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// Package packed provides read access to packed Git objects from objects/pack.
package packed
import (
"errors"
"os"
"sync"
"codeberg.org/lindenii/furgit/objectid"
"codeberg.org/lindenii/furgit/objectstore"
)
// Store reads Git objects from pack/index files under an objects/pack root.
//
// Store does not own root. Callers are responsible for closing root.
type Store struct {
// root is the objects/pack capability used for all file access.
root *os.Root
// algo is the expected object ID algorithm for lookups.
algo objectid.Algorithm
// loadOnce guards one-time index loading.
loadOnce sync.Once
// loadErr stores index loading failures.
loadErr error
// indexesLoaded reports whether indexes/loadErr have been initialized.
indexesLoaded bool
// indexes stores parsed .idx handles.
indexes []*idxFile
// stateMu guards index publication, pack cache, and close state.
stateMu sync.RWMutex
// cacheMu guards delta cache operations.
cacheMu sync.RWMutex
// packs caches opened .pack handles by basename.
packs map[string]*packFile
// deltaCache caches resolved base objects by pack location.
deltaCache *deltaCache
// closed reports whether Close has been called.
closed bool
}
const defaultDeltaCacheMaxBytes = 32 << 20
var _ objectstore.Store = (*Store)(nil)
// New creates a packed-object store rooted at an objects/pack directory.
func New(root *os.Root, algo objectid.Algorithm) (*Store, error) {
if algo.Size() == 0 {
return nil, objectid.ErrInvalidAlgorithm
}
return &Store{
root: root,
algo: algo,
packs: make(map[string]*packFile),
deltaCache: newDeltaCache(defaultDeltaCacheMaxBytes),
}, nil
}
// Close releases mapped pack/index resources associated with the store.
func (store *Store) Close() error {
store.stateMu.Lock()
if store.closed {
store.stateMu.Unlock()
return nil
}
store.closed = true
packs := store.packs
store.packs = make(map[string]*packFile)
indexes := store.indexes
store.indexes = nil
store.stateMu.Unlock()
var closeErr error
for _, pack := range packs {
if err := pack.close(); err != nil && closeErr == nil {
closeErr = err
}
}
for _, index := range indexes {
if index == nil {
continue
}
if err := index.close(); err != nil && closeErr == nil {
closeErr = err
}
}
store.cacheMu.Lock()
if store.deltaCache != nil {
store.deltaCache.clear()
}
store.cacheMu.Unlock()
return closeErr
}
// ensureIndexes loads and validates all pack indexes once.
func (store *Store) ensureIndexes() error {
store.loadOnce.Do(func() {
indexes, err := store.loadIndexes()
store.stateMu.Lock()
store.indexes = indexes
store.loadErr = err
store.indexesLoaded = true
store.stateMu.Unlock()
})
store.stateMu.RLock()
defer store.stateMu.RUnlock()
if store.indexesLoaded {
return store.loadErr
}
return errors.New("objectstore/packed: indexes were not initialized")
}
// lookup resolves one object ID to its pack location.
func (store *Store) lookup(id objectid.ObjectID) (location, error) {
var zero location
if id.Algorithm() != store.algo {
return zero, errors.New("objectstore/packed: object id algorithm mismatch")
}
if err := store.ensureIndexes(); err != nil {
return zero, err
}
for _, index := range store.indexes {
offset, ok, err := index.lookup(id)
if err != nil {
return zero, err
}
if ok {
return location{packName: index.packName, offset: offset}, nil
}
}
return zero, objectstore.ErrObjectNotFound
}
// openPack returns one opened and validated pack handle.
func (store *Store) openPack(name string) (*packFile, error) {
store.stateMu.RLock()
if pack, ok := store.packs[name]; ok {
store.stateMu.RUnlock()
return pack, nil
}
store.stateMu.RUnlock()
file, err := store.root.Open(name)
if err != nil {
return nil, err
}
info, err := file.Stat()
if err != nil {
_ = file.Close()
return nil, err
}
pack, err := openPackFile(name, file, info.Size())
if err != nil {
_ = file.Close()
return nil, err
}
store.stateMu.Lock()
if existing, ok := store.packs[name]; ok {
store.stateMu.Unlock()
_ = pack.close()
return existing, nil
}
store.packs[name] = pack
store.stateMu.Unlock()
return pack, nil
}
// entryMetaAt parses one pack entry header at location.
func (store *Store) entryMetaAt(loc location) (*packFile, entryMeta, error) {
pack, err := store.openPack(loc.packName)
if err != nil {
return nil, entryMeta{}, err
}
meta, err := parseEntryMeta(pack, store.algo, loc.offset)
if err != nil {
return nil, entryMeta{}, err
}
return pack, meta, nil
}
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