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-rw-r--r--erts/emulator/beam/big.c56
1 files changed, 56 insertions, 0 deletions
diff --git a/erts/emulator/beam/big.c b/erts/emulator/beam/big.c
index d18de9ae5d..b90ea6b478 100644
--- a/erts/emulator/beam/big.c
+++ b/erts/emulator/beam/big.c
@@ -1584,6 +1584,62 @@ big_to_double(Wterm x, double* resp)
return 0;
}
+/*
+ * Logic has been copied from erl_bif_guard.c and slightly
+ * modified to use a static instead of dynamic heap
+ */
+Eterm
+double_to_big(double x, Eterm *heap)
+{
+ int is_negative;
+ int ds;
+ ErtsDigit* xp;
+ Eterm res;
+ int i;
+ size_t sz;
+ Eterm* hp;
+ double dbase;
+
+ if (x >= 0) {
+ is_negative = 0;
+ } else {
+ is_negative = 1;
+ x = -x;
+ }
+
+ /* Unscale & (calculate exponent) */
+ ds = 0;
+ dbase = ((double) (D_MASK) + 1);
+ while (x >= 1.0) {
+ x /= dbase; /* "shift" right */
+ ds++;
+ }
+ sz = BIG_NEED_SIZE(ds); /* number of words including arity */
+
+ hp = heap;
+ res = make_big(hp);
+ xp = (ErtsDigit*) (hp + 1);
+
+ for (i = ds - 1; i >= 0; i--) {
+ ErtsDigit d;
+
+ x *= dbase; /* "shift" left */
+ d = x; /* trunc */
+ xp[i] = d; /* store digit */
+ x -= d; /* remove integer part */
+ }
+ while ((ds & (BIG_DIGITS_PER_WORD - 1)) != 0) {
+ xp[ds++] = 0;
+ }
+
+ if (is_negative) {
+ *hp = make_neg_bignum_header(sz-1);
+ } else {
+ *hp = make_pos_bignum_header(sz-1);
+ }
+ return res;
+}
+
/*
** Estimate the number of decimal digits (include sign)