80 lines
1.4 KiB
Go
80 lines
1.4 KiB
Go
package xtfs
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import (
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"io/fs"
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"os"
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"path"
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)
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// XTFS is an eXTended File System
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type XTFS struct {
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fs fs.FS
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root string
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doCache bool
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cache map[string]bool
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}
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func (x *XTFS) apn(name string) string {
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return path.Join(x.root, name)
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}
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func (x *XTFS) exists(name string) bool {
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if has, ok := x.cache[name]; ok && x.doCache {
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return has
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}
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_, err := os.Stat(x.apn(name))
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if err != nil {
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x.cache[name] = false
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return false
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}
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x.cache[name] = true
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return true
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}
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// Open opens an fs.File, preferring disk
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func (x *XTFS) Open(name string) (fs.File, error) {
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if x.exists(name) {
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return os.Open(x.apn(name))
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}
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return x.fs.Open(name)
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}
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// Option is a functional option for an XTFS
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type Option func(*XTFS) error
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// New returns a new XTFS
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func New(root string, fs fs.FS, opts ...Option) (*XTFS, error) {
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x := &XTFS{
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fs: fs,
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root: root,
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doCache: true,
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cache: make(map[string]bool),
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}
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for _, opt := range opts {
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if err := opt(x); err != nil {
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return x, err
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}
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}
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return x, nil
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}
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// WithSub sets a fs.Sub for an XTFS
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func WithSub(sub string) Option {
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return func(x *XTFS) (err error) {
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x.fs, err = fs.Sub(x.fs, sub)
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return
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}
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}
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// WithCaching sets a caching mode for an XTFS
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// Caching avoids subsequent os.Stat to determine if a file exists on disk
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// See bench.txt for differences in usage
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func WithCaching(doCache bool) Option {
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return func(x *XTFS) error {
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x.doCache = doCache
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return nil
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}
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}
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