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stage.go
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stage.go
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package ocfl
import (
"context"
"errors"
"fmt"
"io/fs"
"path"
"sort"
"strings"
"testing/fstest"
)
// Stage is used to create/update objects.
type Stage struct {
// State is a DigestMap representing the new object version state.
State DigestMap
// DigestAlgorithm is the primary digest algorithm (sha512 or sha256) used by the stage
// state.
DigestAlgorithm string
// ContentSource is used to access new content needed to construct
// an object. It may be nil
ContentSource
// FixitySource is used to access fixity information for new
// content. It may be nil
FixitySource
}
// HasContent returns true if the stage's content source provides an FS and path
// for the digest
func (s Stage) HasContent(digest string) bool {
if s.ContentSource == nil {
return false
}
f, p := s.ContentSource.GetContent(digest)
return f != nil && p != ""
}
// Overlay merges the state and content/fixity sources from all stages into s.
// All stages mush share the same digest algorithm.
func (s *Stage) Overlay(stages ...*Stage) error {
if s.State == nil {
s.State = DigestMap{}
}
if alg := s.DigestAlgorithm; alg == "" || (alg != SHA512 && alg != SHA256) {
return errors.New("stage's digest algorithm must be 'sha512' or 'sha256'")
}
var err error
for _, over := range stages {
if s.DigestAlgorithm != over.DigestAlgorithm {
return errors.New("can't overlay stage with different digest algorithm than the base")
}
s.State, err = s.State.Merge(over.State, true)
if err != nil {
return err
}
s.addContentSource(over.ContentSource)
s.addFixitySource(over.FixitySource)
}
if err := s.State.Valid(); err != nil {
return err
}
return nil
}
func (s *Stage) addContentSource(cs ContentSource) {
var sources contentSources
switch current := s.ContentSource.(type) {
case contentSources:
sources = current
case nil:
default:
sources = contentSources{current}
}
switch p := cs.(type) {
case contentSources:
sources = append(sources, p...)
case nil:
default:
sources = append(sources, p)
}
s.ContentSource = sources
}
func (s *Stage) addFixitySource(fs FixitySource) {
var sources fixitySources
switch current := s.FixitySource.(type) {
case fixitySources:
sources = current
case nil:
default:
sources = fixitySources{current}
}
switch p := fs.(type) {
case fixitySources:
sources = append(sources, p...)
case nil:
default:
sources = append(sources, p)
}
s.FixitySource = sources
}
// ContentSource is used to access content with a given digest when
// creating and upadting objects.
type ContentSource interface {
// GetContent returns an FS and path to a file in FS for a file with the given digest.
// If no content is associated with the digest, fsys is nil and path is an empty string.
GetContent(digest string) (fsys FS, path string)
}
// FixitySource is used to access alternate digests for content with a given digest
// (sha512 or sha256) when creating or updating objects.
type FixitySource interface {
// GetFixity returns a DigestSet with alternate digests for the content with
// the digest derrived using the stage's primary digest algorithm.
GetFixity(digest string) DigestSet
}
type contentSources []ContentSource
func (ps contentSources) GetContent(digest string) (FS, string) {
for _, provider := range ps {
fsys, pth := provider.GetContent(digest)
if fsys != nil {
return fsys, pth
}
}
return nil, ""
}
type fixitySources []FixitySource
func (ps fixitySources) GetFixity(digest string) DigestSet {
set := DigestSet{}
for _, fixer := range ps {
for fixAlg, fixDigest := range fixer.GetFixity(digest) {
set[fixAlg] = fixDigest
}
}
return set
}
// StageDir builds a stage based on the contents of the directory dir in FS.
// All files in dir and its subdirectories are digested with the given digest
// algs and added to the stage. The algs must include sha512 or sha256 or an
// error is returned
func StageDir(ctx context.Context, fsys FS, dir string, algs ...string) (*Stage, error) {
if len(algs) < 1 || (algs[0] != SHA512 && algs[0] != SHA256) {
return nil, fmt.Errorf("must use sha512 or sha256 as the primary digest algorithm for the stage")
}
if !fs.ValidPath(dir) {
return nil, fmt.Errorf("invalid stage directory: %q", dir)
}
alg := algs[0]
dirMan := &dirManifest{
fs: fsys,
root: dir,
manifest: map[string]dirManifestEntry{},
}
var walkErr error
walkFS := func(digestFile func(name string, algs []string) bool) {
// add files to digest work queue
Files(ctx, dirMan.fs, dir)(func(info FileInfo, err error) bool {
if err != nil {
walkErr = err
return false
}
digestFile(info.Path, algs)
return true
})
}
// digest result: add results to the stage
var digestErr error
Digest(ctx, dirMan.fs, walkFS)(func(r PathDigests, err error) bool {
name := r.Path
if err != nil {
digestErr = err
return false
}
if dirMan.root != "." {
// Trim name so it's relative to root, not FS
name = strings.TrimPrefix(name, dirMan.root+"/")
}
primary, fixity, err := splitDigests(r.Digests, alg)
if err != nil {
digestErr = err
return false
}
if dirMan.manifest == nil {
dirMan.manifest = make(map[string]dirManifestEntry)
}
entry := dirMan.manifest[primary]
entry.addPaths(name)
entry.addFixity(fixity)
dirMan.manifest[primary] = entry
return true
})
// run checksum
if err := errors.Join(walkErr, digestErr); err != nil {
return nil, err
}
state := DigestMap{}
for dig, entry := range dirMan.manifest {
state[dig] = entry.paths
}
return &Stage{
State: state,
DigestAlgorithm: alg,
ContentSource: dirMan,
FixitySource: dirMan,
}, nil
}
type dirManifest struct {
fs FS
root string
manifest map[string]dirManifestEntry
}
func (s *dirManifest) ContentFS() FS {
return s.fs
}
func (s *dirManifest) GetContent(digest string) (FS, string) {
if s.fs == nil || s.manifest == nil || len(s.manifest[digest].paths) == 0 {
return nil, ""
}
return s.fs, path.Join(s.root, s.manifest[digest].paths[0])
}
func (s *dirManifest) GetFixity(dig string) DigestSet {
return s.manifest[dig].fixity
}
type dirManifestEntry struct {
paths []string // content paths relative to Root in FS
fixity DigestSet // additional digests associate with paths
}
func (entry *dirManifestEntry) addPaths(paths ...string) {
for _, stagePath := range paths {
i := sort.SearchStrings(entry.paths, stagePath)
if i < len(entry.paths) && entry.paths[i] == stagePath {
return // already present
}
entry.paths = append(entry.paths, "")
copy(entry.paths[i+1:], entry.paths[i:])
entry.paths[i] = stagePath
}
}
func (entry *dirManifestEntry) addFixity(fixity DigestSet) {
if len(fixity) == 0 {
return
}
if entry.fixity == nil {
entry.fixity = fixity
return
}
for alg, dig := range fixity {
entry.fixity[alg] = dig
}
}
func splitDigests(set DigestSet, alg string) (string, DigestSet, error) {
newSet := DigestSet{}
dig := ""
for setAlg, setVal := range set {
if setAlg == alg {
dig = setVal
continue
}
newSet[setAlg] = setVal
}
if dig == "" {
return "", nil, fmt.Errorf("missing %s value", alg)
}
return dig, newSet, nil
}
// StageBytes builds a stage from a map of filenames to file contents
func StageBytes(content map[string][]byte, algs ...string) (*Stage, error) {
mapFS := fstest.MapFS{}
for file, bytes := range content {
mapFS[file] = &fstest.MapFile{Data: bytes}
}
ctx := context.Background()
return StageDir(ctx, NewFS(mapFS), ".", algs...)
}