[crypto] Fix rand_uniform for negative values

Also let it throw badarg if 'Hi' is not larger than 'Lo'.

3 files changed, 20 insertions, 4 deletions

diff --git a/lib/crypto/doc/src/crypto.xml b/lib/crypto/doc/src/crypto.xml
index 179ba4498c..96c4a072e1 100644
--- a/lib/crypto/doc/src/crypto.xml
+++ b/lib/crypto/doc/src/crypto.xml
@@ -744,7 +744,7 @@ Mpint() = <![CDATA[<<ByteLen:32/integer-big, Bytes:ByteLen/binary>>]]>
         <p>Generate a random number <c><![CDATA[N, Lo =< N < Hi.]]></c> Uses the
           <c>crypto</c> library pseudo-random number generator. The
           arguments (and result) can be either erlang integers or binary
-          multi-precision integers.</p>
+          multi-precision integers. <c>Hi</c> must be larger than <c>Lo</c>.</p>
       </desc>
     </func>
     <func>
diff --git a/lib/crypto/src/crypto.erl b/lib/crypto/src/crypto.erl
index c35dfcebab..c3e13d6b91 100644
--- a/lib/crypto/src/crypto.erl
+++ b/lib/crypto/src/crypto.erl
@@ -415,6 +415,13 @@ rand_uniform(From,To) when is_binary(From), is_binary(To) ->
 	    Whatever
     end;
 rand_uniform(From,To) when is_integer(From),is_integer(To) ->
+    if From < 0 -> 
+	    rand_uniform_pos(0, To - From) + From;
+       true ->
+	    rand_uniform_pos(From, To)
+    end.
+
+rand_uniform_pos(From,To) when From < To ->
     BinFrom = mpint(From),
     BinTo = mpint(To),
     case rand_uniform(BinFrom, BinTo) of
@@ -422,7 +429,9 @@ rand_uniform(From,To) when is_integer(From),is_integer(To) ->
             erlint(Result);
         Other ->
             Other
-    end.
+    end;
+rand_uniform_pos(_,_) ->
+    error(badarg).
 
 rand_uniform_nif(_From,_To) -> ?nif_stub.     
 
diff --git a/lib/crypto/test/crypto_SUITE.erl b/lib/crypto/test/crypto_SUITE.erl
index 283aadb6ea..8d2f42469b 100644
--- a/lib/crypto/test/crypto_SUITE.erl
+++ b/lib/crypto/test/crypto_SUITE.erl
@@ -878,10 +878,17 @@ rand_uniform_aux_test(0) ->
 rand_uniform_aux_test(N) ->
     ?line L = N*1000,
     ?line H = N*100000+1,
+    ?line crypto_rand_uniform(L, H),
+    ?line crypto_rand_uniform(-L, L),
+    ?line crypto_rand_uniform(-H, -L),
+    ?line crypto_rand_uniform(-H, L),
+    ?line rand_uniform_aux_test(N-1).
+
+crypto_rand_uniform(L,H) ->
     ?line R1 = crypto:rand_uniform(L, H),
     ?line t(R1 >= L),
-    ?line t(R1 < H),
-    ?line rand_uniform_aux_test(N-1).
+    ?line t(R1 < H).
+
 
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