7 files changed, 52 insertions, 2 deletions

diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index 5c955b9566..1cad31be2c 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -5080,6 +5080,8 @@ translate_gc_bif(void* gcf)
 	return bit_size_1;
     } else if (gcf == erts_gc_byte_size_1) {
 	return byte_size_1;
+    } else if (gcf == erts_gc_map_size_1) {
+	return map_size_1;
     } else if (gcf == erts_gc_abs_1) {
 	return abs_1;
     } else if (gcf == erts_gc_float_1) {
diff --git a/erts/emulator/beam/beam_load.c b/erts/emulator/beam/beam_load.c
index 58207ec75b..b589d1c930 100644
--- a/erts/emulator/beam/beam_load.c
+++ b/erts/emulator/beam/beam_load.c
@@ -3783,6 +3783,8 @@ gen_guard_bif1(LoaderState* stp, GenOpArg Fail, GenOpArg Live, GenOpArg Bif,
 	op->a[1].val = (BeamInstr) (void *) erts_gc_bit_size_1;
     } else if (bf == byte_size_1) {
 	op->a[1].val = (BeamInstr) (void *) erts_gc_byte_size_1;
+    } else if (bf == map_size_1) {
+	op->a[1].val = (BeamInstr) (void *) erts_gc_map_size_1;
     } else if (bf == abs_1) {
 	op->a[1].val = (BeamInstr) (void *) erts_gc_abs_1;
     } else if (bf == float_1) {
diff --git a/erts/emulator/beam/bif.tab b/erts/emulator/beam/bif.tab
index 42515d0494..a8623fcf61 100644
--- a/erts/emulator/beam/bif.tab
+++ b/erts/emulator/beam/bif.tab
@@ -579,6 +579,7 @@ bif os:unsetenv/1
 bif re:inspect/2
 
 ubif erlang:is_map/1
+ubif erlang:map_size/1
 bif map:to_list/1
 bif map:new/0
 bif map:get/2
diff --git a/erts/emulator/beam/erl_bif_guard.c b/erts/emulator/beam/erl_bif_guard.c
index a715756c15..bbd8aa31d9 100644
--- a/erts/emulator/beam/erl_bif_guard.c
+++ b/erts/emulator/beam/erl_bif_guard.c
@@ -33,6 +33,7 @@
 #include "bif.h"
 #include "big.h"
 #include "erl_binary.h"
+#include "erl_map.h"
 
 static Eterm gc_double_to_integer(Process* p, double x, Eterm* reg, Uint live);
 
@@ -455,6 +456,28 @@ Eterm erts_gc_byte_size_1(Process* p, Eterm* reg, Uint live)
     }
 }
 
+Eterm erts_gc_map_size_1(Process* p, Eterm* reg, Uint live)
+{
+    Eterm arg = reg[live];
+    if (is_map(arg)) {
+	map_t *mp = (map_t*)map_val(arg);
+	Uint size = map_get_size(mp);
+	if (IS_USMALL(0, size)) {
+	    return make_small(size);
+	} else {
+	    Eterm* hp;
+	    if (ERTS_NEED_GC(p, BIG_UINT_HEAP_SIZE)) {
+		erts_garbage_collect(p, BIG_UINT_HEAP_SIZE, reg, live);
+	    }
+	    hp = p->htop;
+	    p->htop += BIG_UINT_HEAP_SIZE;
+	    return uint_to_big(size, hp);
+	}
+    } else {
+	BIF_ERROR(p, BADARG);
+    }
+}
+
 Eterm erts_gc_abs_1(Process* p, Eterm* reg, Uint live)
 {
     Eterm arg;
diff --git a/erts/emulator/beam/erl_map.c b/erts/emulator/beam/erl_map.c
index 1fd7943c30..6a59fa29b8 100644
--- a/erts/emulator/beam/erl_map.c
+++ b/erts/emulator/beam/erl_map.c
@@ -30,10 +30,8 @@
 #include "error.h"
 #include "bif.h"
 
-
 #include "erl_map.h"
 
-
 BIF_RETTYPE map_to_list_1(BIF_ALIST_1) {
     if (is_map(BIF_ARG_1)) {
 	Uint n;
@@ -58,6 +56,27 @@ BIF_RETTYPE map_to_list_1(BIF_ALIST_1) {
     BIF_ERROR(BIF_P, BADARG);
 }
 
+
+/* erlang:map_size/1
+ * the corresponding instruction is implemented in:
+ *     beam/erl_bif_guard.c
+ */
+
+BIF_RETTYPE map_size_1(BIF_ALIST_1) {
+    if (is_map(BIF_ARG_1)) {
+	Eterm *hp;
+	Uint hsz  = 0;
+	map_t *mp = (map_t*)map_val(BIF_ARG_1);
+	Uint n    = map_get_size(mp);
+
+	erts_bld_uint(NULL, &hsz, n);
+	hp = HAlloc(BIF_P, hsz);
+	BIF_RET(erts_bld_uint(&hp, NULL, n));
+    }
+
+    BIF_ERROR(BIF_P, BADARG);
+}
+
 BIF_RETTYPE map_new_0(BIF_ALIST_0) {
     Eterm* hp;
     Eterm tup;
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index 83a8911a36..8fcb95d0e2 100755
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -998,6 +998,7 @@ Eterm erts_gc_length_1(Process* p, Eterm* reg, Uint live);
 Eterm erts_gc_size_1(Process* p, Eterm* reg, Uint live);
 Eterm erts_gc_bit_size_1(Process* p, Eterm* reg, Uint live);
 Eterm erts_gc_byte_size_1(Process* p, Eterm* reg, Uint live);
+Eterm erts_gc_map_size_1(Process* p, Eterm* reg, Uint live);
 Eterm erts_gc_abs_1(Process* p, Eterm* reg, Uint live);
 Eterm erts_gc_float_1(Process* p, Eterm* reg, Uint live);
 Eterm erts_gc_round_1(Process* p, Eterm* reg, Uint live);
diff --git a/lib/stdlib/src/erl_internal.erl b/lib/stdlib/src/erl_internal.erl
index 28de7205ea..480675554a 100644
--- a/lib/stdlib/src/erl_internal.erl
+++ b/lib/stdlib/src/erl_internal.erl
@@ -70,6 +70,7 @@ guard_bif(bit_size, 1) -> true;
 guard_bif(byte_size, 1) -> true;
 guard_bif(element, 2) -> true;
 guard_bif(self, 0) -> true;
+guard_bif(map_size, 1) -> true;
 guard_bif(node, 0) -> true;
 guard_bif(node, 1) -> true;
 guard_bif(tuple_size, 1) -> true;
@@ -335,6 +336,7 @@ bif(list_to_pid, 1) -> true;
 bif(list_to_tuple, 1) -> true;
 bif(load_module, 2) -> true;
 bif(make_ref, 0) -> true;
+bif(map_size,1) -> true;
 bif(max,2) -> true;
 bif(min,2) -> true;
 bif(module_loaded, 1) -> true;