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#pragma once
#include "cyson_enums.h"
#include "scalar.h"
#include <util/generic/strbuf.h>
#include <util/system/types.h>
#include <util/system/yassert.h>
namespace NYsonPull {
//! A well-formed decoded YSON stream can be described by the following grammar:
//!
//! STREAM[node] ::= begin_stream VALUE end_stream
//! STREAM[list_fragment] ::= begin_stream LIST_FRAGMENT end_stream
//! STREAM[map_fragment] ::= begin_stream MAP_FRAGMENT end_stream
//! LIST_FRAGMENT ::= { VALUE; }
//! MAP_FRAGMENT ::= { KEY VALUE; }
//! KEY ::= key(String)
//! VALUE ::= VALUE_NOATTR | ATTRIBUTES VALUE_NOATTR
//! ATTRIBUTES ::= begin_attributes MAP_FRAGMENT end_attributes
//! VALUE_NOATTR ::= scalar(Scalar) | LIST | MAP
//! LIST ::= begin_list LIST_FRAGMENT end_list
//! MAP ::= begin_map MAP_FRAGMENT end_map
//! \brief YSON event type tag. Corresponds to YSON grammar.
enum class EEventType {
BeginStream = YSON_EVENT_BEGIN_STREAM,
EndStream = YSON_EVENT_END_STREAM,
BeginList = YSON_EVENT_BEGIN_LIST,
EndList = YSON_EVENT_END_LIST,
BeginMap = YSON_EVENT_BEGIN_MAP,
EndMap = YSON_EVENT_END_MAP,
BeginAttributes = YSON_EVENT_BEGIN_ATTRIBUTES,
EndAttributes = YSON_EVENT_END_ATTRIBUTES,
Key = YSON_EVENT_KEY,
Scalar = YSON_EVENT_SCALAR,
};
//! \brief YSON event variant type.
class TEvent {
EEventType Type_;
TScalar Value_;
public:
//! \brief Construct a tag-only event.
explicit constexpr TEvent(EEventType type = EEventType::BeginStream)
: Type_{type} {
}
//! \brief Construct a tag+value event.
//!
//! Only \p EEventType::key is meaningful.
constexpr TEvent(EEventType type, const TScalar& value)
: Type_{type}
, Value_{value} {
}
//! \brief Construct a \p EEventType::scalar event.
explicit constexpr TEvent(const TScalar& value)
: Type_{EEventType::Scalar}
, Value_{value} {
}
EEventType Type() const {
return Type_;
}
//! \brief Get TScalar value.
//!
//! Undefined behaviour when event type is not \p EEventType::scalar.
const TScalar& AsScalar() const {
Y_ASSERT(Type_ == EEventType::Scalar || Type_ == EEventType::Key);
return Value_;
}
//! \brief Get string value.
//!
//! Undefined behaviour when event type is not \p EEventType::key.
TStringBuf AsString() const {
Y_ASSERT(Type_ == EEventType::Key || (Type_ == EEventType::Scalar && Value_.Type() == EScalarType::String));
return Value_.AsString();
}
};
}
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