/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying

   file LICENSE.rst or https://cmake.org/licensing for details.  */

#include "cmBase32.h"

// -- Static functions

static unsigned char const Base32EncodeTable[33] =

  "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";

inline unsigned char Base32EncodeChar(int schar)

{

  return Base32EncodeTable[schar];

}

static void Base32Encode5(unsigned char const src[5], char dst[8])

{

  // [0]:5 bits

  dst[0] = Base32EncodeChar((src[0] >> 3) & 0x1F);

  // [0]:3 bits + [1]:2 bits

  dst[1] = Base32EncodeChar(((src[0] << 2) & 0x1C) + ((src[1] >> 6) & 0x03));

  // [1]:5 bits

  dst[2] = Base32EncodeChar((src[1] >> 1) & 0x1F);

  // [1]:1 bit + [2]:4 bits

  dst[3] = Base32EncodeChar(((src[1] << 4) & 0x10) + ((src[2] >> 4) & 0x0F));

  // [2]:4 bits + [3]:1 bit

  dst[4] = Base32EncodeChar(((src[2] << 1) & 0x1E) + ((src[3] >> 7) & 0x01));

  // [3]:5 bits

  dst[5] = Base32EncodeChar((src[3] >> 2) & 0x1F);

  // [3]:2 bits + [4]:3 bit

  dst[6] = Base32EncodeChar(((src[3] << 3) & 0x18) + ((src[4] >> 5) & 0x07));

  // [4]:5 bits

  dst[7] = Base32EncodeChar((src[4] << 0) & 0x1F);

}

// -- Class methods

cmBase32Encoder::cmBase32Encoder() = default;

std::string cmBase32Encoder::encodeString(unsigned char const* input,

                                          size_t len, bool padding)

{

  std::string res;

  static size_t const blockSize = 5;

  static size_t const bufferSize = 8;

  char buffer[bufferSize];

  unsigned char const* end = input + len;

  while ((input + blockSize) <= end) {

    Base32Encode5(input, buffer);

    res.append(buffer, bufferSize);

    input += blockSize;

  }

  size_t remain = static_cast<size_t>(end - input);

  if (remain != 0) {

    // Temporary source buffer filled up with 0s

    unsigned char padded[blockSize];

    for (size_t ii = 0; ii != remain; ++ii) {

      padded[ii] = input[ii];

    }

    for (size_t ii = remain; ii != blockSize; ++ii) {

      padded[ii] = 0;

    }

    Base32Encode5(padded, buffer);

    size_t numPad(0);

    switch (remain) {

      case 1:

        numPad = 6;

        break;

      case 2:

        numPad = 4;

        break;

      case 3:

        numPad = 3;

        break;

      case 4:

        numPad = 1;

        break;

      default:

        break;

    }

    res.append(buffer, bufferSize - numPad);

    if (padding) {

      for (size_t ii = 0; ii != numPad; ++ii) {

        res.push_back(paddingChar);

      }

    }

  }

  return res;

}