add base_I op that converts a bigint to a string with a given base

Author: moritz

src/PAST/NQP.pir

@@ -565,6 +565,7 @@ entry to produce the node to be returned.
     # bigint ops
     maphash['fromstr_I'] = 'nqp_bigint_from_str__PPs'
     maphash['tostr_I']   = 'nqp_bigint_to_str__SP'
+    maphash['base_I']    = 'nqp_bigint_to_str_base__SPI'
     maphash['isbig_I']   = 'nqp_bigint_is_big__IP'
     maphash['fromnum_I'] = 'nqp_bigint_from_num__PNP'
     maphash['tonum_I']   = 'nqp_bigint_to_num__NP'

src/ops/nqp_bigint.ops

@@ -270,6 +270,18 @@ inline op nqp_bigint_to_str(out STR, in PMC) :base_core {
     mem_sys_free(buf);
 }
 
+inline op nqp_bigint_to_str_base(out STR, in PMC, in INT) :base_core {
+    mp_int *i = get_bigint(interp, $2);
+    int len;
+    char *buf;
+    mp_radix_size(i, $3, &len);
+    buf = mem_sys_allocate(len);
+    mp_toradix_n(i, buf, $3, len);
+    /* len - 1 because buf is \0-terminated */
+    $1 = Parrot_str_new(interp, buf, len - 1);
+    mem_sys_free(buf);
+}
+
 inline op nqp_bigint_to_num(out NUM, in PMC) :base_core {
     mp_int  *a = get_bigint(interp, $2);
     $1         = mp_get_double(a);

t/nqp/60-bigint.t

@@ -1,7 +1,7 @@
 #! nqp
 use nqpmo;
 
-plan(28);
+plan(30);
 
 my $knowhow := pir::get_knowhow__P();
 my $bi_type := $knowhow.new_type(:name('TestBigInt'), :repr('P6bigint'));
@@ -82,3 +82,5 @@ $float := -$float;
 ok(nqp::iseq_n($float, nqp::tonum_I(nqp::fromnum_I($float, $bi_type))),
     'to_num and from_num round-trip (negative number)');
 
+ok(nqp::base_I(box(-1234), 10) eq '-1234', 'base_I with base 10');
+ok(nqp::base_I(box(-1234), 16) eq '-4D2',  'base_I with base 16');