libws_base64.h

/*

  https://github.com/superwills/NibbleAndAHalf
  base64.h -- Fast base64 encoding and decoding.
  version 1.0.0, April 17, 2013 143a

  Copyright (C) 2013 William Sherif

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.

  William Sherif
  will.sherif@gmail.com

  YWxsIHlvdXIgYmFzZSBhcmUgYmVsb25nIHRvIHVz

*/
#ifndef __LIBWS_BASE64_H__
#define __LIBWS_BASE64_H__

#include <stdio.h>
#include <stdlib.h>
#include <libws.h>
#include <libws_private.h>

const static char* b64="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" ;

// maps A=>0,B=>1..
const static unsigned char unb64[]={
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //10 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //20 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //30 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //40 
  0,   0,   0,  62,   0,   0,   0,  63,  52,  53, //50 
 54,  55,  56,  57,  58,  59,  60,  61,   0,   0, //60 
  0,   0,   0,   0,   0,   0,   1,   2,   3,   4, //70 
  5,   6,   7,   8,   9,  10,  11,  12,  13,  14, //80 
 15,  16,  17,  18,  19,  20,  21,  22,  23,  24, //90 
 25,   0,   0,   0,   0,   0,   0,  26,  27,  28, //100 
 29,  30,  31,  32,  33,  34,  35,  36,  37,  38, //110 
 39,  40,  41,  42,  43,  44,  45,  46,  47,  48, //120 
 49,  50,  51,   0,   0,   0,   0,   0,   0,   0, //130 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //140 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //150 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //160 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //170 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //180 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //190 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //200 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //210 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //220 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //230 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //240 
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0, //250 
  0,   0,   0,   0,   0,   0, 
}; // This array has 255 elements

// Converts binary data of length=len to base64 characters.
// Length of the resultant string is stored in flen
// (you must pass pointer flen).
char* libws_base64( const void* binaryData, int len, int *flen )
{
  const unsigned char* bin = (const unsigned char*) binaryData ;
  char* res ;
  
  int rc = 0 ; // result counter
  int byteNo ; // I need this after the loop
  
  int modulusLen = len % 3 ;
  int pad = ((modulusLen&1)<<1) + ((modulusLen&2)>>1) ; // 2 gives 1 and 1 gives 2, but 0 gives 0.
  
  *flen = 4*(len + pad)/3 ;
  res = (char*) _ws_malloc( *flen + 1 ) ; // and one for the null
  if( !res )
  {
    return 0;
  }
  
  for( byteNo = 0 ; byteNo <= len-3 ; byteNo+=3 )
  {
    unsigned char BYTE0=bin[byteNo];
    unsigned char BYTE1=bin[byteNo+1];
    unsigned char BYTE2=bin[byteNo+2];
    res[rc++]  = b64[ BYTE0 >> 2 ] ;
    res[rc++]  = b64[ ((0x3&BYTE0)<<4) + (BYTE1 >> 4) ] ;
    res[rc++]  = b64[ ((0x0f&BYTE1)<<2) + (BYTE2>>6) ] ;
    res[rc++]  = b64[ 0x3f&BYTE2 ] ;
  }
  
  if( pad==2 )
  {
    res[rc++] = b64[ bin[byteNo] >> 2 ] ;
    res[rc++] = b64[ (0x3&bin[byteNo])<<4 ] ;
    res[rc++] = '=';
    res[rc++] = '=';
  }
  else if( pad==1 )
  {
    res[rc++]  = b64[ bin[byteNo] >> 2 ] ;
    res[rc++]  = b64[ ((0x3&bin[byteNo])<<4)   +   (bin[byteNo+1] >> 4) ] ;
    res[rc++]  = b64[ (0x0f&bin[byteNo+1])<<2 ] ;
    res[rc++] = '=';
  }
  
  res[rc]=0; // NULL TERMINATOR! ;)
  return res ;
}

unsigned char* libws_unbase64( const char* ascii, int len, int *flen )
{
  const unsigned char *safeAsciiPtr = (const unsigned char*)ascii ;
  unsigned char *bin ;
  int cb=0;
  int charNo;
  int pad = 0 ;

  if( len < 2 ) { // 2 accesses below would be OOB.
    // catch empty string, return NULL as result.
    *flen=0;
    return 0 ;
  }
  if( safeAsciiPtr[ len-1 ]=='=' )  ++pad ;
  if( safeAsciiPtr[ len-2 ]=='=' )  ++pad ;
  
  *flen = 3*len/4 - pad ;
  bin = (unsigned char*)_ws_malloc( *flen ) ;
  if( !bin )
  {
    return 0;
  }
  
  for( charNo=0; charNo <= len - 4 - pad ; charNo+=4 )
  {
    int A=unb64[safeAsciiPtr[charNo]];
    int B=unb64[safeAsciiPtr[charNo+1]];
    int C=unb64[safeAsciiPtr[charNo+2]];
    int D=unb64[safeAsciiPtr[charNo+3]];
    
    bin[cb++] = (A<<2) | (B>>4) ;
    bin[cb++] = (B<<4) | (C>>2) ;
    bin[cb++] = (C<<6) | (D) ;
  }
  
  if( pad==1 )
  {
    int A=unb64[safeAsciiPtr[charNo]];
    int B=unb64[safeAsciiPtr[charNo+1]];
    int C=unb64[safeAsciiPtr[charNo+2]];
    
    bin[cb++] = (A<<2) | (B>>4) ;
    bin[cb++] = (B<<4) | (C>>2) ;
  }
  else if( pad==2 )
  {
    int A=unb64[safeAsciiPtr[charNo]];
    int B=unb64[safeAsciiPtr[charNo+1]];
    
    bin[cb++] = (A<<2) | (B>>4) ;
  }
  
  return bin ;
}

#endif // __LIBWS_BASE64_H__