Jeremy Soller
108 lines
3.2 KiB
Rust
108 lines
3.2 KiB
Rust
use std::{cmp, ptr};
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use std::collections::{BTreeMap, VecDeque};
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use syscall::error::Result;
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use BLOCK_SIZE;
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use disk::Disk;
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fn copy_memory(src: &[u8], dest: &mut [u8]) -> usize {
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let len = cmp::min(src.len(), dest.len());
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unsafe { ptr::copy(src.as_ptr(), dest.as_mut_ptr(), len) };
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len
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}
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pub struct DiskCache<T> {
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inner: T,
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cache: BTreeMap<u64, [u8; BLOCK_SIZE as usize]>,
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order: VecDeque<u64>,
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size: usize,
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}
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impl<T: Disk> DiskCache<T> {
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pub fn new(inner: T) -> Self {
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DiskCache {
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inner: inner,
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cache: BTreeMap::new(),
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order: VecDeque::new(),
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size: 65536, // 256 MB cache
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}
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}
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fn insert(&mut self, i: u64, data: [u8; BLOCK_SIZE as usize]) {
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while self.order.len() >= self.size {
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let removed = self.order.pop_front().unwrap();
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self.cache.remove(&removed);
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}
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self.cache.insert(i, data);
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self.order.push_back(i);
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}
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}
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impl<T: Disk> Disk for DiskCache<T> {
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fn read_at(&mut self, block: u64, buffer: &mut [u8]) -> Result<usize> {
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// println!("Cache read at {}", block);
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let mut read = 0;
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let mut failed = false;
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for i in 0..(buffer.len() + BLOCK_SIZE as usize - 1)/(BLOCK_SIZE as usize) {
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let block_i = block + i as u64;
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let buffer_i = i * BLOCK_SIZE as usize;
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let buffer_j = cmp::min(buffer_i + BLOCK_SIZE as usize, buffer.len());
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let buffer_slice = &mut buffer[buffer_i .. buffer_j];
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if let Some(cache_buf) = self.cache.get_mut(&block_i) {
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read += copy_memory(cache_buf, buffer_slice);
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}else{
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failed = true;
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break;
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}
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}
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if failed {
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self.inner.read_at(block, buffer)?;
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read = 0;
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for i in 0..(buffer.len() + BLOCK_SIZE as usize - 1)/(BLOCK_SIZE as usize) {
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let block_i = block + i as u64;
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let buffer_i = i * BLOCK_SIZE as usize;
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let buffer_j = cmp::min(buffer_i + BLOCK_SIZE as usize, buffer.len());
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let buffer_slice = &buffer[buffer_i .. buffer_j];
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let mut cache_buf = [0; BLOCK_SIZE as usize];
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read += copy_memory(buffer_slice, &mut cache_buf);
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self.insert(block_i, cache_buf);
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}
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}
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Ok(read)
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}
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fn write_at(&mut self, block: u64, buffer: &[u8]) -> Result<usize> {
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// println!("Cache write at {}", block);
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self.inner.write_at(block, buffer)?;
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let mut written = 0;
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for i in 0..(buffer.len() + BLOCK_SIZE as usize - 1)/(BLOCK_SIZE as usize) {
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let block_i = block + i as u64;
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let buffer_i = i * BLOCK_SIZE as usize;
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let buffer_j = cmp::min(buffer_i + BLOCK_SIZE as usize, buffer.len());
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let buffer_slice = &buffer[buffer_i .. buffer_j];
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let mut cache_buf = [0; BLOCK_SIZE as usize];
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written += copy_memory(buffer_slice, &mut cache_buf);
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self.insert(block_i, cache_buf);
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}
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Ok(written)
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}
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fn size(&mut self) -> Result<u64> {
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self.inner.size()
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}
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}
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