diff options
Diffstat (limited to 'src/memory/cached_block.rs')
-rw-r--r-- | src/memory/cached_block.rs | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/src/memory/cached_block.rs b/src/memory/cached_block.rs new file mode 100644 index 0000000..0c401ff --- /dev/null +++ b/src/memory/cached_block.rs @@ -0,0 +1,84 @@ +use and_then_some::BoolExt; +use crate::AyaFS; +use crate::block_device::BLOCK_SIZE; +use crate::disk::data_block::{Block, DataBlock}; + +#[derive(Clone)] +pub struct CachedBlock<T: Block> { + pub block: T, + pub index: usize, + pub dirty: bool, +} + +impl<T: Block> CachedBlock<T> { + fn cast<U: Block>(&self) -> CachedBlock<U> { + unsafe { std::mem::transmute_copy(&self) } + } +} + +pub fn convert_mut<U: Block, T: Block>(input_block: &mut CachedBlock<U>) -> &mut CachedBlock<T> { + let ptr = input_block as *const CachedBlock<U> as *mut u8; + let block = ptr.cast::<CachedBlock<T>>(); + unsafe { &mut *block } +} + +pub fn convert<U: Block, T: Block>(input_block: &CachedBlock<U>) -> &CachedBlock<T> { + let ptr = input_block as *const CachedBlock<U> as *mut u8; + let block = ptr.cast::<CachedBlock<T>>(); + unsafe { &*block } +} + +impl AyaFS { + pub(crate) fn update_block<T: Block>(&mut self, block: CachedBlock<T>) -> bool { + if self.cached_blocks.contains(&block.index) { + let data_block = convert::<T, DataBlock>(&block).clone(); + self.cached_blocks.push(block.index, data_block); + true + } else { + false + } + } + pub(crate) fn get_block<T: Block>(&mut self, index: usize) -> Option<&CachedBlock<T>> { + self.load_block(index) + .and_then(|| self.cached_blocks.get(&index).map(convert::<DataBlock, T>)) + } + + pub(crate) fn get_block_mut<T: Block>(&mut self, index: usize) -> Option<&mut CachedBlock<T>> { + self.load_block(index).and_then(|| { + self.cached_blocks + .get_mut(&index) + .map(convert_mut::<DataBlock, T>) + }) + } + + pub(crate) fn load_block(&mut self, index: usize) -> bool { + // 反正我自己保证所有实现了 Block trait 的数据结构都是 4K bytes 长, 来回 cast 没问题 + // 如果 block cache 里没有这个 block + if self.cached_blocks.contains(&index) == false { + if self.data_bitmap.query(index) == false { + return false; + } // 先看这个 block 是不是 valid, 不 valid 直接返回 None + let block = DataBlock::default(); + let buffer = unsafe { + std::slice::from_raw_parts_mut(&block as *const DataBlock as *mut u8, BLOCK_SIZE) + }; + self.device.read(index, buffer); + let cached_block = CachedBlock { + block, + index, + dirty: false, + }; + if let Some((old_index, old_block)) = self.cached_blocks.push(index, cached_block) { + assert_ne!(old_index, index); // 只有 block 不在 cache 里的时候才会插入 + if old_block.dirty { + let old_block_ptr = &old_block.block as *const DataBlock as *mut u8; + let old_block_buffer = + unsafe { std::slice::from_raw_parts(old_block_ptr, BLOCK_SIZE) }; + self.device.write(old_index, old_block_buffer); + } + } // 如果 valid 就放到 block cache 里, 同时将(可能)被驱逐的 block 依据其是否为脏块进行写回 + } + + true + } +} |