1 files changed, 152 insertions, 0 deletions
diff --git a/src/database/include/env_esp.hpp b/src/database/include/env_esp.hpp
new file mode 100644
index 00000000..c9b3fbc8
--- /dev/null
+++ b/src/database/include/env_esp.hpp
@@ -0,0 +1,152 @@
+#pragma once
+
+#include <mutex>
+#include <set>
+
+#include "freertos/FreeRTOS.h"
+#include "freertos/queue.h"
+#include "leveldb/env.h"
+#include "leveldb/status.h"
+
+namespace leveldb {
+
+// Tracks the files locked by EspEnv::LockFile().
+//
+// We maintain a separate set instead of relying on fcntl(F_SETLK) because
+// fcntl(F_SETLK) does not provide any protection against multiple uses from the
+// same process.
+//
+// Instances are thread-safe because all member data is guarded by a mutex.
+class InMemoryLockTable {
+ public:
+  bool Insert(const std::string& fname) {
+    mu_.lock();
+    bool succeeded = locked_files_.insert(fname).second;
+    mu_.unlock();
+    return succeeded;
+  }
+  void Remove(const std::string& fname) {
+    mu_.lock();
+    locked_files_.erase(fname);
+    mu_.unlock();
+  }
+
+ private:
+  std::mutex mu_;
+  std::set<std::string> locked_files_;
+};
+
+class EspEnv : public leveldb::Env {
+ public:
+  EspEnv();
+  ~EspEnv() override;
+
+  Status NewSequentialFile(const std::string& filename,
+                           SequentialFile** result) override;
+
+  Status NewRandomAccessFile(const std::string& filename,
+                             RandomAccessFile** result) override;
+
+  Status NewWritableFile(const std::string& filename,
+                         WritableFile** result) override;
+
+  Status NewAppendableFile(const std::string& filename,
+                           WritableFile** result) override;
+
+  bool FileExists(const std::string& filename) override;
+
+  Status GetChildren(const std::string& directory_path,
+                     std::vector<std::string>* result) override;
+
+  Status RemoveFile(const std::string& filename) override;
+
+  Status CreateDir(const std::string& dirname) override;
+
+  Status RemoveDir(const std::string& dirname) override;
+
+  Status GetFileSize(const std::string& filename, uint64_t* size) override;
+
+  Status RenameFile(const std::string& from, const std::string& to) override;
+
+  Status LockFile(const std::string& filename, FileLock** lock) override;
+
+  Status UnlockFile(FileLock* lock) override;
+
+  void Schedule(void (*background_work_function)(void* background_work_arg),
+                void* background_work_arg) override;
+
+  void StartThread(void (*thread_main)(void* thread_main_arg),
+                   void* thread_main_arg) override;
+
+  Status GetTestDirectory(std::string* result) override;
+
+  Status NewLogger(const std::string& filename, Logger** result) override;
+
+  uint64_t NowMicros() override;
+
+  void SleepForMicroseconds(int micros) override;
+
+  void BackgroundThreadMain();
+
+ private:
+  // Stores the work item data in a Schedule() call.
+  //
+  // Instances are constructed on the thread calling Schedule() and used on the
+  // background thread.
+  //
+  // This structure is thread-safe beacuse it is immutable.
+  struct BackgroundWorkItem {
+    explicit BackgroundWorkItem(void (*f)(void*), void* a)
+        : function(f), arg(a) {}
+
+    void (*const function)(void*);
+    void* const arg;
+  };
+
+  std::mutex background_work_mutex_;
+  bool started_background_thread_;
+
+  QueueHandle_t background_work_queue_;
+
+  InMemoryLockTable locks_;  // Thread-safe.
+};
+
+} // namespace leveldb
+
+namespace database {
+
+// Wraps an Env instance whose destructor is never created.
+//
+// Intended usage:
+//   using PlatformSingletonEnv = SingletonEnv<PlatformEnv>;
+//   void ConfigurePosixEnv(int param) {
+//     PlatformSingletonEnv::AssertEnvNotInitialized();
+//     // set global configuration flags.
+//   }
+//   Env* Env::Default() {
+//     static PlatformSingletonEnv default_env;
+//     return default_env.env();
+//   }
+template <typename EnvType>
+class SingletonEnv {
+ public:
+  SingletonEnv() {
+    static_assert(sizeof(env_storage_) >= sizeof(EnvType),
+                  "env_storage_ will not fit the Env");
+    static_assert(alignof(decltype(env_storage_)) >= alignof(EnvType),
+                  "env_storage_ does not meet the Env's alignment needs");
+    new (&env_storage_) EnvType();
+  }
+  ~SingletonEnv() = default;
+
+  SingletonEnv(const SingletonEnv&) = delete;
+  SingletonEnv& operator=(const SingletonEnv&) = delete;
+
+  leveldb::Env* env() { return reinterpret_cast<leveldb::Env*>(&env_storage_); }
+
+ private:
+  typename std::aligned_storage<sizeof(EnvType), alignof(EnvType)>::type
+      env_storage_;
+};
+
+} // namespace database