Question

我有一个垃圾邮件的二进制文件。我正在使用MATLAB来查找好东西的开头，并希望将文件的其余部分从例如位置1388复制到新文件中。我知道我可以通过十六进制轻松地将十六进制文件读入一个新文件，但是我循环浏览了很多大文件，我会经常这样做，所以我希望有人知道某种方式倾倒部分文件进入新文件？

Answer 1

fidin = fopen('input.txt','r');
fseek(fidin, 1388, 'bof');
bulksize = 8192;
count = bulksize;
fid = fopen('output.txt', 'a');
while (count >= bulksize) do
    [A count] = fread(fidin, bulksize, '*uint8');
    fwrite(fid, A);
end_while
fclose(fidin);
fclose(fid);

input.txt输入文件 Output.txt输出文件 1388偏离文件开头。

更大的文件微调bulksize

Answer 2

我认为amald有正确的想法（+1），但我的经验告诉我，当实际情况发生时，他的实施无疑会让你受伤“:)

这是（IMO）更好的方法：

function yourFcn

    % File names
    inputFile  = 'input.bin';
    outputFile = 'output.bin';

    % The computed offset (ideally, this is also done inside a try/catch)
    offset = 1388;

    % Amount of bytes per read
    N  = 8192; 



    % Open the files
    fin = fopen(inputFile, 'r');
    assert(fin > 0, 'yourFcn:ioError',...
        'Error opening input file.');

    fout = fopen(outputFile, 'w+');
    if fout < 0        
        ME = MException('yourFcn:ioError',...
            'Error opening output file.');        
        throw( closeFile(fin, inputFile, ME) );         
    end


    % Set file pointer to computed offset
    try
        fseek(fin, offset, 'bof');
    catch ME
        ME = addCause(ME, MException('yourFcn:seekFailure',...
            'Error applying offset to input file'));        
        closeBoth(ME);        
    end

    % Read N bytes at a time, and dump them in the new file
    try
        while ~feof(fin)
            assert(fwrite(fout,fread(fin,N)) == N, 'yourFcn:ioError',...
                'Mismatch between bytes read and bytes written.');
        end

    catch ME
        ME = addCause(ME, MException('yourFcn:writeError',...
            'Error writing to output file'));
        closeBoth(ME);        
    end

    closeBoth();


    % Safely close one of the files
    function ME = closeFile(fid, fileName, ME)
        try
            fclose(fid);
        catch ME2
            errMsg = sprintf(['Error closing file ''%s''; ',...
                'all file handles have been forcibly closed.'], fileName);
            if isempty(ME_in)
                ME = MException('yourFcn:closeError', errMsg);
            else
                ME.message = char(ME.message, errMsg);
            end

            ME = addCause(ME2, ME);
            fclose('all');

        end        
    end

    % Safely close both files
    function ME = closeBoth(ME_in) 
        if nargin == 0
            ME_in = []; end            
        ME = closeFile(fin, inputFile, ME_in);
        if isequal(ME,ME_in)
            ME = closeFile(fout, outputFile, ME); end 
        if ~isempty(ME)
            throw(ME); end
    end

end

将2个文件位置之间的二进制文件的一部分复制到Matlab中的新文件中

2 个答案: