B-trees & serialization with bencode

1 files changed, 23 insertions, 0 deletions

diff --git a/lib/concepts/Hash.ml b/lib/concepts/Hash.ml
index f467ee7..aac7428 100644
--- a/lib/concepts/Hash.ml
+++ b/lib/concepts/Hash.ml
@@ -2,8 +2,31 @@
 
 type hash = Digestif.SHA256.t
 
+let size = 256/8
+
+let compare h1 h2 = Digestif.SHA256.unsafe_compare h1 h2
+                    |> Ordering.of_int
+
 let hash_of_value (v : Value.value) =
   Representation.(blob_of_value v |> bytes_of_blob) |> Digestif.SHA256.digest_bytes
 
+let hash_of_bytes bytes = Digestif.SHA256.digest_bytes bytes
+
+let hash_of_blob blob = Representation.bytes_of_blob blob |> Digestif.SHA256.digest_bytes
+
+let to_raw_string hash = Digestif.SHA256.to_raw_string hash
+
+let of_raw_string str = Digestif.SHA256.of_raw_string str
+
 let hash_equals = Digestif.SHA256.equal
 let bytes_of_hash (h : hash) = Bytes.of_string (Digestif.SHA256.to_raw_string h)
+
+let power_of_two p =
+  let b = Bytes.make 32 '\x00' in
+  let byte = 31 - (p / 8) in
+  Bytes.set b byte (Char.chr (1 lsl (p mod 8)));
+  Bytes.unsafe_to_string b
+
+let pick n hash =
+  let threshold = Digestif.SHA256.of_raw_string (power_of_two (256 - n)) in
+  compare hash threshold = Ordering.Smaller