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macro_rules! then_inc { ($v:expr) => {{ $v = $v.wrapping_add(1); $v as usize }}; }
type Page = [u8; 65536];
fn new_blank_page() -> [u8; 65536] { [0; 65536] }
pub struct MemoryDevice {
// Hard limit on the number of pages which can be allocated
pub page_limit: u16,
// Pages which have actually been allocated
pub pages: Vec<Page>,
pub page_1: u16,
pub address_1: u16,
pub page_2: u16,
pub address_2: u16,
pub copy_length: u16,
}
impl MemoryDevice {
pub fn new() -> Self {
Self {
page_limit: 0,
pages: Vec::new(),
page_1: 0,
address_1: 0,
page_2: 0,
address_2: 0,
copy_length: 0,
}
}
pub fn copy(&mut self) {
let count = std::cmp::max(self.page_1, self.page_2) as usize + 1;
if count <= self.page_limit as usize {
if self.pages.len() < count {
self.pages.resize_with(count, new_blank_page);
}
let p1 = self.page_1 as usize;
let p2 = self.page_2 as usize;
let a1 = self.address_1;
let a2 = self.address_2;
for i in 0..=self.copy_length {
let byte = self.pages[p2][a2.wrapping_add(i) as usize];
self.pages[p1][a1.wrapping_add(i) as usize] = byte;
}
}
}
pub fn read_from_head_1(&mut self) -> u8 {
let address = then_inc!(self.address_1);
if let Some(page) = self.pages.get(self.page_1 as usize) {
page[address]
} else {
0x00
}
}
pub fn read_from_head_2(&mut self) -> u8 {
let address = then_inc!(self.address_2);
if let Some(page) = self.pages.get(self.page_2 as usize) {
page[address]
} else {
0x00
}
}
pub fn write_to_head_1(&mut self, byte: u8) {
let address = then_inc!(self.address_1);
let page = self.page_1 as usize;
if self.page_limit as usize > page {
if self.pages.len() <= page {
self.pages.resize_with(page + 1, new_blank_page);
}
self.pages[page][address] = byte;
}
}
pub fn write_to_head_2(&mut self, byte: u8) {
let address = then_inc!(self.address_1);
let page = self.page_2 as usize;
if self.page_limit as usize > page {
if self.pages.len() <= page {
self.pages.resize_with(page + 1, new_blank_page);
}
self.pages[page][address] = byte;
}
}
}
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