Open source pure native binary.

java/com/google/BUILD

@@ -0,0 +1,24 @@
+load("@rules_java//java:defs.bzl", "java_library")
+
+licenses(["notice"])
+
+java_library(
+    name = "random_string_java",
+    srcs = ["RandomString.java"],
+)
+
+cc_library(
+    name = "java_runtime_environment",
+    hdrs = ["java_runtime_environment.h"],
+    deps = ["//:jni_bind"],
+)
+
+cc_binary(
+    name = "main",
+    srcs = ["main.cc"],
+    data = [":random_string_java"],
+    deps = [
+        ":java_runtime_environment",
+        "//:jni_bind",
+    ],
+)

java/com/google/README.md

@@ -0,0 +1,3 @@
+This binary is meant to demonstrate a simple binary that is entirely written in native.
+
+This is experimental.

java/com/google/RandomString.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2021 Google LLC
+ *
+ * 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.
+ */
+
+package com.google;
+
+import java.util.Random;
+
+/** Just a toy model to make sure that we have a large data structure in memory. */
+class RandomString {
+  public RandomString() {}
+
+  public static String generateRandomString(int length) {
+    String characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+
+    Random random = new Random();
+    StringBuilder sb = new StringBuilder(length);
+
+    for (int i = 0; i < length; i++) {
+      int randomIndex = random.nextInt(characters.length());
+      char randomChar = characters.charAt(randomIndex);
+      sb.append(randomChar);
+    }
+
+    return sb.toString();
+  }
+
+  public String format() {
+    return generateRandomString(50);
+  }
+}

java/com/google/java_runtime_environment.h

@@ -0,0 +1,110 @@
+#ifndef JNI_BIND_JAVA_COM_GOOGLE_JAVA_RUNTIME_ENVIRONMENT_H_
+#define JNI_BIND_JAVA_COM_GOOGLE_JAVA_RUNTIME_ENVIRONMENT_H_
+
+#include <dlfcn.h>
+#include <sys/stat.h>
+
+#include <cstdio>
+#include <optional>
+#include <string_view>
+
+#include "jni_bind.h"
+
+namespace jni_bind_sample_binary {
+
+// True if `path` is present on disk.
+inline bool FileExists(std::string_view path) {
+  struct stat buf;
+
+  return stat(path.data(), &buf) == 0 && S_ISREG(buf.st_mode);
+}
+
+inline std::optional<void *> LoadLibrary(std::string_view lib_path) {
+  void *lib_handle = dlopen(lib_path.data(), RTLD_NOW);
+  if (lib_handle == nullptr) {
+    printf("Failed to load libjvm so lib: %s\n", dlerror());
+    return std::nullopt;
+  }
+
+  return lib_handle;
+}
+
+// Represents JVM so lib, normally launched by some kind of launcher, but in
+// this sample the JVM is driven entirely by native. This class may be suitable
+// for use beyond this toy binary, but needs more rigorous review.
+class JavaRuntimeEnvironment {
+  using CreateJvmFunc = jint (*)(JavaVM **, JNIEnv **, JavaVMInitArgs *);
+  using GetJvmFunc = jint (*)(JavaVM **, jsize, jsize *);
+
+ private:
+  inline JavaRuntimeEnvironment(void *lib_handle,
+                                std::string_view class_collection)
+      : lib_handle_(lib_handle),
+        create_function_(reinterpret_cast<CreateJvmFunc>(
+            dlsym(lib_handle_, "JNI_CreateJavaVM"))),
+        get_jvm_function_(reinterpret_cast<GetJvmFunc>(
+            dlsym(lib_handle_, "JNI_GetCreatedJavaVMs"))) {
+    auto *vm_options = new JavaVMOption[1];
+    vm_options[0] = {.optionString =
+                         const_cast<char *>(class_collection.data())};
+
+    vm_args_ = JavaVMInitArgs{.version = JNI_VERSION_1_6,
+                              .nOptions = 1,
+                              .options = vm_options,
+                              .ignoreUnrecognized = JNI_FALSE};
+
+    jint result = create_function_(&jvm_, &jenv_, &vm_args_);
+    if (result < 0) {
+      printf("JNI_CreateJavaVM() failed\n");
+      return;
+    }
+
+    success_loading_jvm_ = true;
+    printf("JVM created.\n");
+  }
+
+ public:
+  ~JavaRuntimeEnvironment() { dlclose(lib_handle_); }
+
+  // Builds a `JavaRuntimeEnvironment`, or nothing if failure.
+  static inline std::optional<JavaRuntimeEnvironment> Build(
+      std::string_view jvm_so_lib, std::string_view class_collection) {
+    if (!FileExists(jvm_so_lib.data())) {
+      printf("libjvm so solib does not exist.");
+      return std::nullopt;
+    }
+
+    auto lib_handle = LoadLibrary(jvm_so_lib);
+    if (lib_handle == std::nullopt) {
+      printf("Failed to load libjvm so lib.\n");
+      return std::nullopt;
+    }
+
+    JavaRuntimeEnvironment ret(*lib_handle, class_collection);
+    if (ret.success_loading_jvm_ == false) {
+      printf("Initializing JVM failed.\n");
+      return std::nullopt;
+    }
+
+    printf("Loading succeeded.\n");
+
+    return ret;
+  }
+
+  JavaVM *GetJvm() { return jvm_; }
+
+ private:
+  void *lib_handle_;
+  const CreateJvmFunc create_function_;
+  const GetJvmFunc get_jvm_function_;
+  JavaVMInitArgs vm_args_;
+
+  JavaVM *jvm_;
+  JNIEnv *jenv_;
+
+  bool success_loading_jvm_ = false;
+};
+
+}  // namespace jni_bind_sample_binary
+
+#endif  // JNI_BIND_JAVA_COM_GOOGLE_JAVA_RUNTIME_ENVIRONMENT_H_

java/com/google/main.cc

@@ -0,0 +1,100 @@
+/*
+ * Copyright 2021 Google LLC
+ *
+ * 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.
+ */
+
+#include <dlfcn.h>
+#include <sys/stat.h>
+
+#include <cstdint>
+#include <cstdio>
+#include <iostream>
+#include <optional>
+#include <string>
+#include <string_view>
+
+#include "java_runtime_environment.h"  // NOLINT
+#include "jni_bind.h"
+
+// This binary is meant as a test to exercise a JVM loaded entirely from
+// native. For now the path to the JVM so lib is hard coded, but it should be
+// an argument to the binary.
+
+namespace {
+
+using ::jni_bind_sample_binary::JavaRuntimeEnvironment;
+
+static constexpr int32_t kNumIterations = 1000;
+
+void RunIterationsToCompletion(jni::JvmRef<jni::kDefaultJvm> *jvm_ref) {
+  static constexpr jni::Class kRandomString{
+      "com/google/RandomString", jni::Constructor{},
+      jni::Method{"format", jni::Return<jstring>{}, jni::Params{}}};
+
+  jni::GlobalObject<kRandomString> random_string;
+
+  for (int i = 0; i < kNumIterations; ++i) {
+    printf("Iteration %i: %s\n", i,
+           random_string("format").Pin().ToString().data());
+  }
+}
+
+std::string LibNameToFullPath(std::string runfiles_path, std::string lib_name) {
+  return runfiles_path + lib_name;
+}
+
+}  // namespace
+
+int main(int argc, char *argv[]) {
+  std::string execution_path = argv[0];
+  std::string runfiles_path = execution_path + ".runfiles";
+
+  std::cout
+      << "##############################################################"
+      << '\n'
+      << "Application Run Directory: " << execution_path << "\n"
+      << "Runfiles Directory: " << runfiles_path << "\n"
+      << "Number of iterations: " << kNumIterations
+      << "\n##############################################################"
+      << std::endl;
+  ;
+
+  std::string full_class_collection =
+      "-Djava.class.path=" +
+      LibNameToFullPath(runfiles_path,
+                        "/google3/third_party/jni_wrapper/java/com/google/"
+                        "librandom_string_java.jar");
+
+  auto java_runtime_environment = JavaRuntimeEnvironment::Build(
+      "/usr/local/buildtools/java/jdk/lib/server/libjvm.so",
+      full_class_collection);
+
+  if (java_runtime_environment == std::nullopt) {
+    return -1;
+  }
+
+  {
+    jni::JvmRef<jni::kDefaultJvm> jvm_ref{(*java_runtime_environment).GetJvm()};
+    RunIterationsToCompletion(&jvm_ref);
+  }
+
+  std::cout << '\n'
+            << "##############################################################"
+            << '\n'
+            << "DONE." << '\n'
+            << "##############################################################"
+            << std::endl;
+
+  return 0;
+}

metaprogramming/BUILD

@@ -1179,8 +1179,6 @@ cc_test(
 cc_library(
     name = "unfurl",
     hdrs = ["unfurl.h"],
-    deps = [
-    ],
 )
 
 cc_test(