format/commitgraph/bloom: Add commit-graph bloom filters

1 files changed, 31 insertions, 0 deletions

diff --git a/format/commitgraph/bloom/settings.go b/format/commitgraph/bloom/settings.go
new file mode 100644
index 00000000..5aa122a9
--- /dev/null
+++ b/format/commitgraph/bloom/settings.go
@@ -0,0 +1,31 @@
+package bloom
+
+import "encoding/binary"
+
+// 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,
+	}
+
+	return settings, nil
+}