// SPDX-FileCopyrightText: Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
// SPDX-License-Identifier: BSD-3-Clause
/**
 * @class   vtkBase64Utilities
 * @brief   base64 encode and decode utilities.
 *
 * vtkBase64Utilities implements base64 encoding and decoding.
 */

#ifndef vtkBase64Utilities_h
#define vtkBase64Utilities_h

#include "vtkIOCoreModule.h" // For export macro
#include "vtkObject.h"

VTK_ABI_NAMESPACE_BEGIN
class VTKIOCORE_EXPORT vtkBase64Utilities : public vtkObject
{
public:
  static vtkBase64Utilities* New();
  vtkTypeMacro(vtkBase64Utilities, vtkObject);
  void PrintSelf(ostream& os, vtkIndent indent) override;

  /**
   * Encode 3 bytes into 4 bytes
   */
  static void EncodeTriplet(unsigned char i0, unsigned char i1, unsigned char i2, unsigned char* o0,
    unsigned char* o1, unsigned char* o2, unsigned char* o3);

  /**
   * Encode 2 bytes into 4 bytes
   */
  static void EncodePair(unsigned char i0, unsigned char i1, unsigned char* o0, unsigned char* o1,
    unsigned char* o2, unsigned char* o3);

  /**
   * Encode 1 byte into 4 bytes
   */
  static void EncodeSingle(
    unsigned char i0, unsigned char* o0, unsigned char* o1, unsigned char* o2, unsigned char* o3);

  /**
   * Encode 'length' bytes from the input buffer and store the
   * encoded stream into the output buffer. Return the length of
   * the encoded stream. Note that the output buffer must be allocated
   * by the caller (length * 1.5 should be a safe estimate).
   * If 'mark_end' is true then an extra set of 4 bytes is added
   * to the end of the stream if the input is a multiple of 3 bytes.
   * These bytes are invalid chars and therefore they will stop the decoder
   * thus enabling the caller to decode a stream without actually knowing
   * how much data to expect (if the input is not a multiple of 3 bytes then
   * the extra padding needed to complete the encode 4 bytes will stop the
   * decoding anyway).
   */
  static unsigned long Encode(
    const unsigned char* input, unsigned long length, unsigned char* output, int mark_end = 0);

  /**
   * Decode 4 bytes into 3 bytes.
   * Return the number of bytes actually decoded (0 to 3, inclusive).
   */
  static int DecodeTriplet(unsigned char i0, unsigned char i1, unsigned char i2, unsigned char i3,
    unsigned char* o0, unsigned char* o1, unsigned char* o2);

  /**
   * Decode 4 bytes at a time from the input buffer and store the decoded
   * stream into the output buffer. The required output buffer size must be
   * determined and allocated by the caller. The needed output space is
   * always less than the input buffer size, so a good first order
   * approximation is to allocate the same size. Base64 encoding is about
   * 4/3 overhead, so a tighter bound is possible.
   * Return the number of bytes atually placed into the output buffer.
   */
  static size_t DecodeSafely(
    const unsigned char* input, size_t inputLen, unsigned char* output, size_t outputLen);

protected:
  vtkBase64Utilities() = default;
  ~vtkBase64Utilities() override = default;

private:
  vtkBase64Utilities(const vtkBase64Utilities&) = delete;
  void operator=(const vtkBase64Utilities&) = delete;
};

VTK_ABI_NAMESPACE_END
#endif
