talk/base/base64.cc

//*********************************************************************
//* Base64 - a simple base64 encoder and decoder.
//*
//*     Copyright (c) 1999, Bob Withers - bwit@pobox.com
//*
//* This code may be freely used for any purpose, either personal
//* or commercial, provided the authors copyright notice remains
//* intact.
//*
//* Enhancements by Stanley Yamane:
//*     o reverse lookup table for the decode function
//*     o reserve string buffer space in advance
//*
//*********************************************************************

#include "talk/base/base64.h"

using std::string;

namespace talk_base {

static const char fillchar = '=';
static const string::size_type np = string::npos;

const string Base64::Base64Table(
  // 0000000000111111111122222222223333333333444444444455555555556666
  // 0123456789012345678901234567890123456789012345678901234567890123
  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");

// Decode Table gives the index of any valid base64 character in the 
// Base64 table
// 65 == A, 97 == a, 48 == 0, 43 == +, 47 == /

const string::size_type Base64::DecodeTable[] = {
// 0  1  2  3  4  5  6  7  8  9
  np,np,np,np,np,np,np,np,np,np,  // 0 - 9
  np,np,np,np,np,np,np,np,np,np,  //10 -19
  np,np,np,np,np,np,np,np,np,np,  //20 -29
  np,np,np,np,np,np,np,np,np,np,  //30 -39
  np,np,np,62,np,np,np,63,52,53,  //40 -49
  54,55,56,57,58,59,60,61,np,np,  //50 -59
  np,np,np,np,np, 0, 1, 2, 3, 4,  //60 -69
   5, 6, 7, 8, 9,10,11,12,13,14,  //70 -79
  15,16,17,18,19,20,21,22,23,24,  //80 -89
  25,np,np,np,np,np,np,26,27,28,  //90 -99
  29,30,31,32,33,34,35,36,37,38,  //100 -109
  39,40,41,42,43,44,45,46,47,48,  //110 -119
  49,50,51,np,np,np,np,np,np,np,  //120 -129
  np,np,np,np,np,np,np,np,np,np,  //130 -139
  np,np,np,np,np,np,np,np,np,np,  //140 -149
  np,np,np,np,np,np,np,np,np,np,  //150 -159
  np,np,np,np,np,np,np,np,np,np,  //160 -169
  np,np,np,np,np,np,np,np,np,np,  //170 -179
  np,np,np,np,np,np,np,np,np,np,  //180 -189
  np,np,np,np,np,np,np,np,np,np,  //190 -199
  np,np,np,np,np,np,np,np,np,np,  //200 -209
  np,np,np,np,np,np,np,np,np,np,  //210 -219
  np,np,np,np,np,np,np,np,np,np,  //220 -229
  np,np,np,np,np,np,np,np,np,np,  //230 -239
  np,np,np,np,np,np,np,np,np,np,  //240 -249
  np,np,np,np,np,np               //250 -256
};

string Base64::encodeFromArray(const char * data, size_t len) {
  size_t i;
  char c;
  string ret;

  ret.reserve(len * 2);

  for (i = 0; i < len; ++i) {
    c = (data[i] >> 2) & 0x3f;
    ret.append(1, Base64Table[c]);
    c = (data[i] << 4) & 0x3f;
    if (++i < len) {
      c |= (data[i] >> 4) & 0x0f;
    }

    ret.append(1, Base64Table[c]);
    if (i < len) {
      c = (data[i] << 2) & 0x3f;
      if (++i < len) {
        c |= (data[i] >> 6) & 0x03;
      }
      ret.append(1, Base64Table[c]);
    } else {
        ++i;
        ret.append(1, fillchar);
    }

    if (i < len) {
        c = data[i] & 0x3f;
        ret.append(1, Base64Table[c]);
    } else {
        ret.append(1, fillchar);
    }
  }

  return(ret);
}

string Base64::encode(const string& data) {
  string::size_type i;
  char c;
  string::size_type len = data.length();
  string ret;

  ret.reserve(len * 2);

  for (i = 0; i < len; ++i) {
    c = (data[i] >> 2) & 0x3f;
    ret.append(1, Base64Table[c]);
    c = (data[i] << 4) & 0x3f;
    if (++i < len) {
      c |= (data[i] >> 4) & 0x0f;
    }

    ret.append(1, Base64Table[c]);
    if (i < len) {
      c = (data[i] << 2) & 0x3f;
      if (++i < len) {
        c |= (data[i] >> 6) & 0x03;
      }

      ret.append(1, Base64Table[c]);
    } else {
      ++i;
      ret.append(1, fillchar);
    }

    if (i < len) {
      c = data[i] & 0x3f;
      ret.append(1, Base64Table[c]);
    } else {
      ret.append(1, fillchar);
    }
  }

  return(ret);
}

string Base64::decode(const string& data) {
  string::size_type i;
  char c;
  char c1;
  string::size_type len = data.length();
  string ret;

  ret.reserve(len);

  for (i = 0; i < len; ++i) {
    do {
      c = static_cast<char>(DecodeTable[static_cast<unsigned char>(data[i])]);
    } while (c == np && ++i < len);

    ++i;

    do {
      c1 = static_cast<char>(DecodeTable[static_cast<unsigned char>(data[i])]);
    } while (c == np && ++i < len);

    c = (c << 2) | ((c1 >> 4) & 0x3);
    ret.append(1, c);
    if (++i < len) {
      c = data[i];
      if (fillchar == c) {         
        break;
      }

      do {
        c = static_cast<char>(DecodeTable[static_cast<unsigned char>(data[i])]);
      } while (c == np && ++i < len);
      c1 = ((c1 << 4) & 0xf0) | ((c >> 2) & 0xf);
      ret.append(1, c1);
    }

    if (++i < len) {
      c1 = data[i];
      if (fillchar == c1) {
        break;
      }

      do {
        c1 = static_cast<char>(DecodeTable[static_cast<unsigned char>(data[i])]);
      } while (c == np && ++i < len);

      c = ((c << 6) & 0xc0) | c1;
      ret.append(1, c);
    }
  }

  return(ret);
}

} // namespace talk_base