flambda-backend: Backport caml_string_hash from OCaml 5 to runtime 4 (#2045)

Author: xclerc

runtime4/hash.c

@@ -301,6 +301,15 @@ CAMLprim value caml_hash(value count, value limit, value seed, value obj)
   return Val_int(h & 0x3FFFFFFFU);
 }
 
+CAMLprim value caml_string_hash(value seed, value string)
+{
+  uint32_t h;
+  h = Int_val(seed);
+  h = caml_hash_mix_string (h, string);
+  FINAL_MIX(h);
+  return Val_int(h & 0x3FFFFFFFU);
+}
+
 /* Hashing variant tags */
 
 CAMLexport value caml_hash_variant(char const * tag)

stdlib/string.ml

@@ -223,10 +223,8 @@ let ends_with ~suffix s =
     else aux (i + 1)
   in diff >= 0 && aux 0
 
-(* BACKPORT
 external seeded_hash : int -> string -> int = "caml_string_hash" [@@noalloc]
 let hash x = seeded_hash 0 x
-*)
 
 (* duplicated in bytes.ml *)
 let split_on_char sep s =

stdlib/string.mli

@@ -483,8 +483,6 @@ val get_int32_ne : string -> int -> int32
     @since 4.13
 *)
 
-(* BACKPORT
-   not in 4.x runtime (caml_string_hash)
 val hash : t -> int
 (** An unseeded hash function for strings, with the same output value as
     {!Hashtbl.hash}. This function allows this module to be passed as argument
@@ -498,7 +496,6 @@ val seeded_hash : int -> t -> int
     argument to the functor {!Hashtbl.MakeSeeded}.
 
     @since 5.0 *)
-*)
 
 val get_int32_be : string -> int -> int32
 (** [get_int32_be b i] is [b]'s big-endian 32-bit integer

stdlib/stringLabels.mli

@@ -485,9 +485,6 @@ val get_int32_ne : string -> int -> int32
     @since 4.13
 *)
 
-(* BACKPORT
-   not in 4.x runtime (caml_string_hash)
-
 val hash : t -> int
 (** An unseeded hash function for strings, with the same output value as
     {!Hashtbl.hash}. This function allows this module to be passed as argument
@@ -501,7 +498,6 @@ val seeded_hash : int -> t -> int
     argument to the functor {!Hashtbl.MakeSeeded}.
 
     @since 5.0 *)
-*)
 
 val get_int32_be : string -> int -> int32
 (** [get_int32_be b i] is [b]'s big-endian 32-bit integer

testsuite/tests/lib-string/test_string.ml

@@ -41,15 +41,12 @@ let () =
   done
 ;;
 
-
-(* BACKPORT
 let () =
   printf "-- Hashtbl.hash raw_string: %x\n%!" (Hashtbl.hash raw_string);
   printf "-- String.hash raw_string: %x\n%!" (String.hash raw_string);
   printf "-- Hashtbl.seeded_hash 16 raw_string: %x\n%!" (Hashtbl.seeded_hash 16 raw_string);
   printf "-- String.seeded_hash 16 raw_string: %x\n%!" (String.seeded_hash 16 raw_string);
 ;;
-*)
 
 (* GPR#805/815/833 *)
 

testsuite/tests/lib-string/test_string.reference

@@ -0,0 +1,4 @@
+-- Hashtbl.hash raw_string: 240a0e56
+-- String.hash raw_string: 240a0e56
+-- Hashtbl.seeded_hash 16 raw_string: 3210af30
+-- String.seeded_hash 16 raw_string: 3210af30