Introduce mjpEncoder plugin architecture

Add a new mjpEncoder plugin type mirroring the existing mjpDecoder pattern. Encoders serialize an mjSpec + mjModel to an mjResource for a given format. New API functions: - mjp_registerEncoder: globally register an encoder - mjp_defaultEncoder: zero-initialize an encoder struct - mjp_findEncoder: look up an encoder by filename extension or content type The mjfEncode callback takes (mjSpec*, mjModel*, mjVFS*, mjResource*) and returns 0 on success. Writing to mjResource keeps symmetry with the decoder reading from mjResource and leaves the door open for writable resource providers. PiperOrigin-RevId: 889187898 Change-Id: I180771b2255b91dea188ac5e2cdc3a8f0fb85364
2026-03-25 05:34:48 -07:00
parent 2d33b50243
commit f5d3ce3451
15 changed files with 617 additions and 0 deletions
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+// Copyright 2025 DeepMind Technologies Limited
+//
+// 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.
+
+// Tests for encoder plugins.
+
+#include <cstdio>
+#include <string>
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+#include <mujoco/mjmodel.h>
+#include <mujoco/mjplugin.h>
+#include <mujoco/mujoco.h>
+#include "test/fixture.h"
+
+namespace mujoco {
+namespace {
+
+struct FakeEncoderOutput {
+  int nbody;
+  int ngeom;
+  int njnt;
+  char resource_name[512];
+};
+
+int FakeEncode(const mjSpec* s, const mjModel* m, const mjVFS* vfs,
+               mjResource* resource) {
+  auto* output = new FakeEncoderOutput;
+  output->nbody = m->nbody;
+  output->ngeom = m->ngeom;
+  output->njnt = m->njnt;
+  std::snprintf(output->resource_name, sizeof(output->resource_name), "%s",
+                resource->name);
+  resource->data = output;
+  return sizeof(FakeEncoderOutput);
+}
+
+void CloseResource(mjResource* resource) {
+  delete static_cast<FakeEncoderOutput*>(resource->data);
+  delete resource;
+}
+
+mjpEncoder FakeEncoder() {
+  mjpEncoder encoder;
+  mjp_defaultEncoder(&encoder);
+  encoder.content_type = "model/fakeformat";
+  encoder.extension = ".fakeformat|.alsoFakeFormat";
+  encoder.encode = FakeEncode;
+  encoder.close_resource = CloseResource;
+  return encoder;
+}
+
+using EncoderPluginTest = MujocoTest;
+
+TEST_F(EncoderPluginTest, RegisterAndFindByExtension) {
+  mjpEncoder encoder = FakeEncoder();
+  mjp_registerEncoder(&encoder);
+
+  const mjpEncoder* found = mjp_findEncoder("output.fakeformat", nullptr);
+  ASSERT_THAT(found, testing::NotNull());
+  EXPECT_EQ(found->encode, FakeEncode);
+}
+
+TEST_F(EncoderPluginTest, FindByAlternateExtension) {
+  const mjpEncoder* found = mjp_findEncoder("output.alsoFakeFormat", nullptr);
+  ASSERT_THAT(found, testing::NotNull());
+  EXPECT_EQ(found->encode, FakeEncode);
+}
+
+TEST_F(EncoderPluginTest, FindByContentType) {
+  const mjpEncoder* found = mjp_findEncoder(nullptr, "model/fakeformat");
+  ASSERT_THAT(found, testing::NotNull());
+  EXPECT_EQ(found->encode, FakeEncode);
+}
+
+TEST_F(EncoderPluginTest, FindUnknownExtensionReturnsNull) {
+  const mjpEncoder* found = mjp_findEncoder("output.unknown", nullptr);
+  EXPECT_THAT(found, testing::IsNull());
+}
+
+TEST_F(EncoderPluginTest, DefaultEncoderIsZeroed) {
+  mjpEncoder encoder;
+  mjp_defaultEncoder(&encoder);
+  EXPECT_EQ(encoder.content_type, nullptr);
+  EXPECT_EQ(encoder.extension, nullptr);
+  EXPECT_EQ(encoder.encode, nullptr);
+}
+
+TEST_F(EncoderPluginTest, EncodeModel) {
+  mjSpec* spec = mj_makeSpec();
+  mjsBody* world = mjs_findBody(spec, "world");
+  mjsBody* body = mjs_addBody(world, nullptr);
+  mjsGeom* geom = mjs_addGeom(body, nullptr);
+  geom->size[0] = 1.0;
+  geom->size[1] = 1.0;
+  geom->size[2] = 1.0;
+
+  mjModel* model = mj_compile(spec, nullptr);
+  ASSERT_THAT(model, testing::NotNull());
+
+  const mjpEncoder* found = mjp_findEncoder("output.fakeformat", nullptr);
+  ASSERT_THAT(found, testing::NotNull());
+
+  mjResource resource = {};
+  resource.name = const_cast<char*>("output.fakeformat");
+
+  int result = found->encode(spec, model, nullptr, &resource);
+  EXPECT_GT(result, 0);
+
+  auto* output = static_cast<FakeEncoderOutput*>(resource.data);
+  ASSERT_THAT(output, testing::NotNull());
+  EXPECT_EQ(output->nbody, 2);
+  EXPECT_EQ(output->ngeom, 1);
+  EXPECT_EQ(output->njnt, 0);
+  EXPECT_STREQ(output->resource_name, "output.fakeformat");
+
+  delete output;
+  mj_deleteModel(model);
+  mj_deleteSpec(spec);
+}
+
+}  // namespace
+}  // namespace mujoco