NIFs: add atomvm:get_entry_point/1

Add function for getting the entry point for a given .avm file.

Signed-off-by: Davide Bettio <[email protected]>

src/libAtomVM/nifs.c

@@ -152,6 +152,7 @@ static term nif_erlang_unlink(Context *ctx, int argc, term argv[]);
 static term nif_atomvm_add_avm_pack_binary(Context *ctx, int argc, term argv[]);
 static term nif_atomvm_add_avm_pack_file(Context *ctx, int argc, term argv[]);
 static term nif_atomvm_close_avm_pack(Context *ctx, int argc, term argv[]);
+static term nif_atomvm_get_entry_point(Context *ctx, int argc, term argv[]);
 static term nif_atomvm_read_priv(Context *ctx, int argc, term argv[]);
 static term nif_console_print(Context *ctx, int argc, term argv[]);
 static term nif_base64_encode(Context *ctx, int argc, term argv[]);
@@ -641,6 +642,11 @@ static const struct Nif atomvm_close_avm_pack_nif =
     .base.type = NIFFunctionType,
     .nif_ptr = nif_atomvm_close_avm_pack
 };
+static const struct Nif atomvm_get_entry_point_nif =
+{
+    .base.type = NIFFunctionType,
+    .nif_ptr = nif_atomvm_get_entry_point
+};
 static const struct Nif atomvm_read_priv_nif =
 {
     .base.type = NIFFunctionType,
@@ -3483,6 +3489,47 @@ static term nif_atomvm_close_avm_pack(Context *ctx, int argc, term argv[])
     return OK_ATOM;
 }
 
+// AtomVM extension
+static term nif_atomvm_get_entry_point(Context *ctx, int argc, term argv[])
+{
+    UNUSED(argc);
+
+    term name = argv[0];
+    if (UNLIKELY(!term_is_atom(name))) {
+        RAISE_ERROR(BADARG_ATOM);
+    }
+
+    int name_atom_id = term_to_atom_index(name);
+
+    struct ListHead *open_avm_packs = synclist_wrlock(&ctx->global->avmpack_data);
+    struct ListHead *item;
+    LIST_FOR_EACH (item, open_avm_packs) {
+        struct AVMPackData *avmpack_data = GET_LIST_ENTRY(item, struct AVMPackData, avmpack_head);
+        if (avmpack_data->name_atom_id == name_atom_id) {
+            uint32_t size;
+            const void *beam;
+            const char *module_name;
+            if (!avmpack_find_section_by_flag(avmpack_data->data, BEAM_START_FLAG, &beam, &size, &module_name)) {
+                synclist_unlock(&ctx->global->avmpack_data);
+                return UNDEFINED_ATOM;
+            }
+
+            int module_name_len = strlen(module_name);
+            int needed = term_binary_heap_size(module_name_len);
+            if (UNLIKELY(memory_ensure_free(ctx, needed) != MEMORY_GC_OK)) {
+                synclist_unlock(&ctx->global->avmpack_data);
+                RAISE_ERROR(OUT_OF_MEMORY_ATOM);
+            }
+            term entry_bin = term_from_literal_binary(module_name, module_name_len, &ctx->heap, ctx->global);
+            synclist_unlock(&ctx->global->avmpack_data);
+            return entry_bin;
+        }
+    }
+    synclist_unlock(&ctx->global->avmpack_data);
+
+    return UNDEFINED_ATOM;
+}
+
 // AtomVM extension
 static term nif_atomvm_read_priv(Context *ctx, int argc, term argv[])
 {

src/libAtomVM/nifs.gperf

@@ -119,6 +119,7 @@ erts_debug:flat_size/1, &flat_size_nif
 atomvm:add_avm_pack_binary/2, &atomvm_add_avm_pack_binary_nif
 atomvm:add_avm_pack_file/2, &atomvm_add_avm_pack_file_nif
 atomvm:close_avm_pack/2, &atomvm_close_avm_pack_nif
+atomvm:get_entry_point/1, &atomvm_get_entry_point_nif
 atomvm:read_priv/2, &atomvm_read_priv_nif
 atomvm:posix_open/2, IF_HAVE_OPEN_CLOSE(&atomvm_posix_open_nif)
 atomvm:posix_open/3, IF_HAVE_OPEN_CLOSE(&atomvm_posix_open_nif)