add Status data structure

src/iceberg/CMakeLists.txt

@@ -15,7 +15,7 @@
 # specific language governing permissions and limitations
 # under the License.
 
-set(ICEBERG_SOURCES demo_table.cc)
+set(ICEBERG_SOURCES demo_table.cc status.cc)
 
 add_iceberg_lib(iceberg
                 SOURCES

src/iceberg/status.cc

@@ -0,0 +1,97 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 "iceberg/status.h"
+
+#include <cassert>
+#include <cstdlib>
+#include <iostream>
+#include <sstream>
+
+namespace iceberg {
+
+Status::Status(StatusCode code, const std::string& msg)
+    : Status::Status(code, msg, nullptr) {}
+
+Status::Status(StatusCode code, std::string msg, std::shared_ptr<StatusDetail> detail) {
+  state_ = new State{code, std::move(msg), std::move(detail)};
+}
+
+void Status::CopyFrom(const Status& s) {
+  if (ICEBERG_PREDICT_FALSE(state_ != nullptr)) {
+    DeleteState();
+  }
+  if (s.state_ == nullptr) {
+    state_ = nullptr;
+  } else {
+    state_ = new State(*s.state_);
+  }
+}
+
+std::string Status::CodeAsString() const {
+  if (state_ == nullptr) {
+    return "OK";
+  }
+  return CodeAsString(code());
+}
+
+std::string Status::CodeAsString(StatusCode code) {
+  const char* type;
+  switch (code) {
+    case StatusCode::OK:
+      type = "OK";
+      break;
+    case StatusCode::IOError:
+      type = "IOError";
+      break;
+    case StatusCode::NotImplemented:
+      type = "NotImplemented";
+      break;
+    case StatusCode::UnknownError:
+      type = "Unknown error";
+      break;
+    default:
+      type = "Unknown";
+      break;
+  }
+  return std::string(type);
+}
+
+std::string Status::ToString() const {
+  std::ostringstream oss;
+  oss << CodeAsString();
+  if (state_ == nullptr) {
+    return oss.str();
+  }
+  oss << ": ";
+  oss << state_->msg;
+  if (state_->detail != nullptr) {
+    oss << ". Detail: " << state_->detail->ToString();
+  }
+
+  return oss.str();
+}
+
+void Status::Warn() const { std::cerr << *this; }
+
+void Status::Warn(const std::string& message) const {
+  std::cerr << message << ": " << *this;
+}
+
+}  // namespace iceberg

src/iceberg/status.h

@@ -0,0 +1,278 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+#pragma once
+
+#include <cstring>
+#include <format>
+#include <iosfwd>
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "util/compare.h"
+#include "util/macros.h"
+#include "util/to_string_ostreamable.h"
+
+namespace iceberg {
+
+enum class StatusCode : char {
+  OK = 0,
+  IOError = 1,
+  NotImplemented = 2,
+  UnknownError = 127
+};
+
+/// \brief An opaque class that allows subsystems to retain
+/// additional information inside the Status.
+class StatusDetail {
+ public:
+  virtual ~StatusDetail() = default;
+  /// \brief Return a unique id for the type of the StatusDetail
+  /// (effectively a poor man's substitute for RTTI).
+  virtual const char* type_id() const = 0;
+  /// \brief Produce a human-readable description of this status.
+  virtual std::string ToString() const = 0;
+
+  bool operator==(const StatusDetail& other) const noexcept {
+    return std::string(type_id()) == other.type_id() && ToString() == other.ToString();
+  }
+};
+
+/// \brief Status outcome object (success or error)
+///
+/// The Status object is an object holding the outcome of an operation.
+/// The outcome is represented as a StatusCode, either success
+/// (StatusCode::OK) or an error (any other of the StatusCode enumeration values).
+///
+/// Additionally, if an error occurred, a specific error message is generally
+/// attached.
+class [[nodiscard]] Status : public util::EqualityComparable<Status>,
+                             public util::ToStringOstreamable<Status> {
+ public:
+  // Create a success status.
+  constexpr Status() noexcept : state_(nullptr) {}
+  ~Status() noexcept {
+    if (ICEBERG_PREDICT_FALSE(state_ != nullptr)) {
+      DeleteState();
+    }
+  }
+
+  Status(StatusCode code, const std::string& msg);
+  /// \brief Pluggable constructor for use by sub-systems. detail cannot be null.
+  Status(StatusCode code, std::string msg, std::shared_ptr<StatusDetail> detail);
+
+  // Copy the specified status.
+  inline Status(const Status& s);
+  inline Status& operator=(const Status& s);
+
+  // Move the specified status.
+  inline Status(Status&& s) noexcept;
+  inline Status& operator=(Status&& s) noexcept;
+
+  inline bool Equals(const Status& other) const;
+
+  // AND the statuses.
+  inline Status operator&(const Status& s) const noexcept;
+  inline Status operator&(Status&& s) const noexcept;
+  inline Status& operator&=(const Status& s) noexcept;
+  inline Status& operator&=(Status&& s) noexcept;
+
+  /// Return a success status.
+  static Status OK() { return Status(); }
+
+  template <typename... Args>
+  static Status FromArgs(StatusCode code, std::string_view fmt, Args&&... args) {
+    return Status(code, std::vformat(fmt, std::make_format_args(args...)));
+  }
+
+  template <typename... Args>
+  static Status FromDetailAndArgs(StatusCode code, std::shared_ptr<StatusDetail> detail,
+                                  std::string_view fmt, Args&&... args) {
+    return Status(code, std::vformat(fmt, std::make_format_args(args...)),
+                  std::move(detail));
+  }
+
+  /// Return an error status when some IO-related operation failed
+  template <typename... Args>
+  static Status IOError(Args&&... args) {
+    return Status::FromArgs(StatusCode::IOError, std::forward<Args>(args)...);
+  }
+
+  /// Return an error status when an operation or a combination of operation and
+  /// data types is unimplemented
+  template <typename... Args>
+  static Status NotImplemented(Args&&... args) {
+    return Status::FromArgs(StatusCode::NotImplemented, std::forward<Args>(args)...);
+  }
+
+  /// Return an error status for unknown errors
+  template <typename... Args>
+  static Status UnknownError(Args&&... args) {
+    return Status::FromArgs(StatusCode::UnknownError, std::forward<Args>(args)...);
+  }
+
+  /// Return true if the status indicates success.
+  constexpr bool ok() const { return (state_ == nullptr); }
+
+  /// Return true if the status indicates an IO-related failure.
+  constexpr bool IsIOError() const { return code() == StatusCode::IOError; }
+  /// Return true if the status indicates an unimplemented operation.
+  constexpr bool IsNotImplemented() const { return code() == StatusCode::NotImplemented; }
+  /// Return true if the status indicates an unknown error.
+  constexpr bool IsUnknownError() const { return code() == StatusCode::UnknownError; }
+
+  /// \brief Return a string representation of this status suitable for printing.
+  ///
+  /// The string "OK" is returned for success.
+  std::string ToString() const;
+
+  /// \brief Return a string representation of the status code, without the message
+  /// text or POSIX code information.
+  std::string CodeAsString() const;
+  static std::string CodeAsString(StatusCode);
+
+  /// \brief Return the StatusCode value attached to this status.
+  constexpr StatusCode code() const { return ok() ? StatusCode::OK : state_->code; }
+
+  /// \brief Return the specific error message attached to this status.
+  const std::string& message() const {
+    static const std::string no_message = "";
+    return ok() ? no_message : state_->msg;
+  }
+
+  /// \brief Return the status detail attached to this message.
+  const std::shared_ptr<StatusDetail>& detail() const {
+    static std::shared_ptr<StatusDetail> no_detail = nullptr;
+    return state_ ? state_->detail : no_detail;
+  }
+
+  /// \brief Return a new Status copying the existing status, but
+  /// updating with the existing detail.
+  Status WithDetail(std::shared_ptr<StatusDetail> new_detail) const {
+    return Status(code(), message(), std::move(new_detail));
+  }
+
+  /// \brief Return a new Status with changed message, copying the
+  /// existing status code and detail.
+  template <typename... Args>
+  Status WithMessage(Args&&... args) const {
+    return FromArgs(code(), std::forward<Args>(args)...).WithDetail(detail());
+  }
+
+  void Warn() const;
+  void Warn(const std::string& message) const;
+
+ private:
+  struct State {
+    StatusCode code;
+    std::string msg;
+    std::shared_ptr<StatusDetail> detail;
+  };
+  // OK status has a `NULL` state_.  Otherwise, `state_` points to
+  // a `State` structure containing the error code and message(s)
+  State* state_;
+
+  void DeleteState() noexcept {
+    // On certain compilers, splitting off the slow path improves performance
+    // significantly.
+    delete state_;
+    state_ = nullptr;
+  }
+
+  void CopyFrom(const Status& s);
+  inline void MoveFrom(Status& s);
+};
+
+void Status::MoveFrom(Status& s) {
+  if (ICEBERG_PREDICT_FALSE(state_ != nullptr)) {
+    DeleteState();
+  }
+  state_ = s.state_;
+  s.state_ = nullptr;
+}
+
+Status::Status(const Status& s) : state_{nullptr} { CopyFrom(s); }
+
+Status& Status::operator=(const Status& s) {
+  // The following condition catches both aliasing (when this == &s),
+  // and the common case where both s and *this are ok.
+  if (state_ != s.state_) {
+    CopyFrom(s);
+  }
+  return *this;
+}
+
+Status::Status(Status&& s) noexcept : state_(s.state_) { s.state_ = nullptr; }
+
+Status& Status::operator=(Status&& s) noexcept {
+  MoveFrom(s);
+  return *this;
+}
+
+bool Status::Equals(const Status& s) const {
+  if (state_ == s.state_) {
+    return true;
+  }
+
+  if (ok() || s.ok()) {
+    return false;
+  }
+
+  if (detail() != s.detail()) {
+    if ((detail() && !s.detail()) || (!detail() && s.detail())) {
+      return false;
+    }
+    return *detail() == *s.detail();
+  }
+
+  return code() == s.code() && message() == s.message();
+}
+
+Status Status::operator&(const Status& s) const noexcept {
+  if (ok()) {
+    return s;
+  } else {
+    return *this;
+  }
+}
+
+Status Status::operator&(Status&& s) const noexcept {
+  if (ok()) {
+    return std::move(s);
+  } else {
+    return *this;
+  }
+}
+
+Status& Status::operator&=(const Status& s) noexcept {
+  if (ok() && !s.ok()) {
+    CopyFrom(s);
+  }
+  return *this;
+}
+
+Status& Status::operator&=(Status&& s) noexcept {
+  if (ok() && !s.ok()) {
+    MoveFrom(s);
+  }
+  return *this;
+}
+
+}  // namespace iceberg