ref: 0a4686c132052d9b01ac5d438c6a46e7b4fe22e5
parent: 5eda091d68a427e9f23e120bad1767f796ae58b6
author: Runxi Yu <me@runxiyu.org>
date: Sat Feb 21 14:44:12 EST 2026
objectstore/packed: Separate idx candidate lookup vs actually opening it
--- a/objectstore/packed/idx_load.go
+++ /dev/null
@@ -1,241 +1,0 @@
-package packed
-
-import (
- "fmt"
- "os"
- "slices"
- "strings"
- "syscall"
-
- "codeberg.org/lindenii/furgit/internal/intconv"
- "codeberg.org/lindenii/furgit/objectid"
-)
-
-// location identifies one object entry in a specific pack file.
-type location struct {- packName string
- offset uint64
-}
-
-// packCandidate describes one discovered pack/index pair.
-type packCandidate struct {- // packName is the .pack basename.
- packName string
- // idxName is the .idx basename.
- idxName string
- // mtime is the pack file modification time for initial ordering.
- mtime int64
-}
-
-// idxFile stores one mapped and validated idx v2 file.
-type idxFile struct {- // idxName is the basename of this .idx file.
- idxName string
- // packName is the matching .pack basename.
- packName string
- // algo is the hash algorithm encoded by the index.
- algo objectid.Algorithm
-
- // file is the opened index file descriptor.
- file *os.File
- // data is the mapped index bytes.
- data []byte
-
- // fanout stores fanout table values.
- fanout [256]uint32
- // numObjects equals fanout[255].
- numObjects int
-
- // namesOffset starts the sorted object-id table.
- namesOffset int
- // offset32Offset starts the 32-bit offset table.
- offset32Offset int
- // offset64Offset starts the 64-bit offset table.
- offset64Offset int
- // offset64Count is the number of 64-bit offset entries.
- offset64Count int
-}
-
-// ensureCandidates discovers pack/index pairs once.
-func (store *Store) ensureCandidates() error {- store.discoverOnce.Do(func() {- candidates, err := store.discoverCandidates()
- candidateByPack := make(map[string]packCandidate, len(candidates))
- for _, candidate := range candidates {- candidateByPack[candidate.packName] = candidate
- }
- store.stateMu.Lock()
- store.candidates = candidates
- store.candidateByPack = candidateByPack
- store.discoverErr = err
- store.stateMu.Unlock()
- })
-
- store.stateMu.RLock()
- err := store.discoverErr
- store.stateMu.RUnlock()
- return err
-}
-
-// discoverCandidates scans the objects/pack root and returns sorted pack/index
-// pairs.
-func (store *Store) discoverCandidates() ([]packCandidate, error) {- dir, err := store.root.Open(".")- if err != nil {- if os.IsNotExist(err) {- return nil, nil
- }
- return nil, err
- }
- defer func() { _ = dir.Close() }()-
- entries, err := dir.ReadDir(-1)
- if err != nil {- return nil, err
- }
-
- candidates := make([]packCandidate, 0, len(entries))
- for _, entry := range entries {- if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".idx") {- continue
- }
-
- idxName := entry.Name()
- packName := strings.TrimSuffix(idxName, ".idx") + ".pack"
- packInfo, err := store.root.Stat(packName)
- if err != nil {- if os.IsNotExist(err) {- return nil, fmt.Errorf("objectstore/packed: missing pack file for index %q", idxName)- }
- return nil, err
- }
-
- candidates = append(candidates, packCandidate{- packName: packName,
- idxName: idxName,
- mtime: packInfo.ModTime().UnixNano(),
- })
- }
-
- slices.SortFunc(candidates, func(a, b packCandidate) int {- if a.mtime != b.mtime {- if a.mtime > b.mtime {- return -1
- }
- return 1
- }
- return strings.Compare(a.packName, b.packName)
- })
-
- return candidates, nil
-}
-
-// candidateForPack returns one discovered candidate for a pack basename.
-func (store *Store) candidateForPack(packName string) (packCandidate, bool) {- store.stateMu.RLock()
- candidate, ok := store.candidateByPack[packName]
- store.stateMu.RUnlock()
- return candidate, ok
-}
-
-// openIndex returns one opened and parsed index, caching it by pack basename.
-func (store *Store) openIndex(candidate packCandidate) (*idxFile, error) {- store.stateMu.RLock()
- if index, ok := store.idxByPack[candidate.packName]; ok {- store.stateMu.RUnlock()
- return index, nil
- }
- store.stateMu.RUnlock()
-
- index, err := openIdxFile(store.root, candidate.idxName, candidate.packName, store.algo)
- if err != nil {- return nil, err
- }
-
- store.stateMu.Lock()
- if existing, ok := store.idxByPack[candidate.packName]; ok {- store.stateMu.Unlock()
- _ = index.close()
- return existing, nil
- }
- store.idxByPack[candidate.packName] = index
- store.stateMu.Unlock()
- return index, nil
-}
-
-// touchCandidate moves one candidate to the front of the lookup order.
-func (store *Store) touchCandidate(packName string) {- store.stateMu.Lock()
- defer store.stateMu.Unlock()
- for i := range store.candidates {- if store.candidates[i].packName != packName {- continue
- }
- if i == 0 {- return
- }
- candidate := store.candidates[i]
- copy(store.candidates[1:i+1], store.candidates[0:i])
- store.candidates[0] = candidate
- return
- }
-}
-
-// openIdxFile maps and validates one idx v2 file.
-func openIdxFile(root *os.Root, idxName, packName string, algo objectid.Algorithm) (*idxFile, error) {- file, err := root.Open(idxName)
- if err != nil {- return nil, err
- }
- info, err := file.Stat()
- if err != nil {- _ = file.Close()
- return nil, err
- }
- size := info.Size()
- if size < 0 || size > int64(int(^uint(0)>>1)) {- _ = file.Close()
- return nil, fmt.Errorf("objectstore/packed: idx %q has unsupported size", idxName)- }
- fd, err := intconv.UintptrToInt(file.Fd())
- if err != nil {- _ = file.Close()
- return nil, err
- }
- data, err := syscall.Mmap(fd, 0, int(size), syscall.PROT_READ, syscall.MAP_PRIVATE)
- if err != nil {- _ = file.Close()
- return nil, err
- }
-
- index := &idxFile{- idxName: idxName,
- packName: packName,
- algo: algo,
- file: file,
- data: data,
- }
- if err := index.parse(); err != nil {- _ = index.close()
- return nil, err
- }
- return index, nil
-}
-
-// close unmaps and closes one idx handle.
-func (index *idxFile) close() error {- var closeErr error
- if index.data != nil {- if err := syscall.Munmap(index.data); err != nil && closeErr == nil {- closeErr = err
- }
- index.data = nil
- }
- if index.file != nil {- if err := index.file.Close(); err != nil && closeErr == nil {- closeErr = err
- }
- index.file = nil
- }
- return closeErr
-}
--- /dev/null
+++ b/objectstore/packed/idx_lookup_candidates.go
@@ -1,0 +1,116 @@
+package packed
+
+import (
+ "fmt"
+ "os"
+ "slices"
+ "strings"
+)
+
+// location identifies one object entry in a specific pack file.
+type location struct {+ packName string
+ offset uint64
+}
+
+// packCandidate describes one discovered pack/index pair.
+type packCandidate struct {+ // packName is the .pack basename.
+ packName string
+ // idxName is the .idx basename.
+ idxName string
+ // mtime is the pack file modification time for initial ordering.
+ mtime int64
+}
+
+// ensureCandidates discovers pack/index pairs once.
+func (store *Store) ensureCandidates() error {+ store.discoverOnce.Do(func() {+ candidates, err := store.discoverCandidates()
+ candidateByPack := make(map[string]packCandidate, len(candidates))
+ for _, candidate := range candidates {+ candidateByPack[candidate.packName] = candidate
+ }
+ store.stateMu.Lock()
+ store.candidates = candidates
+ store.candidateByPack = candidateByPack
+ store.discoverErr = err
+ store.stateMu.Unlock()
+ })
+
+ store.stateMu.RLock()
+ err := store.discoverErr
+ store.stateMu.RUnlock()
+ return err
+}
+
+// discoverCandidates scans the objects/pack root and returns sorted pack/index
+// pairs.
+func (store *Store) discoverCandidates() ([]packCandidate, error) {+ dir, err := store.root.Open(".")+ if err != nil {+ if os.IsNotExist(err) {+ return nil, nil
+ }
+ return nil, err
+ }
+ defer func() { _ = dir.Close() }()+
+ entries, err := dir.ReadDir(-1)
+ if err != nil {+ return nil, err
+ }
+
+ candidates := make([]packCandidate, 0, len(entries))
+ for _, entry := range entries {+ if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".idx") {+ continue
+ }
+
+ idxName := entry.Name()
+ packName := strings.TrimSuffix(idxName, ".idx") + ".pack"
+ packInfo, err := store.root.Stat(packName)
+ if err != nil {+ if os.IsNotExist(err) {+ return nil, fmt.Errorf("objectstore/packed: missing pack file for index %q", idxName)+ }
+ return nil, err
+ }
+
+ candidates = append(candidates, packCandidate{+ packName: packName,
+ idxName: idxName,
+ mtime: packInfo.ModTime().UnixNano(),
+ })
+ }
+
+ slices.SortFunc(candidates, func(a, b packCandidate) int {+ if a.mtime != b.mtime {+ if a.mtime > b.mtime {+ return -1
+ }
+ return 1
+ }
+ return strings.Compare(a.packName, b.packName)
+ })
+
+ return candidates, nil
+}
+
+// touchCandidate moves one candidate to the front of the lookup order.
+func (store *Store) touchCandidate(packName string) {+ store.stateMu.Lock()
+ defer store.stateMu.Unlock()
+ for i := range store.candidates {+ if store.candidates[i].packName != packName {+ continue
+ }
+ if i == 0 {+ return
+ }
+ candidate := store.candidates[i]
+ copy(store.candidates[1:i+1], store.candidates[0:i])
+ store.candidates[0] = candidate
+ return
+ }
+}
--- /dev/null
+++ b/objectstore/packed/idx_open.go
@@ -1,0 +1,131 @@
+package packed
+
+import (
+ "fmt"
+ "os"
+ "syscall"
+
+ "codeberg.org/lindenii/furgit/internal/intconv"
+ "codeberg.org/lindenii/furgit/objectid"
+)
+
+// idxFile stores one mapped and validated idx v2 file.
+type idxFile struct {+ // idxName is the basename of this .idx file.
+ idxName string
+ // packName is the matching .pack basename.
+ packName string
+ // algo is the hash algorithm encoded by the index.
+ algo objectid.Algorithm
+
+ // file is the opened index file descriptor.
+ file *os.File
+ // data is the mapped index bytes.
+ data []byte
+
+ // fanout stores fanout table values.
+ fanout [256]uint32
+ // numObjects equals fanout[255].
+ numObjects int
+
+ // namesOffset starts the sorted object-id table.
+ namesOffset int
+ // offset32Offset starts the 32-bit offset table.
+ offset32Offset int
+ // offset64Offset starts the 64-bit offset table.
+ offset64Offset int
+ // offset64Count is the number of 64-bit offset entries.
+ offset64Count int
+}
+
+// candidateForPack returns one discovered candidate for a pack basename.
+func (store *Store) candidateForPack(packName string) (packCandidate, bool) {+ store.stateMu.RLock()
+ candidate, ok := store.candidateByPack[packName]
+ store.stateMu.RUnlock()
+ return candidate, ok
+}
+
+// openIndex returns one opened and parsed index, caching it by pack basename.
+func (store *Store) openIndex(candidate packCandidate) (*idxFile, error) {+ store.stateMu.RLock()
+ if index, ok := store.idxByPack[candidate.packName]; ok {+ store.stateMu.RUnlock()
+ return index, nil
+ }
+ store.stateMu.RUnlock()
+
+ index, err := openIdxFile(store.root, candidate.idxName, candidate.packName, store.algo)
+ if err != nil {+ return nil, err
+ }
+
+ store.stateMu.Lock()
+ if existing, ok := store.idxByPack[candidate.packName]; ok {+ store.stateMu.Unlock()
+ _ = index.close()
+ return existing, nil
+ }
+ store.idxByPack[candidate.packName] = index
+ store.stateMu.Unlock()
+ return index, nil
+}
+
+// openIdxFile maps and validates one idx v2 file.
+func openIdxFile(root *os.Root, idxName, packName string, algo objectid.Algorithm) (*idxFile, error) {+ file, err := root.Open(idxName)
+ if err != nil {+ return nil, err
+ }
+ info, err := file.Stat()
+ if err != nil {+ _ = file.Close()
+ return nil, err
+ }
+ size := info.Size()
+ if size < 0 || size > int64(int(^uint(0)>>1)) {+ _ = file.Close()
+ return nil, fmt.Errorf("objectstore/packed: idx %q has unsupported size", idxName)+ }
+ fd, err := intconv.UintptrToInt(file.Fd())
+ if err != nil {+ _ = file.Close()
+ return nil, err
+ }
+ data, err := syscall.Mmap(fd, 0, int(size), syscall.PROT_READ, syscall.MAP_PRIVATE)
+ if err != nil {+ _ = file.Close()
+ return nil, err
+ }
+
+ index := &idxFile{+ idxName: idxName,
+ packName: packName,
+ algo: algo,
+ file: file,
+ data: data,
+ }
+ if err := index.parse(); err != nil {+ _ = index.close()
+ return nil, err
+ }
+ return index, nil
+}
+
+// close unmaps and closes one idx handle.
+func (index *idxFile) close() error {+ var closeErr error
+ if index.data != nil {+ if err := syscall.Munmap(index.data); err != nil && closeErr == nil {+ closeErr = err
+ }
+ index.data = nil
+ }
+ if index.file != nil {+ if err := index.file.Close(); err != nil && closeErr == nil {+ closeErr = err
+ }
+ index.file = nil
+ }
+ return closeErr
+}
--
⑨