// Copyright 2011 Google Inc. All Rights Reserved.

#include "src/globals.h"
#include "src/scoped_ptr.h"

#include <vector>

namespace art {

static const byte kMap[256] = {
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255,  62, 255, 255, 255,  63,
  52,  53,  54,  55,  56,  57,  58,  59,  60,  61, 255, 255,
  255, 254, 255, 255, 255,   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, 255, 255, 255, 255, 255,
  255,  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, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255
};

byte* DecodeBase64(const char* src, size_t size, size_t* dst_size) {
  std::vector<byte> tmp;
  unsigned long t = 0, y = 0;
  int g = 3;
  for (size_t i = 0; i < size; ++i) {
    byte c = kMap[src[i] & 0xFF];
    if (c == 255) continue;
    // the final = symbols are read and used to trim the remaining bytes
    if (c == 254) {
      c = 0;
      // prevent g < 0 which would potentially allow an overflow later
      if (--g < 0) {
        return NULL;
      }
    } else if (g != 3) {
      // we only allow = to be at the end
      return NULL;
    }
    t = (t << 6) | c;
    if (++y == 4) {
      tmp.push_back((t >> 16) & 255);
      if (g > 1) {
        tmp.push_back((t >> 8) & 255);
      }
      if (g > 2) {
        tmp.push_back(t & 255);
      }
      y = t = 0;
    }
  }
  if (y != 0) {
    return NULL;
  }
  scoped_ptr<byte> dst(new byte[tmp.size()]);
  if (dst_size != NULL) {
    *dst_size = tmp.size();
  }
  std::copy(tmp.begin(), tmp.end(), dst.get());
  return dst.release();
}

};