Implement atomvm:random/0 on emscripten

src/platforms/emscripten/src/lib/platform_nifs.c

@@ -23,6 +23,7 @@
 #include <erl_nif_priv.h>
 #include <globalcontext.h>
 #include <interop.h>
+#include <memory.h>
 #include <nifs.h>
 #include <term.h>
 #include <term_typedef.h>
@@ -32,6 +33,8 @@
 #include <emscripten/proxying.h>
 #include <emscripten/threading.h>
 
+#include <math.h>
+
 //#define ENABLE_TRACE
 #include <trace.h>
 
@@ -47,6 +50,20 @@ static term nif_atomvm_platform(Context *ctx, int argc, term argv[])
     return EMSCRIPTEN_ATOM;
 }
 
+static term nif_atomvm_random(Context *ctx, int argc, term argv[])
+{
+    UNUSED(ctx);
+    UNUSED(argc);
+    UNUSED(argv);
+    float val1 = emscripten_random();
+    float val2 = emscripten_random();
+    uint32_t result = ((uint32_t) floor(val1 * (1 << 16))) << 16 | ((uint32_t) floor(val2 * (1 << 16)));
+    if (UNLIKELY(memory_ensure_free(ctx, BOXED_INT64_SIZE) != MEMORY_GC_OK)) {
+        RAISE_ERROR(OUT_OF_MEMORY_ATOM);
+    }
+    return term_make_maybe_boxed_int64(result, &ctx->heap);
+}
+
 static void do_run_script(GlobalContext *global, char *script, int sync, int sync_caller_pid)
 {
     emscripten_run_script(script);
@@ -143,6 +160,10 @@ static const struct Nif atomvm_platform_nif = {
     .base.type = NIFFunctionType,
     .nif_ptr = nif_atomvm_platform
 };
+static const struct Nif atomvm_random_nif = {
+    .base.type = NIFFunctionType,
+    .nif_ptr = nif_atomvm_random
+};
 static const struct Nif emscripten_run_script_nif = {
     .base.type = NIFFunctionType,
     .nif_ptr = nif_emscripten_run_script
@@ -162,6 +183,9 @@ const struct Nif *platform_nifs_get_nif(const char *nifname)
         TRACE("Resolved platform nif %s ...\n", nifname);
         return &atomvm_platform_nif;
     }
+    if (strcmp("atomvm:random/0", nifname) == 0) {
+        return &atomvm_random_nif;
+    }
     if (strcmp("emscripten:run_script/1", nifname) == 0) {
         TRACE("Resolved platform nif %s ...\n", nifname);
         return &emscripten_run_script_nif;

src/platforms/emscripten/tests/cypress/e2e/atomvm.spec.cy.js

@@ -0,0 +1,31 @@
+/*
+ * This file is part of AtomVM.
+ *
+ * Copyright 2023 by Paul Guyot <pguyot@kallisys.net>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
+ */
+describe("atomvm", () => {
+  beforeEach(() => {
+    cy.visit("/tests/src/test_atomvm.html");
+  });
+
+  it("should return platform", () => {
+    cy.get("#platform").should("contain", "emscripten");
+  });
+  it("should compute pi with a reasonable error", () => {
+    cy.get("#pierror").should("contain", "true");
+  });
+});

src/platforms/emscripten/tests/src/CMakeLists.txt

@@ -29,8 +29,10 @@ function(compile_erlang module_name)
     )
 endfunction()
 
+compile_erlang(test_atomvm)
 compile_erlang(test_call)
 
 add_custom_target(emscripten_erlang_test_modules DEPENDS
+    test_atomvm.beam
     test_call.beam
 )

src/platforms/emscripten/tests/src/test_atomvm.erl

@@ -0,0 +1,72 @@
+%
+% This file is part of AtomVM.
+%
+% Copyright 2023 Paul Guyot <pguyot@kallisys.net>
+%
+% Licensed under the Apache License, Version 2.0 (the "License");
+% you may not use this file except in compliance with the License.
+% You may obtain a copy of the License at
+%
+%    http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, software
+% distributed under the License is distributed on an "AS IS" BASIS,
+% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+% See the License for the specific language governing permissions and
+% limitations under the License.
+%
+% SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
+%
+
+-module(test_atomvm).
+-export([start/0]).
+
+start() ->
+    erlang:display({?MODULE, ?LINE}),
+    Platform = atomvm:platform(),
+    erlang:display({?MODULE, ?LINE}),
+    Random = atomvm:random(),
+    erlang:display({?MODULE, ?LINE}),
+    PI = pi_by_random(),
+    PIError = abs((PI - 3.141592653589793) / 3.141592653589793),
+    PIErrorThreshold = PIError < 0.01,
+    erlang:display({?MODULE, ?LINE}),
+    emscripten:run_script(
+        [
+            <<"document.querySelector('#platform').append('">>,
+            atom_to_list(Platform),
+            <<"');">>,
+            <<"document.querySelector('#random').append('">>,
+            integer_to_list(Random),
+            <<"');">>,
+            <<"document.querySelector('#pi').append('">>,
+            float_to_list(PI),
+            <<"');">>,
+            <<"document.querySelector('#pierror').append('">>,
+            atom_to_list(PIErrorThreshold),
+            <<"');">>
+        ],
+        [main_thread, async]
+    ),
+    loop().
+
+loop() ->
+    receive
+    after infinity -> ok
+    end.
+
+pi_by_random() ->
+    pi_by_random(100000, 0, 0).
+
+pi_by_random(0, AccHit, AccTotal) ->
+    4 * AccHit / AccTotal;
+pi_by_random(N, AccHit, AccTotal) ->
+    X = atomvm:random(),
+    Y = atomvm:random(),
+    SqDistance = (X - 16#80000000) * (X - 16#80000000) + (Y - 16#80000000) * (Y - 16#80000000),
+    NewAccHit =
+        case SqDistance > (16#80000000 * 16#80000000) of
+            true -> AccHit;
+            false -> AccHit + 1
+        end,
+    pi_by_random(N - 1, NewAccHit, AccTotal + 1).

src/platforms/emscripten/tests/src/test_atomvm.html

@@ -0,0 +1,44 @@
+<!--
+This file is part of AtomVM.
+
+Copyright 2023 Paul Guyot <pguyot@kallisys.net>
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
+-->
+<!doctype html>
+<html lang="en" dir="ltr">
+  <head>
+    <meta charset="utf-8" />
+  </head>
+  <body>
+    <div id="platform"></div>
+    <div id="random"></div>
+    <div id="pi"></div>
+    <div id="pierror"></div>
+    <script>
+      // Arguments are loaded using fetch API.
+      // wasm_webserver serves under /tests/build/ files in src/platform/escripten/build/tests/src subdirectory
+      // and under /build/ files in build/ subdirectory.
+      var Module = {
+        arguments: [
+          "/tests/build/test_atomvm.beam",
+          "/build/libs/estdlib/src/estdlib.avm",
+          "/build/libs/eavmlib/src/eavmlib.avm",
+        ],
+      };
+    </script>
+    <script async src="/AtomVM.js"></script>
+  </body>
+</html>