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package datafs
import (
"bytes"
"fmt"
"io"
"io/fs"
"net/url"
"os"
"strings"
"time"
"github.com/hairyhenderson/go-fsimpl"
)
// newEnvFS returns a filesystem (an fs.FS) that can be used to read data from
// environment variables.
func newEnvFS(_ *url.URL) (fs.FS, error) {
return &envFS{locfs: os.DirFS("/")}, nil
}
type envFS struct {
locfs fs.FS
}
//nolint:gochecknoglobals
var EnvFS = fsimpl.FSProviderFunc(newEnvFS, "env")
var _ fs.FS = (*envFS)(nil)
func (f *envFS) Open(name string) (fs.File, error) {
if !fs.ValidPath(name) {
return nil, &fs.PathError{
Op: "open",
Path: name,
Err: fs.ErrInvalid,
}
}
return &envFile{locfs: f.locfs, name: name}, nil
}
type envFile struct {
locfs fs.FS
body io.Reader
name string
dirents []fs.DirEntry
diroff int
}
var (
_ fs.File = (*envFile)(nil)
_ fs.ReadDirFile = (*envFile)(nil)
)
// overridable env functions
var (
lookupEnv = os.LookupEnv
environ = os.Environ
)
func (e *envFile) Close() error {
e.body = nil
return nil
}
func (e *envFile) envReader() (int, io.Reader, error) {
v, found := lookupEnv(e.name)
if found {
return len(v), bytes.NewBufferString(v), nil
}
fname, found := lookupEnv(e.name + "_FILE")
if found && fname != "" {
fname = strings.TrimPrefix(fname, "/")
b, err := fs.ReadFile(e.locfs, fname)
if err != nil {
return 0, nil, err
}
b = bytes.TrimSpace(b)
return len(b), bytes.NewBuffer(b), nil
}
return 0, nil, fs.ErrNotExist
}
func (e *envFile) Stat() (fs.FileInfo, error) {
n, _, err := e.envReader()
if err != nil {
return nil, err
}
return FileInfo(e.name, int64(n), 0o444, time.Time{}, ""), nil
}
func (e *envFile) Read(p []byte) (int, error) {
if e.body == nil {
_, r, err := e.envReader()
if err != nil {
return 0, err
}
e.body = r
}
return e.body.Read(p)
}
func (e *envFile) ReadDir(n int) ([]fs.DirEntry, error) {
// envFS has no concept of subdirectories, but we can support a root
// directory by listing all environment variables.
if e.name != "." {
return nil, fmt.Errorf("%s: not a directory", e.name)
}
if e.dirents == nil {
envs := environ()
e.dirents = make([]fs.DirEntry, 0, len(envs))
for _, env := range envs {
parts := strings.SplitN(env, "=", 2)
name, value := parts[0], parts[1]
if name == "" {
// this might be a Windows =C: style env var, so skip it
continue
}
e.dirents = append(e.dirents, FileInfoDirEntry(
FileInfo(name, int64(len(value)), 0o444, time.Time{}, ""),
))
}
}
if n > 0 && e.diroff >= len(e.dirents) {
return nil, io.EOF
}
low := e.diroff
high := e.diroff + n
// clamp high at the max, and ensure it's higher than low
if high >= len(e.dirents) || high <= low {
high = len(e.dirents)
}
entries := make([]fs.DirEntry, high-low)
copy(entries, e.dirents[e.diroff:])
e.diroff = high
return entries, nil
}
// FileInfo/DirInfo/FileInfoDirEntry/etc are taken from go-fsimpl's internal
// package, and may be exported in the future...
// FileInfo creates a static fs.FileInfo with the given properties.
// The result is also a fs.DirEntry and can be safely cast.
func FileInfo(name string, size int64, mode fs.FileMode, modTime time.Time, contentType string) fs.FileInfo {
return &staticFileInfo{
name: name,
size: size,
mode: mode,
modTime: modTime,
contentType: contentType,
}
}
// DirInfo creates a fs.FileInfo for a directory with the given name. Use
// FileInfo to set other values.
func DirInfo(name string, modTime time.Time) fs.FileInfo {
return FileInfo(name, 0, fs.ModeDir, modTime, "")
}
type staticFileInfo struct {
modTime time.Time
name string
contentType string
size int64
mode fs.FileMode
}
var (
_ fs.FileInfo = (*staticFileInfo)(nil)
_ fs.DirEntry = (*staticFileInfo)(nil)
)
func (fi staticFileInfo) ContentType() string { return fi.contentType }
func (fi staticFileInfo) IsDir() bool { return fi.Mode().IsDir() }
func (fi staticFileInfo) Mode() fs.FileMode { return fi.mode }
func (fi *staticFileInfo) ModTime() time.Time { return fi.modTime }
func (fi staticFileInfo) Name() string { return fi.name }
func (fi staticFileInfo) Size() int64 { return fi.size }
func (fi staticFileInfo) Sys() any { return nil }
func (fi *staticFileInfo) Info() (fs.FileInfo, error) { return fi, nil }
func (fi staticFileInfo) Type() fs.FileMode { return fi.Mode().Type() }
// FileInfoDirEntry adapts a fs.FileInfo into a fs.DirEntry. If it doesn't
// already implement fs.DirEntry, it will be wrapped to always return the
// same fs.FileInfo.
func FileInfoDirEntry(fi fs.FileInfo) fs.DirEntry {
de, ok := fi.(fs.DirEntry)
if ok {
return de
}
return &fileinfoDirEntry{fi}
}
// a wrapper to make a fs.FileInfo into an fs.DirEntry
type fileinfoDirEntry struct {
fs.FileInfo
}
var _ fs.DirEntry = (*fileinfoDirEntry)(nil)
func (fi *fileinfoDirEntry) Info() (fs.FileInfo, error) { return fi, nil }
func (fi *fileinfoDirEntry) Type() fs.FileMode { return fi.Mode().Type() }
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