/*

 * Copyright (c) Meta Platforms, Inc. and affiliates.

 *

 * This source code is licensed under the MIT license found in the

 * LICENSE file in the root directory of this source tree.

 */

#ifndef HERMES_BCGEN_HBC_SERIALIZEDLITERALPARSERBASE_H

#define HERMES_BCGEN_HBC_SERIALIZEDLITERALPARSERBASE_H

#include "hermes/Support/Conversions.h"

#include "llvh/ADT/ArrayRef.h"

namespace hermes {

namespace hbc {

/// SerializedLiteralParserBase is the base class for SerializedLiteralParser

/// containing VM independent parsing logic.

class SerializedLiteralParserBase {

 protected:

  using CharArray = llvh::ArrayRef<unsigned char>;

  /// Stores the unsigned char buffer in which the literals are serialized.

  CharArray buffer_;

  /// Stores the elements left in the generator.

  unsigned int elemsLeft_;

  /// Stores the last sequence type.

  unsigned char lastTag_;

  /// Stores the amount of consecutive elements of the same type that are ahead

  /// of the current index.

  int leftInSeq_{0};

  /// Stores the current index into the buffer.

  int currIdx_{0};

  /// Called whenever the parser needs to read in the tag from the buffer

  ///   i.e. during the first call to get, and whenever leftInSeq_ == 0

  /// Checks the first byte (or two) of the buffer and treats it as a tag

  /// of the same format as outlined above.

  /// It sets `lastTag_` and `leftInSeq_`, and increments `currIdx_`

  /// to make it point to the next byte after the tag.

  void parseTagAndSeqLength();

 protected:

  /// Creates a parser which generates HermesValues from a char buffer.

  /// buff represents the char buffer that will be parsed.

  /// totalLen represents the amount of elements to be parsed.

  /// runtimeModule represents the runtimeModule from which to get

  /// string primitives.

  ///   If the nullptr is passed instead of a runtimeModule, the parser

  ///   knows to return the StringID directly (for object keys)

  explicit SerializedLiteralParserBase(CharArray buff, unsigned int totalLen)

      : buffer_(buff), elemsLeft_(totalLen) {}

 public:

  bool hasNext() const {

    return elemsLeft_ != 0;

  }

};

} // namespace hbc

} // namespace hermes

#endif // HERMES_BCGEN_HBC_SERIALIZEDLITERALPARSERBASE_H