OpenVMS Source Code Demos

base64

/*

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

#include <stdio.h>
#include <stdlib.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* base64( const void* binaryData, int len, int *flen )
{
  unsigned char* bin = (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*) malloc( *flen + 1 ) ; // and one for the null
  if( !res )
  {
    puts( "ERROR: base64 could not allocate enough memory." ) ;
    puts( "I must stop because I could not get enough" ) ;
    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* unbase64( const char* ascii, int len, int *flen )
{
  unsigned char *safeAsciiPtr = (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.
    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 ;
  bin = (unsigned char*)malloc( *flen ) ;
  if( !bin )
  {
    puts( "ERROR: unbase64 could not allocate enough memory." ) ;
    puts( "I must stop because I could not get enough" ) ;
    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

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Neil Rieck
Waterloo, Ontario, Canada.