erts: Add enif_term_type

This helps avoid long sequences of enif_is_xxx in code that
serializes terms (such as JSON encoders) by letting the user
switch on the type.

3 files changed, 66 insertions, 1 deletions

diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index 349d9bf13a..dd9210a888 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -1158,6 +1158,47 @@ int enif_is_number(ErlNifEnv* env, ERL_NIF_TERM term)
     return is_number(term);
 }
 
+ErlNifTermType enif_term_type(ErlNifEnv* env, ERL_NIF_TERM term) {
+    (void)env;
+
+    switch (tag_val_def(term)) {
+    case ATOM_DEF:
+        return ERL_NIF_TERM_TYPE_ATOM;
+    case BINARY_DEF:
+        return ERL_NIF_TERM_TYPE_BITSTRING;
+    case FLOAT_DEF:
+        return ERL_NIF_TERM_TYPE_FLOAT;
+    case EXPORT_DEF:
+    case FUN_DEF:
+        return ERL_NIF_TERM_TYPE_FUN;
+    case BIG_DEF:
+    case SMALL_DEF:
+        return ERL_NIF_TERM_TYPE_INTEGER;
+    case LIST_DEF:
+    case NIL_DEF:
+        return ERL_NIF_TERM_TYPE_LIST;
+    case MAP_DEF:
+        return ERL_NIF_TERM_TYPE_MAP;
+    case EXTERNAL_PID_DEF:
+    case PID_DEF:
+        return ERL_NIF_TERM_TYPE_PID;
+    case EXTERNAL_PORT_DEF:
+    case PORT_DEF:
+        return ERL_NIF_TERM_TYPE_PORT;
+    case EXTERNAL_REF_DEF:
+    case REF_DEF:
+        return ERL_NIF_TERM_TYPE_REFERENCE;
+    case TUPLE_DEF:
+        return ERL_NIF_TERM_TYPE_TUPLE;
+    default:
+        /* tag_val_def() aborts on its own when passed complete garbage, but
+         * it's possible that the user has given us garbage that just happens
+         * to match something that tag_val_def() accepts but we don't, like
+         * binary match contexts. */
+        ERTS_INTERNAL_ERROR("Invalid term passed to enif_term_type");
+    }
+}
+
 static void aligned_binary_dtor(struct enif_tmp_obj_t* obj)
 {
     erts_free_aligned_binary_bytes_extra((byte*)obj, obj->allocator);
diff --git a/erts/emulator/beam/erl_nif.h b/erts/emulator/beam/erl_nif.h
index 3fd1a8fd4c..a599511c78 100644
--- a/erts/emulator/beam/erl_nif.h
+++ b/erts/emulator/beam/erl_nif.h
@@ -55,6 +55,7 @@
 ** 2.14: 21.0 add enif_ioq_peek_head, enif_(mutex|cond|rwlock|thread)_name
 **                enif_vfprintf, enif_vsnprintf, enif_make_map_from_arrays
 ** 2.15: 22.0 ERL_NIF_SELECT_CANCEL, enif_select_(read|write)
+**            enif_term_type
 */
 #define ERL_NIF_MAJOR_VERSION 2
 #define ERL_NIF_MINOR_VERSION 15
@@ -63,7 +64,7 @@
  * with ticket syntax like "erts-@OTP-12345@", or a temporary placeholder
  * between two @ like "erts-@MyName@", if you don't know what a ticket is.
  */
-#define ERL_NIF_MIN_ERTS_VERSION "erts-@OTP-15095@ (OTP-22)"
+#define ERL_NIF_MIN_ERTS_VERSION "erts-@OTP-15095 OTP-15640@ (OTP-22)"
 
 /*
  * The emulator will refuse to load a nif-lib with a major version
@@ -282,6 +283,26 @@ typedef enum {
     ERL_NIF_IOQ_NORMAL = 1
 } ErlNifIOQueueOpts;
 
+typedef enum {
+    ERL_NIF_TERM_TYPE_ATOM = 1,
+    ERL_NIF_TERM_TYPE_BITSTRING = 2,
+    ERL_NIF_TERM_TYPE_FLOAT = 3,
+    ERL_NIF_TERM_TYPE_FUN = 4,
+    ERL_NIF_TERM_TYPE_INTEGER = 5,
+    ERL_NIF_TERM_TYPE_LIST = 6,
+    ERL_NIF_TERM_TYPE_MAP = 7,
+    ERL_NIF_TERM_TYPE_PID = 8,
+    ERL_NIF_TERM_TYPE_PORT = 9,
+    ERL_NIF_TERM_TYPE_REFERENCE = 10,
+    ERL_NIF_TERM_TYPE_TUPLE = 11,
+
+    /* This is a dummy value intended to coax the compiler into warning about
+     * unhandled values in a switch even if all the above values have been
+     * handled. We can add new entries at any time so the user must always
+     * have a default case. */
+    ERL_NIF_TERM_TYPE__MISSING_DEFAULT_CASE__READ_THE_MANUAL = -1
+} ErlNifTermType;
+
 /*
  * Return values from enif_thread_type(). Negative values
  * reserved for specific types of non-scheduler threads.
diff --git a/erts/emulator/beam/erl_nif_api_funcs.h b/erts/emulator/beam/erl_nif_api_funcs.h
index 8ab454c8dd..d57f6ec97c 100644
--- a/erts/emulator/beam/erl_nif_api_funcs.h
+++ b/erts/emulator/beam/erl_nif_api_funcs.h
@@ -215,6 +215,8 @@ ERL_NIF_API_FUNC_DECL(ERL_NIF_TERM,enif_make_monitor_term,(ErlNifEnv* env, const
 ERL_NIF_API_FUNC_DECL(void,enif_set_pid_undefined,(ErlNifPid* pid));
 ERL_NIF_API_FUNC_DECL(int,enif_is_pid_undefined,(const ErlNifPid* pid));
 
+ERL_NIF_API_FUNC_DECL(ErlNifTermType,enif_term_type,(ErlNifEnv* env, ERL_NIF_TERM term));
+
 /*
 ** ADD NEW ENTRIES HERE (before this comment) !!!
 */
@@ -401,6 +403,7 @@ ERL_NIF_API_FUNC_DECL(int,enif_is_pid_undefined,(const ErlNifPid* pid));
 #  define enif_make_monitor_term ERL_NIF_API_FUNC_MACRO(enif_make_monitor_term)
 #  define enif_set_pid_undefined ERL_NIF_API_FUNC_MACRO(enif_set_pid_undefined)
 #  define enif_is_pid_undefined ERL_NIF_API_FUNC_MACRO(enif_is_pid_undefined)
+#  define enif_term_type ERL_NIF_API_FUNC_MACRO(enif_term_type)
 
 /*
 ** ADD NEW ENTRIES HERE (before this comment)