52 lines
1.2 KiB
Rust
52 lines
1.2 KiB
Rust
use std::io;
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use std::io::{Read, Seek};
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use std::fs::OpenOptions;
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use std::os::unix::fs::OpenOptionsExt;
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use std::fs::File;
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pub const BLOCK_SIZE: usize = 4096;
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#[repr(align(4096))]
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pub struct Block {
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pub data: [u8; BLOCK_SIZE as usize],
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}
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pub struct BlockManager {
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pub nr_blocks: u64,
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input: File,
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}
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fn get_nr_blocks(path: &str) -> io::Result<u64> {
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let metadata = std::fs::metadata(path)?;
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Ok(metadata.len() / (BLOCK_SIZE as u64))
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}
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impl BlockManager {
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pub fn new(path: &str, _cache_size: usize) -> io::Result<BlockManager> {
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let input = OpenOptions::new()
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.read(true)
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.write(false)
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.custom_flags(libc::O_DIRECT)
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.open(path)?;
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Ok(BlockManager {
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nr_blocks: get_nr_blocks(path)?,
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input: input,
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})
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}
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pub fn get(&mut self, b: u64) -> io::Result<Block> {
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self.read_block(b)
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}
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fn read_block(&mut self, b: u64) -> io::Result<Block>
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{
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let mut buf = Block {data: [0; BLOCK_SIZE]};
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self.input.seek(io::SeekFrom::Start(b * (BLOCK_SIZE as u64)))?;
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self.input.read_exact(&mut buf.data)?;
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Ok(buf)
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}
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}
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