src: modified RealEnvStore methods to use libuv functions

Modified RealEnvStore::Get, Set, Query and Delete methods
to use libuv methods environment variables operations instead
of using os specific logic and switches.

Fixes: https://github.com/nodejs/node/issues/27211
Refs: http://docs.libuv.org/en/v1.x/misc.html

PR-URL: https://github.com/nodejs/node/pull/27310
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

3 files changed, 58 insertions, 73 deletions

diff --git a/src/env.h b/src/env.h
index 87d71bbc9f..74d65f4fbb 100644
--- a/src/env.h
+++ b/src/env.h
@@ -610,8 +610,8 @@ class KVStore {
   KVStore(KVStore&&) = delete;
   KVStore& operator=(KVStore&&) = delete;
 
-  virtual v8::Local<v8::String> Get(v8::Isolate* isolate,
-                                    v8::Local<v8::String> key) const = 0;
+  virtual v8::MaybeLocal<v8::String> Get(v8::Isolate* isolate,
+                                         v8::Local<v8::String> key) const = 0;
   virtual void Set(v8::Isolate* isolate,
                    v8::Local<v8::String> key,
                    v8::Local<v8::String> value) = 0;
diff --git a/src/inspector_profiler.cc b/src/inspector_profiler.cc
index e5e01dc3c9..867f145ff5 100644
--- a/src/inspector_profiler.cc
+++ b/src/inspector_profiler.cc
@@ -340,7 +340,8 @@ std::string GetCwd(Environment* env) {
 void StartProfilers(Environment* env) {
   Isolate* isolate = env->isolate();
   Local<String> coverage_str = env->env_vars()->Get(
-      isolate, FIXED_ONE_BYTE_STRING(isolate, "NODE_V8_COVERAGE"));
+      isolate, FIXED_ONE_BYTE_STRING(isolate, "NODE_V8_COVERAGE"))
+      .FromMaybe(Local<String>());
   if (!coverage_str.IsEmpty() && coverage_str->Length() > 0) {
     CHECK_NULL(env->coverage_connection());
     env->set_coverage_connection(std::make_unique<V8CoverageConnection>(env));
diff --git a/src/node_env_var.cc b/src/node_env_var.cc
index ef2b78d664..2c1af65b86 100644
--- a/src/node_env_var.cc
+++ b/src/node_env_var.cc
@@ -36,7 +36,7 @@ using v8::Value;
 
 class RealEnvStore final : public KVStore {
  public:
-  Local<String> Get(Isolate* isolate, Local<String> key) const override;
+  MaybeLocal<String> Get(Isolate* isolate, Local<String> key) const override;
   void Set(Isolate* isolate, Local<String> key, Local<String> value) override;
   int32_t Query(Isolate* isolate, Local<String> key) const override;
   void Delete(Isolate* isolate, Local<String> key) override;
@@ -45,7 +45,7 @@ class RealEnvStore final : public KVStore {
 
 class MapKVStore final : public KVStore {
  public:
-  Local<String> Get(Isolate* isolate, Local<String> key) const override;
+  MaybeLocal<String> Get(Isolate* isolate, Local<String> key) const override;
   void Set(Isolate* isolate, Local<String> key, Local<String> value) override;
   int32_t Query(Isolate* isolate, Local<String> key) const override;
   void Delete(Isolate* isolate, Local<String> key) override;
@@ -79,93 +79,73 @@ void DateTimeConfigurationChangeNotification(Isolate* isolate, const T& key) {
   }
 }
 
-Local<String> RealEnvStore::Get(Isolate* isolate,
-                                Local<String> property) const {
+MaybeLocal<String> RealEnvStore::Get(Isolate* isolate,
+                                     Local<String> property) const {
   Mutex::ScopedLock lock(per_process::env_var_mutex);
-#ifdef __POSIX__
+
   node::Utf8Value key(isolate, property);
-  const char* val = getenv(*key);
-  if (val) {
-    return String::NewFromUtf8(isolate, val, NewStringType::kNormal)
-        .ToLocalChecked();
+  size_t init_sz = 256;
+  MaybeStackBuffer<char, 256> val;
+  int ret = uv_os_getenv(*key, *val, &init_sz);
+
+  if (ret == UV_ENOBUFS) {
+    // Buffer is not large enough, reallocate to the updated init_sz
+    // and fetch env value again.
+    val.AllocateSufficientStorage(init_sz);
+    ret = uv_os_getenv(*key, *val, &init_sz);
   }
-#else  // _WIN32
-  node::TwoByteValue key(isolate, property);
-  WCHAR buffer[32767];  // The maximum size allowed for environment variables.
-  SetLastError(ERROR_SUCCESS);
-  DWORD result = GetEnvironmentVariableW(
-      reinterpret_cast<WCHAR*>(*key), buffer, arraysize(buffer));
-  // If result >= sizeof buffer the buffer was too small. That should never
-  // happen. If result == 0 and result != ERROR_SUCCESS the variable was not
-  // found.
-  if ((result > 0 || GetLastError() == ERROR_SUCCESS) &&
-      result < arraysize(buffer)) {
-    const uint16_t* two_byte_buffer = reinterpret_cast<const uint16_t*>(buffer);
-    v8::MaybeLocal<String> rc = String::NewFromTwoByte(
-        isolate, two_byte_buffer, NewStringType::kNormal);
-    if (rc.IsEmpty()) {
-      isolate->ThrowException(ERR_STRING_TOO_LONG(isolate));
-      return Local<String>();
-    }
-    return rc.ToLocalChecked();
+
+  if (ret >= 0) {  // Env key value fetch success.
+    MaybeLocal<String> value_string =
+        String::NewFromUtf8(isolate, *val, NewStringType::kNormal, init_sz);
+    return value_string;
   }
-#endif
-  return Local<String>();
+
+  return MaybeLocal<String>();
 }
 
 void RealEnvStore::Set(Isolate* isolate,
                        Local<String> property,
                        Local<String> value) {
   Mutex::ScopedLock lock(per_process::env_var_mutex);
-#ifdef __POSIX__
+
   node::Utf8Value key(isolate, property);
   node::Utf8Value val(isolate, value);
-  setenv(*key, *val, 1);
-#else  // _WIN32
-  node::TwoByteValue key(isolate, property);
-  node::TwoByteValue val(isolate, value);
-  WCHAR* key_ptr = reinterpret_cast<WCHAR*>(*key);
-  // Environment variables that start with '=' are read-only.
-  if (key_ptr[0] != L'=') {
-    SetEnvironmentVariableW(key_ptr, reinterpret_cast<WCHAR*>(*val));
-  }
+
+#ifdef _WIN32
+  if (key[0] == L'=') return;
 #endif
+  uv_os_setenv(*key, *val);
   DateTimeConfigurationChangeNotification(isolate, key);
 }
 
 int32_t RealEnvStore::Query(Isolate* isolate, Local<String> property) const {
   Mutex::ScopedLock lock(per_process::env_var_mutex);
-#ifdef __POSIX__
+
   node::Utf8Value key(isolate, property);
-  if (getenv(*key)) return 0;
-#else  // _WIN32
-  node::TwoByteValue key(isolate, property);
-  WCHAR* key_ptr = reinterpret_cast<WCHAR*>(*key);
-  SetLastError(ERROR_SUCCESS);
-  if (GetEnvironmentVariableW(key_ptr, nullptr, 0) > 0 ||
-      GetLastError() == ERROR_SUCCESS) {
-    if (key_ptr[0] == L'=') {
-      // Environment variables that start with '=' are hidden and read-only.
-      return static_cast<int32_t>(v8::ReadOnly) |
-             static_cast<int32_t>(v8::DontDelete) |
-             static_cast<int32_t>(v8::DontEnum);
-    }
-    return 0;
-  }
+#ifdef _WIN32
+  if (key[0] == L'=')
+    return static_cast<int32_t>(v8::ReadOnly) |
+           static_cast<int32_t>(v8::DontDelete) |
+           static_cast<int32_t>(v8::DontEnum);
 #endif
-  return -1;
+
+  char val[2];
+  size_t init_sz = sizeof(val);
+  int ret = uv_os_getenv(*key, val, &init_sz);
+
+  if (ret == UV_ENOENT) {
+    return -1;
+  }
+
+  return 0;
 }
 
 void RealEnvStore::Delete(Isolate* isolate, Local<String> property) {
   Mutex::ScopedLock lock(per_process::env_var_mutex);
-#ifdef __POSIX__
+
   node::Utf8Value key(isolate, property);
-  unsetenv(*key);
-#else
-  node::TwoByteValue key(isolate, property);
-  WCHAR* key_ptr = reinterpret_cast<WCHAR*>(*key);
-  SetEnvironmentVariableW(key_ptr, nullptr);
-#endif
+  uv_os_unsetenv(*key);
   DateTimeConfigurationChangeNotification(isolate, key);
 }
 
@@ -231,19 +211,20 @@ std::shared_ptr<KVStore> KVStore::Clone(v8::Isolate* isolate) const {
   for (uint32_t i = 0; i < keys_length; i++) {
     Local<Value> key = keys->Get(context, i).ToLocalChecked();
     CHECK(key->IsString());
-    copy->Set(isolate, key.As<String>(), Get(isolate, key.As<String>()));
+    copy->Set(isolate,
+              key.As<String>(),
+              Get(isolate, key.As<String>()).ToLocalChecked());
   }
   return copy;
 }
 
-Local<String> MapKVStore::Get(Isolate* isolate, Local<String> key) const {
+MaybeLocal<String> MapKVStore::Get(Isolate* isolate, Local<String> key) const {
   Mutex::ScopedLock lock(mutex_);
   Utf8Value str(isolate, key);
   auto it = map_.find(std::string(*str, str.length()));
   if (it == map_.end()) return Local<String>();
   return String::NewFromUtf8(isolate, it->second.data(),
-                             NewStringType::kNormal, it->second.size())
-      .ToLocalChecked();
+                             NewStringType::kNormal, it->second.size());
 }
 
 void MapKVStore::Set(Isolate* isolate, Local<String> key, Local<String> value) {
@@ -323,8 +304,11 @@ static void EnvGetter(Local<Name> property,
     return info.GetReturnValue().SetUndefined();
   }
   CHECK(property->IsString());
-  info.GetReturnValue().Set(
-      env->env_vars()->Get(env->isolate(), property.As<String>()));
+  MaybeLocal<String> value_string =
+      env->env_vars()->Get(env->isolate(), property.As<String>());
+  if (!value_string.IsEmpty()) {
+    info.GetReturnValue().Set(value_string.ToLocalChecked());
+  }
 }
 
 static void EnvSetter(Local<Name> property,