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 BASE64_H
#define BASE64_H

// MODIFICATION Rob Meades 2021/09/07: headers removed so
// that puts() can be redirected and because malloc() is no longer used

// MODIFICATION Rob Meades 2021/09/07: prevent AStyle formatting
// *INDENT-OFF*

// MODIFICATION Rob Meades 2021/09/07: move static to start and add extra const
static const char * const b64="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" ;

// MODIFICATION Rob Meades 2021/09/07: move static to start
// maps A=>0,B=>1..
static const 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 256 elements

// Converts binary data of length=len to base64 characters.
// Length of the resultant string is stored in flen
// (you must pass pointer flen).
// MODIFICATION Rob Meades 2021/09/07: res made a parameter
// so that we can pass in external memory.
char* base64( const void* binaryData, int len, int *flen,
              char *res)
{
  const unsigned char* bin = (const unsigned char*) binaryData ;

  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 ;
  // MODIFICATION Rob Meades 2021/09/07: NULL check added so that
  // the caller can do a dummy run to just obtain the value
  // passed back in flen
  if ( res != NULL ) {
    // MODIFICATION Rob Meades 2021/09/07: no malloc() here, memory
    // is passed in
    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++] = '=';
    }
    // MODIFICATION Rob Meades 2021/09/07:  no null terminator is included
  }

  return res ;
}

// MODIFICATION Rob Meades 2021/09/07: buffer added as a parameter so that
// we can pass in external memory.
unsigned char* unbase64( const char* ascii, int len, int *flen,
                         char *buffer)
{
  const unsigned char *safeAsciiPtr = (const unsigned char*)ascii ;
  unsigned char *bin = (unsigned char *) buffer;
  int cb=0;
  int charNo;
  int pad = 0 ;

  if( len < 2 ) { // 2 accesses below would be OOB.
    // catch empty string, return NULL as result.
    puts( "ERROR: You passed an invalid base64 string (too short). You get NULL back." ) ;
    *flen=0;
    return 0 ;
  }
  if( safeAsciiPtr[ len-1 ]=='=' )  ++pad ;
  if( safeAsciiPtr[ len-2 ]=='=' )  ++pad ;

  *flen = 3*len/4 - pad ;
  // MODIFICATION Rob Meades 2021/09/07:: no malloc() here, memory
  // is passed in
  // MODIFICATION Rob Meades 2021/09/07: NULL check added so that
  // the caller can do a dummy run to just obtain the value
  // passed back in flen
  if( bin != NULL) 
  {

    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 ;
}

// MODIFICATION: by Rob Meades on 7 September 2021, restore AStyle formatting
// *INDENT-ON*

#endif