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pub struct Metadata<'a> {
program: &'a [u8],
}
impl<'a> Metadata<'a> {
pub fn from(program: &'a [u8]) -> Option<Self> {
if program.len() < 10 {
return None;
}
let identifier = [0xE8,0x00,0x18,0x42,0x45,0x44,0x52,0x4F,0x43,0x4B];
match program[0..10] == identifier {
true => Some(Self { program }),
false => None,
}
}
pub fn name(&self) -> Option<String> {
let pointer = self.get_pointer(0x000A)?;
self.get_string(pointer)
}
pub fn authors(&self) -> Option<Vec<String>> {
let pointer = self.get_pointer(0x000C)?;
let string = self.get_string(pointer)?;
Some(string.lines().map(String::from).collect())
}
pub fn description(&self) -> Option<String> {
let pointer = self.get_pointer(0x000E)?;
self.get_string(pointer)
}
pub fn bg_colour(&self) -> Option<MetadataColour> {
let pointer = self.get_pointer(0x0010)?;
let colour = self.get_pointer(pointer)?;
Some(MetadataColour::from_double(colour))
}
pub fn fg_colour(&self) -> Option<MetadataColour> {
let pointer = self.get_pointer(0x0012)?;
let colour = self.get_pointer(pointer)?;
Some(MetadataColour::from_double(colour))
}
pub fn small_icon(&self) -> Option<Vec<u8>> {
let pointer = self.get_pointer(0x0014)?;
self.get_icon(pointer, 72)
}
pub fn large_icon(&self) -> Option<Vec<u8>> {
let pointer = self.get_pointer(0x0016)?;
self.get_icon(pointer, 512)
}
fn get_byte(&self, address: u16) -> Option<u8> {
self.program.get(address as usize).copied()
}
fn get_pointer(&self, address: u16) -> Option<u16> {
let high = self.get_byte(address)?;
let low = self.get_byte(address.checked_add(1)?)?;
let pointer = u16::from_be_bytes([high, low]);
if pointer != 0 { Some(pointer) } else { None }
}
fn get_string(&self, address: u16) -> Option<String> {
let start = address as usize;
let mut end = address as usize;
loop {
match self.program.get(end) {
Some(0) => break,
Some(_) => end += 1,
None => return None,
}
}
let vec = self.program[start..end].to_vec();
String::from_utf8(vec).ok()
}
fn get_icon(&self, address: u16, length: usize) -> Option<Vec<u8>> {
let address = address as usize;
let data = &self.program[address..address+length];
match data.len() == length {
true => Some(data.to_vec()),
false => None,
}
}
}
pub struct MetadataColour {
pub red: u8,
pub green: u8,
pub blue: u8,
}
impl MetadataColour {
pub fn from_double(colour: u16) -> Self {
let red = (colour & 0x0F00 >> 8) as u8 * 17;
let green = (colour & 0x00F0 >> 4) as u8 * 17;
let blue = (colour & 0x000F >> 0) as u8 * 17;
Self { red, green, blue }
}
}
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