BIFs: implement float to big integer support

Allow functions such as trunc, round, etc... to return a big integer,
when a number above 2^63 or below -2^63 is given.

Signed-off-by: Davide Bettio <davide@uninstall.it>

Author: bettio

src/libAtomVM/bif.c

@@ -1273,6 +1273,13 @@ static term float_to_integer_helper(
 #else
             return make_maybe_boxed_int(ctx, fail_label, live, fresult);
 #endif
+        } else {
+            intn_digit_t res[INTN_MAX_RES_LEN];
+            intn_integer_sign_t sign;
+            size_t len = intn_from_double(fresult, res, &sign);
+            if (LIKELY(len > 0)) {
+                return make_bigint(ctx, fail_label, live, res, len, sign);
+            }
         }
     }
 

src/libAtomVM/intn.h

@@ -71,6 +71,7 @@ int intn_parse(
     const char buf[], size_t buf_len, int base, intn_digit_t *out, intn_integer_sign_t *out_sign);
 
 double intn_to_double(const intn_digit_t *num, size_t len, intn_integer_sign_t sign);
+int intn_from_double(double dnum, intn_digit_t *out, intn_integer_sign_t *out_sign);
 
 static inline void intn_copy(
     const intn_digit_t *num, size_t num_len, intn_digit_t *out, size_t extend_to)

tests/erlang_tests/bigint.erl

@@ -48,7 +48,7 @@ start() ->
     test_mul() +
         parse_bigint() +
         test_cmp() +
-        conv_to_float().
+        conv_to_from_float().
 
 test_mul() ->
     Expected_INT64_MIN = ?MODULE:pow(-2, 63),
@@ -516,14 +516,17 @@ sort([Pivot | T]) ->
 sort([]) ->
     [].
 
-conv_to_float() ->
+conv_to_from_float() ->
+    % to float
+
     Int0 = ?MODULE:id(erlang:binary_to_integer(?MODULE:id(<<"1000000000000000000">>), 16)),
     Int1 = ?MODULE:id(
         erlang:binary_to_integer(?MODULE:id(<<"CAFECAFE1234000000000000000000">>), 16)
     ),
     Int2 = ?MODULE:id(
         erlang:binary_to_integer(?MODULE:id(<<"-CAFECAFE1234000000000000000000">>), 16)
     ),
+    Int3 = ?MODULE:mul(?MODULE:id(Int1), 2),
     Num1 = ?MODULE:mul(?MODULE:id(Int1), ?MODULE:id(erlang:binary_to_float(?MODULE:id(<<"1.0">>)))),
     Num2 = ?MODULE:mul(?MODULE:id(Int2), ?MODULE:id(erlang:binary_to_float(?MODULE:id(<<"1.0">>)))),
     Num3 = ?MODULE:id(Int1) * ?MODULE:id(erlang:binary_to_float(?MODULE:id(<<"2.0">>))),
@@ -536,6 +539,22 @@ conv_to_float() ->
     true =
         erlang:binary_to_integer(?MODULE:id(<<"195FD95FC2468">>), 16) =:=
             ?MODULE:divtrunc(?MODULE:id(Num3), Int0),
+
+    % from float
+
+    Int1 = ?MODULE:id(trunc(?MODULE:id(Num1))),
+    Int2 = ?MODULE:id(round(?MODULE:id(Num2))),
+    Int3 = ?MODULE:id(floor(?MODULE:id(Num3))),
+    Int3 = ?MODULE:id(ceil(?MODULE:id(Num3))),
+
+    Int64Max = ?MODULE:id(erlang:binary_to_integer(?MODULE:id(<<"7FFFFFFFFFFFFFFF">>), 16)),
+    true = (Int64Max >= ?MODULE:id(trunc(?MODULE:id(9223372036854775295.0)))),
+    true = (Int64Max < ?MODULE:id(trunc(?MODULE:id(9223372036854775296.0)))),
+
+    Int64Min = ?MODULE:id(erlang:binary_to_integer(?MODULE:id(<<"-8000000000000000">>), 16)),
+    true = (Int64Min =< ?MODULE:id(trunc(?MODULE:id(-9223372036854776832.0)))),
+    true = (Int64Min > ?MODULE:id(trunc(?MODULE:id(-9223372036854776833.0)))),
+
     0.
 
 divtrunc(X, Y) ->

tests/erlang_tests/ceilfloatovf.erl

@@ -23,13 +23,13 @@
 -export([start/0]).
 
 start() ->
-    to_int(id(id([1.0e+20, 0]))).
+    to_int(id(id([1.0e+280, 0]))).
 
 to_int(A) ->
     try ceil(id(A)) of
         B when is_integer(B) ->
             "BEAM" = erlang:system_info(machine),
-            "100000000000000000000" = integer_to_list(B),
+            281 = length(integer_to_list(B)),
             0;
         _Other ->
             1

tests/erlang_tests/floorfloatovf.erl

@@ -23,13 +23,13 @@
 -export([start/0]).
 
 start() ->
-    to_int(id(id([1.0e+20, 0]))).
+    to_int(id(id([-1.0e+257, 0]))).
 
 to_int(A) ->
     try floor(id(A)) of
         B when is_integer(B) ->
             "BEAM" = erlang:system_info(machine),
-            "100000000000000000000" = integer_to_list(B),
+            259 = length(integer_to_list(B)),
             0;
         _Other ->
             1

tests/erlang_tests/roundfloatovf.erl

@@ -23,13 +23,13 @@
 -export([start/0]).
 
 start() ->
-    to_int(id(id([1.0e+20, 0]))).
+    to_int(id(id([1.0e+300, 0]))).
 
 to_int(A) ->
     try round(id(A)) of
         B when is_integer(B) ->
             "BEAM" = erlang:system_info(machine),
-            "100000000000000000000" = integer_to_list(B),
+            301 = length(integer_to_list(B)),
             0;
         _Other ->
             1

tests/erlang_tests/truncfloatovf.erl

@@ -23,13 +23,13 @@
 -export([start/0]).
 
 start() ->
-    to_int(id(id([1.0e+20, 0]))).
+    to_int(id(id([1.0e+257, 0]))).
 
 to_int(A) ->
     try trunc(id(A)) of
         B when is_integer(B) ->
             "BEAM" = erlang:system_info(machine),
-            "100000000000000000000" = integer_to_list(B),
+            258 = length(integer_to_list(B)),
             0;
         _Other ->
             1