压缩解压

开发平台：
Matlab

encode_lz77.m：源码内容
							function encode_lz77(str)
sliding_window_length=20;
search_buffer_length=0;
search_buffer='';
look_buffer=str;
num_match = 0;
index=0;
match_index_insearch_arr=[];
big_match=0;
        big_match_insearch_arr = [];
        index_of_matched_look_arr =[];
big_match_inlook_arr=[];
code='';
while( length(look_buffer)>0 && search_buffer_length <= sliding_window_length)
    % the index of the character that we will start from it
      char_index=1;
    char=look_buffer(char_index);
    % array of the indexes that match the char in search buffer
    char_index_arr=find(search_buffer == char);
v='aaaaaaa';
% condition if there is a match in search buffer
    if(char_index_arr >0)
        [big_match_insearch_arr index_big_match chars_matched_inlook]=get_biggest_match(sliding_window_length,char_index,char_index_arr,search_buffer,look_buffer); 
              num_match = length(big_match_insearch_arr);
              index=index_big_match;
              node=write_code(index,num_match,look_buffer);
    %next character to be added to search buffer with the matched data
              if(numel(look_buffer)< (length(chars_matched_inlook)+1))
                  search_buffer = add_search_buffer(search_buffer,sliding_window_length,chars_matched_inlook);
              else
              chars_matched_inlook(length(chars_matched_inlook)+1)= look_buffer(length(chars_matched_inlook)+1);
              search_buffer = add_search_buffer(search_buffer,sliding_window_length,chars_matched_inlook); 
              end
    else
        d='eeeeeeeeee';
        num_match=0;
        index  = 0;
        node=write_code(index,num_match,look_buffer);
        search_buffer=add_search_buffer(search_buffer,sliding_window_length,char); 
    end
   
    
    n_look_buffer=modify_look_buffer(look_buffer,num_match);
    search_buffer;
    look_buffer = n_look_buffer;
    code=[code,node];
    e=length(search_buffer);
end
    code
end
function look_buffer=modify_look_buffer(look_buffer,num_match)
for i=1:length(look_buffer)-num_match-1
    look_buffer(i)=look_buffer(num_match+i+1);
end
look_buffer = look_buffer(1:length(look_buffer)-num_match-1);
end
function code=write_code(index,num_match,look_buffer)
if (numel(look_buffer)< num_match+1 )
    code=['(' num2str(index) ',' num2str(num_match) ', *)'];
else
code=['(' num2str(index) ',' num2str(num_match) ',' look_buffer(num_match+1) ')'];
end
end
function search_buffer = add_search_buffer(search_buffer,sliding_window_length,new_data_arr)
new_data_arr;
for i=1:length(new_data_arr)
if(length(search_buffer) == sliding_window_length )
      % modified_search_buffer = modified_buffer(search_buffer,new_data_arr);
      for j=length(search_buffer)-1 :-1:1
      search_buffer(j+1) = search_buffer(j);
      end
  search_buffer(1)=new_data_arr(i); 
else
    for k=length(search_buffer):-1:1
        search_buffer(k+1)=search_buffer(k);
    end
    search_buffer(1)=new_data_arr(i);
end
end
end
function [big_match_insearch_arr index_big_match chars_matched_inlook] = get_biggest_match(sliding_window_length,char_index,char_index_arr,search_buffer,look_buffer)
z='yes';
big_match=0;
index_big_match=0;
look_buffer_length = length(look_buffer);
        big_match_insearch_arr = [];
        chars_matched_inlook=[];
        
big_match_inlook_arr=[];
% counter that hold the biggest match of symbols
        big_match=0;
        
        % loop on the array which hold search buffer index number of match 
       for i=1:length(char_index_arr)
           r='bbbbbbbbbbbb';
           % pointer on search buffer
        p_search = char_index_arr(i);
        % pointer on Look buffer
        p_look = char_index;
                % arrays that will hold the sequenced indexes that have a
                % match in both buffers
        match_index_insearch_arr=[];
        index_of_matched_look_arr =[];
        matched_chars_inlook=[];
        % a loop that find the  match indexes that follow every char in the array in search & look buffer
        for j=0:p_search
           if(p_look+j<= length(look_buffer)& look_buffer(p_look+j) == search_buffer(p_search-j) )
               % add the matched index in look buffer 
               index_of_matched_look_arr(length(index_of_matched_look_arr)+1) = p_look+j;
               %the actual symbols in match in look buffer
               matched_chars_inlook(length(matched_chars_inlook)+1)=look_buffer(p_look+j);
              
              % add index number to array of the number of indexes in search buffer which has a match 
              match_index_insearch_arr(length(match_index_insearch_arr)+1) = p_search-j; 
           else
               break;
           end
        end
    %Hold the big match to a variables  & hold he array of matched indexes in both buffers 
        num_match=length(index_of_matched_look_arr);
        if(num_match >= big_match)
            %start index of big match
            index_big_match=p_search;
            big_match=num_match;
            big_match_insearch_arr = match_index_insearch_arr;
        big_match_inlook_arr = index_of_matched_look_arr;
        chars_matched_inlook = matched_chars_inlook;
       end
       end
        
end

						