## Struct collector

boost::log::sinks::file::collector — Base class for file collectors.

## Synopsis

    // In header: <boost/log/sinks/text_file_backend.hpp>

    struct collector {
      // construct/copy/destruct
      collector();
      collector(collector const &);
      collector & operator=(collector const &);
      ~collector();

      // public member functions
      virtual void store_file(filesystem::path const &) = 0;
      virtual uintmax_t
      scan_for_files(scan_method, filesystem::path const & = filesystem::path(),
                     unsigned int * = 0) = 0;
    };

## Description

All file collectors, supported by file sink backends, should inherit this class.

### `collector` public construct/copy/destruct

1.     collector();

   Default constructor

2.     collector(collector const &);

3.     collector & operator=(collector const &);

4.     ~collector();

   Virtual destructor

### `collector` public member functions

1.     virtual void store_file(filesystem::path const & src_path) = 0;

   The function stores the specified file in the storage. May lead to an older file deletion and a long file moving.

   Parameters:

   `src_path` | The name of the file to be stored

2.     virtual uintmax_t
       scan_for_files(scan_method method,
                      filesystem::path const & pattern = filesystem::path(),
                      unsigned int * counter = 0) = 0;

   Scans the target directory for the files that have already been stored. The found files are added to the collector in order to be tracked and erased, if needed.

   The function may scan the directory in two ways: it will either consider every file in the directory a log file, or will only consider files with names that match the specified pattern. The pattern may contain the following placeholders:

   - y, Y, m, d - date components, in Boost.DateTime meaning.

   - H, M, S, f - time components, in Boost.DateTime meaning.

   - N - numeric file counter. May also contain width specification in printf-compatible form (e.g. %5N). The resulting number will always be zero-filled.

   - %% - a percent sign

   All other placeholders are not supported.

   | Note
   In case if method is `scan_matching` the effect of this function is highly dependent on the pattern definition. It is recommended to choose patterns with easily distinguished placeholders (i.e. having delimiters between them). Otherwise either some files can be mistakenly found or not found, which in turn may lead to an incorrect file deletion.

   Parameters:

   `counter` | If not `NULL` and method is `scan_matching`, the method suggests initial value of a file counter that may be used in the file name pattern. The parameter is not used otherwise.
   `method` | The method of scanning. If `no_scan` is specified, the call has no effect.
   `pattern` | The file name pattern if method is `scan_matching`. Otherwise the parameter is not used.

   Returns: | The number of found files.