shithub: furgit

Download patch

ref: 52a2b00e1ab5a4bfe8c516e46424fc2dc3178be2
parent: c3f07de7f820290639c66cad605a8a7a55345c57
author: Runxi Yu <me@runxiyu.org>
date: Wed Jan 28 15:44:51 EST 2026

pack: Add _read to filenames

--- a/pack_idx.go
+++ /dev/null
@@ -1,290 +1,0 @@
-package furgit
-
-import (
-	"bytes"
-	"errors"
-	"fmt"
-	"os"
-	"path/filepath"
-	"strings"
-	"sync"
-	"syscall"
-)
-
-const (
-	idxMagic    = 0xff744f63
-	idxVersion2 = 2
-)
-
-type packIndex struct {
-	repo     *Repository
-	idxRel   string
-	packPath string
-
-	loadOnce sync.Once
-	loadErr  error
-
-	numObjects int
-	fanout     []byte
-	names      []byte
-	crcs       []byte
-	offset32   []byte
-	offset64   []byte
-	data       []byte
-
-	closeOnce sync.Once
-}
-
-func (pi *packIndex) Close() error {
-	if pi == nil {
-		return nil
-	}
-	var closeErr error
-	pi.closeOnce.Do(func() {
-		if len(pi.data) > 0 {
-			if err := syscall.Munmap(pi.data); closeErr == nil {
-				closeErr = err
-			}
-			pi.data = nil
-			pi.fanout = nil
-			pi.names = nil
-			pi.crcs = nil
-			pi.offset32 = nil
-			pi.offset64 = nil
-			pi.numObjects = 0
-		}
-	})
-	return closeErr
-}
-
-func (pi *packIndex) ensureLoaded() error {
-	pi.loadOnce.Do(func() {
-		pi.loadErr = pi.load()
-	})
-	return pi.loadErr
-}
-
-func (pi *packIndex) load() error {
-	if pi.repo == nil {
-		return ErrInvalidObject
-	}
-	f, err := os.Open(pi.repo.repoPath(pi.idxRel))
-	if err != nil {
-		return err
-	}
-	stat, err := f.Stat()
-	if err != nil {
-		_ = f.Close()
-		return err
-	}
-	if stat.Size() < 8+256*4 {
-		_ = f.Close()
-		return ErrInvalidObject
-	}
-	region, err := syscall.Mmap(
-		int(f.Fd()),
-		0,
-		int(stat.Size()),
-		syscall.PROT_READ,
-		syscall.MAP_PRIVATE,
-	)
-	if err != nil {
-		_ = f.Close()
-		return err
-	}
-	err = f.Close()
-	if err != nil {
-		_ = syscall.Munmap(region)
-		return err
-	}
-	err = pi.parse(region)
-	if err != nil {
-		_ = syscall.Munmap(region)
-		return err
-	}
-	pi.data = region
-	return nil
-}
-
-func (repo *Repository) packIndexes() ([]*packIndex, error) {
-	repo.packIdxOnce.Do(func() {
-		repo.packIdx, repo.packIdxErr = repo.loadPackIndexes()
-	})
-	return repo.packIdx, repo.packIdxErr
-}
-
-func (repo *Repository) loadPackIndexes() ([]*packIndex, error) {
-	dir := filepath.Join(repo.rootPath, "objects", "pack")
-	entries, err := os.ReadDir(dir)
-	if err != nil {
-		if os.IsNotExist(err) {
-			return nil, ErrNotFound
-		}
-		return nil, err
-	}
-
-	idxs := make([]*packIndex, 0, len(entries))
-	for _, entry := range entries {
-		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".idx") {
-			continue
-		}
-		rel := filepath.Join("objects", "pack", entry.Name())
-		packRel := strings.TrimSuffix(rel, ".idx") + ".pack"
-		idxs = append(idxs, &packIndex{
-			repo:     repo,
-			idxRel:   rel,
-			packPath: packRel,
-		})
-	}
-	if len(idxs) == 0 {
-		return nil, ErrNotFound
-	}
-	return idxs, nil
-}
-
-func (pi *packIndex) parse(buf []byte) error {
-	if len(buf) < 8+256*4 {
-		return ErrInvalidObject
-	}
-	if readBE32(buf[0:4]) != idxMagic {
-		return ErrInvalidObject
-	}
-	if readBE32(buf[4:8]) != idxVersion2 {
-		return ErrInvalidObject
-	}
-
-	const fanoutBytes = 256 * 4
-	fanoutStart := 8
-	fanoutEnd := fanoutStart + fanoutBytes
-	if fanoutEnd > len(buf) {
-		return ErrInvalidObject
-	}
-	pi.fanout = buf[fanoutStart:fanoutEnd]
-	nobj := int(readBE32(pi.fanout[len(pi.fanout)-4:]))
-
-	namesStart := fanoutEnd
-	namesEnd := namesStart + nobj*pi.repo.hashAlgo.Size()
-	if namesEnd > len(buf) {
-		return ErrInvalidObject
-	}
-
-	crcStart := namesEnd
-	crcEnd := crcStart + nobj*4
-	if crcEnd > len(buf) {
-		return ErrInvalidObject
-	}
-
-	off32Start := crcEnd
-	off32End := off32Start + nobj*4
-	if off32End > len(buf) {
-		return ErrInvalidObject
-	}
-
-	pi.offset32 = buf[off32Start:off32End]
-
-	off64Start := off32End
-	trailerStart := len(buf) - 2*pi.repo.hashAlgo.Size()
-	if trailerStart < off64Start {
-		return ErrInvalidObject
-	}
-	if (trailerStart-off64Start)%8 != 0 {
-		return ErrInvalidObject
-	}
-	off64End := trailerStart
-	pi.offset64 = buf[off64Start:off64End]
-
-	pi.numObjects = nobj
-	pi.names = buf[namesStart:namesEnd]
-	pi.crcs = buf[crcStart:crcEnd]
-	return nil
-}
-
-func readBE32(b []byte) uint32 {
-	_ = b[3]
-	return uint32(b[0])<<24 | uint32(b[1])<<16 | uint32(b[2])<<8 | uint32(b[3])
-}
-
-func readBE64(b []byte) uint64 {
-	_ = b[7]
-	return (uint64(b[0]) << 56) | (uint64(b[1]) << 48) |
-		(uint64(b[2]) << 40) | (uint64(b[3]) << 32) |
-		(uint64(b[4]) << 24) | (uint64(b[5]) << 16) |
-		(uint64(b[6]) << 8) | uint64(b[7])
-}
-
-func (pi *packIndex) fanoutEntry(i int) uint32 {
-	if len(pi.fanout) == 0 {
-		return 0
-	}
-	entries := len(pi.fanout) / 4
-	if i < 0 || i >= entries {
-		return 0
-	}
-	start := i * 4
-	return readBE32(pi.fanout[start : start+4])
-}
-
-func (pi *packIndex) offset(idx int) (uint64, error) {
-	start := idx * 4
-	word := readBE32(pi.offset32[start : start+4])
-	if word&0x80000000 == 0 {
-		return uint64(word), nil
-	}
-	pos := int(word & 0x7fffffff)
-	entries := len(pi.offset64) / 8
-	if pos < 0 || pos >= entries {
-		return 0, errors.New("furgit: pack: corrupt 64-bit offset table")
-	}
-	base := pos * 8
-	return readBE64(pi.offset64[base : base+8]), nil
-}
-
-func (pi *packIndex) lookup(id Hash) (packlocation, error) {
-	err := pi.ensureLoaded()
-	if err != nil {
-		return packlocation{}, err
-	}
-	if id.algo != pi.repo.hashAlgo {
-		return packlocation{}, fmt.Errorf("furgit: hash algorithm mismatch: got %s, expected %s", id.algo.String(), pi.repo.hashAlgo.String())
-	}
-	first := int(id.data[0])
-	var lo int
-	if first > 0 {
-		lo = int(pi.fanoutEntry(first - 1))
-	}
-	hi := int(pi.fanoutEntry(first))
-	idx, found := bsearchHash(pi.names, pi.repo.hashAlgo.Size(), lo, hi, id)
-	if !found {
-		return packlocation{}, ErrNotFound
-	}
-	ofs, err := pi.offset(idx)
-	if err != nil {
-		return packlocation{}, err
-	}
-	return packlocation{
-		PackPath: pi.packPath,
-		Offset:   ofs,
-	}, nil
-}
-
-func bsearchHash(names []byte, stride, lo, hi int, want Hash) (int, bool) {
-	for lo < hi {
-		mid := lo + (hi-lo)/2
-		cmp := compareHash(names, stride, mid, want.data[:stride])
-		if cmp == 0 {
-			return mid, true
-		}
-		if cmp > 0 {
-			hi = mid
-		} else {
-			lo = mid + 1
-		}
-	}
-	return lo, false
-}
-
-func compareHash(names []byte, stride, idx int, want []byte) int {
-	base := idx * stride
-	end := base + stride
-	return bytes.Compare(names[base:end], want)
-}
--- /dev/null
+++ b/pack_idx_read.go
@@ -1,0 +1,290 @@
+package furgit
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"syscall"
+)
+
+const (
+	idxMagic    = 0xff744f63
+	idxVersion2 = 2
+)
+
+type packIndex struct {
+	repo     *Repository
+	idxRel   string
+	packPath string
+
+	loadOnce sync.Once
+	loadErr  error
+
+	numObjects int
+	fanout     []byte
+	names      []byte
+	crcs       []byte
+	offset32   []byte
+	offset64   []byte
+	data       []byte
+
+	closeOnce sync.Once
+}
+
+func (pi *packIndex) Close() error {
+	if pi == nil {
+		return nil
+	}
+	var closeErr error
+	pi.closeOnce.Do(func() {
+		if len(pi.data) > 0 {
+			if err := syscall.Munmap(pi.data); closeErr == nil {
+				closeErr = err
+			}
+			pi.data = nil
+			pi.fanout = nil
+			pi.names = nil
+			pi.crcs = nil
+			pi.offset32 = nil
+			pi.offset64 = nil
+			pi.numObjects = 0
+		}
+	})
+	return closeErr
+}
+
+func (pi *packIndex) ensureLoaded() error {
+	pi.loadOnce.Do(func() {
+		pi.loadErr = pi.load()
+	})
+	return pi.loadErr
+}
+
+func (pi *packIndex) load() error {
+	if pi.repo == nil {
+		return ErrInvalidObject
+	}
+	f, err := os.Open(pi.repo.repoPath(pi.idxRel))
+	if err != nil {
+		return err
+	}
+	stat, err := f.Stat()
+	if err != nil {
+		_ = f.Close()
+		return err
+	}
+	if stat.Size() < 8+256*4 {
+		_ = f.Close()
+		return ErrInvalidObject
+	}
+	region, err := syscall.Mmap(
+		int(f.Fd()),
+		0,
+		int(stat.Size()),
+		syscall.PROT_READ,
+		syscall.MAP_PRIVATE,
+	)
+	if err != nil {
+		_ = f.Close()
+		return err
+	}
+	err = f.Close()
+	if err != nil {
+		_ = syscall.Munmap(region)
+		return err
+	}
+	err = pi.parse(region)
+	if err != nil {
+		_ = syscall.Munmap(region)
+		return err
+	}
+	pi.data = region
+	return nil
+}
+
+func (repo *Repository) packIndexes() ([]*packIndex, error) {
+	repo.packIdxOnce.Do(func() {
+		repo.packIdx, repo.packIdxErr = repo.loadPackIndexes()
+	})
+	return repo.packIdx, repo.packIdxErr
+}
+
+func (repo *Repository) loadPackIndexes() ([]*packIndex, error) {
+	dir := filepath.Join(repo.rootPath, "objects", "pack")
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, ErrNotFound
+		}
+		return nil, err
+	}
+
+	idxs := make([]*packIndex, 0, len(entries))
+	for _, entry := range entries {
+		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".idx") {
+			continue
+		}
+		rel := filepath.Join("objects", "pack", entry.Name())
+		packRel := strings.TrimSuffix(rel, ".idx") + ".pack"
+		idxs = append(idxs, &packIndex{
+			repo:     repo,
+			idxRel:   rel,
+			packPath: packRel,
+		})
+	}
+	if len(idxs) == 0 {
+		return nil, ErrNotFound
+	}
+	return idxs, nil
+}
+
+func (pi *packIndex) parse(buf []byte) error {
+	if len(buf) < 8+256*4 {
+		return ErrInvalidObject
+	}
+	if readBE32(buf[0:4]) != idxMagic {
+		return ErrInvalidObject
+	}
+	if readBE32(buf[4:8]) != idxVersion2 {
+		return ErrInvalidObject
+	}
+
+	const fanoutBytes = 256 * 4
+	fanoutStart := 8
+	fanoutEnd := fanoutStart + fanoutBytes
+	if fanoutEnd > len(buf) {
+		return ErrInvalidObject
+	}
+	pi.fanout = buf[fanoutStart:fanoutEnd]
+	nobj := int(readBE32(pi.fanout[len(pi.fanout)-4:]))
+
+	namesStart := fanoutEnd
+	namesEnd := namesStart + nobj*pi.repo.hashAlgo.Size()
+	if namesEnd > len(buf) {
+		return ErrInvalidObject
+	}
+
+	crcStart := namesEnd
+	crcEnd := crcStart + nobj*4
+	if crcEnd > len(buf) {
+		return ErrInvalidObject
+	}
+
+	off32Start := crcEnd
+	off32End := off32Start + nobj*4
+	if off32End > len(buf) {
+		return ErrInvalidObject
+	}
+
+	pi.offset32 = buf[off32Start:off32End]
+
+	off64Start := off32End
+	trailerStart := len(buf) - 2*pi.repo.hashAlgo.Size()
+	if trailerStart < off64Start {
+		return ErrInvalidObject
+	}
+	if (trailerStart-off64Start)%8 != 0 {
+		return ErrInvalidObject
+	}
+	off64End := trailerStart
+	pi.offset64 = buf[off64Start:off64End]
+
+	pi.numObjects = nobj
+	pi.names = buf[namesStart:namesEnd]
+	pi.crcs = buf[crcStart:crcEnd]
+	return nil
+}
+
+func readBE32(b []byte) uint32 {
+	_ = b[3]
+	return uint32(b[0])<<24 | uint32(b[1])<<16 | uint32(b[2])<<8 | uint32(b[3])
+}
+
+func readBE64(b []byte) uint64 {
+	_ = b[7]
+	return (uint64(b[0]) << 56) | (uint64(b[1]) << 48) |
+		(uint64(b[2]) << 40) | (uint64(b[3]) << 32) |
+		(uint64(b[4]) << 24) | (uint64(b[5]) << 16) |
+		(uint64(b[6]) << 8) | uint64(b[7])
+}
+
+func (pi *packIndex) fanoutEntry(i int) uint32 {
+	if len(pi.fanout) == 0 {
+		return 0
+	}
+	entries := len(pi.fanout) / 4
+	if i < 0 || i >= entries {
+		return 0
+	}
+	start := i * 4
+	return readBE32(pi.fanout[start : start+4])
+}
+
+func (pi *packIndex) offset(idx int) (uint64, error) {
+	start := idx * 4
+	word := readBE32(pi.offset32[start : start+4])
+	if word&0x80000000 == 0 {
+		return uint64(word), nil
+	}
+	pos := int(word & 0x7fffffff)
+	entries := len(pi.offset64) / 8
+	if pos < 0 || pos >= entries {
+		return 0, errors.New("furgit: pack: corrupt 64-bit offset table")
+	}
+	base := pos * 8
+	return readBE64(pi.offset64[base : base+8]), nil
+}
+
+func (pi *packIndex) lookup(id Hash) (packlocation, error) {
+	err := pi.ensureLoaded()
+	if err != nil {
+		return packlocation{}, err
+	}
+	if id.algo != pi.repo.hashAlgo {
+		return packlocation{}, fmt.Errorf("furgit: hash algorithm mismatch: got %s, expected %s", id.algo.String(), pi.repo.hashAlgo.String())
+	}
+	first := int(id.data[0])
+	var lo int
+	if first > 0 {
+		lo = int(pi.fanoutEntry(first - 1))
+	}
+	hi := int(pi.fanoutEntry(first))
+	idx, found := bsearchHash(pi.names, pi.repo.hashAlgo.Size(), lo, hi, id)
+	if !found {
+		return packlocation{}, ErrNotFound
+	}
+	ofs, err := pi.offset(idx)
+	if err != nil {
+		return packlocation{}, err
+	}
+	return packlocation{
+		PackPath: pi.packPath,
+		Offset:   ofs,
+	}, nil
+}
+
+func bsearchHash(names []byte, stride, lo, hi int, want Hash) (int, bool) {
+	for lo < hi {
+		mid := lo + (hi-lo)/2
+		cmp := compareHash(names, stride, mid, want.data[:stride])
+		if cmp == 0 {
+			return mid, true
+		}
+		if cmp > 0 {
+			hi = mid
+		} else {
+			lo = mid + 1
+		}
+	}
+	return lo, false
+}
+
+func compareHash(names []byte, stride, idx int, want []byte) int {
+	base := idx * stride
+	end := base + stride
+	return bytes.Compare(names[base:end], want)
+}
--- a/pack_pack.go
+++ /dev/null
@@ -1,578 +1,0 @@
-package furgit
-
-import (
-	"encoding/binary"
-	"errors"
-	"io"
-	"os"
-	"sync"
-	"syscall"
-
-	"codeberg.org/lindenii/furgit/internal/bufpool"
-	"codeberg.org/lindenii/furgit/internal/zlibx"
-)
-
-const (
-	packMagic    = 0x5041434b
-	packVersion2 = 2
-)
-
-type packlocation struct {
-	PackPath string
-	Offset   uint64
-}
-
-func (repo *Repository) packRead(id Hash) (ObjectType, bufpool.Buffer, error) {
-	loc, err := repo.packIndexFind(id)
-	if err != nil {
-		return ObjectTypeInvalid, bufpool.Buffer{}, err
-	}
-	return repo.packReadAt(loc, id)
-}
-
-func (repo *Repository) packIndexFind(id Hash) (packlocation, error) {
-	idxs, err := repo.packIndexes()
-	if err != nil {
-		return packlocation{}, err
-	}
-	for _, idx := range idxs {
-		loc, err := idx.lookup(id)
-		if errors.Is(err, ErrNotFound) {
-			continue
-		}
-		if err != nil {
-			return packlocation{}, err
-		}
-		return loc, nil
-	}
-	return packlocation{}, ErrNotFound
-}
-
-func (repo *Repository) packReadAt(loc packlocation, want Hash) (ObjectType, bufpool.Buffer, error) {
-	ty, body, err := repo.packBodyResolveAtLocation(loc)
-	if err != nil {
-		return ObjectTypeInvalid, bufpool.Buffer{}, err
-	}
-	return ty, body, nil
-}
-
-func (repo *Repository) packBodyResolveAtLocation(loc packlocation) (ObjectType, bufpool.Buffer, error) {
-	pf, err := repo.packFile(loc.PackPath)
-	if err != nil {
-		return ObjectTypeInvalid, bufpool.Buffer{}, err
-	}
-	return repo.packBodyResolveWithin(pf, loc.Offset)
-}
-
-func (repo *Repository) packTypeSizeAtLocation(loc packlocation, seen map[packKey]struct{}) (ObjectType, int64, error) {
-	pf, err := repo.packFile(loc.PackPath)
-	if err != nil {
-		return ObjectTypeInvalid, 0, err
-	}
-	return repo.packTypeSizeWithin(pf, loc.Offset, seen)
-}
-
-func packHeaderParse(data []byte) (ObjectType, int, int, error) {
-	if len(data) == 0 {
-		return ObjectTypeInvalid, 0, 0, io.ErrUnexpectedEOF
-	}
-	b := data[0]
-	ty := ObjectType((b >> 4) & 0x07)
-	size := int(b & 0x0f)
-	shift := 4
-	consumed := 1
-	for (b & 0x80) != 0 {
-		if consumed >= len(data) {
-			return ObjectTypeInvalid, 0, 0, io.ErrUnexpectedEOF
-		}
-		b = data[consumed]
-		size |= int(b&0x7f) << shift
-		shift += 7
-		consumed++
-	}
-	return ty, size, consumed, nil
-}
-
-func packSectionInflate(pf *packFile, start uint64, sizeHint int) (bufpool.Buffer, error) {
-	if start > uint64(len(pf.data)) {
-		return bufpool.Buffer{}, ErrInvalidObject
-	}
-	body, err := zlibx.DecompressSized(pf.data[start:], sizeHint)
-	if err != nil {
-		return bufpool.Buffer{}, err
-	}
-	if sizeHint > 0 && len(body.Bytes()) != sizeHint {
-		body.Release()
-		return bufpool.Buffer{}, ErrInvalidObject
-	}
-	return body, nil
-}
-
-func packDeltaReadOfsDistance(data []byte) (uint64, int, error) {
-	if len(data) == 0 {
-		return 0, 0, io.ErrUnexpectedEOF
-	}
-	b := data[0]
-	dist := uint64(b & 0x7f)
-	consumed := 1
-	for (b & 0x80) != 0 {
-		if consumed >= len(data) {
-			return 0, 0, io.ErrUnexpectedEOF
-		}
-		b = data[consumed]
-		consumed++
-		dist = ((dist + 1) << 7) + uint64(b&0x7f)
-	}
-	return dist, consumed, nil
-}
-
-type packKey struct {
-	path string
-	ofs  uint64
-}
-
-func (repo *Repository) packTypeSizeWithin(pf *packFile, ofs uint64, seen map[packKey]struct{}) (ObjectType, int64, error) {
-	if pf == nil {
-		return ObjectTypeInvalid, 0, ErrInvalidObject
-	}
-	if seen == nil {
-		seen = make(map[packKey]struct{})
-	}
-	var visited []packKey
-	defer func() {
-		for _, key := range visited {
-			delete(seen, key)
-		}
-	}()
-
-	var declaredSize int64
-	firstHeader := true
-
-	for {
-		key := packKey{path: pf.relPath, ofs: ofs}
-		if _, dup := seen[key]; dup {
-			return ObjectTypeInvalid, 0, ErrInvalidObject
-		}
-		seen[key] = struct{}{}
-		visited = append(visited, key)
-
-		if ofs >= uint64(len(pf.data)) {
-			return ObjectTypeInvalid, 0, ErrInvalidObject
-		}
-		ty, size, consumed, err := packHeaderParse(pf.data[ofs:])
-		if err != nil {
-			return ObjectTypeInvalid, 0, err
-		}
-		if firstHeader {
-			declaredSize = int64(size)
-			firstHeader = false
-		}
-
-		if uint64(consumed) > uint64(len(pf.data))-ofs {
-			return ObjectTypeInvalid, 0, io.ErrUnexpectedEOF
-		}
-		dataStart := ofs + uint64(consumed)
-		switch ty {
-		case ObjectTypeCommit, ObjectTypeTree, ObjectTypeBlob, ObjectTypeTag:
-			return ty, declaredSize, nil
-		case ObjectTypeRefDelta:
-			hashEnd := dataStart + uint64(repo.hashAlgo.Size())
-			if hashEnd > uint64(len(pf.data)) {
-				return ObjectTypeInvalid, 0, io.ErrUnexpectedEOF
-			}
-			var base Hash
-			copy(base.data[:], pf.data[dataStart:hashEnd])
-			base.algo = repo.hashAlgo
-			loc, err := repo.packIndexFind(base)
-			if err == nil {
-				pf, err = repo.packFile(loc.PackPath)
-				if err != nil {
-					return ObjectTypeInvalid, 0, err
-				}
-				ofs = loc.Offset
-				continue
-			}
-			if !errors.Is(err, ErrNotFound) {
-				return ObjectTypeInvalid, 0, err
-			}
-			baseTy, _, err := repo.looseTypeSize(base)
-			if err != nil {
-				return ObjectTypeInvalid, 0, err
-			}
-			return baseTy, declaredSize, nil
-		case ObjectTypeOfsDelta:
-			dist, distConsumed, err := packDeltaReadOfsDistance(pf.data[dataStart:])
-			if err != nil {
-				return ObjectTypeInvalid, 0, err
-			}
-			if ofs <= dist {
-				return ObjectTypeInvalid, 0, ErrInvalidObject
-			}
-			dataStart += uint64(distConsumed)
-			if dataStart > uint64(len(pf.data)) {
-				return ObjectTypeInvalid, 0, ErrInvalidObject
-			}
-			ofs -= dist
-		case ObjectTypeInvalid, ObjectTypeFuture:
-			return ObjectTypeInvalid, 0, ErrInvalidObject
-		default:
-			return ObjectTypeInvalid, 0, ErrInvalidObject
-		}
-	}
-}
-
-func (repo *Repository) packBodyResolveWithin(pf *packFile, ofs uint64) (ObjectType, bufpool.Buffer, error) {
-	if pf == nil {
-		return ObjectTypeInvalid, bufpool.Buffer{}, ErrInvalidObject
-	}
-
-	type deltaFrame struct {
-		delta bufpool.Buffer
-	}
-	var frames []deltaFrame
-	defer func() {
-		for i := range frames {
-			frames[i].delta.Release()
-		}
-	}()
-
-	var (
-		body      bufpool.Buffer
-		bodyReady bool
-		resultTy  ObjectType
-	)
-	fail := func(err error) (ObjectType, bufpool.Buffer, error) {
-		if bodyReady {
-			body.Release()
-			bodyReady = false
-		}
-		return ObjectTypeInvalid, bufpool.Buffer{}, err
-	}
-
-	resolved := false
-	for !resolved {
-		if ofs >= uint64(len(pf.data)) {
-			return fail(ErrInvalidObject)
-		}
-		ty, size, consumed, err := packHeaderParse(pf.data[ofs:])
-		if err != nil {
-			return fail(err)
-		}
-		if uint64(consumed) > uint64(len(pf.data))-ofs {
-			return fail(io.ErrUnexpectedEOF)
-		}
-		dataStart := ofs + uint64(consumed)
-
-		switch ty {
-		case ObjectTypeCommit, ObjectTypeTree, ObjectTypeBlob, ObjectTypeTag:
-			body, err = packSectionInflate(pf, dataStart, size)
-			if err != nil {
-				return fail(err)
-			}
-			bodyReady = true
-			resultTy = ty
-			resolved = true
-		case ObjectTypeRefDelta:
-			hashEnd := dataStart + uint64(repo.hashAlgo.Size())
-			if hashEnd > uint64(len(pf.data)) {
-				return fail(io.ErrUnexpectedEOF)
-			}
-			var base Hash
-			copy(base.data[:], pf.data[dataStart:hashEnd])
-			base.algo = repo.hashAlgo
-			delta, err := packSectionInflate(pf, hashEnd, 0)
-			if err != nil {
-				return fail(err)
-			}
-			frames = append(frames, deltaFrame{delta: delta})
-
-			loc, err := repo.packIndexFind(base)
-			if err == nil {
-				pf, err = repo.packFile(loc.PackPath)
-				if err != nil {
-					return fail(err)
-				}
-				ofs = loc.Offset
-				continue
-			}
-			if !errors.Is(err, ErrNotFound) {
-				return fail(err)
-			}
-			resultTy, body, err = repo.looseReadTyped(base)
-			if err != nil {
-				return fail(err)
-			}
-			bodyReady = true
-			resolved = true
-		case ObjectTypeOfsDelta:
-			dist, distConsumed, err := packDeltaReadOfsDistance(pf.data[dataStart:])
-			if err != nil {
-				return fail(err)
-			}
-			if ofs <= dist {
-				return fail(ErrInvalidObject)
-			}
-			deltaStart := dataStart + uint64(distConsumed)
-			if deltaStart > uint64(len(pf.data)) {
-				return fail(ErrInvalidObject)
-			}
-			delta, err := packSectionInflate(pf, deltaStart, 0)
-			if err != nil {
-				return fail(err)
-			}
-			frames = append(frames, deltaFrame{delta: delta})
-			ofs -= dist
-		case ObjectTypeInvalid, ObjectTypeFuture:
-			return fail(ErrInvalidObject)
-		default:
-			return fail(ErrInvalidObject)
-		}
-	}
-
-	for i := len(frames) - 1; i >= 0; i-- {
-		out, err := packDeltaApply(body, frames[i].delta)
-		body.Release()
-		bodyReady = false
-		frames[i].delta.Release()
-		if err != nil {
-			return fail(err)
-		}
-		body = out
-		bodyReady = true
-	}
-	frames = nil
-	return resultTy, body, nil
-}
-
-func packDeltaApply(base, delta bufpool.Buffer) (bufpool.Buffer, error) {
-	pos := 0
-	baseBytes := base.Bytes()
-	deltaBytes := delta.Bytes()
-	srcSize, err := packVarintRead(deltaBytes, &pos)
-	if err != nil {
-		return bufpool.Buffer{}, err
-	}
-	dstSize, err := packVarintRead(deltaBytes, &pos)
-	if err != nil {
-		return bufpool.Buffer{}, err
-	}
-	if srcSize != len(baseBytes) {
-		return bufpool.Buffer{}, ErrInvalidObject
-	}
-	out := bufpool.Borrow(dstSize)
-	out.Resize(dstSize)
-	outBytes := out.Bytes()
-	outPos := 0
-
-	for pos < len(deltaBytes) {
-		op := deltaBytes[pos]
-		pos++
-		switch {
-		case op&0x80 != 0:
-			off := 0
-			n := 0
-			if op&0x01 != 0 {
-				if pos >= len(deltaBytes) {
-					out.Release()
-					return bufpool.Buffer{}, ErrInvalidObject
-				}
-				off |= int(deltaBytes[pos])
-				pos++
-			}
-			if op&0x02 != 0 {
-				if pos >= len(deltaBytes) {
-					out.Release()
-					return bufpool.Buffer{}, ErrInvalidObject
-				}
-				off |= int(deltaBytes[pos]) << 8
-				pos++
-			}
-			if op&0x04 != 0 {
-				if pos >= len(deltaBytes) {
-					out.Release()
-					return bufpool.Buffer{}, ErrInvalidObject
-				}
-				off |= int(deltaBytes[pos]) << 16
-				pos++
-			}
-			if op&0x08 != 0 {
-				if pos >= len(deltaBytes) {
-					out.Release()
-					return bufpool.Buffer{}, ErrInvalidObject
-				}
-				off |= int(deltaBytes[pos]) << 24
-				pos++
-			}
-			if op&0x10 != 0 {
-				if pos >= len(deltaBytes) {
-					out.Release()
-					return bufpool.Buffer{}, ErrInvalidObject
-				}
-				n |= int(deltaBytes[pos])
-				pos++
-			}
-			if op&0x20 != 0 {
-				if pos >= len(deltaBytes) {
-					out.Release()
-					return bufpool.Buffer{}, ErrInvalidObject
-				}
-				n |= int(deltaBytes[pos]) << 8
-				pos++
-			}
-			if op&0x40 != 0 {
-				if pos >= len(deltaBytes) {
-					out.Release()
-					return bufpool.Buffer{}, ErrInvalidObject
-				}
-				n |= int(deltaBytes[pos]) << 16
-				pos++
-			}
-			if n == 0 {
-				n = 0x10000
-			}
-			if off+n > len(baseBytes) || outPos+n > len(outBytes) {
-				out.Release()
-				return bufpool.Buffer{}, ErrInvalidObject
-			}
-			copy(outBytes[outPos:], baseBytes[off:off+n])
-			outPos += n
-		case op != 0:
-			n := int(op)
-			if pos+n > len(deltaBytes) || outPos+n > len(outBytes) {
-				out.Release()
-				return bufpool.Buffer{}, ErrInvalidObject
-			}
-			copy(outBytes[outPos:], deltaBytes[pos:pos+n])
-			pos += n
-			outPos += n
-		default:
-			out.Release()
-			return bufpool.Buffer{}, ErrInvalidObject
-		}
-	}
-
-	if outPos != len(outBytes) {
-		out.Release()
-		return bufpool.Buffer{}, ErrInvalidObject
-	}
-	return out, nil
-}
-
-func packVarintRead(buf []byte, pos *int) (int, error) {
-	res := 0
-	shift := 0
-	for {
-		if *pos >= len(buf) {
-			return 0, ErrInvalidObject
-		}
-		b := buf[*pos]
-		*pos++
-		res |= int(b&0x7f) << shift
-		if (b & 0x80) == 0 {
-			break
-		}
-		shift += 7
-	}
-	return res, nil
-}
-
-type packFile struct {
-	relPath string
-	size    int64
-	data    []byte
-	closeMu sync.Once
-}
-
-func openPackFile(absPath, rel string) (*packFile, error) {
-	f, err := os.Open(absPath)
-	if err != nil {
-		return nil, err
-	}
-
-	stat, err := f.Stat()
-	if err != nil {
-		_ = f.Close()
-		return nil, err
-	}
-	if stat.Size() < 12 {
-		_ = f.Close()
-		return nil, ErrInvalidObject
-	}
-
-	var headerArr [12]byte
-	header := headerArr[:]
-	_, err = io.ReadFull(f, header)
-	if err != nil {
-		_ = f.Close()
-		return nil, err
-	}
-	magic := binary.BigEndian.Uint32(header[:4])
-	ver := binary.BigEndian.Uint32(header[4:8])
-	if magic != packMagic || ver != packVersion2 {
-		_ = f.Close()
-		return nil, ErrInvalidObject
-	}
-
-	region, err := syscall.Mmap(
-		int(f.Fd()),
-		0,
-		int(stat.Size()),
-		syscall.PROT_READ,
-		syscall.MAP_PRIVATE,
-	)
-	if err != nil {
-		_ = f.Close()
-		return nil, err
-	}
-	err = f.Close()
-	if err != nil {
-		_ = syscall.Munmap(region)
-		return nil, err
-	}
-
-	return &packFile{
-		relPath: rel,
-		size:    stat.Size(),
-		data:    region,
-	}, nil
-}
-
-func (pf *packFile) Close() error {
-	if pf == nil {
-		return nil
-	}
-	var closeErr error
-	pf.closeMu.Do(func() {
-		if len(pf.data) > 0 {
-			if err := syscall.Munmap(pf.data); closeErr == nil {
-				closeErr = err
-			}
-			pf.data = nil
-		}
-	})
-	return closeErr
-}
-
-func (repo *Repository) packFile(rel string) (*packFile, error) {
-	repo.packFilesMu.RLock()
-	pf, ok := repo.packFiles[rel]
-	repo.packFilesMu.RUnlock()
-	if ok {
-		return pf, nil
-	}
-
-	pf, err := openPackFile(repo.repoPath(rel), rel)
-	if err != nil {
-		return nil, err
-	}
-
-	repo.packFilesMu.Lock()
-	if existing, ok := repo.packFiles[rel]; ok {
-		repo.packFilesMu.Unlock()
-		_ = pf.Close()
-		return existing, nil
-	}
-	repo.packFiles[rel] = pf
-	repo.packFilesMu.Unlock()
-	return pf, nil
-}
--- /dev/null
+++ b/pack_pack_read.go
@@ -1,0 +1,578 @@
+package furgit
+
+import (
+	"encoding/binary"
+	"errors"
+	"io"
+	"os"
+	"sync"
+	"syscall"
+
+	"codeberg.org/lindenii/furgit/internal/bufpool"
+	"codeberg.org/lindenii/furgit/internal/zlibx"
+)
+
+const (
+	packMagic    = 0x5041434b
+	packVersion2 = 2
+)
+
+type packlocation struct {
+	PackPath string
+	Offset   uint64
+}
+
+func (repo *Repository) packRead(id Hash) (ObjectType, bufpool.Buffer, error) {
+	loc, err := repo.packIndexFind(id)
+	if err != nil {
+		return ObjectTypeInvalid, bufpool.Buffer{}, err
+	}
+	return repo.packReadAt(loc, id)
+}
+
+func (repo *Repository) packIndexFind(id Hash) (packlocation, error) {
+	idxs, err := repo.packIndexes()
+	if err != nil {
+		return packlocation{}, err
+	}
+	for _, idx := range idxs {
+		loc, err := idx.lookup(id)
+		if errors.Is(err, ErrNotFound) {
+			continue
+		}
+		if err != nil {
+			return packlocation{}, err
+		}
+		return loc, nil
+	}
+	return packlocation{}, ErrNotFound
+}
+
+func (repo *Repository) packReadAt(loc packlocation, want Hash) (ObjectType, bufpool.Buffer, error) {
+	ty, body, err := repo.packBodyResolveAtLocation(loc)
+	if err != nil {
+		return ObjectTypeInvalid, bufpool.Buffer{}, err
+	}
+	return ty, body, nil
+}
+
+func (repo *Repository) packBodyResolveAtLocation(loc packlocation) (ObjectType, bufpool.Buffer, error) {
+	pf, err := repo.packFile(loc.PackPath)
+	if err != nil {
+		return ObjectTypeInvalid, bufpool.Buffer{}, err
+	}
+	return repo.packBodyResolveWithin(pf, loc.Offset)
+}
+
+func (repo *Repository) packTypeSizeAtLocation(loc packlocation, seen map[packKey]struct{}) (ObjectType, int64, error) {
+	pf, err := repo.packFile(loc.PackPath)
+	if err != nil {
+		return ObjectTypeInvalid, 0, err
+	}
+	return repo.packTypeSizeWithin(pf, loc.Offset, seen)
+}
+
+func packHeaderParse(data []byte) (ObjectType, int, int, error) {
+	if len(data) == 0 {
+		return ObjectTypeInvalid, 0, 0, io.ErrUnexpectedEOF
+	}
+	b := data[0]
+	ty := ObjectType((b >> 4) & 0x07)
+	size := int(b & 0x0f)
+	shift := 4
+	consumed := 1
+	for (b & 0x80) != 0 {
+		if consumed >= len(data) {
+			return ObjectTypeInvalid, 0, 0, io.ErrUnexpectedEOF
+		}
+		b = data[consumed]
+		size |= int(b&0x7f) << shift
+		shift += 7
+		consumed++
+	}
+	return ty, size, consumed, nil
+}
+
+func packSectionInflate(pf *packFile, start uint64, sizeHint int) (bufpool.Buffer, error) {
+	if start > uint64(len(pf.data)) {
+		return bufpool.Buffer{}, ErrInvalidObject
+	}
+	body, err := zlibx.DecompressSized(pf.data[start:], sizeHint)
+	if err != nil {
+		return bufpool.Buffer{}, err
+	}
+	if sizeHint > 0 && len(body.Bytes()) != sizeHint {
+		body.Release()
+		return bufpool.Buffer{}, ErrInvalidObject
+	}
+	return body, nil
+}
+
+func packDeltaReadOfsDistance(data []byte) (uint64, int, error) {
+	if len(data) == 0 {
+		return 0, 0, io.ErrUnexpectedEOF
+	}
+	b := data[0]
+	dist := uint64(b & 0x7f)
+	consumed := 1
+	for (b & 0x80) != 0 {
+		if consumed >= len(data) {
+			return 0, 0, io.ErrUnexpectedEOF
+		}
+		b = data[consumed]
+		consumed++
+		dist = ((dist + 1) << 7) + uint64(b&0x7f)
+	}
+	return dist, consumed, nil
+}
+
+type packKey struct {
+	path string
+	ofs  uint64
+}
+
+func (repo *Repository) packTypeSizeWithin(pf *packFile, ofs uint64, seen map[packKey]struct{}) (ObjectType, int64, error) {
+	if pf == nil {
+		return ObjectTypeInvalid, 0, ErrInvalidObject
+	}
+	if seen == nil {
+		seen = make(map[packKey]struct{})
+	}
+	var visited []packKey
+	defer func() {
+		for _, key := range visited {
+			delete(seen, key)
+		}
+	}()
+
+	var declaredSize int64
+	firstHeader := true
+
+	for {
+		key := packKey{path: pf.relPath, ofs: ofs}
+		if _, dup := seen[key]; dup {
+			return ObjectTypeInvalid, 0, ErrInvalidObject
+		}
+		seen[key] = struct{}{}
+		visited = append(visited, key)
+
+		if ofs >= uint64(len(pf.data)) {
+			return ObjectTypeInvalid, 0, ErrInvalidObject
+		}
+		ty, size, consumed, err := packHeaderParse(pf.data[ofs:])
+		if err != nil {
+			return ObjectTypeInvalid, 0, err
+		}
+		if firstHeader {
+			declaredSize = int64(size)
+			firstHeader = false
+		}
+
+		if uint64(consumed) > uint64(len(pf.data))-ofs {
+			return ObjectTypeInvalid, 0, io.ErrUnexpectedEOF
+		}
+		dataStart := ofs + uint64(consumed)
+		switch ty {
+		case ObjectTypeCommit, ObjectTypeTree, ObjectTypeBlob, ObjectTypeTag:
+			return ty, declaredSize, nil
+		case ObjectTypeRefDelta:
+			hashEnd := dataStart + uint64(repo.hashAlgo.Size())
+			if hashEnd > uint64(len(pf.data)) {
+				return ObjectTypeInvalid, 0, io.ErrUnexpectedEOF
+			}
+			var base Hash
+			copy(base.data[:], pf.data[dataStart:hashEnd])
+			base.algo = repo.hashAlgo
+			loc, err := repo.packIndexFind(base)
+			if err == nil {
+				pf, err = repo.packFile(loc.PackPath)
+				if err != nil {
+					return ObjectTypeInvalid, 0, err
+				}
+				ofs = loc.Offset
+				continue
+			}
+			if !errors.Is(err, ErrNotFound) {
+				return ObjectTypeInvalid, 0, err
+			}
+			baseTy, _, err := repo.looseTypeSize(base)
+			if err != nil {
+				return ObjectTypeInvalid, 0, err
+			}
+			return baseTy, declaredSize, nil
+		case ObjectTypeOfsDelta:
+			dist, distConsumed, err := packDeltaReadOfsDistance(pf.data[dataStart:])
+			if err != nil {
+				return ObjectTypeInvalid, 0, err
+			}
+			if ofs <= dist {
+				return ObjectTypeInvalid, 0, ErrInvalidObject
+			}
+			dataStart += uint64(distConsumed)
+			if dataStart > uint64(len(pf.data)) {
+				return ObjectTypeInvalid, 0, ErrInvalidObject
+			}
+			ofs -= dist
+		case ObjectTypeInvalid, ObjectTypeFuture:
+			return ObjectTypeInvalid, 0, ErrInvalidObject
+		default:
+			return ObjectTypeInvalid, 0, ErrInvalidObject
+		}
+	}
+}
+
+func (repo *Repository) packBodyResolveWithin(pf *packFile, ofs uint64) (ObjectType, bufpool.Buffer, error) {
+	if pf == nil {
+		return ObjectTypeInvalid, bufpool.Buffer{}, ErrInvalidObject
+	}
+
+	type deltaFrame struct {
+		delta bufpool.Buffer
+	}
+	var frames []deltaFrame
+	defer func() {
+		for i := range frames {
+			frames[i].delta.Release()
+		}
+	}()
+
+	var (
+		body      bufpool.Buffer
+		bodyReady bool
+		resultTy  ObjectType
+	)
+	fail := func(err error) (ObjectType, bufpool.Buffer, error) {
+		if bodyReady {
+			body.Release()
+			bodyReady = false
+		}
+		return ObjectTypeInvalid, bufpool.Buffer{}, err
+	}
+
+	resolved := false
+	for !resolved {
+		if ofs >= uint64(len(pf.data)) {
+			return fail(ErrInvalidObject)
+		}
+		ty, size, consumed, err := packHeaderParse(pf.data[ofs:])
+		if err != nil {
+			return fail(err)
+		}
+		if uint64(consumed) > uint64(len(pf.data))-ofs {
+			return fail(io.ErrUnexpectedEOF)
+		}
+		dataStart := ofs + uint64(consumed)
+
+		switch ty {
+		case ObjectTypeCommit, ObjectTypeTree, ObjectTypeBlob, ObjectTypeTag:
+			body, err = packSectionInflate(pf, dataStart, size)
+			if err != nil {
+				return fail(err)
+			}
+			bodyReady = true
+			resultTy = ty
+			resolved = true
+		case ObjectTypeRefDelta:
+			hashEnd := dataStart + uint64(repo.hashAlgo.Size())
+			if hashEnd > uint64(len(pf.data)) {
+				return fail(io.ErrUnexpectedEOF)
+			}
+			var base Hash
+			copy(base.data[:], pf.data[dataStart:hashEnd])
+			base.algo = repo.hashAlgo
+			delta, err := packSectionInflate(pf, hashEnd, 0)
+			if err != nil {
+				return fail(err)
+			}
+			frames = append(frames, deltaFrame{delta: delta})
+
+			loc, err := repo.packIndexFind(base)
+			if err == nil {
+				pf, err = repo.packFile(loc.PackPath)
+				if err != nil {
+					return fail(err)
+				}
+				ofs = loc.Offset
+				continue
+			}
+			if !errors.Is(err, ErrNotFound) {
+				return fail(err)
+			}
+			resultTy, body, err = repo.looseReadTyped(base)
+			if err != nil {
+				return fail(err)
+			}
+			bodyReady = true
+			resolved = true
+		case ObjectTypeOfsDelta:
+			dist, distConsumed, err := packDeltaReadOfsDistance(pf.data[dataStart:])
+			if err != nil {
+				return fail(err)
+			}
+			if ofs <= dist {
+				return fail(ErrInvalidObject)
+			}
+			deltaStart := dataStart + uint64(distConsumed)
+			if deltaStart > uint64(len(pf.data)) {
+				return fail(ErrInvalidObject)
+			}
+			delta, err := packSectionInflate(pf, deltaStart, 0)
+			if err != nil {
+				return fail(err)
+			}
+			frames = append(frames, deltaFrame{delta: delta})
+			ofs -= dist
+		case ObjectTypeInvalid, ObjectTypeFuture:
+			return fail(ErrInvalidObject)
+		default:
+			return fail(ErrInvalidObject)
+		}
+	}
+
+	for i := len(frames) - 1; i >= 0; i-- {
+		out, err := packDeltaApply(body, frames[i].delta)
+		body.Release()
+		bodyReady = false
+		frames[i].delta.Release()
+		if err != nil {
+			return fail(err)
+		}
+		body = out
+		bodyReady = true
+	}
+	frames = nil
+	return resultTy, body, nil
+}
+
+func packDeltaApply(base, delta bufpool.Buffer) (bufpool.Buffer, error) {
+	pos := 0
+	baseBytes := base.Bytes()
+	deltaBytes := delta.Bytes()
+	srcSize, err := packVarintRead(deltaBytes, &pos)
+	if err != nil {
+		return bufpool.Buffer{}, err
+	}
+	dstSize, err := packVarintRead(deltaBytes, &pos)
+	if err != nil {
+		return bufpool.Buffer{}, err
+	}
+	if srcSize != len(baseBytes) {
+		return bufpool.Buffer{}, ErrInvalidObject
+	}
+	out := bufpool.Borrow(dstSize)
+	out.Resize(dstSize)
+	outBytes := out.Bytes()
+	outPos := 0
+
+	for pos < len(deltaBytes) {
+		op := deltaBytes[pos]
+		pos++
+		switch {
+		case op&0x80 != 0:
+			off := 0
+			n := 0
+			if op&0x01 != 0 {
+				if pos >= len(deltaBytes) {
+					out.Release()
+					return bufpool.Buffer{}, ErrInvalidObject
+				}
+				off |= int(deltaBytes[pos])
+				pos++
+			}
+			if op&0x02 != 0 {
+				if pos >= len(deltaBytes) {
+					out.Release()
+					return bufpool.Buffer{}, ErrInvalidObject
+				}
+				off |= int(deltaBytes[pos]) << 8
+				pos++
+			}
+			if op&0x04 != 0 {
+				if pos >= len(deltaBytes) {
+					out.Release()
+					return bufpool.Buffer{}, ErrInvalidObject
+				}
+				off |= int(deltaBytes[pos]) << 16
+				pos++
+			}
+			if op&0x08 != 0 {
+				if pos >= len(deltaBytes) {
+					out.Release()
+					return bufpool.Buffer{}, ErrInvalidObject
+				}
+				off |= int(deltaBytes[pos]) << 24
+				pos++
+			}
+			if op&0x10 != 0 {
+				if pos >= len(deltaBytes) {
+					out.Release()
+					return bufpool.Buffer{}, ErrInvalidObject
+				}
+				n |= int(deltaBytes[pos])
+				pos++
+			}
+			if op&0x20 != 0 {
+				if pos >= len(deltaBytes) {
+					out.Release()
+					return bufpool.Buffer{}, ErrInvalidObject
+				}
+				n |= int(deltaBytes[pos]) << 8
+				pos++
+			}
+			if op&0x40 != 0 {
+				if pos >= len(deltaBytes) {
+					out.Release()
+					return bufpool.Buffer{}, ErrInvalidObject
+				}
+				n |= int(deltaBytes[pos]) << 16
+				pos++
+			}
+			if n == 0 {
+				n = 0x10000
+			}
+			if off+n > len(baseBytes) || outPos+n > len(outBytes) {
+				out.Release()
+				return bufpool.Buffer{}, ErrInvalidObject
+			}
+			copy(outBytes[outPos:], baseBytes[off:off+n])
+			outPos += n
+		case op != 0:
+			n := int(op)
+			if pos+n > len(deltaBytes) || outPos+n > len(outBytes) {
+				out.Release()
+				return bufpool.Buffer{}, ErrInvalidObject
+			}
+			copy(outBytes[outPos:], deltaBytes[pos:pos+n])
+			pos += n
+			outPos += n
+		default:
+			out.Release()
+			return bufpool.Buffer{}, ErrInvalidObject
+		}
+	}
+
+	if outPos != len(outBytes) {
+		out.Release()
+		return bufpool.Buffer{}, ErrInvalidObject
+	}
+	return out, nil
+}
+
+func packVarintRead(buf []byte, pos *int) (int, error) {
+	res := 0
+	shift := 0
+	for {
+		if *pos >= len(buf) {
+			return 0, ErrInvalidObject
+		}
+		b := buf[*pos]
+		*pos++
+		res |= int(b&0x7f) << shift
+		if (b & 0x80) == 0 {
+			break
+		}
+		shift += 7
+	}
+	return res, nil
+}
+
+type packFile struct {
+	relPath string
+	size    int64
+	data    []byte
+	closeMu sync.Once
+}
+
+func openPackFile(absPath, rel string) (*packFile, error) {
+	f, err := os.Open(absPath)
+	if err != nil {
+		return nil, err
+	}
+
+	stat, err := f.Stat()
+	if err != nil {
+		_ = f.Close()
+		return nil, err
+	}
+	if stat.Size() < 12 {
+		_ = f.Close()
+		return nil, ErrInvalidObject
+	}
+
+	var headerArr [12]byte
+	header := headerArr[:]
+	_, err = io.ReadFull(f, header)
+	if err != nil {
+		_ = f.Close()
+		return nil, err
+	}
+	magic := binary.BigEndian.Uint32(header[:4])
+	ver := binary.BigEndian.Uint32(header[4:8])
+	if magic != packMagic || ver != packVersion2 {
+		_ = f.Close()
+		return nil, ErrInvalidObject
+	}
+
+	region, err := syscall.Mmap(
+		int(f.Fd()),
+		0,
+		int(stat.Size()),
+		syscall.PROT_READ,
+		syscall.MAP_PRIVATE,
+	)
+	if err != nil {
+		_ = f.Close()
+		return nil, err
+	}
+	err = f.Close()
+	if err != nil {
+		_ = syscall.Munmap(region)
+		return nil, err
+	}
+
+	return &packFile{
+		relPath: rel,
+		size:    stat.Size(),
+		data:    region,
+	}, nil
+}
+
+func (pf *packFile) Close() error {
+	if pf == nil {
+		return nil
+	}
+	var closeErr error
+	pf.closeMu.Do(func() {
+		if len(pf.data) > 0 {
+			if err := syscall.Munmap(pf.data); closeErr == nil {
+				closeErr = err
+			}
+			pf.data = nil
+		}
+	})
+	return closeErr
+}
+
+func (repo *Repository) packFile(rel string) (*packFile, error) {
+	repo.packFilesMu.RLock()
+	pf, ok := repo.packFiles[rel]
+	repo.packFilesMu.RUnlock()
+	if ok {
+		return pf, nil
+	}
+
+	pf, err := openPackFile(repo.repoPath(rel), rel)
+	if err != nil {
+		return nil, err
+	}
+
+	repo.packFilesMu.Lock()
+	if existing, ok := repo.packFiles[rel]; ok {
+		repo.packFilesMu.Unlock()
+		_ = pf.Close()
+		return existing, nil
+	}
+	repo.packFiles[rel] = pf
+	repo.packFilesMu.Unlock()
+	return pf, nil
+}
--- /dev/null
+++ b/pack_read_test.go
@@ -1,0 +1,149 @@
+package furgit
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestPackfileRead(t *testing.T) {
+	repoPath, cleanup := setupTestRepo(t)
+	defer cleanup()
+
+	gitCmd(t, repoPath, "config", "gc.auto", "0")
+
+	workDir, cleanupWork := setupWorkDir(t)
+	defer cleanupWork()
+
+	err := os.WriteFile(filepath.Join(workDir, "file1.txt"), []byte("content1"), 0o644)
+	if err != nil {
+		t.Fatalf("failed to write file1.txt: %v", err)
+	}
+	err = os.WriteFile(filepath.Join(workDir, "file2.txt"), []byte("content2"), 0o644)
+	if err != nil {
+		t.Fatalf("failed to write file2.txt: %v", err)
+	}
+
+	gitCmd(t, repoPath, "--work-tree="+workDir, "add", ".")
+	gitCmd(t, repoPath, "--work-tree="+workDir, "commit", "-m", "Test commit")
+	commitHash := gitCmd(t, repoPath, "rev-parse", "HEAD")
+
+	gitCmd(t, repoPath, "repack", "-a", "-d")
+
+	repo, err := OpenRepository(repoPath)
+	if err != nil {
+		t.Fatalf("OpenRepository failed: %v", err)
+	}
+	defer func() { _ = repo.Close() }()
+
+	hashObj, _ := repo.ParseHash(commitHash)
+	obj, err := repo.ReadObject(hashObj)
+	if err != nil {
+		t.Fatalf("ReadObject from pack failed: %v", err)
+	}
+
+	commit, ok := obj.(*StoredCommit)
+	if !ok {
+		t.Fatalf("expected *StoredCommit, got %T", obj)
+	}
+
+	treeObj, err := repo.ReadObject(commit.Tree)
+	if err != nil {
+		t.Fatalf("ReadObject tree failed: %v", err)
+	}
+
+	tree, ok := treeObj.(*StoredTree)
+	if !ok {
+		t.Fatalf("expected *StoredTree, got %T", treeObj)
+	}
+
+	if len(tree.Entries) != 2 {
+		t.Errorf("tree entries: got %d, want 2", len(tree.Entries))
+	}
+
+	gitLsTree := gitCmd(t, repoPath, "ls-tree", commit.Tree.String())
+	for _, entry := range tree.Entries {
+		if !strings.Contains(gitLsTree, string(entry.Name)) {
+			t.Errorf("git ls-tree doesn't contain %s", entry.Name)
+		}
+	}
+}
+
+func TestPackfileLarge(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping large packfile test in short mode")
+	}
+
+	repoPath, cleanup := setupTestRepo(t)
+	defer cleanup()
+
+	gitCmd(t, repoPath, "config", "gc.auto", "0")
+
+	workDir, cleanupWork := setupWorkDir(t)
+	defer cleanupWork()
+
+	numFiles := 1000
+	for i := 0; i < numFiles; i++ {
+		filename := filepath.Join(workDir, fmt.Sprintf("file%04d.txt", i))
+		content := fmt.Sprintf("Content for file %d\n", i)
+		err := os.WriteFile(filename, []byte(content), 0o644)
+		if err != nil {
+			t.Fatalf("failed to write %s: %v", filename, err)
+		}
+	}
+
+	gitCmd(t, repoPath, "--work-tree="+workDir, "add", ".")
+	gitCmd(t, repoPath, "--work-tree="+workDir, "commit", "-m", "Large commit")
+	commitHash := gitCmd(t, repoPath, "rev-parse", "HEAD")
+
+	gitCmd(t, repoPath, "repack", "-a", "-d")
+
+	repo, err := OpenRepository(repoPath)
+	if err != nil {
+		t.Fatalf("OpenRepository failed: %v", err)
+	}
+	defer func() { _ = repo.Close() }()
+
+	hashObj, _ := repo.ParseHash(commitHash)
+	obj, _ := repo.ReadObject(hashObj)
+	commit := obj.(*StoredCommit)
+
+	treeObj, _ := repo.ReadObject(commit.Tree)
+	tree := treeObj.(*StoredTree)
+
+	if len(tree.Entries) != numFiles {
+		t.Errorf("tree entries: got %d, want %d", len(tree.Entries), numFiles)
+	}
+
+	gitCount := gitCmd(t, repoPath, "ls-tree", commit.Tree.String())
+	gitLines := strings.Count(gitCount, "\n") + 1
+	if len(tree.Entries) != gitLines {
+		t.Errorf("furgit found %d entries, git found %d", len(tree.Entries), gitLines)
+	}
+
+	for i := 0; i < 10; i++ {
+		idx := i * (numFiles / 10)
+		expectedName := fmt.Sprintf("file%04d.txt", idx)
+		entry := tree.Entry([]byte(expectedName))
+		if entry == nil {
+			t.Errorf("expected to find entry %s", expectedName)
+			continue
+		}
+
+		blobObj, _ := repo.ReadObject(entry.ID)
+		blob := blobObj.(*StoredBlob)
+
+		expectedContent := fmt.Sprintf("Content for file %d\n", idx)
+		if string(blob.Data) != expectedContent {
+			t.Errorf("blob %s: got %q, want %q", expectedName, blob.Data, expectedContent)
+		}
+
+		gitData := gitCatFile(t, repoPath, "blob", entry.ID.String())
+		if !bytes.Equal(blob.Data, gitData) {
+			t.Errorf("blob %s: furgit data doesn't match git data", expectedName)
+		}
+	}
+}
--- a/pack_test.go
+++ /dev/null
@@ -1,149 +1,0 @@
-package furgit
-
-import (
-	"bytes"
-	"fmt"
-	"os"
-	"path/filepath"
-	"strings"
-	"testing"
-)
-
-func TestPackfileRead(t *testing.T) {
-	repoPath, cleanup := setupTestRepo(t)
-	defer cleanup()
-
-	gitCmd(t, repoPath, "config", "gc.auto", "0")
-
-	workDir, cleanupWork := setupWorkDir(t)
-	defer cleanupWork()
-
-	err := os.WriteFile(filepath.Join(workDir, "file1.txt"), []byte("content1"), 0o644)
-	if err != nil {
-		t.Fatalf("failed to write file1.txt: %v", err)
-	}
-	err = os.WriteFile(filepath.Join(workDir, "file2.txt"), []byte("content2"), 0o644)
-	if err != nil {
-		t.Fatalf("failed to write file2.txt: %v", err)
-	}
-
-	gitCmd(t, repoPath, "--work-tree="+workDir, "add", ".")
-	gitCmd(t, repoPath, "--work-tree="+workDir, "commit", "-m", "Test commit")
-	commitHash := gitCmd(t, repoPath, "rev-parse", "HEAD")
-
-	gitCmd(t, repoPath, "repack", "-a", "-d")
-
-	repo, err := OpenRepository(repoPath)
-	if err != nil {
-		t.Fatalf("OpenRepository failed: %v", err)
-	}
-	defer func() { _ = repo.Close() }()
-
-	hashObj, _ := repo.ParseHash(commitHash)
-	obj, err := repo.ReadObject(hashObj)
-	if err != nil {
-		t.Fatalf("ReadObject from pack failed: %v", err)
-	}
-
-	commit, ok := obj.(*StoredCommit)
-	if !ok {
-		t.Fatalf("expected *StoredCommit, got %T", obj)
-	}
-
-	treeObj, err := repo.ReadObject(commit.Tree)
-	if err != nil {
-		t.Fatalf("ReadObject tree failed: %v", err)
-	}
-
-	tree, ok := treeObj.(*StoredTree)
-	if !ok {
-		t.Fatalf("expected *StoredTree, got %T", treeObj)
-	}
-
-	if len(tree.Entries) != 2 {
-		t.Errorf("tree entries: got %d, want 2", len(tree.Entries))
-	}
-
-	gitLsTree := gitCmd(t, repoPath, "ls-tree", commit.Tree.String())
-	for _, entry := range tree.Entries {
-		if !strings.Contains(gitLsTree, string(entry.Name)) {
-			t.Errorf("git ls-tree doesn't contain %s", entry.Name)
-		}
-	}
-}
-
-func TestPackfileLarge(t *testing.T) {
-	if testing.Short() {
-		t.Skip("skipping large packfile test in short mode")
-	}
-
-	repoPath, cleanup := setupTestRepo(t)
-	defer cleanup()
-
-	gitCmd(t, repoPath, "config", "gc.auto", "0")
-
-	workDir, cleanupWork := setupWorkDir(t)
-	defer cleanupWork()
-
-	numFiles := 1000
-	for i := 0; i < numFiles; i++ {
-		filename := filepath.Join(workDir, fmt.Sprintf("file%04d.txt", i))
-		content := fmt.Sprintf("Content for file %d\n", i)
-		err := os.WriteFile(filename, []byte(content), 0o644)
-		if err != nil {
-			t.Fatalf("failed to write %s: %v", filename, err)
-		}
-	}
-
-	gitCmd(t, repoPath, "--work-tree="+workDir, "add", ".")
-	gitCmd(t, repoPath, "--work-tree="+workDir, "commit", "-m", "Large commit")
-	commitHash := gitCmd(t, repoPath, "rev-parse", "HEAD")
-
-	gitCmd(t, repoPath, "repack", "-a", "-d")
-
-	repo, err := OpenRepository(repoPath)
-	if err != nil {
-		t.Fatalf("OpenRepository failed: %v", err)
-	}
-	defer func() { _ = repo.Close() }()
-
-	hashObj, _ := repo.ParseHash(commitHash)
-	obj, _ := repo.ReadObject(hashObj)
-	commit := obj.(*StoredCommit)
-
-	treeObj, _ := repo.ReadObject(commit.Tree)
-	tree := treeObj.(*StoredTree)
-
-	if len(tree.Entries) != numFiles {
-		t.Errorf("tree entries: got %d, want %d", len(tree.Entries), numFiles)
-	}
-
-	gitCount := gitCmd(t, repoPath, "ls-tree", commit.Tree.String())
-	gitLines := strings.Count(gitCount, "\n") + 1
-	if len(tree.Entries) != gitLines {
-		t.Errorf("furgit found %d entries, git found %d", len(tree.Entries), gitLines)
-	}
-
-	for i := 0; i < 10; i++ {
-		idx := i * (numFiles / 10)
-		expectedName := fmt.Sprintf("file%04d.txt", idx)
-		entry := tree.Entry([]byte(expectedName))
-		if entry == nil {
-			t.Errorf("expected to find entry %s", expectedName)
-			continue
-		}
-
-		blobObj, _ := repo.ReadObject(entry.ID)
-		blob := blobObj.(*StoredBlob)
-
-		expectedContent := fmt.Sprintf("Content for file %d\n", idx)
-		if string(blob.Data) != expectedContent {
-			t.Errorf("blob %s: got %q, want %q", expectedName, blob.Data, expectedContent)
-		}
-
-		gitData := gitCatFile(t, repoPath, "blob", entry.ID.String())
-		if !bytes.Equal(blob.Data, gitData) {
-			t.Errorf("blob %s: furgit data doesn't match git data", expectedName)
-		}
-	}
-}
--