From 76d8ee79e15cfffe165fa9a07774f71840097542 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Thu, 19 Mar 2026 21:05:23 -0400
Subject: [PATCH] cchash64: add apply and combine*

---
 src/core/CCHash64.ml  | 16 ++++++++++++++++
 src/core/CCHash64.mli | 10 ++++++++++
 2 files changed, 26 insertions(+)

diff --git a/src/core/CCHash64.ml b/src/core/CCHash64.ml
index 79838e31..4cabb288 100644
--- a/src/core/CCHash64.ml
+++ b/src/core/CCHash64.ml
@@ -10,6 +10,8 @@ let[@inline] finalize (s : state) : int = Hash_impl_.finalize s
 
 type 'a t = state -> 'a -> state
 
+let[@inline] apply h x = finalize64 (h seed x)
+let apply_int h x = Int64.to_int (finalize64 (h seed x))
 let[@inline] int s x = Hash_impl_.combine_int s x
 
 let[@inline] bool s b =
@@ -77,6 +79,20 @@ let gen f s g =
   in
   aux s
 
+let[@inline] combine2 a b =
+  Hash_impl_.(finalize64 (combine_i64 (combine_i64 seed a) b))
+
+let combine3 a b c =
+  Hash_impl_.(
+    let s = combine_i64 (combine_i64 seed a) b in
+    finalize64 (combine_i64 s c))
+
+let combine4 a b c d =
+  Hash_impl_.(
+    let s = combine_i64 (combine_i64 seed a) b in
+    let s = combine_i64 s c in
+    finalize64 (combine_i64 s d))
+
 let array_comm f s a =
   let hashes = Array.map (fun x -> finalize64 (f seed x)) a in
   Array.sort Int64.compare hashes;
diff --git a/src/core/CCHash64.mli b/src/core/CCHash64.mli
index 6c31e192..2909e824 100644
--- a/src/core/CCHash64.mli
+++ b/src/core/CCHash64.mli
@@ -37,6 +37,12 @@ type 'a t = state -> 'a -> state
 (** A hash combiner: takes the current state, mixes in a value, returns the
     updated state. *)
 
+val apply : 'a t -> 'a -> int64
+(** Hash the input *)
+
+val apply_int : 'a t -> 'a -> int
+(** Hash the input and truncate to [int] *)
+
 val int : int t
 val bool : bool t
 val char : char t
@@ -66,6 +72,10 @@ val map : ('a -> 'b) -> 'b t -> 'a t
 val if_ : bool -> 'a t -> 'a t -> 'a t
 (** [if_ b t e] uses hasher [t] when [b] is true, [e] otherwise. *)
 
+val combine2 : int64 -> int64 -> int64
+val combine3 : int64 -> int64 -> int64 -> int64
+val combine4 : int64 -> int64 -> int64 -> int64 -> int64
+
 val poly : 'a t
 (** Uses [Hashtbl.hash] internally. *)