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// Copyright (C) 2022 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package diskio
import (
"sync"
"git.lukeshu.com/btrfs-progs-ng/lib/containers"
)
type bufferedBlock struct {
Dat []byte
Err error
}
type bufferedFile[A ~int64] struct {
inner File[A]
mu sync.RWMutex
blockSize A
blockCache *containers.LRUCache[A, bufferedBlock]
}
var _ File[assertAddr] = (*bufferedFile[assertAddr])(nil)
func NewBufferedFile[A ~int64](file File[A], blockSize A, cacheSize int) *bufferedFile[A] {
return &bufferedFile[A]{
inner: file,
blockSize: blockSize,
blockCache: containers.NewLRUCache[A, bufferedBlock](cacheSize),
}
}
func (bf *bufferedFile[A]) Name() string { return bf.inner.Name() }
func (bf *bufferedFile[A]) Size() A { return bf.inner.Size() }
func (bf *bufferedFile[A]) Close() error { return bf.inner.Close() }
func (bf *bufferedFile[A]) ReadAt(dat []byte, off A) (n int, err error) {
done := 0
for done < len(dat) {
n, err := bf.maybeShortReadAt(dat[done:], off+A(done))
done += n
if err != nil {
return done, err
}
}
return done, nil
}
func (bf *bufferedFile[A]) maybeShortReadAt(dat []byte, off A) (n int, err error) {
bf.mu.RLock()
defer bf.mu.RUnlock()
offsetWithinBlock := off % bf.blockSize
blockOffset := off - offsetWithinBlock
cachedBlock, ok := bf.blockCache.Get(blockOffset)
if !ok {
cachedBlock.Dat = make([]byte, bf.blockSize)
n, err := bf.inner.ReadAt(cachedBlock.Dat, blockOffset)
cachedBlock.Dat = cachedBlock.Dat[:n]
cachedBlock.Err = err
bf.blockCache.Add(blockOffset, cachedBlock)
}
n = copy(dat, cachedBlock.Dat[offsetWithinBlock:])
if n < len(dat) {
return n, cachedBlock.Err
}
return n, nil
}
func (bf *bufferedFile[A]) WriteAt(dat []byte, off A) (n int, err error) {
bf.mu.Lock()
defer bf.mu.Unlock()
// Do the work
n, err = bf.inner.WriteAt(dat, off)
// Cache invalidation
for blockOffset := off - (off % bf.blockSize); blockOffset < off+A(n); blockOffset += bf.blockSize {
bf.blockCache.Remove(blockOffset)
}
return
}
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