src/google/protobuf/util/internal/datapiece.h

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
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#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_DATAPIECE_H__
#define GOOGLE_PROTOBUF_UTIL_CONVERTER_DATAPIECE_H__

#include <string>

#include <google/protobuf/stubs/common.h>
#include <google/protobuf/stubs/stringpiece.h>
#include <google/protobuf/stubs/statusor.h>


namespace google {
namespace protobuf {
class Enum;
}  // namespace protobuf


namespace protobuf {
namespace util {
namespace converter {

// Container for a single piece of data together with its data type.
//
// For primitive types (int32, int64, uint32, uint64, double, float, bool),
// the data is stored by value.
//
// For string, a StringPiece is stored. For Cord, a pointer to Cord is stored.
// Just like StringPiece, the DataPiece class does not own the storage for
// the actual string or Cord, so it is the user's responsiblity to guarantee
// that the underlying storage is still valid when the DataPiece is accessed.
class LIBPROTOBUF_EXPORT DataPiece {
 public:
  // Identifies data type of the value.
  // These are the types supported by DataPiece.
  enum Type {
    TYPE_INT32 = 1,
    TYPE_INT64 = 2,
    TYPE_UINT32 = 3,
    TYPE_UINT64 = 4,
    TYPE_DOUBLE = 5,
    TYPE_FLOAT = 6,
    TYPE_BOOL = 7,
    TYPE_ENUM = 8,
    TYPE_STRING = 9,
    TYPE_BYTES = 10,
    TYPE_NULL = 11,  // explicit NULL type
  };

  // Constructors and Destructor
  explicit DataPiece(const int32 value) : type_(TYPE_INT32), i32_(value) {}
  explicit DataPiece(const int64 value) : type_(TYPE_INT64), i64_(value) {}
  explicit DataPiece(const uint32 value) : type_(TYPE_UINT32), u32_(value) {}
  explicit DataPiece(const uint64 value) : type_(TYPE_UINT64), u64_(value) {}
  explicit DataPiece(const double value) : type_(TYPE_DOUBLE), double_(value) {}
  explicit DataPiece(const float value) : type_(TYPE_FLOAT), float_(value) {}
  explicit DataPiece(const bool value) : type_(TYPE_BOOL), bool_(value) {}
  explicit DataPiece(StringPiece value)
      : type_(TYPE_STRING),
        str_(StringPiecePod::CreateFromStringPiece(value)) {}
  // Constructor for bytes. The second parameter is not used.
  explicit DataPiece(StringPiece value, bool dummy)
      : type_(TYPE_BYTES), str_(StringPiecePod::CreateFromStringPiece(value)) {}
  DataPiece(const DataPiece& r) : type_(r.type_), str_(r.str_) {}
  DataPiece& operator=(const DataPiece& x) {
    type_ = x.type_;
    str_ = x.str_;
    return *this;
  }

  static DataPiece NullData() { return DataPiece(TYPE_NULL, 0); }

  virtual ~DataPiece() {
  }

  // Accessors
  Type type() const { return type_; }

  StringPiece str() const {
    GOOGLE_LOG_IF(DFATAL, type_ != TYPE_STRING) << "Not a string type.";
    return str_;
  }


  // Parses, casts or converts the value stored in the DataPiece into an int32.
  util::StatusOr<int32> ToInt32() const;

  // Parses, casts or converts the value stored in the DataPiece into a uint32.
  util::StatusOr<uint32> ToUint32() const;

  // Parses, casts or converts the value stored in the DataPiece into an int64.
  util::StatusOr<int64> ToInt64() const;

  // Parses, casts or converts the value stored in the DataPiece into a uint64.
  util::StatusOr<uint64> ToUint64() const;

  // Parses, casts or converts the value stored in the DataPiece into a double.
  util::StatusOr<double> ToDouble() const;

  // Parses, casts or converts the value stored in the DataPiece into a float.
  util::StatusOr<float> ToFloat() const;

  // Parses, casts or converts the value stored in the DataPiece into a bool.
  util::StatusOr<bool> ToBool() const;

  // Parses, casts or converts the value stored in the DataPiece into a string.
  util::StatusOr<string> ToString() const;

  // Tries to convert the value contained in this datapiece to string. If the
  // conversion fails, it returns the default_string.
  string ValueAsStringOrDefault(StringPiece default_string) const;

  util::StatusOr<string> ToBytes() const;

  // Converts a value into protocol buffer enum number. If the value is a
  // string, first attempts conversion by name, trying names as follows:
  //   1) the directly provided string value.
  //   2) the value upper-cased and replacing '-' by '_'
  // If the value is not a string, attempts to convert to a 32-bit integer.
  // If none of these succeeds, returns a conversion error status.
  util::StatusOr<int> ToEnum(const google::protobuf::Enum* enum_type) const;

 private:
  // Disallow implicit constructor.
  DataPiece();

  // Helper to create NULL or ENUM types.
  DataPiece(Type type, int32 val) : type_(type), i32_(val) {}

  // For numeric conversion between
  //     int32, int64, uint32, uint64, double, float and bool
  template <typename To>
  util::StatusOr<To> GenericConvert() const;

  // For conversion from string to
  //     int32, int64, uint32, uint64, double, float and bool
  template <typename To>
  util::StatusOr<To> StringToNumber(bool (*func)(StringPiece, To*)) const;

  // Data type for this piece of data.
  Type type_;

  // StringPiece is not a POD and can not be used in an union (pre C++11). We
  // need a POD version of it.
  struct StringPiecePod {
    const char* data;
    int size;

    // Create from a StringPiece.
    static StringPiecePod CreateFromStringPiece(StringPiece str) {
      StringPiecePod pod;
      pod.data = str.data();
      pod.size = str.size();
      return pod;
    }

    // Cast to StringPiece.
    operator StringPiece() const { return StringPiece(data, size); }

    bool operator==(const char* value) const {
      return StringPiece(data, size) == StringPiece(value);
    }

    string ToString() const { return string(data, size); }
  };

  // Stored piece of data.
  union {
    int32 i32_;
    int64 i64_;
    uint32 u32_;
    uint64 u64_;
    double double_;
    float float_;
    bool bool_;
    StringPiecePod str_;
  };
};

}  // namespace converter
}  // namespace util
}  // namespace protobuf

}  // namespace google
#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_DATAPIECE_H__