81 lines
2.4 KiB
Go
81 lines
2.4 KiB
Go
package fs
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import (
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"context"
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"fmt"
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"os"
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)
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// FileSpec describes a single synthetic file exposed by a Tree.
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type FileSpec struct {
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Name string
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Mode os.FileMode
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Read func() ([]byte, error)
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Write func([]byte) error // nil = read-only
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Wait func(ctx context.Context, base string) (content []byte, nextBase string, err error) // nil = not waitable
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Size func() int64 // optional; if nil, len(Read())
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OneShot bool // true = yields data once per open
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Async bool // true = writes dispatched asynchronously
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}
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// NewSynth creates a Tree backed by a table of FileSpecs (synthetic files).
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func NewSynth(specs []FileSpec) *Tree {
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index := make(map[string]int, len(specs))
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for i, s := range specs {
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index[s.Name] = i
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}
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lookup := func(name string) (*FileSpec, bool) {
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i, ok := index[name]
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if !ok {
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return nil, false
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}
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return &specs[i], true
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}
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return NewTree(nil, 0,
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WithLister(func(_ []string) ([]os.DirEntry, error) {
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entries := make([]os.DirEntry, len(specs))
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for i, s := range specs {
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entries[i] = FileEntry(s.Name, s.Mode)
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}
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return entries, nil
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}),
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WithOpener(func(_ []string, name string) (File, error) {
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spec, ok := lookup(name)
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if !ok {
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return nil, fmt.Errorf("%s: not found", name)
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}
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writeFn := func([]byte) error { return fmt.Errorf("%s: read-only", name) }
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if spec.Write != nil {
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writeFn = spec.Write
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}
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waitFn := func(context.Context, string) ([]byte, string, error) {
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return nil, "", fmt.Errorf("%s: not a wait file", name)
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}
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if spec.Wait != nil {
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waitFn = spec.Wait
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}
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return &FileConfig{
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StatFn: func() (os.FileInfo, error) {
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var size int64
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if spec.Size != nil {
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size = spec.Size()
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} else if spec.Wait != nil {
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size = 4096
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} else if data, err := spec.Read(); err == nil {
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size = int64(len(data))
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}
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return &SyntheticFileInfo{Name_: name, Mode_: spec.Mode, Size_: size}, nil
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},
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ReadFn: spec.Read,
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WriteFn: writeFn,
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BlockingReadFn: waitFn,
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OneShot_: spec.OneShot || spec.Wait != nil,
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IsBlocking_: spec.Wait != nil,
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Async_: spec.Async,
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}, nil
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}),
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)
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}
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