ExNext.md

NAME

ExNext -- Examine the next entry in a directory

SYNOPSIS

    success = ExNext( lock, FileInfoBlock )
    D0                 D1        D2

    BOOL ExNext(BPTR, struct FileInfoBlock *)

Links: FileInfoBlock FileInfoBlock

FUNCTION

This routine is passed a directory lock and a FileInfoBlock that have been initialized by a previous call to Examine, or updated by a previous call to ExNext(). ExNext() gives a return code of zero on failure. The most common cause of failure is reaching the end of the list of files in the owning directory. In this case, IoErr will return ERROR_NO_MORE_ENTRIES and a good exit is appropriate.

So, follow these steps to examine a directory:

1. Pass a Lock and a FileInfoBlock to Examine. The lock must be on the directory you wish to examine.
2. Pass ExNext() the same lock and FileInfoBlock.
3. Do something with the information returned in the FileInfoBlock. Note that the fib_DirEntryType field is positive for directories, negative for files.
4. Keep calling ExNext() until it returns FALSE. Check IoErr to ensure that the reason for failure was ERROR_NO_MORE_ENTRIES.

Note: if you wish to recursively scan the file tree and you find another directory while ExNext()ing you must Lock that directory and Examine it using a new FileInfoBlock. Use of the same FileInfoBlock to enter a directory would lose important state information such that it will be impossible to continue scanning the parent directory. While it is permissible to UnLock and Lock the parent directory between ExNext() calls, this is NOT recommended. Important state information is associated with the parent lock, so if it is freed between ExNext() calls this information has to be rebuilt on each new ExNext() call, and will significantly slow down directory scanning.

It is NOT legal to Examine a file, and then to ExNext() from that FileInfoBlock. You may make a local copy of the FileInfoBlock, as long as it is never passed back to the operating system.

INPUTS

lock - BCPL pointer to a lock originally used for the Examine call infoBlock - pointer to a FileInfoBlock used on the previous Examine or ExNext() call.

RESULTS

success - boolean

SPECIAL NOTE FileInfoBlock must be longword-aligned. AllocDosObject will allocate them correctly for you.

SEE ALSO

Examine, Lock, UnLock, IoErr, ExamineFH, AllocDosObject, ExAll