base64.cc

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#include "base64.h"
#include <string>
#include <iostream>
 
using namespace ::std;
 
typedef unsigned char bbyte;        /* Byte type */
 
#define TRUE  1
#define FALSE 0
 
#define LINELEN 72          /* Encoded line length (max 76) */
 
static bbyte dtable[256];
 
string Binc::base64encode(const string &s_in)
{
  int i;
  string result;
 
  /*  Fill dtable with character encodings.  */
 
  for (i = 0; i < 26; i++) {
    dtable[i] = 'A' + i;
    dtable[26 + i] = 'a' + i;
  }
  for (i = 0; i < 10; i++) {
    dtable[52 + i] = '0' + i;
  }
  dtable[62] = '+';
  dtable[63] = '/';
 
  string::const_iterator s_i = s_in.begin();
  while (s_i != s_in.end()) {
 
    bbyte igroup[3], ogroup[4];
    int c, n;
 
    igroup[0] = igroup[1] = igroup[2] = 0;
    for (n = 0; n < 3 && s_i != s_in.end(); n++) {
      c = *s_i++;
      igroup[n] = (bbyte) c;
    }
    if (n > 0) {
      ogroup[0] = dtable[igroup[0] >> 2];
      ogroup[1] = dtable[((igroup[0] & 3) << 4) | (igroup[1] >> 4)];
      ogroup[2] = dtable[((igroup[1] & 0xF) << 2) | (igroup[2] >> 6)];
      ogroup[3] = dtable[igroup[2] & 0x3F];
 
   /* Replace characters in output stream with "=" pad
   characters if fewer than three characters were
   read from the end of the input stream. */
 
      if (n < 3) {
        ogroup[3] = '=';
        if (n < 2) {
          ogroup[2] = '=';
        }
      }
 
      for (i = 0; i < 4; i++)
        result += ogroup[i];
    }
  }
 
  return result;
}
 
string Binc::base64decode(const string &s_in)
{
  string result;
  int i;
 
  for (i = 0; i < 255; i++) {
    dtable[i] = 0x80;
  }
  for (i = 'A'; i <= 'Z'; i++) {
    dtable[i] = 0 + (i - 'A');
  }
  for (i = 'a'; i <= 'z'; i++) {
    dtable[i] = 26 + (i - 'a');
  }
  for (i = '0'; i <= '9'; i++) {
    dtable[i] = 52 + (i - '0');
  }
  dtable[(int) '+'] = 62;
  dtable[(int) '/'] = 63;
  dtable[(int) '='] = 0;
 
  /*CONSTANTCONDITION*/
  string::const_iterator s_i = s_in.begin();
  while (s_i != s_in.end()) {
    bbyte a[4], b[4], o[3];
 
    for (i = 0; i < 4 && s_i != s_in.end(); i++) {
      int c = *s_i++;
      if (dtable[c] & 0x80) return result;
      a[i] = (bbyte) c;
      b[i] = (bbyte) dtable[c];
    }
 
    o[0] = (b[0] << 2) | (b[1] >> 4);
    o[1] = (b[1] << 4) | (b[2] >> 2);
    o[2] = (b[2] << 6) | b[3];
 
    i = a[2] == '=' ? 1 : (a[3] == '=' ? 2 : 3);
 
    for (int j = 0; j < i; ++j)
      result += o[j];
 
    if (i < 3) break;
  }
 
  return result;
}