 0..2 {
self.frame[skip + 2] = hi;
self.frame[skip + 3] = hi;
self.frame[skip] = lo;
self.frame[skip + 1] = lo;
skip += w;
}
}
}
5 => {
// V4 HALF BLOCK: each 2x2 quadrant gets its own pair
// of pixels, duplicated across 2 rows.
for _ in 0..2 {
let val = self.tree[TREE_FULL].lookup(&mut bs)?;
let hi = ((val >> 8) & 0xFF) as u8;
let lo = (val & 0xFF) as u8;
self.frame[skip + 3] = hi;
self.frame[skip + 2] = lo;
self.frame[skip + w + 3] = hi;
self.frame[skip + w + 2] = lo;
let val = self.tree[TREE_FULL].lookup(&mut bs)?;
let hi = ((val >> 8) & 0xFF) as u8;
let lo = (val & 0xFF) as u8;
self.frame[skip + 1] = hi;
self.frame[skip] = lo;
self.frame[skip + w + 1] = hi;
self.frame[skip + w] = lo;
skip += w * 2;
}
}
_ => unreachable!(),
}
col += 4;
if col >= w {
col = 0;
row += 4;
}
}
}
Ok(())
}
}
#[cfg(test)]
mod tests {
use super::*;
fn make_video() -> Video {
Video {
enable: true,
w: 8,
h: 8,
y_scale_mode: YScaleMode::None,
version: b'4',
tree: Default::default(),
palette: [[0; 3]; 256],
frame: vec![0; 64],
}
}
#[test]
fn palette_direct_set_all() {
let mut v = make_video();
// Set all 256 entries directly: 3 bytes each, all value 0x3F => maps to 0xFF
let mut data = Vec::new();
for _ in 0..256 {
data.extend_from_slice(&[0x3F, 0x3F, 0x3F]);
}
v.render_palette(&data).unwrap();
for i in 0..256 {
assert_eq!(v.palette[i], [0xFF, 0xFF, 0xFF]);
}
}
#[test]
fn palette_skip_all() {
let mut v = make_video();
// Pre-fill with a known palette
for i in 0..256 {
v.palette[i] = [i as u8, 0, 0];
}
// Skip all 256 entries: 0x80 | (256-1) = 0xFF, but max is 0x7F+1=128.
// So we need two skip blocks of 128 each.
let data = [0xFF, 0xFF]; // two blocks of 128
v.render_palette(&data).unwrap();
// All entries should be preserved.
for i in 0..256 {
assert_eq!(v.palette[i], [i as u8, 0, 0]);
}
}
#[test]
fn palette_copy_block() {
let mut v = make_video();
// Set first 4 entries to known colors
v.palette[0] = [10, 20, 30];
v.palette[1] = [40, 50, 60];
v.palette[2] = [70, 80, 90];
v.palette[3] = [100, 110, 120];
// Skip first 4, then copy 4 entries from src=0 to entries 4-7,
// then set remaining 248 entries directly.
let mut data = Vec::new();
// Skip 4: 0x80 | 3 = 0x83
data.push(0x83);
// Copy 4 from src=0: 0x40 | 3 = 0x43, src=0
data.push(0x43);
data.push(0x00);
// Set remaining 248 entries to (0, 0, 0)
for _ in 0..248 {
data.extend_from_slice(&[0x00, 0x00, 0x00]);
}
v.render_palette(&data).unwrap();
assert_eq!(v.palette[4], [10, 20, 30]);
assert_eq!(v.palette[5], [40, 50, 60]);
assert_eq!(v.palette[6], [70, 80, 90]);
assert_eq!(v.palette[7], [100, 110, 120]);
}
#[test]
fn palette_value_exceeds_6bit() {
let mut v = make_video();
// 0x40 is > 0x3F, should error
let _data = [0x40, 0x00, 0x00];
// But 0x40 is actually the copy-block prefix, not a direct-set.
// For a direct-set error, the first byte must be < 0x40 (the flag byte)
// and one of the color bytes must be > 0x3F.
// First byte 0x00 means direct-set. Then bytes [0x40, 0x00, 0x00] for colors.
// Wait — first byte IS 0x40, which triggers the copy path. Let me fix the test.
// To trigger the > 0x3F check, we need first byte < 0x40, then a color byte > 0x3F.
// entry: first byte 0x00 (< 0x40, < 0x80) = direct set,
// then R=0x00, G=0x00, B=0x40 (> 0x3F)
let data2 = [0x00, 0x00, 0x40];
let err = v.render_palette(&data2);
assert!(err.is_err());
}
#[test]
fn palette_incomplete() {
let mut v = make_video();
// Only set 1 entry, palette should be incomplete.
let data = [0x00, 0x00, 0x00];
let err = v.render_palette(&data);
assert!(err.is_err());
}
}