erts: Add enif_phash2 and enif_phash2_ranged

These allow one to hash VM terms from NIF code.

5 files changed, 41 insertions, 11 deletions

diff --git a/erts/emulator/beam/bif.c b/erts/emulator/beam/bif.c
index 214de3652f..d59adc18d6 100644
--- a/erts/emulator/beam/bif.c
+++ b/erts/emulator/beam/bif.c
@@ -4888,7 +4888,6 @@ BIF_RETTYPE phash2_1(BIF_ALIST_1)
 BIF_RETTYPE phash2_2(BIF_ALIST_2)
 {
     Uint32 hash;
-    Uint32 final_hash;
     Uint32 range;
 
     /* Check for special case 2^32 */
@@ -4901,23 +4900,19 @@ BIF_RETTYPE phash2_2(BIF_ALIST_2)
 	}
 	range = (Uint32) u;
     }
-    hash = make_hash2(BIF_ARG_1);
-    if (range) {
-	final_hash = hash % range; /* [0..range-1] */
-    } else {
-	final_hash = hash;
-    }
+    hash = make_hash2_within_range(BIF_ARG_1, range);
+
     /*
      * Return either a small or a big. Use the heap for bigs if there is room.
      */
 #if defined(ARCH_64)
-    BIF_RET(make_small(final_hash));
+    BIF_RET(make_small(hash));
 #else
-    if (IS_USMALL(0, final_hash)) {
-	BIF_RET(make_small(final_hash));
+    if (IS_USMALL(0, hash)) {
+	BIF_RET(make_small(hash));
     } else {
 	Eterm* hp = HAlloc(BIF_P, BIG_UINT_HEAP_SIZE);
-	BIF_RET(uint_to_big(final_hash, hp));
+	BIF_RET(uint_to_big(hash, hp));
     }
 #endif
 }
diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index f86b9739fa..14abf461a3 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -55,6 +55,7 @@
 #include "dtrace-wrapper.h"
 #include "erl_process.h"
 #include "erl_bif_unique.h"
+#include "erl_utils.h"
 #undef ERTS_WANT_NFUNC_SCHED_INTERNALS__
 #define ERTS_WANT_NFUNC_SCHED_INTERNALS__
 #include "erl_nfunc_sched.h"
@@ -1213,6 +1214,25 @@ int enif_compare(Eterm lhs, Eterm rhs)
     return result;
 }
 
+#if SIZEOF_LONG < 4
+/* This *really* shouldn't happen */
+#  error Incompatible long word size
+#endif
+
+unsigned long enif_phash2(Eterm term)
+{
+    return make_hash2(term) & ((1 << 27) - 1);
+}
+
+unsigned long enif_phash2_ranged(Eterm term, unsigned long range)
+{
+#if SIZEOF_LONG > 4
+    if (range > (unsigned long) UINT32_MAX)
+        range = 0;
+#endif
+    return make_hash2_within_range(term, range);
+}
+
 int enif_get_tuple(ErlNifEnv* env, Eterm tpl, int* arity, const Eterm** array)
 {
     Eterm* ptr;
diff --git a/erts/emulator/beam/erl_nif_api_funcs.h b/erts/emulator/beam/erl_nif_api_funcs.h
index 01d9e386ed..8a3f9165d9 100644
--- a/erts/emulator/beam/erl_nif_api_funcs.h
+++ b/erts/emulator/beam/erl_nif_api_funcs.h
@@ -47,6 +47,8 @@ ERL_NIF_API_FUNC_DECL(int,enif_get_list_cell,(ErlNifEnv* env, ERL_NIF_TERM term,
 ERL_NIF_API_FUNC_DECL(int,enif_get_tuple,(ErlNifEnv* env, ERL_NIF_TERM tpl, int* arity, const ERL_NIF_TERM** array));
 ERL_NIF_API_FUNC_DECL(int,enif_is_identical,(ERL_NIF_TERM lhs, ERL_NIF_TERM rhs));
 ERL_NIF_API_FUNC_DECL(int,enif_compare,(ERL_NIF_TERM lhs, ERL_NIF_TERM rhs));
+ERL_NIF_API_FUNC_DECL(unsigned long,enif_phash2,(ERL_NIF_TERM term));
+ERL_NIF_API_FUNC_DECL(unsigned long,enif_phash2_ranged,(ERL_NIF_TERM term, unsigned long));
 ERL_NIF_API_FUNC_DECL(ERL_NIF_TERM,enif_make_binary,(ErlNifEnv* env, ErlNifBinary* bin));
 ERL_NIF_API_FUNC_DECL(ERL_NIF_TERM,enif_make_badarg,(ErlNifEnv* env));
 ERL_NIF_API_FUNC_DECL(ERL_NIF_TERM,enif_make_int,(ErlNifEnv* env, int i));
@@ -208,6 +210,8 @@ ERL_NIF_API_FUNC_DECL(int, enif_compare_monitors,(const ErlNifMonitor*,const Erl
 #  define enif_get_list_cell ERL_NIF_API_FUNC_MACRO(enif_get_list_cell)
 #  define enif_is_identical ERL_NIF_API_FUNC_MACRO(enif_is_identical)
 #  define enif_compare ERL_NIF_API_FUNC_MACRO(enif_compare)
+#  define enif_phash2 ERL_NIF_API_FUNC_MACRO(enif_phash2)
+#  define enif_phash2_ranged ERL_NIF_API_FUNC_MACRO(enif_phash2_ranged)
 
 #  define enif_make_binary ERL_NIF_API_FUNC_MACRO(enif_make_binary)
 #  define enif_make_badarg ERL_NIF_API_FUNC_MACRO(enif_make_badarg)
diff --git a/erts/emulator/beam/erl_utils.h b/erts/emulator/beam/erl_utils.h
index 47289a0af1..75578c26d6 100644
--- a/erts/emulator/beam/erl_utils.h
+++ b/erts/emulator/beam/erl_utils.h
@@ -119,6 +119,7 @@ Sint erts_list_length(Eterm);
 int erts_is_builtin(Eterm, Eterm, int);
 Uint32 block_hash(byte *, unsigned, Uint32);
 Uint32 make_hash2(Eterm);
+Uint32 make_hash2_within_range(Eterm, Uint32);
 Uint32 make_hash(Eterm);
 Uint32 make_internal_hash(Eterm);
 
diff --git a/erts/emulator/beam/utils.c b/erts/emulator/beam/utils.c
index 8f3f48f38f..72c59b33c6 100644
--- a/erts/emulator/beam/utils.c
+++ b/erts/emulator/beam/utils.c
@@ -1552,6 +1552,16 @@ make_hash2(Eterm term)
     }
 }
 
+Uint32
+make_hash2_within_range(Eterm term, Uint32 range)
+{
+    Uint32 hash = make_hash2(term);
+    if (range)
+        return hash % range; /* [0..range-1] */
+    else
+        return hash; /* Special case: 2**32 */
+}
+
 /* Term hash function for internal use.
  *
  * Limitation #1: Is not "portable" in any way between different VM instances.