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package bloom
import (
"encoding/binary"
"codeberg.org/lindenii/furgit/internal/intconv"
)
// Settings describe the changed-paths Bloom filter parameters stored in
// commit-graph BDAT chunks.
//
// Obviously, they must match the repository's commit-graph settings to
// interpret filters correctly.
type Settings struct {
HashVersion uint32
NumHashes uint32
BitsPerEntry uint32
MaxChangePaths uint32
}
// ParseSettings reads Bloom filter settings from a BDAT chunk header.
func ParseSettings(bdat []byte) (*Settings, error) {
if len(bdat) < DataHeaderSize {
return nil, ErrInvalid
}
settings := &Settings{
HashVersion: binary.BigEndian.Uint32(bdat[0:4]),
NumHashes: binary.BigEndian.Uint32(bdat[4:8]),
BitsPerEntry: binary.BigEndian.Uint32(bdat[8:12]),
MaxChangePaths: DefaultMaxChange,
}
switch settings.HashVersion {
case 1, 2:
default:
return nil, ErrInvalid
}
if settings.NumHashes == 0 {
return nil, ErrInvalid
}
_, err := intconv.Uint32ToInt(settings.NumHashes)
if err != nil {
return nil, ErrInvalid
}
return settings, nil
}
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