개발 공부 - [Huffman Coding] 압축 (Compression) - 7

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class HuffmanDecoder

public class HuffmanDecoder {

     static public void main (String args[]) {

         String fileName = "";

         HuffmanCoding app = new HuffmanCoding();

         RandomAccessFile fIn;

         Scanner kb = new Scanner(System.in);

         try {

             System.out.print("Enter a file name: ");

             fileName = kb.next();

             fIn = new RandomAccessFile(fileName,"r");

             app.decompressFile(fileName,fIn);

             fIn.close();

         } catch (IOException io) {

             System.err.println("Cannot open " + fileName);

         }

     }

}

//실제 추가할 함수

decompressFile

public void decompressFile(String inFileName, RandomAccessFile fIn)

 throws IOException {

     String outFileName = new String(inFileName+".dec");

     RandomAccessFile fOut = new

     RandomAccessFile(outFileName,"rw");

     inputFrequencies(fIn);

     createHuffmanTree();

     assignCodewords(theRoot,0,0);

     decode(fIn,fOut);

}

inputFrequencies

private void inputFrequencies(RandomAccessFile fIn)

 throws IOException {

int dataIndex = fIn.readInt();

sizeOriginalFile = fIn.readLong();

runs.ensureCapacity(dataIndex);

for (int j = 0; j < dataIndex; j++) {

Run r = new Run();

r.symbol = (byte) fIn.read();

r.runLen = fIn.readInt();

r.freq = fIn.readInt();

runs.add(r);

}

}

decode

private void decode(RandomAccessFile fIn, RandomAccessFile fOut)

 throws IOException {

//Fin = 압축파일

     int nbrBytesRead=0, j, ch, bitCnt = 1, mask = 1, bits = 8;

     mask <<= bits - 1; // change 00000001 to 100000000

     for (ch=fIn.read(); ch!=-1 && nbrBytesRead<sizeOriginalFile;) {

         Run p = theRoot;

    

     while(true) {

         if (p.left == null && p.right == null) {

             for (j = 0; j < p.runLen; j++)

                 fOut.write(p.symbol);

                 nbrBytesRead += p.runLen;

                 break;

             }

             else if ((ch & mask) == 0) /* if the most significant bit is 0 */

             p = p.left;

         else /* if the most significant bit is 1 */

             p = p.right;

         if (bitCnt++ == bits) { /* if done with the current byte */

         ch = fIn.read();

         bitCnt = 1;

         }

     else

         ch <<= 1; /* left-shift the current byte */

 }

 }

}