zdir(3)
=======

NAME
----
zdir - work with file-system directories

SYNOPSIS
--------
----
//  This is a stable class, and may not change except for emergencies. It
//  is provided in stable builds.
//  Create a new directory item that loads in the full tree of the specified
//  path, optionally located under some parent path. If parent is "-", then 
//  loads only the top-level directory, and does not use parent as a path.  
CZMQ_EXPORT zdir_t *
    zdir_new (const char *path, const char *parent);

//  Destroy a directory tree and all children it contains.
CZMQ_EXPORT void
    zdir_destroy (zdir_t **self_p);

//  Return directory path
CZMQ_EXPORT const char *
    zdir_path (zdir_t *self);

//  Return last modification time for directory.
CZMQ_EXPORT time_t
    zdir_modified (zdir_t *self);

//  Return total hierarchy size, in bytes of data contained in all files
//  in the directory tree.                                              
CZMQ_EXPORT off_t
    zdir_cursize (zdir_t *self);

//  Return directory count
CZMQ_EXPORT size_t
    zdir_count (zdir_t *self);

//  Returns a sorted list of zfile objects; Each entry in the list is a pointer
//  to a zfile_t item already allocated in the zdir tree. Do not destroy the   
//  original zdir tree until you are done with this list.                      
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zlist_t *
    zdir_list (zdir_t *self);

//  Remove directory, optionally including all files that it contains, at  
//  all levels. If force is false, will only remove the directory if empty.
//  If force is true, will remove all files and all subdirectories.        
CZMQ_EXPORT void
    zdir_remove (zdir_t *self, bool force);

//  Calculate differences between two versions of a directory tree.    
//  Returns a list of zdir_patch_t patches. Either older or newer may  
//  be null, indicating the directory is empty/absent. If alias is set,
//  generates virtual filename (minus path, plus alias).               
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zlist_t *
    zdir_diff (zdir_t *older, zdir_t *newer, const char *alias);

//  Return full contents of directory as a zdir_patch list.
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zlist_t *
    zdir_resync (zdir_t *self, const char *alias);

//  Load directory cache; returns a hash table containing the SHA-1 digests
//  of every file in the tree. The cache is saved between runs in .cache.  
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zhash_t *
    zdir_cache (zdir_t *self);

//  Print contents of directory to open stream
CZMQ_EXPORT void
    zdir_fprint (zdir_t *self, FILE *file, int indent);

//  Print contents of directory to stdout
CZMQ_EXPORT void
    zdir_print (zdir_t *self, int indent);

//  Create a new zdir_watch actor instance:                       
//                                                                
//      zactor_t *watch = zactor_new (zdir_watch, NULL);          
//                                                                
//  Destroy zdir_watch instance:                                  
//                                                                
//      zactor_destroy (&watch);                                  
//                                                                
//  Enable verbose logging of commands and activity:              
//                                                                
//      zstr_send (watch, "VERBOSE");                             
//                                                                
//  Subscribe to changes to a directory path:                     
//                                                                
//      zsock_send (watch, "ss", "SUBSCRIBE", "directory_path");  
//                                                                
//  Unsubscribe from changes to a directory path:                 
//                                                                
//      zsock_send (watch, "ss", "UNSUBSCRIBE", "directory_path");
//                                                                
//  Receive directory changes:                                    
//      zsock_recv (watch, "sp", &path, &patches);                
//                                                                
//      // Delete the received data.                              
//      free (path);                                              
//      zlist_destroy (&patches);                                 
CZMQ_EXPORT void
    zdir_watch (zsock_t *pipe, void *unused);

//  Self test of this class.
CZMQ_EXPORT void
    zdir_test (bool verbose);

----

DESCRIPTION
-----------

The zdir class gives access to the file system index. It will load
a directory tree (a directory plus all child directories) into a
zdir structure and then let you navigate that structure. It exists
mainly to wrap non-portable OS functions to do this.

Please add @discuss section in ../src/zdir.c.

EXAMPLE
-------
.From zdir_test method
----
// need to create a file in the test directory we're watching
// in order to ensure the directory exists
zfile_t *initfile = zfile_new ("./zdir-test-dir", "initial_file");
assert (initfile);
zfile_output (initfile);
fprintf (zfile_handle (initfile), "initial file\n");
zfile_close (initfile);
zfile_destroy (&initfile);

zdir_t *older = zdir_new ("zdir-test-dir", NULL);
assert (older);
if (verbose) {
    printf ("\n");
    zdir_dump (older, 0);
}
zdir_t *newer = zdir_new (".", NULL);
assert (newer);
zlist_t *patches = zdir_diff (older, newer, "/");
assert (patches);
while (zlist_size (patches)) {
    zdir_patch_t *patch = (zdir_patch_t *) zlist_pop (patches);
    zdir_patch_destroy (&patch);
}
zlist_destroy (&patches);
zdir_destroy (&older);
zdir_destroy (&newer);

zdir_t *nosuch = zdir_new ("does-not-exist", NULL);
assert (nosuch == NULL);

// zdir_watch test:
zactor_t *watch = zactor_new (zdir_watch, NULL);
assert (watch);

if (verbose) {
    zsock_send (watch, "s", "VERBOSE");
    assert (zsock_wait (watch) == 0);
}

zclock_sleep (1001); // wait for initial file to become 'stable'

zsock_send (watch, "si", "TIMEOUT", 100);
assert (zsock_wait (watch) == 0);

zsock_send (watch, "ss", "SUBSCRIBE", "zdir-test-dir");
assert (zsock_wait (watch) == 0);

zsock_send (watch, "ss", "UNSUBSCRIBE", "zdir-test-dir");
assert (zsock_wait (watch) == 0);

zsock_send (watch, "ss", "SUBSCRIBE", "zdir-test-dir");
assert (zsock_wait (watch) == 0);

zfile_t *newfile = zfile_new ("zdir-test-dir", "test_abc");
zfile_output (newfile);
fprintf (zfile_handle (newfile), "test file\n");
zfile_close (newfile);

zpoller_t *watch_poll = zpoller_new (watch, NULL);

// poll for a certain timeout before giving up and failing the test.
assert (zpoller_wait (watch_poll, 1001) == watch);

// wait for notification of the file being added
char *path;
int rc = zsock_recv (watch, "sp", &path, &patches);
assert (rc == 0);

assert (streq (path, "zdir-test-dir"));
free (path);

assert (zlist_size (patches) == 1);

zdir_patch_t *patch = (zdir_patch_t *) zlist_pop (patches);
assert (streq (zdir_patch_path (patch), "zdir-test-dir"));

zfile_t *patch_file = zdir_patch_file (patch);
assert (streq (zfile_filename (patch_file, ""), "zdir-test-dir/test_abc"));

zdir_patch_destroy (&patch);
zlist_destroy (&patches);

// remove the file
zfile_remove (newfile);
zfile_destroy (&newfile);

// poll for a certain timeout before giving up and failing the test.
assert (zpoller_wait (watch_poll, 1001) == watch);

// wait for notification of the file being removed
rc = zsock_recv (watch, "sp", &path, &patches);
assert (rc == 0);

assert (streq (path, "zdir-test-dir"));
free (path);

assert (zlist_size (patches) == 1);

patch = (zdir_patch_t *) zlist_pop (patches);
assert (streq (zdir_patch_path (patch), "zdir-test-dir"));

patch_file = zdir_patch_file (patch);
assert (streq (zfile_filename (patch_file, ""), "zdir-test-dir/test_abc"));

zdir_patch_destroy (&patch);
zlist_destroy (&patches);

zpoller_destroy (&watch_poll);
zactor_destroy (&watch);

// clean up by removing the test directory.
zdir_t *testdir = zdir_new ("zdir-test-dir", NULL);
zdir_remove (testdir, true);
zdir_destroy (&testdir);
----
