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package packfile
import (
"fmt"
objecttype "codeberg.org/lindenii/furgit/object/type"
)
// Entry is one parsed pack entry prefix, including any delta base reference
// data that appears before the compressed payload.
type Entry struct {
// Type is the pack entry type.
Type objecttype.Type
// Size is the declared resulting object size.
Size int64
// DataOffset is the byte offset from the start of the entry to the zlib
// payload bytes.
DataOffset int
// RefBaseID is the referenced base object ID bytes for ref-delta entries.
RefBaseID []byte
// OfsBaseDistance is the backward distance for ofs-delta entries.
OfsBaseDistance uint64
}
// ParseEntry parses one full pack entry prefix from data.
//
// hashSize must match the hash algorithm size used by the pack/index.
func ParseEntry(data []byte, hashSize int) (Entry, error) {
var zero Entry
header, err := ParseEntryHeader(data)
if err != nil {
return zero, err
}
entry := Entry{
Type: header.Type,
Size: header.Size,
DataOffset: header.HeaderSize,
}
switch entry.Type {
case objecttype.TypeCommit, objecttype.TypeTree, objecttype.TypeBlob, objecttype.TypeTag:
// Base object entries have no extra prefix fields.
case objecttype.TypeRefDelta:
if hashSize <= 0 {
return zero, fmt.Errorf("packfile: invalid hash size %d", hashSize)
}
end := entry.DataOffset + hashSize
if end > len(data) {
return zero, fmt.Errorf("packfile: truncated ref-delta base id")
}
entry.RefBaseID = data[entry.DataOffset:end]
entry.DataOffset = end
case objecttype.TypeOfsDelta:
dist, consumed, err := ParseOfsDeltaDistance(data[entry.DataOffset:])
if err != nil {
return zero, err
}
entry.OfsBaseDistance = dist
entry.DataOffset += consumed
case objecttype.TypeInvalid, objecttype.TypeFuture:
return zero, fmt.Errorf("packfile: unsupported object type %d", entry.Type)
default:
return zero, fmt.Errorf("packfile: unsupported object type %d", entry.Type)
}
if entry.DataOffset > len(data) {
return zero, fmt.Errorf("packfile: entry data offset out of bounds")
}
return entry, nil
}
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