/*

  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

*/

#include "base64.h"

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

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

// 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).
char* UA_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*) malloc( (size_t)(*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* UA_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.
        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( (size_t) (*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++] = (unsigned char)((A<<2) | (B>>4)) ;
        bin[cb++] = (unsigned char)((B<<4) | (C>>2)) ;
        bin[cb++] = (unsigned char)((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++] = (unsigned char)((A<<2) | (B>>4)) ;
        bin[cb++] = (unsigned char)((B<<4) | (C>>2)) ;
    }
    else if( pad==2 )
    {
        int A=unb64[safeAsciiPtr[charNo]];
        int B=unb64[safeAsciiPtr[charNo+1]];

        bin[cb++] = (unsigned char)((A<<2) | (B>>4)) ;
    }

    return bin ;
}