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package packed
import (
"fmt"
"codeberg.org/lindenii/furgit/internal/intconv"
"codeberg.org/lindenii/furgit/objectid"
objecttype "codeberg.org/lindenii/furgit/object/type"
packfmt "codeberg.org/lindenii/furgit/packfile"
)
// entryMeta describes one parsed pack entry header.
type entryMeta struct {
// ty is the pack entry type tag.
ty objecttype.Type
// size is the declared resulting content size.
size int64
// dataOffset points to the zlib payload start.
dataOffset int
// baseRefID is set for ref-delta entries.
baseRefID objectid.ObjectID
// baseOfs is set for ofs-delta entries.
baseOfs uint64
}
// parseEntryMeta parses one pack entry header at offset.
func parseEntryMeta(pack *packFile, algo objectid.Algorithm, offset uint64) (entryMeta, error) {
var zero entryMeta
if offset >= uint64(len(pack.data)) {
return zero, fmt.Errorf("objectstore/packed: pack %q offset %d out of bounds", pack.name, offset)
}
pos, err := intconv.Uint64ToInt(offset)
if err != nil {
return zero, fmt.Errorf("objectstore/packed: pack %q offset conversion: %w", pack.name, err)
}
entry, err := packfmt.ParseEntry(pack.data[pos:], algo.Size())
if err != nil {
return zero, fmt.Errorf("objectstore/packed: pack %q: %w", pack.name, err)
}
meta := entryMeta{
ty: entry.Type,
size: entry.Size,
dataOffset: pos + entry.DataOffset,
}
switch meta.ty {
case objecttype.TypeRefDelta:
baseID, err := objectid.FromBytes(algo, entry.RefBaseID)
if err != nil {
return zero, fmt.Errorf("objectstore/packed: pack %q invalid ref-delta base id: %w", pack.name, err)
}
meta.baseRefID = baseID
case objecttype.TypeOfsDelta:
if offset <= entry.OfsBaseDistance {
return zero, fmt.Errorf("objectstore/packed: pack %q has invalid ofs-delta base", pack.name)
}
meta.baseOfs = offset - entry.OfsBaseDistance
case objecttype.TypeCommit, objecttype.TypeTree, objecttype.TypeBlob, objecttype.TypeTag:
// Base object types do not have delta base metadata.
case objecttype.TypeInvalid, objecttype.TypeFuture:
return zero, fmt.Errorf("objectstore/packed: pack %q has unsupported entry type %d", pack.name, meta.ty)
default:
return zero, fmt.Errorf("objectstore/packed: pack %q has unsupported entry type %d", pack.name, meta.ty)
}
return meta, nil
}
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