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// Package pack provides Git packfile format parsing primitives.
package pack
import (
"fmt"
"codeberg.org/lindenii/furgit/objecttype"
)
// Signature is the 4-byte "PACK" magic at the start of pack files.
const Signature = 0x5041434b
// VersionSupported reports whether one pack version is supported.
func VersionSupported(version uint32) bool {
return version == 2 || version == 3
}
// IsBaseObjectType reports whether ty is one of the four canonical object
// types encoded directly in pack entries.
func IsBaseObjectType(ty objecttype.Type) bool {
switch ty {
case objecttype.TypeCommit, objecttype.TypeTree, objecttype.TypeBlob, objecttype.TypeTag:
return true
case objecttype.TypeInvalid, objecttype.TypeFuture, objecttype.TypeOfsDelta, objecttype.TypeRefDelta:
return false
default:
return false
}
}
// ParseOfsDeltaDistance parses one ofs-delta backward distance.
func ParseOfsDeltaDistance(buf []byte) (uint64, int, error) {
if len(buf) == 0 {
return 0, 0, fmt.Errorf("format/pack: malformed ofs-delta distance")
}
b := buf[0]
dist := uint64(b & 0x7f)
consumed := 1
for b&0x80 != 0 {
if consumed >= len(buf) {
return 0, 0, fmt.Errorf("format/pack: malformed ofs-delta distance")
}
b = buf[consumed]
consumed++
dist = ((dist + 1) << 7) + uint64(b&0x7f)
}
return dist, consumed, nil
}
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