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encoding/decoding base64

Oct 1, 2011 at 5:13pm
cristi92b (5)
I tried to make a simple c++ console program that encodes an ascii text to base64 text and then decode base64 text to ascii, but is shows nothig... can you please help me?

#include <iostream>
#include <string.h>
#include <fstream>
#include <math.h>
using namespace std;


int dec_to_bin(int value){
int c,r,r2,n;
c=value/2;
r2=value%2;
n=r2;
while(value!=0){
c=value/2;
r=value%2;
n=n*10+r;
}
return n;
}

void init_istring(char cstring[],int istring[],int n){
int subint[8],j,k,value,decvalue;
for(int i=0;i<n;i++){
decvalue=int(cstring[i]);
value=dec_to_bin(decvalue);
for(j=7;j>=0;j--){
subint[j]=value%10;
}
for(k=0;k<8;k++){
if(p>=8){
subint[k]=istring[k+(p-k)/8];
p++;
}
else{
subint[k]=istring[k];
p++;
}

}


}

}

void convert_istring(int istring[],int n){
int i,d=0,j=0,value=0;
for(d=0;d<n;d++){
for(i=d*6+5;i>=d*6;i--){
value=value*powl(10,j)+istring[i];
j++;
}
cout<<value<<" ";
value=0;
}
}
void main(){
char string[]="wgrt";
int s[32];
int n=4,x=3;
init_istring(string,s,n);
convert_istring(s,x);
cin>>n;


}
Oct 1, 2011 at 5:24pm
modoran (2077)
Here it is, I used this code myself:

base64.h:
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#ifndef _BASE64_H_
#define _BASE64_H_
#include <string>
std::string base64_encode(unsigned char const* , unsigned int len);
std::string base64_decode(std::string const& s);
#endif



base64.cpp:
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#include "base64.h"

static const std::string base64_chars = 
             "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
             "abcdefghijklmnopqrstuvwxyz"
             "0123456789+/";


static inline bool is_base64(unsigned char c) {
  return (isalnum(c) || (c == '+') || (c == '/'));
}

std::string base64_encode(unsigned char const* bytes_to_encode, unsigned int in_len) {
  std::string ret;
  int i = 0;
  int j = 0;
  unsigned char char_array_3[3];
  unsigned char char_array_4[4];

  while (in_len--) {
    char_array_3[i++] = *(bytes_to_encode++);
    if (i == 3) {
      char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
      char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
      char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
      char_array_4[3] = char_array_3[2] & 0x3f;

      for(i = 0; (i <4) ; i++)
        ret += base64_chars[char_array_4[i]];
      i = 0;
    }
  }

  if (i)
  {
    for(j = i; j < 3; j++)
      char_array_3[j] = '\0';

    char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
    char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
    char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
    char_array_4[3] = char_array_3[2] & 0x3f;

    for (j = 0; (j < i + 1); j++)
      ret += base64_chars[char_array_4[j]];

    while((i++ < 3))
      ret += '=';

  }

  return ret;

}

std::string base64_decode(std::string const& encoded_string) {
  size_t in_len = encoded_string.size();
  size_t i = 0;
  size_t j = 0;
  int in_ = 0;
  unsigned char char_array_4[4], char_array_3[3];
  std::string ret;

  while (in_len-- && ( encoded_string[in_] != '=') && is_base64(encoded_string[in_])) {
    char_array_4[i++] = encoded_string[in_]; in_++;
    if (i ==4) {
      for (i = 0; i <4; i++)
        char_array_4[i] = static_cast<unsigned char>(base64_chars.find(char_array_4[i]));

      char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
      char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
      char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

      for (i = 0; (i < 3); i++)
        ret += char_array_3[i];
      i = 0;
    }
  }

  if (i) {
    for (j = i; j <4; j++)
      char_array_4[j] = 0;

    for (j = 0; j <4; j++)
      char_array_4[j] = static_cast<unsigned char>(base64_chars.find(char_array_4[j]));

    char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
    char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
    char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

    for (j = 0; (j < i - 1); j++) ret += char_array_3[j];
  }

  return ret;
}

Oct 1, 2011 at 5:30pm
cristi92b (5)
I tested this code in visual studio and I got this error:

LNK1561: entry point must be defined
Oct 1, 2011 at 5:37pm
modoran (2077)
Create a new console application with default settings, then add base64.h and base64.cpp to your project.

Add #include "base64.h" to stdafx.h and edit main() to use base64_encode() or base64_decode() for testing.
Oct 1, 2011 at 5:52pm
cristi92b (5)
Thank you!
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