67 lines
1.6 KiB
Go
67 lines
1.6 KiB
Go
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package mergefs
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import (
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"errors"
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"io/fs"
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"os"
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)
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// Merge merges the given filesystems together,
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func Merge(filesystems ...fs.FS) fs.FS {
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return MergedFS{filesystems: filesystems}
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}
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// MergedFS combines filesystems. Each filesystem can serve different paths.
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// The first FS takes precedence
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type MergedFS struct {
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filesystems []fs.FS
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}
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// Open opens the named file.
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func (mfs MergedFS) Open(name string) (fs.File, error) {
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for _, fs := range mfs.filesystems {
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file, err := fs.Open(name)
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if err == nil { // TODO should we return early when it's not an os.ErrNotExist? Should we offer options to decide this behaviour?
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return file, nil
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}
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}
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return nil, os.ErrNotExist
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}
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// ReadDir reads from the directory, and produces a DirEntry array of different
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// directories.
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//
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// It iterates through all different filesystems that exist in the mfs MergeFS
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// filesystem slice and it identifies overlapping directories that exist in different
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// filesystems
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func (mfs MergedFS) ReadDir(name string) ([]fs.DirEntry, error) {
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dirsMap := make(map[string]fs.DirEntry)
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notExistCount := 0
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for _, filesystem := range mfs.filesystems {
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dir, err := fs.ReadDir(filesystem, name)
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if err != nil {
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if errors.Is(err, fs.ErrNotExist) {
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notExistCount++
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continue
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}
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return nil, err
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}
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for _, v := range dir {
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if _, ok := dirsMap[v.Name()]; !ok {
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dirsMap[v.Name()] = v
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}
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}
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continue
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}
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if len(mfs.filesystems) == notExistCount {
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return nil, fs.ErrNotExist
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}
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dirs := make([]fs.DirEntry, 0, len(dirsMap))
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for _, value := range dirsMap {
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dirs = append(dirs, value)
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}
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return dirs, nil
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}
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