wpiutil/src/main/native/cpp/Base64.cpp

/* ====================================================================
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 *
 * Redistribution and use in source and binary forms, with or without
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 * on public domain software written at the National Center for
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#include "wpi/Base64.h"

#include "wpi/SmallVector.h"
#include "wpi/raw_ostream.h"

namespace wpi {

// 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};

size_t Base64Decode(raw_ostream& os, std::string_view encoded) {
  auto bytes_begin = reinterpret_cast<const unsigned char*>(encoded.data());
  auto bytes_end = bytes_begin + encoded.size();
  const unsigned char* end = bytes_begin;
  while (pr2six[*end] <= 63 && end != bytes_end) {
    ++end;
  }
  size_t nprbytes = end - bytes_begin;
  if (nprbytes == 0) {
    return 0;
  }

  const unsigned char* cur = bytes_begin;

  while (nprbytes > 4) {
    os << static_cast<unsigned char>(pr2six[cur[0]] << 2 | pr2six[cur[1]] >> 4);
    os << static_cast<unsigned char>(pr2six[cur[1]] << 4 | pr2six[cur[2]] >> 2);
    os << static_cast<unsigned char>(pr2six[cur[2]] << 6 | pr2six[cur[3]]);
    cur += 4;
    nprbytes -= 4;
  }

  // Note: (nprbytes == 1) would be an error, so just ignore that case
  if (nprbytes > 1) {
    os << static_cast<unsigned char>(pr2six[cur[0]] << 2 | pr2six[cur[1]] >> 4);
  }
  if (nprbytes > 2) {
    os << static_cast<unsigned char>(pr2six[cur[1]] << 4 | pr2six[cur[2]] >> 2);
  }
  if (nprbytes > 3) {
    os << static_cast<unsigned char>(pr2six[cur[2]] << 6 | pr2six[cur[3]]);
  }

  return (end - bytes_begin) + ((4 - nprbytes) & 3);
}

size_t Base64Decode(std::string_view encoded, std::string* plain) {
  plain->resize(0);
  raw_string_ostream os(*plain);
  size_t rv = Base64Decode(os, encoded);
  os.flush();
  return rv;
}

std::string_view Base64Decode(std::string_view encoded, size_t* num_read,
                              SmallVectorImpl<char>& buf) {
  buf.clear();
  raw_svector_ostream os(buf);
  *num_read = Base64Decode(os, encoded);
  return os.str();
}

size_t Base64Decode(std::string_view encoded, std::vector<uint8_t>* plain) {
  plain->resize(0);
  raw_uvector_ostream os(*plain);
  return Base64Decode(os, encoded);
}

span<uint8_t> Base64Decode(std::string_view encoded, size_t* num_read,
                           SmallVectorImpl<uint8_t>& buf) {
  buf.clear();
  raw_usvector_ostream os(buf);
  *num_read = Base64Decode(os, encoded);
  return os.array();
}

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

void Base64Encode(raw_ostream& os, std::string_view plain) {
  if (plain.empty()) {
    return;
  }
  size_t len = plain.size();

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

void Base64Encode(std::string_view plain, std::string* encoded) {
  encoded->resize(0);
  raw_string_ostream os(*encoded);
  Base64Encode(os, plain);
  os.flush();
}

std::string_view Base64Encode(std::string_view plain,
                              SmallVectorImpl<char>& buf) {
  buf.clear();
  raw_svector_ostream os(buf);
  Base64Encode(os, plain);
  return os.str();
}

void Base64Encode(raw_ostream& os, span<const uint8_t> plain) {
  Base64Encode(os, std::string_view{reinterpret_cast<const char*>(plain.data()),
                                    plain.size()});
}

void Base64Encode(span<const uint8_t> plain, std::string* encoded) {
  encoded->resize(0);
  raw_string_ostream os(*encoded);
  Base64Encode(os, plain);
  os.flush();
}

std::string_view Base64Encode(span<const uint8_t> plain,
                              SmallVectorImpl<char>& buf) {
  buf.clear();
  raw_svector_ostream os(buf);
  Base64Encode(os, plain);
  return os.str();
}

}  // namespace wpi