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// ///////////////////////////////////////////////////////////////////////////////

// Copyright (C) 2010, Frank Blumenberg

//

// See License.txt for complete licensing and attribution information.

// Permission is hereby granted, free of charge, to any person obtaining a copy

// of this software and associated documentation files (the "Software"), to deal

// in the Software without restriction, including without limitation the rights

// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

// copies of the Software, and to permit persons to whom the Software is

// furnished to do so, subject to the following conditions:

//

// The above copyright notice and this permission notice shall be included in all

// copies or substantial portions of the Software.

//

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

// THE SOFTWARE.

//

// ///////////////////////////////////////////////////////////////////////////////

#import "NSData+MKCommandEncode.h"

// ///////////////////////////////////////////////////////////////////////////////

#pragma mark Helper funktions

static NSData * encode64(NSData * inData){

  unsigned int dstIdx = 0;

  unsigned int srcIdx = 0;

  const unsigned char * inBuffer = [inData bytes];

  unsigned int length = [inData length];

  unsigned char a, b, c;

  int outDataLength = (length * 4) / 3;

  if (outDataLength % 4)

    outDataLength += 4 - (outDataLength % 4);

  NSMutableData * outData = [NSMutableData dataWithLength:outDataLength];

  char * outBuffer = [outData mutableBytes];

  while (length > 0) {

    if (length) {

      a = inBuffer[srcIdx++]; length--;

    } else a = 0;

    if (length) {

      b = inBuffer[srcIdx++]; length--;

    } else b = 0;

    if (length) {

      c = inBuffer[srcIdx++]; length--;

    } else c = 0;

    outBuffer[dstIdx++] = '=' + (a >> 2);

    outBuffer[dstIdx++] = '=' + (((a & 0x03) << 4) | ((b & 0xf0) >> 4));

    outBuffer[dstIdx++] = '=' + (((b & 0x0f) << 2) | ((c & 0xc0) >> 6));

    outBuffer[dstIdx++] = '=' + ( c & 0x3f);

  }

  [outData setLength:dstIdx];

  return outData;

}

// ///////////////////////////////////////////////////////////////////////////////

@implementation NSData (MKCommandEncode)

- (NSData *) dataWithCommand:(MKCommandId)aCommand forAddress:(MKAddress)aAddress;

{

  NSMutableData * frameData = [NSMutableData dataWithLength:3];

  char * frameBytes = [frameData mutableBytes];

  frameBytes[0] = '#';

  frameBytes[1] = 'a' + aAddress;

  frameBytes[2] = aCommand;

  [frameData appendData:encode64(self)];

  NSUInteger frameLength =  [frameData length];

  frameBytes = [frameData mutableBytes];

  int crc = 0;

  for (int i = 0; i < frameLength; i++) {

    crc += frameBytes[i];

  }

  crc %= 4096;

  char tmpCrc1 = '=' + (crc / 64);

  char tmpCrc2 = ('=' + crc % 64);

  [frameData appendBytes:&tmpCrc1 length:1];

  [frameData appendBytes:&tmpCrc2 length:1];

  [frameData appendBytes:"\r" length:1];

  return frameData;

}

+ (NSData *) dataWithCommand:(MKCommandId)aCommand forAddress:(MKAddress)aAddress payloadForByte:(uint8_t)byte {

  NSData * payload = [NSData dataWithBytes:&byte length:1];

  return [payload dataWithCommand:aCommand forAddress:aAddress];

}

+ (NSData *) dataWithCommand:(MKCommandId)aCommand

                  forAddress:(MKAddress)aAddress

            payloadWithBytes:(const void *)bytes

                      length:(NSUInteger)length {

  NSData * payload = [NSData dataWithBytes:bytes length:length];

  return [payload dataWithCommand:aCommand forAddress:aAddress];

}

@end