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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package diskio
import (
"context"
"sync"
"github.com/datawire/dlib/derror"
"git.lukeshu.com/btrfs-progs-ng/lib/containers"
)
type bufferedBlock[A ~int64] struct {
Mu sync.RWMutex
Addr A
Dirty bool
Dat []byte
Err error
}
type bufferedFile[A ~int64] struct {
ctx context.Context //nolint:containedctx // don't have an option while keeping the io.ReaderAt/io.WriterAt API
inner File[A]
blockSize A
blockCache containers.Cache[A, bufferedBlock[A]]
flushErrs derror.MultiError
}
var _ File[assertAddr] = (*bufferedFile[assertAddr])(nil)
func NewBufferedFile[A ~int64](ctx context.Context, file File[A], blockSize A, cacheSize int) *bufferedFile[A] {
ret := &bufferedFile[A]{
ctx: ctx,
inner: file,
blockSize: blockSize,
}
ret.blockCache = containers.NewARCache[A, bufferedBlock[A]](cacheSize, bufferedBlockSource[A]{ret})
return ret
}
type bufferedBlockSource[A ~int64] struct {
bf *bufferedFile[A]
}
// Flush implements [containers.Source].
func (src bufferedBlockSource[A]) Flush(_ context.Context, block *bufferedBlock[A]) {
if !block.Dirty {
return
}
if _, err := src.bf.inner.WriteAt(block.Dat, block.Addr); err != nil {
src.bf.flushErrs = append(src.bf.flushErrs, err)
}
block.Dirty = false
}
// Load implements [containers.Source].
func (src bufferedBlockSource[A]) Load(ctx context.Context, blockAddr A, block *bufferedBlock[A]) {
src.Flush(ctx, block)
if block.Dat == nil {
block.Dat = make([]byte, src.bf.blockSize)
}
n, err := src.bf.inner.ReadAt(block.Dat[:src.bf.blockSize], blockAddr)
block.Addr = blockAddr
block.Dat = block.Dat[:n]
block.Err = err
}
// Name implements [File].
func (bf *bufferedFile[A]) Name() string { return bf.inner.Name() }
// Size implements [File].
func (bf *bufferedFile[A]) Size() A { return bf.inner.Size() }
func (bf *bufferedFile[A]) Flush() error {
bf.blockCache.Flush(bf.ctx)
if len(bf.flushErrs) > 0 {
return bf.flushErrs
}
return nil
}
// Close implements [File] and [io.Closer].
func (bf *bufferedFile[A]) Close() error {
flushErr := bf.Flush()
if err := bf.inner.Close(); err != nil {
return err
}
return flushErr
}
// ReadAt implements [File] and [ReaderAt].
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) {
offsetWithinBlock := off % bf.blockSize
blockOffset := off - offsetWithinBlock
cachedBlock := bf.blockCache.Acquire(bf.ctx, blockOffset)
defer bf.blockCache.Release(blockOffset)
cachedBlock.Mu.RLock()
defer cachedBlock.Mu.RUnlock()
n = copy(dat, cachedBlock.Dat[offsetWithinBlock:])
if n < len(dat) {
return n, cachedBlock.Err
}
return n, nil
}
// WriteAt implements [File].
func (bf *bufferedFile[A]) WriteAt(dat []byte, off A) (n int, err error) {
done := 0
for done < len(dat) {
n, err := bf.maybeShortWriteAt(dat[done:], off+A(done))
done += n
if err != nil {
return done, err
}
}
return done, nil
}
func (bf *bufferedFile[A]) maybeShortWriteAt(dat []byte, off A) (n int, err error) {
offsetWithinBlock := off % bf.blockSize
blockOffset := off - offsetWithinBlock
cachedBlock := bf.blockCache.Acquire(bf.ctx, blockOffset)
defer bf.blockCache.Release(blockOffset)
cachedBlock.Mu.Lock()
defer cachedBlock.Mu.Unlock()
cachedBlock.Dirty = true
n = copy(cachedBlock.Dat[offsetWithinBlock:], dat)
if n < len(dat) {
return n, cachedBlock.Err
}
return n, nil
}
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