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

/* ====================================================================
 * Copyright (c) 1995-1999 The Apache Group.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 * on public domain software written at the National Center for
 * Supercomputing Applications, University of Illinois, Urbana-Champaign.
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#include "support/Base64.h"

#include "llvm/SmallVector.h"
#include "llvm/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(llvm::raw_ostream& os, llvm::StringRef encoded) {
  const unsigned char* end = encoded.bytes_begin();
  while (pr2six[*end] <= 63 && end != encoded.bytes_end()) ++end;
  size_t nprbytes = end - encoded.bytes_begin();
  if (nprbytes == 0) return 0;

  const unsigned char* cur = encoded.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 - encoded.bytes_begin()) + ((4 - nprbytes) & 3);
}

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

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

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

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

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

}  // namespace wpi