allwpilib/src/base64.cpp

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#include "base64.h"

namespace ntimpl {

// aaaack but it's fast and const should make it shared text page.
static const unsigned char pr2six[256] =
{
    // ASCII table
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 62, 64, 64, 64, 63,
    52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 64, 64, 64, 64, 64, 64,
    64,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 64, 64, 64, 64, 64,
    64, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64
};

std::size_t Base64DecodeLen(const char *bufcoded) {
  const unsigned char *bufin = (const unsigned char *)bufcoded;
  while (pr2six[*(bufin++)] <= 63) {
  }

  std::size_t nprbytes = (bufin - (const unsigned char *)bufcoded) - 1;
  std::size_t nbytesdecoded = ((nprbytes + 3) / 4) * 3;

  return nbytesdecoded + 1;
}

std::size_t Base64Decode(char *bufplain, const char *bufcoded) {
  const unsigned char *bufin = (const unsigned char *)bufcoded;
  while (pr2six[*(bufin++)] <= 63) {
  }
  std::size_t nprbytes = (bufin - (const unsigned char *)bufcoded) - 1;
  std::size_t nbytesdecoded = ((nprbytes + 3) / 4) * 3;

  unsigned char *bufout = (unsigned char *)bufplain;
  bufin = (const unsigned char *)bufcoded;

  while (nprbytes > 4) {
    *(bufout++) = (unsigned char)(pr2six[*bufin] << 2 | pr2six[bufin[1]] >> 4);
    *(bufout++) =
        (unsigned char)(pr2six[bufin[1]] << 4 | pr2six[bufin[2]] >> 2);
    *(bufout++) = (unsigned char)(pr2six[bufin[2]] << 6 | pr2six[bufin[3]]);
    bufin += 4;
    nprbytes -= 4;
  }

  // Note: (nprbytes == 1) would be an error, so just ignore that case
  if (nprbytes > 1) {
    *(bufout++) = (unsigned char)(pr2six[*bufin] << 2 | pr2six[bufin[1]] >> 4);
  }
  if (nprbytes > 2) {
    *(bufout++) =
        (unsigned char)(pr2six[bufin[1]] << 4 | pr2six[bufin[2]] >> 2);
  }
  if (nprbytes > 3) {
    *(bufout++) = (unsigned char)(pr2six[bufin[2]] << 6 | pr2six[bufin[3]]);
  }

  *(bufout++) = '\0';
  nbytesdecoded -= (4 - nprbytes) & 3;
  return nbytesdecoded;
}

static const char basis_64[] =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

std::size_t Base64EncodeLen(std::size_t len) {
  return ((len + 2) / 3 * 4) + 1;
}

std::size_t Base64Encode(char *encoded, const unsigned char *string,
                         std::size_t len) {
  std::size_t i;
  char *p = encoded;

  for (i = 0; i < len - 2; i += 3) {
    *p++ = basis_64[(string[i] >> 2) & 0x3F];
    *p++ =
        basis_64[((string[i] & 0x3) << 4) | ((int)(string[i + 1] & 0xF0) >> 4)];
    *p++ = basis_64[((string[i + 1] & 0xF) << 2) |
                    ((int)(string[i + 2] & 0xC0) >> 6)];
    *p++ = basis_64[string[i + 2] & 0x3F];
  }
  if (i < len) {
    *p++ = basis_64[(string[i] >> 2) & 0x3F];
    if (i == (len - 1)) {
      *p++ = basis_64[((string[i] & 0x3) << 4)];
      *p++ = '=';
    } else {
      *p++ = basis_64[((string[i] & 0x3) << 4) |
                      ((int)(string[i + 1] & 0xF0) >> 4)];
      *p++ = basis_64[((string[i + 1] & 0xF) << 2)];
    }
    *p++ = '=';
  }

  *p++ = '\0';
  return p - encoded;
}

}  // namespace ntimpl