manpagez: man pages & more
man getdirentriesattr(2)
Home | html | info | man
getdirentriesattr(2)        BSD System Calls Manual       getdirentriesattr(2)


NAME

     getdirentriesattr -- get file system attributes for multiple directory
     entries


SYNOPSIS

     #include <sys/attr.h>
     #include <unistd.h>

     #if __LP64__

     int
     getdirentriesattr(int fd, struct attrlist * attrList, void * attrBuf,
         size_t attrBufSize, unsigned int * count, unsigned int * basep,
         unsigned int * newState, unsigned int options);

     #else

     int
     getdirentriesattr(int fd, struct attrlist * attrList, void * attrBuf,
         size_t attrBufSize, unsigned long * count, unsigned long * basep,
         unsigned long * newState, unsigned long options);

     #endif


DESCRIPTION

     The getdirentriesattr() function reads directory entries and returns
     their attributes (that is, metadata).  You can think of it as a combina-
     tion of getdirentries(2) and getattrlist(2).  getdirentriesattr() iter-
     ates over the items in a directory like getdirentries(2), and returns
     information about each directory entry like getattrlist(2).  Note: when
     getdirentriesattr() returns information about a symbolic link, the infor-
     mation returned is about the link itself, not the target of the link.

     The function reads directory entries from the directory referenced by the
     file descriptor fd.  Attributes of those directory entries are placed
     into the buffer specified by attrBuf and attrBufSize.  The attrList
     parameter determines what attributes are returned for each entry.  The
     count parameter contains the number of directory entries requested and
     returned.  The basep parameter returns the directory offset in a manner
     similar to getdirentries(2).  The newState parameter allows you to check
     whether the directory has been modified while you were reading it.  The
     options parameter lets you control specific aspects of the function's be-
     haviour.

     The getdirentriesattr() function is only supported by certain volume for-
     mat implementations.  For maximum compatibility, client programs should
     use high-level APIs (such as the Carbon File Manager) to access file sys-
     tem attributes.  These high-level APIs include logic to emulate file sys-
     tem attributes on volumes that don't support getdirentriesattr().

     The fd parameter must be a file descriptor that references a directory
     that you have opened for reading.

     The attrList parameter is a pointer to an attrlist structure.  You are
     responsible for filling out all fields of this structure before calling
     the function.  See the discussion of the getattrlist(2) function for a
     detailed description of this structure.  To get an attribute you must set
     the corresponding bit in the appropriate attrgroup_t field of the
     attrlist structure.  You must not request volume attributes.

     The attrBuf and attrBufSize parameters specify a buffer into which the
     function places attribute values.  The attributes for any given directory
     entry are grouped together and packed in exactly the same way as they are
     returned from getattrlist(2).  These groups are then placed into the
     buffer, one after another.  As each group starts with a leading u_int32_t
     that contains the overall length of the group, you can step from one
     group to the next by simply adding this length to your pointer.  The sam-
     ple code (below) shows how to do this.  The initial contents of this
     buffer are ignored.

     The count parameter points to an unsigned long or unsigned int variable.
     You should initialise this variable to be the number of directory entries
     for which you wish to get attributes.  On return, this variable contains
     the number of directory entries whose attributes have been placed into
     the attribute buffer.  This may be smaller than the number that you
     requested.

     The basep parameter returns the offset of the last directory entry read,
     in a manner identical to getdirentries(2).  You can use this value to
     reset a directory iteration to a known position using lseek(2).  However,
     since the variable is too small to hold an off_t, you should use lseek(2)
     to get the directory's current position instead of using this parameter.
     The initial value of the variable is ignored.

     The newState parameter returns a value that changes if the directory has
     been modified.  If you're iterating through the directory by making
     repeated calls to getdirentriesattr(), you can compare subsequent values
     of newState to determine whether the directory has been modified (and
     thus restart your iteration at the beginning).  The initial value of the
     variable is ignored.

     The options parameter is a bit set that controls the behaviour of
     getdirentriesattr().  The following option bits are defined.

     FSOPT_NOINMEMUPDATE  This tells getdirentriesattr() to return the direc-
                          tory entries from disk rather than taking the extra
                          step of looking at data structures in-memory which
                          may contain changes that haven't been flushed to
                          disk.

                          This option allowed for specific performance opti-
                          mizations for specific clients on older systems.  We
                          currently recommend that clients not set this option
                          and that file system implementations ignore it.

     It is typical to ask for a combination of common, file, and directory
     attributes and then use the value of the ATTR_CMN_OBJTYPE attribute to
     parse the resulting attribute buffer.


RETURN VALUES

     Upon successful completion a value of 0 or 1 is returned.  The value 0
     indicates that the routine completed successfully.  The value 1 indicates
     that the routine completed successfully and has returned the last entry
     in the directory.  On error, a value of -1 is returned and errno is set
     to indicate the error.


COMPATIBILITY

     Not all volumes support getdirentriesattr().  You can test whether a vol-
     ume supports getdirentriesattr() by using getattrlist(2) to get the vol-
     ume capabilities attribute ATTR_VOL_CAPABILITIES, and then testing the
     VOL_CAP_INT_READDIRATTR flag.

     The getdirentriesattr() function has been undocumented for more than two
     years.  In that time a number of volume format implementations have been
     created without a proper specification for the behaviour of this routine.
     You may encounter volume format implementations with slightly different
     behaviour than what is described here.  Your program is expected to be
     tolerant of this variant behaviour.

     If you're implementing a volume format that supports getdirentriesattr(),
     you should be careful to support the behaviour specified by this docu-
     ment.

     If the directory contains a mount point, then DIR_MNTSTATUS_MNTPOINT will
     be set in the ATTR_DIR_MOUNTSTATUS for that entry; all other attributes
     for that entry, however, will be for the underlying file system (as
     opposed to the mounted file system).  getattrlist(2) should be used to
     get the attributes for the mount point.


ERRORS

     getdirentriesattr() will fail if:

     [ENOTSUP]          The volume does not support getdirentriesattr().

     [EBADF]            fd is not a valid file descriptor for a directory open
                        for reading.

     [EFAULT]           attrList or attrBuf points to an invalid address.

     [EINVAL]           The bitmapcount field of attrList is not
                        ATTR_BIT_MAP_COUNT.

     [EINVAL]           You requested an invalid attribute.

     [EINVAL]           You requested volume attributes.

     [EINVAL]           The options parameter contains an invalid flag.

     [EIO]              An I/O error occurred while reading from or writing to
                        the file system.


EXAMPLES

     The following code lists the contents of a directory using
     getdirentriesattr().  The listing includes the file type and creator for
     files.

     #include <assert.h>
     #include <stdio.h>
     #include <stddef.h>
     #include <string.h>
     #include <sys/attr.h>
     #include <sys/errno.h>
     #include <unistd.h>
     #include <sys/vnode.h>
     #include <stdbool.h>
     #include <fcntl.h>

     typedef struct attrlist attrlist_t;

     struct FInfoAttrBuf {
         u_int32_t       length;
         attrreference_t name;
         fsobj_type_t    objType;
         char            finderInfo[32];
         u_int32_t       dirStatus;
     } __attribute__((aligned(4), packed));
     typedef struct FInfoAttrBuf FInfoAttrBuf;

     enum {
         kEntriesPerCall = 10
     };

     static int FInfoDemo(const char *dirPath)
     {
         int             err;
         int             junk;
         int             dirFD;
         attrlist_t      attrList;
     #ifdef __LP64__
         unsigned int    index;
         unsigned int    count;
         unsigned int    junkBaseP;
         unsigned int    oldState;
         unsigned int    newState;
     #else
         unsigned long   index;
         unsigned long   count;
         unsigned long   junkBaseP;
         unsigned long   oldState;
         unsigned long   newState;
     #endif
         bool            oldStateValid;
         bool            done;
         FInfoAttrBuf *  thisEntry;
         char            attrBuf[kEntriesPerCall * (sizeof(FInfoAttrBuf) + 64)];

         // attrBuf is big enough for kEntriesPerCall entries, assuming that
         // the average name length is less than 64.

         memset(&attrList, 0, sizeof(attrList));
         attrList.bitmapcount = ATTR_BIT_MAP_COUNT;
         attrList.commonattr  =    ATTR_CMN_NAME
                                 | ATTR_CMN_OBJTYPE
                                 | ATTR_CMN_FNDRINFO;
         attrList.dirattr     = ATTR_DIR_MOUNTSTATUS;

         err = 0;
         dirFD = open(dirPath, O_RDONLY, 0);
         if (dirFD < 0) {
             err = errno;
         }
         if (err == 0) {
             oldStateValid = false;
             done = false;
             do {
                 count = kEntriesPerCall;

                 err = getdirentriesattr(
                     dirFD,
                     &attrList,
                     &attrBuf,
                     sizeof(attrBuf),
                     &count,
                     &junkBaseP,
                     &newState,
                     0
                 );
                 if (err < 0) {
                     err = errno;
                 } else {
                     done = err;
                     err = 0;
                 }

                 if (err == 0) {
                     if (oldStateValid) {
                         if (newState != oldState) {
                             printf("*** Directory has changed\n");
                             oldState = newState;
                         }
                     } else {
                         oldState = newState;
                         oldStateValid = true;
                     }

                     thisEntry = (FInfoAttrBuf *) attrBuf;

                     for (index = 0; index < count; index++) {
                         switch (thisEntry->objType) {
                             case VREG:
                                 printf(
                                     "'%4.4s' '%4.4s' ",
                                     &thisEntry->finderInfo[0],
                                     &thisEntry->finderInfo[4]
                                 );
                                 break;
                             case VDIR:
                                 if (thisEntry->dirStatus & DIR_MNTSTATUS_MNTPOINT)
                                     printf("mount-point   ");
                                 else
                                     printf("directory     ");
                                 break;
                             default:
                                 printf(
                                     "objType = %-2d  ",
                                     thisEntry->objType
                                 );
                                 break;
                         }
                         printf(
                             "%s\n",
                             ((char *) &thisEntry->name)
                                 + thisEntry->name.attr_dataoffset
                         );

                         // Advance to the next entry.

                         thisEntry = (FInfoAttrBuf*)((char*)thisEntry + thisEntry->length);
                     }
                 }
             } while ( err == 0 && ! done );
         }

         if (dirFD != -1) {
             junk = close(dirFD);
             assert(junk == 0);
         }

         return err;
     }


SEE ALSO

     getattrlist(2), getdirentries(2), lseek(2)


HISTORY

     A getdirentriesattr() function call appeared in Darwin 1.3.1 (Mac OS X
     version 10.0).

Darwin                         December 15, 2003                        Darwin

Mac OS X 10.9.1 - Generated Sun Jan 5 21:00:00 CST 2014
© manpagez.com 2000-2024
Individual documents may contain additional copyright information.