//===-- DataEncoder.h -------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef LLDB_UTILITY_DATAENCODER_H
#define LLDB_UTILITY_DATAENCODER_H

#if defined(__cplusplus)

#include "lldb/lldb-defines.h"
#include "lldb/lldb-enumerations.h"
#include "lldb/lldb-forward.h"
#include "lldb/lldb-types.h"

#include <cstddef>
#include <cstdint>

namespace lldb_private {

/// \class DataEncoder
///
/// An binary data encoding class.
///
/// DataEncoder is a class that can encode binary data (swapping if needed) to
/// a data buffer. The data buffer can be caller owned, or can be shared data
/// that can be shared between multiple DataEncoder or DataEncoder instances.
///
/// \see DataBuffer
class DataEncoder {
public:
  /// Default constructor.
  ///
  /// Initialize all members to a default empty state.
  DataEncoder();

  /// Construct with a buffer that is owned by the caller.
  ///
  /// This constructor allows us to use data that is owned by the caller. The
  /// data must stay around as long as this object is valid.
  ///
  /// \param[in] data
  ///     A pointer to caller owned data.
  ///
  /// \param[in] data_length
  ///     The length in bytes of \a data.
  ///
  /// \param[in] byte_order
  ///     A byte order of the data that we are extracting from.
  ///
  /// \param[in] addr_size
  ///     A new address byte size value.
  DataEncoder(void *data, uint32_t data_length, lldb::ByteOrder byte_order,
              uint8_t addr_size);

  /// Construct with shared data.
  ///
  /// Copies the data shared pointer which adds a reference to the contained
  /// in \a data_sp. The shared data reference is reference counted to ensure
  /// the data lives as long as anyone still has a valid shared pointer to the
  /// data in \a data_sp.
  ///
  /// \param[in] data_sp
  ///     A shared pointer to data.
  ///
  /// \param[in] byte_order
  ///     A byte order of the data that we are extracting from.
  ///
  /// \param[in] addr_size
  ///     A new address byte size value.
  DataEncoder(const lldb::DataBufferSP &data_sp, lldb::ByteOrder byte_order,
              uint8_t addr_size);

  /// Destructor
  ///
  /// If this object contains a valid shared data reference, the reference
  /// count on the data will be decremented, and if zero, the data will be
  /// freed.
  ~DataEncoder();

  /// Clears the object state.
  ///
  /// Clears the object contents back to a default invalid state, and release
  /// any references to shared data that this object may contain.
  void Clear();

  /// Encode an unsigned integer of size \a byte_size to \a offset.
  ///
  /// Encode a single integer value at \a offset and return the offset that
  /// follows the newly encoded integer when the data is successfully encoded
  /// into the existing data. There must be enough room in the data, else
  /// UINT32_MAX will be returned to indicate that encoding failed.
  ///
  /// \param[in] offset
  ///     The offset within the contained data at which to put the
  ///     encoded integer.
  ///
  /// \param[in] byte_size
  ///     The size in byte of the integer to encode.
  ///
  /// \param[in] value
  ///     The integer value to write. The least significant bytes of
  ///     the integer value will be written if the size is less than
  ///     8 bytes.
  ///
  /// \return
  ///     The next offset in the bytes of this data if the integer
  ///     was successfully encoded, UINT32_MAX if the encoding failed.
  uint32_t PutUnsigned(uint32_t offset, uint32_t byte_size, uint64_t value);

  /// Encode an arbitrary number of bytes.
  ///
  /// \param[in] offset
  ///     The offset in bytes into the contained data at which to
  ///     start encoding.
  ///
  /// \param[in] src
  ///     The buffer that contains the bytes to encode.
  ///
  /// \param[in] src_len
  ///     The number of bytes to encode.
  ///
  /// \return
  ///     The next valid offset within data if the put operation
  ///     was successful, else UINT32_MAX to indicate the put failed.
  uint32_t PutData(uint32_t offset, const void *src, uint32_t src_len);

  /// Encode an address in the existing buffer at \a offset bytes into the
  /// buffer.
  ///
  /// Encode a single address (honoring the m_addr_size member) to the data
  /// and return the next offset where subsequent data would go. pointed to by
  /// \a offset_ptr. The size of the extracted address comes from the \a
  /// m_addr_size member variable and should be set correctly prior to
  /// extracting any address values.
  ///
  /// \param[in] offset
  ///     The offset where to encode the address.
  ///
  /// \param[in] addr
  ///     The address to encode.
  ///
  /// \return
  ///     The next valid offset within data if the put operation
  ///     was successful, else UINT32_MAX to indicate the put failed.
  uint32_t PutAddress(uint32_t offset, lldb::addr_t addr);

  /// Put a C string to \a offset.
  ///
  /// Encodes a C string into the existing data including the terminating
  ///
  /// \param[in] offset
  ///     The offset where to encode the string.
  ///
  /// \param[in] cstr
  ///     The string to encode.
  ///
  /// \return
  ///     A pointer to the C string value in the data. If the offset
  ///     pointed to by \a offset_ptr is out of bounds, or if the
  ///     offset plus the length of the C string is out of bounds,
  ///     NULL will be returned.
  uint32_t PutCString(uint32_t offset, const char *cstr);

private:
  uint32_t PutU8(uint32_t offset, uint8_t value);
  uint32_t PutU16(uint32_t offset, uint16_t value);
  uint32_t PutU32(uint32_t offset, uint32_t value);
  uint32_t PutU64(uint32_t offset, uint64_t value);

  uint32_t BytesLeft(uint32_t offset) const {
    const uint32_t size = GetByteSize();
    if (size > offset)
      return size - offset;
    return 0;
  }

  /// Test the availability of \a length bytes of data from \a offset.
  ///
  /// \return
  ///     \b true if \a offset is a valid offset and there are \a
  ///     length bytes available at that offset, \b false otherwise.
  bool ValidOffsetForDataOfSize(uint32_t offset, uint32_t length) const {
    return length <= BytesLeft(offset);
  }

  /// Adopt a subset of shared data in \a data_sp.
  ///
  /// Copies the data shared pointer which adds a reference to the contained
  /// in \a data_sp. The shared data reference is reference counted to ensure
  /// the data lives as long as anyone still has a valid shared pointer to the
  /// data in \a data_sp. The byte order and address byte size settings remain
  /// the same. If \a offset is not a valid offset in \a data_sp, then no
  /// reference to the shared data will be added. If there are not \a length
  /// bytes available in \a data starting at \a offset, the length will be
  /// truncated to contains as many bytes as possible.
  ///
  /// \param[in] data_sp
  ///     A shared pointer to data.
  ///
  /// \param[in] offset
  ///     The offset into \a data_sp at which the subset starts.
  ///
  /// \param[in] length
  ///     The length in bytes of the subset of \a data_sp.
  ///
  /// \return
  ///     The number of bytes that this object now contains.
  uint32_t SetData(const lldb::DataBufferSP &data_sp, uint32_t offset = 0,
                   uint32_t length = UINT32_MAX);

  /// Test the validity of \a offset.
  ///
  /// \return
  ///     \b true if \a offset is a valid offset into the data in this
  ///     object, \b false otherwise.
  bool ValidOffset(uint32_t offset) const { return offset < GetByteSize(); }

  /// Get the number of bytes contained in this object.
  ///
  /// \return
  ///     The total number of bytes of data this object refers to.
  size_t GetByteSize() const { return m_end - m_start; }

  /// A pointer to the first byte of data.
  uint8_t *m_start = nullptr;

  /// A pointer to the byte that is past the end of the data.
  uint8_t *m_end = nullptr;

  /// The byte order of the data we are extracting from.
  lldb::ByteOrder m_byte_order;

  /// The address size to use when extracting pointers or
  /// addresses
  uint8_t m_addr_size;

  /// The shared pointer to data that can
  /// be shared among multiple instances
  mutable lldb::DataBufferSP m_data_sp;

  DataEncoder(const DataEncoder &) = delete;
  const DataEncoder &operator=(const DataEncoder &) = delete;
};

} // namespace lldb_private

#endif // #if defined (__cplusplus)
#endif // LLDB_UTILITY_DATAENCODER_H