Implement missing random functions* enacl:randombytes_int32/0* enacl:randombytes_uniform/1

src/enacl.erl

@@ -114,7 +114,7 @@
          hash/1,
          verify_16/2,
          verify_32/2,
-         
+
          %% No Tests!
          unsafe_memzero/1
 ]).
@@ -122,7 +122,9 @@
 %% Randomness
 -export([
          %% EQC
-         randombytes/1
+         randombytes/1,
+         randombytes_int32/0,
+         randombytes_uniform/1
 ]).
 
 %%% Specific primitives
@@ -204,6 +206,9 @@
 -define(CRYPTO_GENERICHASH_KEYBYTES_MAX, 64).
 -define(CRYPTO_GENERICHASH_KEYBYTES, 32).
 
+%% Size limits
+-define(MAX_32BIT_INT, 1 bsl 32).
+
 %% @doc Verify makes sure the constants defined in libsodium matches ours
 verify() ->
     true = equals(binary:copy(<<0>>, enacl_nif:crypto_box_ZEROBYTES()), ?P_ZEROBYTES),
@@ -1119,6 +1124,18 @@ aead_chacha20poly1305_MESSAGEBYTES_MAX() ->
 randombytes(N) ->
     enacl_nif:randombytes(N).
 
+%% @doc randombytes_int32/0 produces an integer in the 32bit range
+%% @end
+-spec randombytes_int32() -> integer().
+randombytes_int32() ->
+    enacl_nif:randombytes_int32().
+
+%% @doc randombytes_uniform/1 produces a random integer in the space [0..N)
+%% That is with the upper bound excluded. Fails for integers above 32bit size
+%% @end
+randombytes_uniform(N) when N < ?MAX_32BIT_INT ->
+    enacl_nif:randombytes_uniform(N).
+
 %% Helpers
 
 %% @doc bump/4 bumps a reduction budget linearly before returning the result

src/enacl_nif.erl

@@ -153,7 +153,9 @@
 
 %% Access to the RNG
 -export([
-         randombytes/1
+         randombytes/1,
+         randombytes_int32/0,
+         randombytes_uniform/1
         ]).
 
 %% Undocumented features :>
@@ -296,5 +298,7 @@ crypto_kx_PUBLICKEYBYTES() -> erlang:nif_error(nif_not_loaded).
 crypto_kx_SECRETKEYBYTES() -> erlang:nif_error(nif_not_loaded).
 
 randombytes(_RequestedSize) -> erlang:nif_error(nif_not_loaded).
+randombytes_int32() -> erlang:nif_error(nif_not_loaded).
+randombytes_uniform(_UpperBound) -> erlang:nif_error(nif_not_loaded).
 
 scramble_block_16(_Block, _Key) -> erlang:nif_error(nif_not_loaded).