/*
   Copyright (c) 2005, 2012, Oracle and/or its affiliates

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; see the file COPYING. If not, write to the
   Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
   MA  02110-1301  USA.
*/

/* coding.cpp implements hex and base64 encoding/decoing
*/

#include "runtime.hpp"
#include "coding.hpp"
#include "file.hpp"


namespace TaoCrypt {


namespace { // locals

const byte bad = 0xFF;  // invalid encoding

const byte hexEncode[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                           'A', 'B', 'C', 'D', 'E', 'F'
                         };

const byte hexDecode[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                           bad, bad, bad, bad, bad, bad, bad,
                           10, 11, 12, 13, 14, 15 
                         };  // A starts at 0x41 not 0x3A


const byte base64Encode[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
                              'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
                              'U', 'V', 'W', 'X', 'Y', 'Z',
                              'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
                              'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
                              'u', 'v', 'w', 'x', 'y', 'z',
                              '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                              '+', '/'
                            };

const byte base64Decode[] = { 62, bad, bad, bad, 63,   // + starts at 0x2B
                              52, 53, 54, 55, 56, 57, 58, 59, 60, 61,
                              bad, bad, bad, bad, bad, bad, bad,
                              0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                              10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
                              20, 21, 22, 23, 24, 25,
                              bad, bad, bad, bad, bad, bad,
                              26, 27, 28, 29, 30, 31, 32, 33, 34, 35,
                              36, 37, 38, 39, 40, 41, 42, 43, 44, 45,
                              46, 47, 48, 49, 50, 51
                            };

const byte pad = '=';
const int pemLineSz = 64;

}  // local namespace


// Hex Encode
void HexEncoder::Encode()
{
    word32 bytes = plain_.size();
    encoded_.New(bytes * 2);

    word32 i = 0;

    while (bytes--) {
        byte p = plain_.next();

        byte b  = p >> 4;
        byte b2 = p & 0xF;

        encoded_[i++] = hexEncode[b];
        encoded_[i++] = hexEncode[b2];
    }

    plain_.reset(encoded_);
}


// Hex Decode
void HexDecoder::Decode()
{
    word32 bytes = coded_.size();
    decoded_.New(bytes / 2);

    word32 i(0);

    while (bytes) {
        byte b  = coded_.next() - 0x30;  // 0 starts at 0x30
        byte b2 = coded_.next() - 0x30;

        // sanity checks
        if (b >= sizeof(hexDecode)/sizeof(hexDecode[0])) {
            coded_.SetError(PEM_E);
            return;
        }
        if (b2 >= sizeof(hexDecode)/sizeof(hexDecode[0])) {
            coded_.SetError(PEM_E);
            return;
        }

        b  = hexDecode[b];
        b2 = hexDecode[b2];

        decoded_[i++] = (b << 4) | b2;
        bytes -= 2;
    }

    coded_.reset(decoded_);
}


// Base 64 Encode
void Base64Encoder::Encode()
{
    word32 bytes = plain_.size();
    word32 outSz = (bytes + 3 - 1) / 3 * 4;

    outSz += (outSz + pemLineSz - 1) / pemLineSz;  // new lines
    encoded_.New(outSz);

    word32 i = 0;
    word32 j = 0;
    
    while (bytes > 2) {
        byte b1 = plain_.next();
        byte b2 = plain_.next();
        byte b3 = plain_.next();

        // encoded idx
        byte e1 = b1 >> 2;
        byte e2 = ((b1 & 0x3) << 4) | (b2 >> 4);
        byte e3 = ((b2 & 0xF) << 2) | (b3 >> 6);
        byte e4 = b3 & 0x3F;

        // store
        encoded_[i++] = base64Encode[e1];
        encoded_[i++] = base64Encode[e2];
        encoded_[i++] = base64Encode[e3];
        encoded_[i++] = base64Encode[e4];

        bytes -= 3;

        if ((++j % 16) == 0 && bytes)
            encoded_[i++] = '\n';
    }

    // last integral
    if (bytes) {
        bool twoBytes = (bytes == 2);

        byte b1 = plain_.next();
        byte b2 = (twoBytes) ? plain_.next() : 0;

        byte e1 = b1 >> 2;
        byte e2 = ((b1 & 0x3) << 4) | (b2 >> 4);
        byte e3 =  (b2 & 0xF) << 2;

        encoded_[i++] = base64Encode[e1];
        encoded_[i++] = base64Encode[e2];
        encoded_[i++] = (twoBytes) ? base64Encode[e3] : pad;
        encoded_[i++] = pad;
    } 

    encoded_[i++] = '\n';
    
    if (i == outSz)
        plain_.reset(encoded_);
}


// Base 64 Decode
void Base64Decoder::Decode()
{
    word32 bytes = coded_.size();
    word32 plainSz = bytes - ((bytes + (pemLineSz - 1)) / pemLineSz); 
    const  byte maxIdx = (byte)sizeof(base64Decode) + 0x2B - 1;
    plainSz = ((plainSz * 3) / 4) + 3;
    decoded_.New(plainSz);

    word32 i = 0;
    word32 j = 0;

    while (bytes > 3) {
        byte e1 = coded_.next();
        byte e2 = coded_.next();
        byte e3 = coded_.next();
        byte e4 = coded_.next();

        if (e1 == 0)            // end file 0's
            break;

        bool pad3 = false;
        bool pad4 = false;
        if (e3 == pad)
            pad3 = true;
        if (e4 == pad)
            pad4 = true;

        if (e1 < 0x2B || e2 < 0x2B || e3 < 0x2B || e4 < 0x2B) {
            coded_.SetError(PEM_E);
            return;
        }

        if (e1 > maxIdx || e2 > maxIdx || e3 > maxIdx || e4 > maxIdx) {
            coded_.SetError(PEM_E);
            return;
        }

        e1 = base64Decode[e1 - 0x2B];
        e2 = base64Decode[e2 - 0x2B];
        e3 = (e3 == pad) ? 0 : base64Decode[e3 - 0x2B];
        e4 = (e4 == pad) ? 0 : base64Decode[e4 - 0x2B];

        byte b1 = (e1 << 2) | (e2 >> 4);
        byte b2 = ((e2 & 0xF) << 4) | (e3 >> 2);
        byte b3 = ((e3 & 0x3) << 6) | e4;

        decoded_[i++] = b1;
        if (!pad3)
            decoded_[i++] = b2;
        if (!pad4)
            decoded_[i++] = b3;
        else
            break;
        
        bytes -= 4;
        if ((++j % 16) == 0) {
            byte endLine = coded_.next();
            bytes--;
            while (endLine == ' ') {        // remove possible whitespace
                endLine = coded_.next();
                bytes--;
            }
            if (endLine == '\r') {
                endLine = coded_.next();
                bytes--;
            }
            if (endLine != '\n') {
                coded_.SetError(PEM_E); 
                return;
            }
        }
    }

    if (i != decoded_.size())
        decoded_.resize(i);
    coded_.reset(decoded_);
}


} // namespace