1 #include "DataCompressor.h"
2 #include "DS_HuffmanEncodingTree.h"
3 #include "RakAssert.h"
4 #include <string.h> // Use string.h rather than memory.h for a console
5
Compress(unsigned char * userData,unsigned sizeInBytes,RakNet::BitStream * output)6 void DataCompressor::Compress( unsigned char *userData, unsigned sizeInBytes, RakNet::BitStream * output )
7 {
8 // Don't use this for small files as you will just make them bigger!
9 RakAssert(sizeInBytes > 2048);
10
11 unsigned int frequencyTable[ 256 ];
12 unsigned int i;
13 memset(frequencyTable,0,256*sizeof(unsigned int));
14 for (i=0; i < sizeInBytes; i++)
15 ++frequencyTable[userData[i]];
16 HuffmanEncodingTree tree;
17 BitSize_t writeOffset1, writeOffset2, bitsUsed1, bitsUsed2;
18 tree.GenerateFromFrequencyTable(frequencyTable);
19 output->WriteCompressed(sizeInBytes);
20 for (i=0; i < 256; i++)
21 output->WriteCompressed(frequencyTable[i]);
22 output->AlignWriteToByteBoundary();
23 writeOffset1=output->GetWriteOffset();
24 output->Write((unsigned int)0); // Dummy value
25 bitsUsed1=output->GetNumberOfBitsUsed();
26 tree.EncodeArray(userData, sizeInBytes, output);
27 bitsUsed2=output->GetNumberOfBitsUsed();
28 writeOffset2=output->GetWriteOffset();
29 output->SetWriteOffset(writeOffset1);
30 output->Write(bitsUsed2-bitsUsed1); // Go back and write how many bits were used for the encoding
31 output->SetWriteOffset(writeOffset2);
32 }
33
DecompressAndAllocate(RakNet::BitStream * input,unsigned char ** output)34 unsigned DataCompressor::DecompressAndAllocate( RakNet::BitStream * input, unsigned char **output )
35 {
36 HuffmanEncodingTree tree;
37 unsigned int bitsUsed, destinationSizeInBytes;
38 unsigned int decompressedBytes;
39 unsigned int frequencyTable[ 256 ];
40 unsigned i;
41
42 input->ReadCompressed(destinationSizeInBytes);
43 for (i=0; i < 256; i++)
44 input->ReadCompressed(frequencyTable[i]);
45 input->AlignReadToByteBoundary();
46 if (input->Read(bitsUsed)==false)
47 {
48 // Read error
49 #ifdef _DEBUG
50 RakAssert(0);
51 #endif
52 return 0;
53 }
54 *output = (unsigned char*) rakMalloc_Ex(destinationSizeInBytes, __FILE__, __LINE__);
55 tree.GenerateFromFrequencyTable(frequencyTable);
56 decompressedBytes=tree.DecodeArray(input, bitsUsed, destinationSizeInBytes, *output );
57 RakAssert(decompressedBytes==destinationSizeInBytes);
58 return destinationSizeInBytes;
59 }
60