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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4.  
  5. #define WINDOW_SIZE 1024  // 10-bit sliding window (2^10 = 1024)
  6. #define MAX_LENGTH 15     // 4-bit length (2^4 - 1 = 15)
  7. #define MIN_MATCH 3       // Minimum match length to encode as a pair
  8.  
  9. #define WINDOW_SIZE_N_BITS 10  // 10-bit sliding window 
  10. #define MAX_LENGTH_N_BITS 4     // 4-bit length 
  11.  
  12. #define size_t unsigned int
  13. #define uint8_t unsigned char
  14. #define uint32_t unsigned int
  15.  
  16. uint8_t dict[WINDOW_SIZE+MAX_LENGTH+MIN_MATCH];
  17. int dict_pos = 0;
  18.  
  19. int get_bit(const unsigned char *buffer, size_t bit_position) {
  20.     size_t byte_index = bit_position / 8;
  21.     size_t bit_offset = bit_position % 8;
  22.     return (buffer[byte_index] >> (7 - bit_offset)) & 0x01;
  23. }
  24.  
  25. void set_bit(uint8_t *buffer, size_t bit_position, int value) {
  26.     size_t byte_index = bit_position / 8;
  27.     size_t bit_offset = bit_position % 8;
  28.     if (value) {
  29.         buffer[byte_index] |= (1 << (7 - bit_offset));
  30.     } else {
  31.         buffer[byte_index] &= ~(1 << (7 - bit_offset));
  32.     }
  33. }
  34. void lzss_decompress(const unsigned char *input, int input_size, unsigned char *output, int *output_size) {
  35.     int input_pos = 0;
  36.     int output_pos = 0;
  37.     uint8_t offset[2] = {0};
  38.     uint8_t length = 0;
  39.     uint8_t flag = 0;
  40.  
  41.     while (input_pos < (input_size*8) ) {
  42.         // Read flag bit
  43.         flag = get_bit(input,input_pos++);
  44.         if (flag == 1) {
  45.             // Literal: read the next 8 bits
  46.             for (int i = 0; i < 8; i++) {
  47.                 set_bit(output,output_pos++,get_bit(input,input_pos++));
  48.             }
  49.             dict[dict_pos++] = output[(output_pos-1)/8];
  50.         } else {
  51.             // Pair: read 10-bit offset and 4-bit length
  52.             for (int i = 0; i < WINDOW_SIZE_N_BITS; i++) {
  53.                 set_bit(offset,i,get_bit(input,input_pos++));
  54.             }
  55.             for (int i = 0; i < MAX_LENGTH_N_BITS; i++) {
  56.                 set_bit(&length,i,get_bit(input,input_pos++));
  57.             }
  58.             length +=2;
  59.             for (int i = 0; i < length; i++) {
  60.                 output[(output_pos-1)/8] = dict[dict_pos-(unsigned int)offset[0]+i];
  61.                 output_pos += 8;
  62.                 dict[dict_pos++] = output[(output_pos-1)/8];
  63.  
  64.             }
  65.         }
  66.     }
  67.  
  68.     // *output_size = output_pos;
  69. }
  70.  
  71. int main() {
  72.     // Write C code here
  73.     int size_out = 50;
  74.     unsigned char Buf_Out[1024]={0};
  75.     unsigned char Buf_in[1024]={0xFF,0x80,0x11,0xE2,0xC0,0x40,0x30,0x41,0xA0,0x11,0x29,0xA5,0x58,0x00,0x00};
  76.     lzss_decompress(Buf_in,15,Buf_Out,&size_out);
  77.      for (int i = 0; i < 20; i++) {
  78.         printf("%x ", Buf_Out[i]);
  79.     }
  80.  
  81.     return 0;
  82. }
Success #stdin #stdout 0.01s 5284KB
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 c5
https://ideone.com/C94zuL
language:
C++14 (gcc 8.3)
created:
5 days ago
visibility:
public

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