From da9abd24a93ae8fe174cdd38fc9699bbc45fdf56 Mon Sep 17 00:00:00 2001
From: Guilherme Andrade <g@gandrade.net>
Date: Sat, 22 Apr 2017 20:00:28 +0100
Subject: erts: Allow for easier future enif_hash expansion

Allow for expanding support to 64-bit hashes without breaking the
interface.
---
 erts/doc/src/erl_nif.xml                      | 17 +++++++----------
 erts/emulator/beam/erl_nif.c                  | 10 +++-------
 erts/emulator/beam/erl_nif_api_funcs.h        |  2 +-
 erts/emulator/test/nif_SUITE_data/nif_SUITE.c |  6 +++---
 4 files changed, 14 insertions(+), 21 deletions(-)

diff --git a/erts/doc/src/erl_nif.xml b/erts/doc/src/erl_nif.xml
index 5faf1a05fc..534c90cbdc 100644
--- a/erts/doc/src/erl_nif.xml
+++ b/erts/doc/src/erl_nif.xml
@@ -823,13 +823,13 @@ typedef enum {
           <item>
             <p>Non-portable hash function that only guarantees the same hash
               for the same term within one Erlang VM instance.</p>
-            <p>Generated hash values within <c>0..2^32-1</c>.</p>
+            <p>It takes 32-bit salt values and generates hashes within <c>0..2^32-1</c>.</p>
           </item>
           <tag><c>ERL_NIF_PHASH2</c></tag>
           <item>
             <p>Portable hash function that gives the same hash for the
               same Erlang term regardless of machine architecture and ERTS version.</p>
-            <p>Generated hash values within <c>0..2^27-1</c>.</p>
+            <p>It takes 32-bit salt values and generates hashes within <c>0..2^27-1</c>.</p>
             <p>Slower than <c>ERL_NIF_INTERNAL_HASH.</c>
               When used with <c>salt=0</c>, it corresponds to
               <seealso marker="erlang#phash2-1"><c>erlang:phash2/1</c></seealso>.</p>
@@ -1411,17 +1411,14 @@ typedef enum {
 
     <func>
       <name>
-        <ret>unsigned long</ret>
-        <nametext>
-          enif_hash(ErlNifHash type, ERL_NIF_TERM term, unsigned long salt)
-        </nametext>
+        <ret>ErlNifUInt64</ret>
+        <nametext>enif_hash(ErlNifHash type, ERL_NIF_TERM term, ErlNifUInt64 salt)</nametext>
       </name>
       <fsummary>Hash terms.</fsummary>
       <desc>
-        <p>Hash <c>term</c> according to the specified
-          <seealso marker="#ErlNifHash"><c>ErlNifHash</c></seealso> <c>type</c>
-          and using the least significant 32 bits of <c>salt</c>.</p>
-        <p>Range of returned value depends on the hash type.</p>
+        <p>Hashes <c>term</c> according to the specified
+          <seealso marker="#ErlNifHash"><c>ErlNifHash</c></seealso> <c>type</c>.</p>
+        <p>Ranges of taken salt and returned value depend on the hash type.</p>
       </desc>
     </func>
 
diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index bdfb7f3b8e..3ff6c8d3ed 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -1214,17 +1214,13 @@ int enif_compare(Eterm lhs, Eterm rhs)
     return result;
 }
 
-unsigned long enif_hash(ErlNifHash type, Eterm term, unsigned long salt)
+ErlNifUInt64 enif_hash(ErlNifHash type, Eterm term, ErlNifUInt64 salt)
 {
-#if SIZEOF_LONG < 4
-/* This *really* shouldn't happen */
-#  error Incompatible long word size
-#endif
     switch (type) {
         case ERL_NIF_INTERNAL_HASH:
-            return make_internal_hash(term, salt);
+            return make_internal_hash(term, (Uint32) salt);
         case ERL_NIF_PHASH2:
-            return make_hash2(term, salt) & ((1 << 27) - 1);
+            return make_hash2(term, (Uint32) salt) & ((1 << 27) - 1);
         default:
             return 0;
     }
diff --git a/erts/emulator/beam/erl_nif_api_funcs.h b/erts/emulator/beam/erl_nif_api_funcs.h
index 6b9f78d46b..1a91a04f32 100644
--- a/erts/emulator/beam/erl_nif_api_funcs.h
+++ b/erts/emulator/beam/erl_nif_api_funcs.h
@@ -47,7 +47,7 @@ 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_hash,(ErlNifHash type, ERL_NIF_TERM term, unsigned long salt));
+ERL_NIF_API_FUNC_DECL(ErlNifUInt64,enif_hash,(ErlNifHash type, ERL_NIF_TERM term, ErlNifUInt64 salt));
 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));
diff --git a/erts/emulator/test/nif_SUITE_data/nif_SUITE.c b/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
index 2a80d48b62..a255c9f096 100644
--- a/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
+++ b/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
@@ -704,12 +704,12 @@ static ERL_NIF_TERM hash_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]
         return enif_make_badarg(env);
     }
 
-    unsigned long salt;
-    if (! enif_get_ulong(env, argv[2], &salt)) {
+    ErlNifUInt64 salt;
+    if (! enif_get_uint64(env, argv[2], &salt)) {
         return enif_make_badarg(env);
     }
 
-    return enif_make_ulong(env, enif_hash(type, argv[1], salt));
+    return enif_make_uint64(env, enif_hash(type, argv[1], salt));
 }
 
 static ERL_NIF_TERM many_args_100(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
-- 
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