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- /*
- getdents -- get directory entries in a file system independent format
- (SVR3 system call emulation)
- last edit: 06-Jul-1987 D A Gwyn
- This single source file supports several different methods of
- getting directory entries from the operating system. Define
- whichever one of the following describes your system:
- UFS original UNIX filesystem (14-character name limit)
- BFS 4.2BSD (also 4.3BSD) native filesystem (long names)
- NFS getdirentries() system call
- Also define any of the following that are pertinent:
- ATT_SPEC check user buffer address for longword alignment
- BSD_SYSV BRL UNIX System V emulation environment on 4.nBSD
- UNK have _getdents() system call, but kernel may not
- support it
- If your C library has a getdents() system call interface, but you
- can't count on all kernels on which your application binaries may
- run to support it, change the system call interface name to
- _getdents() and define "UNK" to enable the system-call validity
- test in this "wrapper" around _getdents().
- If your system has a getdents() system call that is guaranteed
- to always work, you shouldn't be using this source file at all.
- */
- #include <errno.h>
- #include <stdlib.h>
- #include <string.h>
- #include <sys/errno.h>
- #include <sys/types.h>
- #ifdef BSD_SYSV
- #include <sys/_dir.h> /* BSD flavor, not System V */
- #else
- #if defined(UFS)
- #define DIRSIZ 14 /* 14 char filename in Version 7 */
- #endif
- #define MAXNAMLEN 255
- struct direct {
- off_t d_off; /* offset of next disk directory entry */
- u_long d_fileno; /* file number of entry */
- u_short d_reclen; /* length of this record */
- u_short d_namlen; /* length of string in d_name */
- char d_name[MAXNAMLEN + 1]; /* name (up to MAXNAMLEN + 1) */
- };
- #undef MAXNAMLEN /* avoid conflict with SVR3 */
- #define d_ino d_fileno /* compatability */
- #ifdef d_ino /* 4.3BSD/NFS using d_fileno */
- #undef d_ino /* (not absolutely necessary) */
- #else
- #define d_fileno d_ino /* (struct direct) member */
- #endif
- #endif
- #include <sys/dirent.h>
- #include <sys/stat.h>
- #ifdef UNK
- #ifndef UFS
- #error UNK applies only to UFS
- /* One could do something similar for getdirentries(), but I didn't bother. */
- #endif
- #include <signal.h>
- #endif
- #if defined(UFS) + defined(BFS) + defined(NFS) != 1 /* sanity check */
- #error exactly one of UFS, BFS, or NFS must be defined
- #endif
- #ifdef UFS
- #define RecLen( dp ) (sizeof(struct direct)) /* fixed-length entries */
- #else /* BFS || NFS */
- #define RecLen( dp ) ((dp)->d_reclen) /* variable-length entries */
- #endif
- #ifdef NFS
- #ifdef BSD_SYSV
- #define getdirentries _getdirentries /* package hides this system call */
- #endif
- extern int getdirentries(int fd, char *buf, int nbytes, long *basep);
- static long dummy; /* getdirentries() needs basep */
- #define GetBlock( fd, buf, n ) getdirentries( fd, buf, (unsigned)n, &dummy )
- #else /* UFS || BFS */
- #ifdef BSD_SYSV
- #define read _read /* avoid emulation overhead */
- #endif
- extern int read();
- #define GetBlock( fd, buf, n ) read( fd, buf, (unsigned)n )
- #endif
- #ifdef UNK
- extern int _getdents(); /* actual system call */
- #endif
- extern int _fstat(int fd, struct stat *buf);
- extern off_t _lseek(int d, int offset, int whence);
- #ifndef DIRBLKSIZ
- #define DIRBLKSIZ 4096 /* directory file read buffer size */
- #endif
- #ifndef NULL
- #define NULL 0
- #endif
- #ifndef SEEK_CUR
- #define SEEK_CUR 1
- #endif
- #ifndef S_ISDIR /* macro to test for directory file */
- #define S_ISDIR( mode ) (((mode) & S_IFMT) == S_IFDIR)
- #endif
- #ifdef UFS
- /*
- The following routine is necessary to handle DIRSIZ-long entry names.
- Thanks to Richard Todd for pointing this out.
- */
- static int
- NameLen( char name[] ) /* return # chars in embedded name */
- /* -> name embedded in struct direct */
- {
- register char *s; /* -> name[.] */
- register char *stop = &name[DIRSIZ]; /* -> past end of name field */
- for ( s = &name[1]; /* (empty names are impossible) */
- *s != '\0' /* not NUL terminator */
- && ++s < stop; /* < DIRSIZ characters scanned */
- )
- ;
- return s - name; /* # valid characters in name */
- }
- #else /* BFS || NFS */
- #define NameLen( name ) strlen( name ) /* names are always NUL-terminated */
- #endif
- #ifdef UNK
- static enum { maybe, no, yes } state = maybe;
- /* does _getdents() work? */
- /*ARGSUSED*/
- static void
- sig_catch(int sig) /* sig must be SIGSYS */
- {
- state = no; /* attempted _getdents() faulted */
- }
- #endif
- int
- getdents(int fildes, char *buf, unsigned nbyte) /* returns # bytes read;
- 0 on EOF, -1 on error */
- /* fildes == directory file descriptor */
- /* *buf == where to put the (struct dirent)s */
- /* nbyte == size of buf[] */
- {
- int serrno; /* entry errno */
- off_t offset; /* initial directory file offset */
- struct stat statb; /* fstat() info */
- union {
- char dblk[DIRBLKSIZ];
- /* directory file block buffer */
- struct direct dummy; /* just for alignment */
- } u; /* (avoids having to malloc()) */
- register struct direct *dp; /* -> u.dblk[.] */
- register struct dirent *bp; /* -> buf[.] */
- #ifdef UNK
- switch ( state )
- {
- void (*shdlr)(); /* entry SIGSYS handler */
- register int retval; /* return from _getdents() if any */
- case yes: /* _getdents() is known to work */
- return _getdents( fildes, buf, nbyte );
- case maybe: /* first time only */
- shdlr = signal( SIGSYS, sig_catch );
- retval = _getdents( fildes, buf, nbyte ); /* try it */
- (void)signal( SIGSYS, shdlr );
- if ( state == maybe ) /* SIGSYS did not occur */
- {
- state = yes; /* so _getdents() must have worked */
- return retval;
- }
- /* else fall through into emulation */
- /* case no:*/ /* fall through into emulation */
- }
- #endif
- if ( buf == NULL
- #ifdef ATT_SPEC
- || (unsigned long)buf % sizeof(long) != 0 /* ugh */
- #endif
- ) {
- errno = EFAULT; /* invalid pointer */
- return -1;
- }
- if ( _fstat( fildes, &statb ) != 0 )
- return -1; /* errno set by fstat() */
- if ( !S_ISDIR( statb.st_mode ) )
- {
- errno = ENOTDIR; /* not a directory */
- return -1;
- }
- if ( (offset = _lseek( fildes, (off_t)0, SEEK_CUR )) < 0 )
- return -1; /* errno set by lseek() */
- #ifdef BFS /* no telling what remote hosts do */
- if ( (unsigned long)offset % DIRBLKSIZ != 0 )
- {
- errno = ENOENT; /* file pointer probably misaligned */
- return -1;
- }
- #endif
- serrno = errno; /* save entry errno */
- for ( bp = (struct dirent *)buf; bp == (struct dirent *)buf; )
- { /* convert next directory block */
- int size;
- do size = GetBlock( fildes, u.dblk, DIRBLKSIZ );
- while ( size == -1 && errno == EINTR );
- if ( size <= 0 )
- return size; /* EOF or error (EBADF) */
- for ( dp = (struct direct *)u.dblk;
- (char *)dp < &u.dblk[size];
- dp = (struct direct *)((char *)dp + RecLen( dp ))
- ) {
- #ifndef UFS
- if ( dp->d_reclen <= 0 )
- {
- errno = EIO; /* corrupted directory */
- return -1;
- }
- #endif
- if ( dp->d_fileno != 0 )
- { /* non-empty; copy to user buffer */
- register int reclen =
- DIRENTSIZ( NameLen( dp->d_name ) );
- if ( (char *)bp + reclen > &buf[nbyte] )
- {
- errno = EINVAL;
- return -1; /* buf too small */
- }
- bp->d_ino = dp->d_fileno;
- bp->d_off = offset + ((char *)dp - u.dblk);
- bp->d_reclen = reclen;
- (void)strncpy( bp->d_name, dp->d_name,
- reclen - DIRENTBASESIZ
- ); /* adds NUL padding */
- bp = (struct dirent *)((char *)bp + reclen);
- }
- }
- #ifndef BFS /* 4.2BSD screwed up; fixed in 4.3BSD */
- if ( (char *)dp > &u.dblk[size] )
- {
- errno = EIO; /* corrupted directory */
- return -1;
- }
- #endif
- }
- errno = serrno; /* restore entry errno */
- return (char *)bp - buf; /* return # bytes read */
- }
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